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play a role during the initial chemotactic response of neutrophils shortly after infection

following vitamin C supplementation, a 20% increase in neutrophil chemotactic activity was observed

also contributes to the phagocytosis and killing of microbes by neutrophils

low levels of vitamin C occurring in high-stress situations

maturation, proliferation, and viability of T cells have all been shown to be upregulated by the presence of normal physiologic concentrations of vitamin C

Vitamin C has been shown to directly affect the number of Igs released from B cells

vitamin C among healthy young adult males showed a significant increase in serum levels of IgA, IgG, and IgM

effects of high-dose vitamin C on cytokine levels in cancer patients, finding decreased amounts of the cytokines Interleukin-1 alpha (IL-1 alpha), IL-2, IL-8, and tumor necrosis factor-alpha (TNF-alpha) after high-dose vitamin C infusion

when vitamin C was supplemented with vitamin E in healthy adults, it increased the production of cytokines IL-1 beta and TNF-alpha

vitamin C acts to modulate the levels of cytokines to prevent them from fluctuating in either direction

vitamin C also acts as an important antioxidant to the cells of the immune system.

human leukocytes, neutrophils, in particular, possess the ability to transport the oxidized form of vitamin C across its membrane to use as a defense mechanism against ROS produced during an immune response

Vitamin C also can recover other endogenous antioxidants in the body such as vitamin E and glutathione, returning them to their active state

vitamin C can decrease the activation of NF-kB

can reduce harmful nitrogen-based compounds such as N-nitrosamines and nitrosamides, both of which are carcinogenic 

subjects taking oral vitamin C supplementation saw a 60% to 90% reduction in oxidative stress compared to a placebo control

subjects infused with vitamin C alone had a 516% increase in glutathione levels compared to subjects not provided the 500 mg daily supplementation

hydroxylating proline and lysine

mature and stabilize the tissue of a healing wound

healing

oral surgery

improved soft tissue regeneration

vitamin C increases the mRNA levels of type I and type III collagen in the human dermis

Studies have demonstrated that those with low levels of vitamin C are at a significantly higher risk of respiratory infection compared to those with normal levels

viral cold duration was reduced by about 8% in adults and 13.5% in children using prophylactic daily doses of 200 mg of oral vitamin C

prophylactically supplementing vitamin C decreases the risk of infection with respiratory viruses such as the common cold

combined with probiotics, oral vitamin C supplementation showed a 33% decrease in the incidence of respiratory tract infections in preschool-age children [

high-dose oral supplementation of vitamin C managed to prevent or reduce symptoms if taken before or just after the onset of cold- or flu-like symptoms

improvements in oxygen saturation and decreased IL-6 levels (a marker of inflammation) in the treatment group compared to the control group

8 g doses of oral vitamin C

there is a negative correlation between age and serum levels of vitamin C

Patients with COVID-19 will likely also experience depletion in serum levels of vitamin C as a direct result of the upregulation of the immune system to combat the infection

Colunga et al. suggested that oral vitamin C can be combined with oral Quercetin, an antiviral flavonoid, to improve Quercetin’s ability to block viral membrane fusion of SARS-CoV-2

high doses of 1-2 g/day of oral vitamin C could prevent other upper respiratory infections

It appears vitamin C supplementation by itself does not provide a striking benefit in preventing COVID-19 infection for those without a deficiency

Hiedra et al. were able to show decreases in inflammatory biomarkers, such as D-dimer and ferritin

some evidence to support that prophylactic use of vitamin C helps reduce the severity of respiratory infection symptoms once a subject has already been infected

oral vitamin C in combination with zinc provided the largest amount of antibody titers 42 days

linear relationship between days of vitamin C therapy and survival duration

other studies were unable to find any definitive improvement concerning therapy with vitamin C

Fowler et al. aimed to see if a high-dose vitamin C infusion would benefit patients affected by ARDS, but they were unable to conclude that vitamin C infusion, compared to a placebo, could decrease vascular inflammation and damage in ARDS

in a sample of 67 COVID-19-positive ICU patients, 82% of them displayed plasma vitamin C levels below 0.4 mg/dL

continuous vitamin C infusion at a rate of 60 mg/kg/day for four days decreased the need for mechanical ventilation and vasopressor use but had no significant effect on overall mortality

Carr et al. suggested that high-dose IV vitamin C is most effective when treating sepsis as septic patients receiving the normal daily recommendations through diet still showed decreased vitamin C levels

High-dose IV vitamin C treatment has also been shown by Kakodkar et al. to decrease syndecan-1, an endothelial glycocalyx that contributes to mortality in septic patients

combined with hydrocortisone and thiamine, septic patients treated with 1.5 g of IV vitamin C every six hours showed a distinct decrease in their SOFA scores and none of the patients treated developed organ failure

combined with hydrocortisone and thiamine, septic patients treated with 1.5 g of IV vitamin C every six hours showed a distinct decrease in their SOFA scores and none of the patients treated developed organ failure

reduced overall mortality

reduced overall mortality

propose the use for high-dose vitamin C to aid in the treatment of septic shock-induced hypotension

treatment of severe sepsis using a high dose (up to 200 mg/kg/day) of IV vitamin C was explored in phase I, a double-blind, randomized, placebo-controlled trial by Fowler et al. [75]. Their findings included a reduction in SOFA scores and decreased vascular injury compared to a placebo control group, all while showing minimal adverse side effects

Maintaining a daily intake of 75 and 100 mg for men and women, respectively, as recommended by the U.S. Institute of Medicine

Patients with higher inflammation or tumor burdens, as measured by CRP levels or tumor antigen levels, tend to show lower peak plasma ascorbate levels after IVC.

