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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

Under steady-state conditions, intracellular GSH is maintained at millimolar concentrations, which keeps cells in a reduced environment and serves as the principal intracellular redox buffer when cells are subjected to an oxidative stressor including H2O2 (26). Glutathione peroxidase (GPx) activity catalyzes the reduction of H2O2 to water with the conversion of GSH to glutathione disulfide (GSSG). Under steady-state conditions