Patients with metastatic tumors tend to achieve lower post infusion plasma ascorbate levels than those with localized tumors.

Meta-analyses of clinical studies involving cancer and vitamins also conclude that antioxidant supplementation does not interfere with the efficacy of chemotherapeutic regiments

Most of the prostate cancer patients studied, 75±19% (95% confidence), showed reductions in PSA levels during the course of their IVC therapy

Laboratory studies suggest that, at high concentrations, ascorbate does not interfere with chemotherapy or irradiation and may enhance efficacy in some situations

Cameron and Pauling observed fourfold survival times in terminal cancer patients treated with intravenous ascorbate infusions followed by oral supplementation

The inflammatory microenvironment of cancer cells leads to increasing oxidative stress, which apparently depletes vitamin C, resulting in lower plasma ascorbate concentrations in blood samples post IVC infusion. Another explanation for this finding may be that cancers are themselves more metabolically active in their uptake of vitamin C, causing subjects to absorb more of the vitamin, and as a results show lower plasma ascorbate concentrations in blood post IVC infusion.

patients with severely elevated CRP levels attain plasma ascorbate concentrations after IVC infusions that are only 65% of those attained for subjects with normal CRP levels

The finding of decreased plasma ascorbate levels in cancer patients may relate to the molecular structure of ascorbic acid; in particular, the similarity of its oxidized form, dihydroascorbic acid, to glucose

Since tumor have increased requirement for glucose [67], transport of dehydroascorbate into the cancer cells via glucose transport molecules and ascorbate through sodium-dependent transporter may be elevated

Increased accumulation of ascorbic acid in the tumor site was supported by measurements of the level of ascorbic acid in tumors in animal experiments

patients with advanced malignancies may have lower level of ascorbic acid in tissue, creating a higher demand for the vitamin C

IVC therapy appears to reduce CRP levels in cancer patients.

CRP concentrations directly correlate with disease activity in many cases and can contribute to disease progression through a range of pro-inflammatory properties.

Being an exquisitely sensitive marker of systemic inflammation and tissue damage, CRP is very useful in screening for organic disease and monitoring treatment responses

ncreases in CRP concentrations have been associated with poorer prognosis of survival in cancer patients, particularly with advance disease independent of tumor stage

Regarding inflammation, 73±13% of subjects (95% confidence) showed a reduction in CRP levels during therapy. This was an even more dramatic 86±13% (95% confidence) in subjects who started therapy with CRP levels above 10 mg/L

patients treated by IVC with follow-up several year showed that suppression of inflammation in cancer patients by high-dose IVC is feasible and potentially beneficial

Inflammation is a marker of high cancer risk, and poor treatment outcome

The subjects with highly elevated CRP concentrations have a three-fold elevation “all-cause” mortality risk and a twenty-eight fold increase in cancer mortality risk

cancer patients may need higher doses to achieve a given plasma concentration.

patients with lower vitamin C levels may see more distribution of intravenously administered ascorbate into tissues and thus attain less in plasma.

When treating patients with IVC, the first treatment likely serves to replenish depleted tissue stores, if those subjects were vitamin C deficient at the beginning of the treatment. Then, in subsequent treatments, with increasing doses, higher plasma concentrations can be attained. On-going treatments serve to progressively reduce oxidative stress in cancer patients.

large doses given intravenously may result in maximum plasma concentrations of roughly 30 mM, a level that has been shown to be sufficient for preferential cytotoxicity against cancer cells

oral intake of vitamin C exceeded 200 mg administered once daily, it was difficult to increase plasma and tissue concentrations above roughly 200 μM.

mitochondrial biogenesis may be a key driver of the CSC phenotype

Our results indicate that increased mitochondrial oxidative stress and high NADH levels are both key characteristics of the CSC metabolic phenotype

high levels of NAD(P)H auto-fluorescence are known to be a surrogate marker for mitochondrial “power”, high OXPHOS capacity and increased ATP production

CSCs may be strictly dependent on NAD(P)H to maintain their enhanced mitochondrial function

an intact NAD+ salvage pathway is strictly required for mammosphere formation, supporting our results using NAD(P)H auto-fluorescence, which enriched CSC activity by more than 5-fold.

Since glycolysis is especially critical for maintaining the TCA cycle, OXPHOS and overall mitochondrial function, we next assessed the effects of known glycolytic inhibitors

we show that two other natural products that function as effective glycolysis inhibitors, also inhibited mammosphere formation. More specifically, vitamin C (ascorbic acid), which induces oxidative stress and inhibits the activity of GAPDH (a key glycolytic enzyme) [17], also inhibited mammosphere formation, with an IC-50 of 1 mM (Figure 7B). Therefore, vitamin C was ~10 times more potent than 2-DG at targeting CSC propagation

silibinin (the major active constituent of silymarin, an extract of milk thistle seeds) [18], which specifically functions as an inhibitor of glucose uptake, blocked mammosphere formation, with an IC-50 between 200 and 400 µM

caffeic acid phenyl ester (CAPE), a key component of honey-bee propolis, has potent anti-cancer properties

Propolis has a strong history of medicinal use, dating back more than 2,000 years

Because of it aromatic ring structure (Figure 8), we speculated that CAPE might function as a potent inhibitor of oxidative mitochondrial metabolism

CAPE quantitatively inhibits the mitochondrial oxygen consumption rate (OCR) and, in turn, induces the onset of aerobic glycolysis (ECAR)

CAPE shows a clear selectivity for targeting CSCs and adherent cancer cells, relative to normal fibroblasts.

CAPE functions as a “natural” mitochondrial OXPHOS inhibitor, that preferentially targets the CSC sub-population. This could explain CAPE’s known anti-cancer properties

Our data directly shows that a small fraction of the total cell population, characterized by increased PGC1α activity, high mitochondrial ROS/H2O2 and high NADH levels, has the ability to survive and grow under anchorage-independent conditions, driving mammosphere formation

We highlight the utility of certain natural products, such as Silibinin, Vitamin C and CAPE, that could be used to therapeutically target CSCs. Silibinin is the major active component of silymarin, which is an extract prepared from milk thistle seeds.

high NADH is a property that is conserved between normal and cancerous stem cells

Previous studies have also shown that when non-CSCs and CSCs are both fed mitochondrial fuels (such as L-lactate or ketone bodies), that CSCs quantitatively produce more NADH in response to this stimulus

CSCs may be strictly dependent on NADH to maintain their enhanced mitochondrial function

The Noble Prize winner, Linus Pauling, was among the first to describe and clinically test the efficacy of Vitamin C, as a relatively non-toxic anti-cancer agent

Vitamin C has two mechanisms of action. First, it is a potent pro-oxidant, that actively depletes the reduced glutathione pool, leading to cellular oxidative stress and apoptosis in cancer cells. Moreover, it also behaves as an inhibitor of glycolysis, by targeting the activity of GAPDH, a key glycolytic enzyme.

Here, we show that Vitamin C can also be used to target the CSC population, as it is an inhibitor of energy metabolism that feeds into the mitochondrial TCA cycle and OXPHOS

Vitamin C may prove to be promising agent for new clinical trials, aimed at testing its ability to reduce CSC activity in cancer patients, as an add-on to more conventional therapies, to prevent tumor recurrence, further disease progression and metastasis

Interestingly, a breast cancer based clinical study has already shown that the use of Vitamin C, concurrent with or within 6 months of chemotherapy, significantly reduces both tumor recurrence and patient mortality

CAPE quantitatively reduces mitochondrial oxygen consumption (OCR), while inducing a reactive increase in glycolysis (ECAR). As such, it potently inhibits mammosphere formation with an IC-50 of ~2.5 µM. Similarly, it also significantly inhibits cell migration

we also demonstrate that 7 different inhibitors of key energetic pathways can be used to effectively block CSC propagation, including three natural products (silibinin, ascorbic acid and CAPE). Future studies will be necessary to test their potential for clinical benefit in cancer patients.

Vitamin C inhibits GAPDH (a glycolytic enzyme) and depletes the cellular pool of glutathione, resulting in high ROS production and oxidative stress

DoxyR CSCs are between 4- to 10-fold more susceptible to the effects of Vitamin C

Doxycycline and Vitamin C may represent a new synthetic lethal drug combination for eradicating CSCs, by ultimately targeting both mitochondrial and glycolytic metabolism

inhibiting their propagation in the range of 100 to 250 µM

metabolic flexibility in cancer cells allows them to escape therapeutic eradication, leading to chemo- and radio-resistance

used doxycycline to pharmacologically induce metabolic inflexibility in CSCs, by chronically inhibiting mitochondrial biogenesis

This treatment resulted in a purely glycolytic population of surviving cancer cells

DoxyR cells are mainly glycolytic

MCF7 cells survive and develop Doxycycline-resistance, by adopting a purely glycolytic phenotype

Cancer stem cells (CSCs) are thought to be the “root cause” of tumor recurrence, distant metastasis and therapy-resistance

the conserved evolutionary similarities between aerobic bacteria and mitochondria, certain classes of antibiotics inhibit mitochondrial protein translation, as an off-target side-effect

Vitamin C was more potent than 2-DG; it inhibited DoxyR CSC propagation by > 90% at 250 µM and 100% at 500 µM

IC-50

DoxyR CSCs are between 4- to 10-fold more sensitive to Vitamin C than control MCF7 CSCs

Berberine, which is a naturally occurring antibiotic that also behaves as an OXPHOS inhibitor

treatment with Berberine effectively inhibited the propagation of the DoxyR CSCs by > 50% at 1 µM and > 80% at 10 µM.

Doxycycline, a clinically approved antibiotic, induces metabolic stress in cancer cells. This allows the remaining cancer cells to be synchronized towards a purely glycolytic phenotype, driving a form of metabolic inflexibility

Doxycycline-driven aerobic glycolysis

new synthetic lethal strategy for eradicating CSCs, by employing i) Doxycycline (to target mitochondria) and ii) Vitamin C (to target glycolysis)

Doxycycline inhibits mitochondrial biogenesis and OXPHOS,

hibits glycolytic metabolism by targeting and inhibiting the enzyme GAPDH

CSCs act as the main promoter of tumor recurrence and patient relapse

a metabolic shift from oxidative to glycolytic metabolism represents an escape mechanism for breast cancer cells chronically-treated with a mitochondrial stressor like Doxycycline, as mitochondrial dys-function leads to a stronger dependence on glucose

Vitamin C has been demonstrated to selectively kill cancer cells in vitro and to inhibit tumor growth in experimental mouse models

many of these actions have been attributed to the ability of Vitamin C to act as a glycolysis inhibitor, by targeting GAPDH and depleting the NAD pool

here we show that DoxyR CSCs are more vulnerable to the inhibitory effects of Vitamin C, at 4- to 10-fold lower concentrations, between 100 to 250 μM

concurrent use of Vitamin C, with standard chemotherapy, reduces tumor recurrence and patient mortality

after oral administration, Vitamin C plasma levels reach concentrations of ~70-220 μM

intravenous administration results in 30- to 70- fold higher plasma concentrations of Vitamin C

pro-oxidant activity results from Vitamin C’s action on metal ions, which generates free radicals and hydrogen peroxide, and is associated with cell toxicity

it has been shown that high-dose Vitamin C is more cytotoxic to cancer cells than to normal cells

This selectivity appears to be due to the higher catalase content observed in normal cells (~10-100 fold greater), as compared to tumor cells. Hence, Vitamin C may be regarded as a safe agent that selectively targets cancer cells

the concurrent use of Doxycycline and Vitamin C, in the context of this infectious disease, appeared to be highly synergistic in patients

Goc et al., 2016, showed that Doxycycline is synergistic in vitro with certain phytochemicals and micronutrients, including Vitamin C, in the in vitro killing of the vegetative spirochete form of Borrelia spp., the causative agent underlying Lyme disease

Doxycycline, an FDA-approved antibiotic, behaves as an inhibitor of mitochondrial protein translation

CSCs successfully escape from the anti-mitochondrial effects of Doxycycline, by assuming a purely glycolytic phenotype. Therefore, DoxyR CSCs are then more susceptible to other metabolic perturbations, because of their metabolic inflexibility

Data from the American Cancer Society show that the rate of increase in cancer deaths/year (3.4%) was two-fold greater than the rate of increase in new cases/year (1.7%) from 2013 to 2017

cancer is predicted to overtake heart disease as the leading cause of death in Western societies

cancer can also be recognized as a metabolic disease.

glucose is first split into two molecules of pyruvate through the Embden–Meyerhof–Parnas glycolytic pathway in the cytosol

Aerobic fermentation, on the other hand, involves the production of lactic acid under normoxic conditions

persistent lactic acid production in the presence of adequate oxygen is indicative of abnormal respiration

Otto Warburg first proposed that all cancers arise from damage to cellular respiration

The Crabtree effect is an artifact of the in vitro environment and involves the glucose-induced suppression of respiration with a corresponding elevation of lactic acid production even under hyperoxic (pO2 = 120–160 mmHg) conditions associated with cell culture

the Warburg theory of insufficient aerobic respiration remains as the most credible explanation for the origin of tumor cells [2, 37, 51, 52, 53, 54, 55, 56, 57].

The main points of Warburg’s theory are; 1) insufficient respiration is the predisposing initiator of tumorigenesis and ultimately cancer, 2) energy through glycolysis gradually compensates for insufficient energy through respiration, 3) cancer cells continue to produce lactic acid in the presence of oxygen, and 4) respiratory insufficiency eventually becomes irreversible

Efraim Racker coined the term “Warburg effect”, which refers to the aerobic glycolysis that occurs in cancer cells

Warburg clearly demonstrated that aerobic fermentation (aerobic glycolysis) is an effect, and not the cause, of insufficient respiration

all tumor cells that have been examined to date contain abnormalities in the content or composition of cardiolipin

The evidence supporting Warburg’s original theory comes from a broad range of cancers and is now overwhelming

respiratory insufficiency, arising from any number mitochondrial defects, can contribute to the fermentation metabolism seen in tumor cells.

data from the nuclear and mitochondrial transfer experiments suggest that oncogene changes are effects, rather than causes, of tumorigenesis

Normal mitochondria can suppress tumorigenesis, whereas abnormal mitochondria can enhance tumorigenesis

In addition to glucose, cancer cells also rely heavily on glutamine for growth and survival

Glutamine is anapleurotic and can be rapidly metabolized to glutamate and then to α-ketoglutarate for entry into the TCA cycle

Glucose and glutamine act synergistically for driving rapid tumor cell growth

Glutamine metabolism can produce ATP from the TCA cycle under aerobic conditions

Amino acid fermentation can generate energy through TCA cycle substrate level phosphorylation under hypoxic conditions

Hif-1α stabilization enhances aerobic fermentation

targeting glucose and glutamine will deprive the microenvironment of fermentable fuels

Although Warburg’s hypothesis on the origin of cancer has created confusion and controversy [37, 38, 39, 40], his hypothesis has never been disproved

Warburg referred to the phenomenon of enhanced glycolysis in cancer cells as “aerobic fermentation” to highlight the abnormal production of lactic acid in the presence of oxygen

Emerging evidence indicates that macrophages, or their fusion hybridization with neoplastic stem cells, are the origin of metastatic cancer cells

Radiation therapy can enhance fusion hybridization that could increase risk for invasive and metastatic tumor cells

Kamphorst et al. in showing that pancreatic ductal adenocarcinoma cells could obtain glutamine under nutrient poor conditions through lysosomal digestion of extracellular proteins

It will therefore become necessary to also target lysosomal digestion, under reduced glucose and glutamine conditions, to effectively manage those invasive and metastatic cancers that express cannibalism and phagocytosis.

Previous studies in yeast and mammalian cells show that disruption of aerobic respiration can cause mutations (loss of heterozygosity, chromosome instability, and epigenetic modifications etc.) in the nuclear genome

The somatic mutations and genomic instability seen in tumor cells thus arise from a protracted reliance on fermentation energy metabolism and a disruption of redox balance through excess oxidative stress.

According to the mitochondrial metabolic theory of cancer, the large genomic heterogeneity seen in tumor cells arises as a consequence, rather than as a cause, of mitochondrial dysfunction

A therapeutic strategy targeting the metabolic abnormality common to most tumor cells should therefore be more effective in managing cancer than would a strategy targeting genetic mutations that vary widely between tumors of the same histological grade and even within the same tumor

Tumor cells are more fit than normal cells to survive in the hypoxic niche of the tumor microenvironment

Hypoxic adaptation of tumor cells allows for them to avoid apoptosis due to their metabolic reprograming following a gradual loss of respiratory function

The high rates of tumor cell glycolysis and glutaminolysis will also make them resistant to apoptosis, ROS, and chemotherapy drugs

Despite having high levels of ROS, glutamate-derived from glutamine contributes to glutathione production that can protect tumor cells from ROS

It is clear that adaptability to environmental stress is greater in normal cells than in tumor cells, as normal cells can transition from the metabolism of glucose to the metabolism of ketone bodies when glucose becomes limiting

Mitochondrial respiratory chain defects will prevent tumor cells from using ketone bodies for energy

glycolysis-dependent tumor cells are less adaptable to metabolic stress than are the normal cells. This vulnerability can be exploited for targeting tumor cell energy metabolism

In contrast to dietary energy reduction, radiation and toxic drugs can damage the microenvironment and transform normal cells into tumor cells while also creating tumor cells that become highly resistant to drugs and radiation

Drug-resistant tumor cells arise in large part from the damage to respiration in bystander pre-cancerous cells

Because energy generated through substrate level phosphorylation is greater in tumor cells than in normal cells, tumor cells are more dependent than normal cells on the availability of fermentable fuels (glucose and glutamine)

Ketone bodies and fats are non-fermentable fuels

Although some tumor cells might appear to oxidize ketone bodies by the presence of ketolytic enzymes [181], it is not clear if ketone bodies and fats can provide sufficient energy for cell viability in the absence of glucose and glutamine

Apoptosis under energy stress is greater in tumor cells than in normal cells

A calorie restricted ketogenic diet or dietary energy reduction creates chronic metabolic stress in the body

. This energy stress acts as a press disturbance

Drugs that target availability of glucose and glutamine would act as pulse disturbances

Hyperbaric oxygen therapy can also be considered another pulse disturbance

The KD can more effectively reduce glucose and elevate blood ketone bodies than can CR alone making the KD potentially more therapeutic against tumors than CR

Campbell showed that tumor growth in rats is greater under high protein (>20%) than under low protein content (<10%) in the diet

Protein amino acids can be metabolized to glucose through the Cori cycle

The fats in KDs used clinically also contain more medium chain triglycerides

Calorie restriction, fasting, and restricted KDs are anti-angiogenic, anti-inflammatory, and pro-apoptotic and thus can target and eliminate tumor cells through multiple mechanisms

Ketogenic diets can also spare muscle protein, enhance immunity, and delay cancer cachexia, which is a major problem in managing metastatic cancer

GKI values of 1.0 or below are considered therapeutic

The GKI can therefore serve as a biomarker to assess the therapeutic efficacy of various diets in a broad range of cancers.

It is important to remember that insulin drives glycolysis through stimulation of the pyruvate dehydrogenase complex

The water-soluble ketone bodies (D-β-hydroxybutyrate and acetoacetate) are produced largely in the liver from adipocyte-derived fatty acids and ketogenic dietary fat. Ketone bodies bypass glycolysis and directly enter the mitochondria for metabolism to acetyl-CoA

Due to mitochondrial defects, tumor cells cannot exploit the therapeutic benefits of burning ketone bodies as normal cells would

Therapeutic ketosis with racemic ketone esters can also make it feasible to safely sustain hypoglycemia for inducing metabolic stress on cancer cells

ketone bodies can inhibit histone deacetylases (HDAC) [229]. HDAC inhibitors play a role in targeting the cancer epigenome

Therapeutic ketosis reduces circulating inflammatory markers, and ketones directly inhibit the NLRP3 inflammasome, an important pro-inflammatory pathway linked to carcinogenesis and an important target for cancer treatment response

Chronic psychological stress is known to promote tumorigenesis through elevations of blood glucose, glucocorticoids, catecholamines, and insulin-like growth factor (IGF-1)

In addition to calorie-restricted ketogenic diets, psychological stress management involving exercise, yoga, music etc. also act as press disturbances that can help reduce fatigue, depression, and anxiety in cancer patients and in animal models

Ketone supplementation has also been shown to reduce anxiety behavior in animal models

This physiological state also enhances the efficacy of chemotherapy and radiation therapy, while reducing the side effects

lower dosages of chemotherapeutic drugs can be used when administered together with calorie restriction or restricted ketogenic diets (KD-R)

Besides 2-DG, a range of other glycolysis inhibitors might also produce similar therapeutic effects when combined with the KD-R including 3-bromopyruvate, oxaloacetate, and lonidamine

A synergistic interaction of the KD diet plus radiation was seen

It is important to recognize, however, that the radiotherapy used in glioma patients can damage the respiration of normal cells and increase availability of glutamine in the microenvironment, which can increase risk of tumor recurrence especially when used together with the steroid drug dexamethasone

Poff and colleagues demonstrated that hyperbaric oxygen therapy (HBOT) enhanced the ability of the KD to reduce tumor growth and metastasis

HBOT also increases oxidative stress and membrane lipid peroxidation of GBM cells in vitro

The effects of the KD and HBOT can be enhanced with administration of exogenous ketones, which further suppressed tumor growth and metastasis

Besides HBOT, intravenous vitamin C and dichloroacetate (DCA) can also be used with the KD to selectively increase oxidative stress in tumor cells

Recent evidence also shows that ketone supplementation may enhance or preserve overall physical and mental health

Some tumors use glucose as a prime fuel for growth, whereas other tumors use glutamine as a prime fuel [102, 186, 262, 263, 264]. Glutamine-dependent tumors are generally less detectable than glucose-dependent under FDG-PET imaging, but could be detected under glutamine-based PET imaging

GBM and use glutamine as a major fuel

Many of the current treatments used for cancer management are based on the view that cancer is a genetic disease

Emerging evidence indicates that cancer is a mitochondrial metabolic disease that depends on availability of fermentable fuels for tumor cell growth and survival

Glucose and glutamine are the most abundant fermentable fuels present in the circulation and in the tumor microenvironment

Low-carbohydrate, high fat-ketogenic diets coupled with glycolysis inhibitors will reduce metabolic flux through the glycolytic and pentose phosphate pathways needed for synthesis of ATP, lipids, glutathione, and nucleotides

Studies have shown that the production of nagalase has a mutual relationship with Gc-MAF level and immunosuppression

It has been demonstrated that serum levels of nagalase are good prognosticators of some types of cancer

The nagalase level in serum correlates with tumor burden and it has been shown that Gc-MAF therapy progresses, nagalase activity decreases

It has been shown that Gc-MAF can inhibit the angiogenesis induced by pro-inflammatory prostaglandin E1

The effect of Gc-MAF on chemotaxis or activation of tumoricidal macrophages is likely the main mechanism against angiogenesis.

Administration of Gc-MAF stimulates immune-cell progenitors for extensive mitogenesis, activates macrophages and produces antibodies. “This indicates that Gc-MAF is a powerful adjuvant for immunization.”

Cancer cell lines do not develop into tumor genes in mouse models after Gc-MAF-primed immunization (29-31) and the effect of Gc-MAF has been approved for macrophage stimulation for angiogenesis, proliferation, migration and metastatic inhibition on tumors induced by MCF-7 human breast cancer cell line

The protocol included: "a high dose of second-generation Gc-MAF (0.5 ml) administered twice a week intramuscularly for a total of 21 injections.”

Yamamoto et al. showed that the administration of Gc-MAF to 16 patients with prostate cancer led to improvements in all patients without recurrence

Inui et al. reported that a 74-year-old man diagnosed with prostate cancer with multiple bone metastases was in complete remission nine months after initiation of GcMAF therapy simultaneously with hyper T/NK cell, high-dose vitamin C and alpha lipoic acid therapy

It has also been approved for non-neoplastic diseases such as autism (41), multiple sclerosis (42, 43), chronic fatigue syndrome (CFS) (40), juvenile osteoporosis (44) and systemic lupus erythematous (45).

Gc-MAF has been verified for use in colon, thyroid (38), lung (39), liver, thymus (36), pancreatic (40), bladder and ovarian cancer and tongue squamous carcinoma

Prostate, breast, colon, liver, stomach, lung (including mesothelioma), kidney, bladder, uterus, ovarian, head/neck and brain cancers, fibrosarcomas and melanomas are the types of cancer tested thus far

weekly administration of 100 ng Gc-MAF to cancer at different stages and types showed curative effects at different follow-up times

this treatment has been suggested for non-anemic patients

Studies have shown that weekly administration of 100 ng Gc-MAF to cancer patients had curative effects on a variety of cancers

Because the half-life of the activated macrophages is approximately one week, it must be administered weekly

In vivo weekly intramuscular administration of Gc-MAF (100 ng) for 16-22 weeks was used to treat patients with breast cancer

individuals harboring different VDR genotypes had different responses to Gc-MAF and that some genotypes were more responsive than others

Administration of Gc-MAF for cancer patients exclusively activates macrophages as an important cell in adaptive immunity

Gc-MAF supports humoral immunity by producing, developing and releasing large quantities of antibodies against cancer. Clinical evidence from a human model of breast cancer patients supports this hypothesis

There is also evidence that confirms the tumoricidal role of Gc-MAF via Fc-receptor mediation

It is likely that the best therapeutic responses will be observed when the nutritional and inflammatory aspects are taken together with stimulation of the immune system

it should be noted that no harmful side effects of Gc-MAF treatment have been reported, even when it was successfully administered to autistic children

The natural activation mechanism of macrophages by Gc-MAF is so natural and it should not have any side effects on humans or animal models even in cell culture

Besides the Gc-MAF efficacy on macrophage activity, it can be a potential anti-angiogenic agent (28) and an inhibitor of the migration of cancerous cells in the absence of macrophages (47).

Activating or modifying natural killer cells, dendritic cells, DC, CTL, INF and IL-2 have all been recommended for cancer immunotherapy

It has been reported that nagalase cannot deglycosylate Gc-MAF as it has specificity for Gc globulin alone

inflammation-derived macrophage activation with the participation of B and T lymphocytes is the main mechanism

macrophages highly-activated by the addition of Gc-MAF can show tumoricidal activity

Previous clinical investigations have confirmed the efficacy of Gc-MAF. In addition to activating existing macrophages, Gc-MAF is a potent mitogenic factor that can stimulate the myeloid progenitor cells to increase systemic macrophage cell counts by 40-fold in four days

whereas the expression of SVCT-2 is ubiquitous

differential sensitivity to VC may result from variations in VC flow into cells, which is dependent on SVCT-2 expression.

high-dose VC significantly impaired both the tumorspheres initiation (Fig. 4d, e) and the growth of established tumorspheres derived from HCC cells (Fig. 4f, g) in a time-dependent and dose-dependent manner.

Hepatocellular carcinoma (HCC)

The antioxidant, N-acetyl-L-cysteine (NAC), preventing VC-induced ROS production (a ROS scavenger), completely restored the viability and colony formation among VC-treated cells

DNA double-strand damage was found following VC treatment

DNA damage was prevented by NAC

Interestingly, the combination of VC and cisplatin was even more effective in reducing tumor growth and weight

Consistent with the in vitro results, stemness-related genes expressions in tumor xenograft were remarkably reduced after VC or VC+cisplatin treatment, whereas conventional cisplatin therapy alone led to the increase of CSCs

VC is one of the numerous common hepatoprotectants.

Interestingly, at extracellular concentrations greater than 1 mM, VC induces strong cytotoxicity to cancer cells including liver cancer cells

we hypothesized that intravenous VC might reduce the risk of recurrence in HCC patients after curative liver resection.

Intriguingly, the 5-year disease-free survival (DFS) for patients who received intravenous VC was 24%, as opposed to 15% for no intravenous VC-treated patients

Median DFS time for VC users was 25.2 vs. 18 months for VC non-users

intravenous VC use is linked to improved DFS in HCC patients.

In this study, based on the elevated expression of SVCT-2, which is responsible for VC uptake, in liver CSCs, we revealed that clinically achievable concentrations of VC preferentially eradicated liver CSCs in vitro and in vivo

Additionally, we found that intravenous VC reduced the risk of post-surgical HCC progression in a retrospective cohort study.

Three hundred thirty-nine participants (55.3%) received 2 g intravenous VC for 4 or more days after initial hepatectomy

As the key protein responsible for VC uptake in the liver, SVCT-2 played crucial roles in regulating the sensitivity to ascorbate-induced cytotoxicity

we also observed that SVCT-2 was highly expressed in human HCC samples and preferentially elevated in liver CSCs

SVCT-2 might serve as a potential CSC marker and therapeutic target in HCC

CSCs play critical roles in regulating tumor initiation, relapse, and chemoresistance

we revealed that VC treatment dramatically reduced the self-renewal ability, expression levels of CSC-associated genes, and percentages of CSCs in HCC, indicating that CSCs were more susceptible to VC-induced cell death

as a drug for eradicating CSCs, VC may represent a promising strategy for treatment of HCC, alone or particularly in combination with chemotherapeutic drugs

In HCC, we found that VC-generated ROS caused genotoxic stress (DNA damage) and metabolic stress (ATP depletion), which further activated the cyclin-dependent kinase inhibitor p21, leading to G2/M phase cell cycle arrest and caspase-dependent apoptosis in HCC cells

we demonstrated a synergistic effect of VC and chemotherapeutic drug cisplatin on killing HCC both in vitro and in vivo

Intravenous VC has also been reported to reduce chemotherapy-associated toxicity of carboplatin and paclitaxel in patients,38 but the specific mechanism needs further investigation

Our retrospective cohort study also showed that intravenous VC use (2 g) was related to the improved DFS in HCC patients after initial hepatectomy

several clinical trials of high-dose intravenous VC have been conducted in patients with advanced cancer and have revealed improved quality of life and prolonged OS

high-dose VC was not toxic to immune cells and major immune cell subpopulations in vivo

high recurrence rate and heterogeneity

tumor progression, metastasis, and chemotherapy-resistance

SVCT-2 was highly expressed in HCC samples in comparison to peri-tumor tissues

high expression (grade 2+/3+) of SVCT-2 was in agreement with poorer overall survival (OS) of HCC patients (Fig. 1c) and more aggressive tumor behavior

SVCT-2 is enriched in liver CSCs

these data suggest that SVCT-2 is preferentially expressed in liver CSCs and is required for the maintenance of liver CSCs.

pharmacologic concentrations of plasma VC higher than 0.3 mM are achievable only from i.v. administration

The viabilities of HCC cells were dramatically decreased after exposure to VC in dose-dependent manner

VC and cisplatin combination further caused cell apoptosis in tumor xenograft

These results verify that VC inhibits tumor growth in HCC PDX models and SVCT-2 expression level is associated with VC response

qPCR and IHC analysis demonstrated that expression levels of CSC-associated genes and percentages of CSCs in PDXs dramatically declined after VC treatment, confirming the inhibitory role of VC in liver CSCs

Vitamin C may serve as a pro-drug for hydrogen peroxide delivery to extravascular tissues, but without the presence of hydrogen peroxide in blood

not all cancer cells were killed by ascorbic acid in vitro

Intravascular hemolysis was reported after massive vitamin C administration in people with glucose-6-phosphate dehydrogenase deficiency

Administration of high-dose vitamin C to patients with systemic iron overload may increase iron absorption and represents a contraindication

Ascorbic acid is metabolized to oxalate, and 2 cases of acute oxalate nephropathy were reported in patients with pre-existing renal insufficiency given massive intravenous doses of vitamin C

Rare cases of acute tumour hemorrhage and necrosis were reported in patients with advanced cancer within a few days of starting high-dose intravenous vitamin C therapy, although this was not independently verified by pathologic review

These data suggest that PAA may show a therapeutic advantage to blood cancers vs solid tumors because of the communication between tumor cells and blood plasma

These results strongly suggest that the mechanism of PAA killing of MM cells is indeed iron-dependent

These results suggest that PAA administration in SMM may be able to prevent progression to symtomatic MM

A recent study by Yun and colleagues demonstrated that vitamin C selectively kills KRAS and BRAF mutant colorectal cancer cells by targeting GAPDH, but spares normal cells

RAS family genes show the most frequent mutations in MM. KRAS, NRAS and BRAF are mutated in 22%, 20% and 7% of MM samples

the disease stage rather than the mutation of RAS and/or BRAF is the major predictive factor for PAA sensitivity in MM treatment

Other molecular mechanisms including ATP depletion and ATM-AMPK signaling have been reported to explain PAA-induced cell death

our pilot study also suggested that PAA could overcome drug resistance to bortezomib in MM cells

Our findings complement reported studies and further address the mechanism of action using clinical samples in which we observed that PAA killed tumor cells with high iron content, suggesting that iron might be the initiator of PAA cytotoxicity

combination of PAA with standard therapeutic drugs, such as melphalan, may significantly reduce the dose of melphalan needed

Combined treatment of reduced dose melphalan with PAA achieved a significantly longer progression-free survival than the same dose of melphalan alone.

These data also suggest that the bone marrow suppression induced by high-dose melphalan can be ameliorated by the combination of PAA with lower dose of melphalan because of the lack of toxicity of PAA on normal cells with low iron content.

if creatinine clearance is <30 mL/min, high dose ascorbic acid should be not administrated.

In MM preclinical and clinical studies, ascorbate was used as an adjunct drug and showed controversial results (Harvey et al., 2009, Perrone et al., 2009, Held et al., 2013, Sharma et al., 2012, Nakano et al., 2011, Takahashi, 2010, Sharma et al., 2009, Qazilbash et al., 2008). However, none of these tests used pharmacological doses of ascorbate and intravenous administration

Multiple myeloma (MM) is a plasma cell neoplasm.

Cameron and Pauling reported that high doses of vitamin C increased survival of patients with cancer

pharmacologically dosed ascorbic acid (PAA) 50–100 g (Chen et al., 2008, Padayatty et al., 2004, Hoffer et al., 2008, Padayatty et al., 2006, Welsh et al., 2013), administered intravenously, has potent anti-cancer activity and its role as anti-cancer therapy is being studied at the University of Iowa and in other centers

In the presence of catalytic metal ions like iron, PAA administered intravenously exerts pro-oxidant effects leading to the formation of highly reactive oxygen species (ROS), resulting in cell death

the labile iron pool (LIP) is significantly elevated in MM cells

The survival of CD138+ cells in vitro was significantly decreased following PAA treatment in all 9 MM

In contrast, no significant change of cell viability was observed in CD138− BM cells from the same patients

The same effect of PAA was also observed in the SMM patients

no response to PAA was detected in CD138+ cells from the 2 MGUS patients

the combination of melphalan plus PAA showed greater tumor burden reduction than each drug alone, suggesting a synergistic activity between these two drugs

Both catalase and NAC protect cells from oxidative damage

cells pretreated with NAC and catalase became resistant to PAA even at high doses

adding deferoxamine (DFO), an iron chelator, to OCI-MY5 cells before PAA treatment was also sufficient to prevent PAA-induced cellular death

iron is essential for PAA to achieve its anti-cancer activity

PAA induced early necrosis (Fig. 3Fig. 3A, 60 min) followed by late apoptosis

results further indicated that PAA induced mitochondria-mediated apoptosis

PAA by reacting with LIP and generating ROS induces mitochondria-mediated apoptosis in which AIF1 cleavage is important for cell death.

ROS and H2O2 are well known factors mediating PAA-induced cancer cell death

PAA was sensitive to all 9 MMs and 2 SMMs

Our data show that ascorbic acid selectively killed cancer but not normal cells, using concentrations that could only be achieved by i.v. administration

Ascorbate-mediated cell death was due to protein-dependent extracellular H2O2 generation, via ascorbate radical formation from ascorbate as the electron donor. Like glucose, when ascorbate is infused i.v., the resulting pharmacologic concentrations should distribute rapidly in the extracellular water space (42). We showed that such pharmacologic ascorbate concentrations in media, as a surrogate for extracellular fluid, generated ascorbate radical and H2O2. In contrast, the same pharmacologic ascorbate concentrations in whole blood generated little detectable ascorbate radical and no detectable H2O2. These findings can be accounted for by efficient and redundant H2O2 catabolic pathways in whole blood (e.g., catalase and glutathione peroxidase) relative to those in media or extracellular fluid

ascorbic acid administered i.v. in pharmacologic concentrations may serve as a pro-drug for H2O2 delivery to the extracellular milieu

H2O2 generated in blood is normally removed by catalase and glutathione peroxidase within red blood cells, with internal glutathione providing reducing equivalents

The electron source for glutathione is NADPH from the pentose shunt, via glucose-6-phosphate dehydrogenase. If activity of this enzyme is diminished, the predicted outcome is impaired H2O2 removal causing intravascular hemolysis, the observed clinical finding.

Only recently has it been understood that the discordant clinical findings can be explained by previously unrecognized fundamental pharmacokinetics properties of ascorbate

Intracellular transport of ascorbate is tightly controlled in relation to extracellular concentration

Intravenous ascorbate infusion is expected to drastically change extracellular but not intracellular concentrations

For i.v. ascorbate to be clinically useful in killing cancer cells, pharmacologic but not physiologic extracellular concentrations should be effective, independent of intracellular ascorbate concentrations.

It is unknown why ascorbate, via H2O2, killed some cancer cells but not normal cells.

There was no correlation with ascorbate-induced cell death and glutathione, catalase activity, or glutathione peroxidase activity.

H2O2, as the product of pharmacologic ascorbate concentrations, has potential therapeutic uses in addition to cancer treatment, especially in infections

Neutrophils generate H2O2 from superoxide,

i.v. ascorbate is effective in some viral infections

H2O2 is toxic to hepatitis C

Use of ascorbate as an H2O2-delivery system against sensitive pathogens, viral or bacterial, has substantial clinical implications that deserve rapid exploration.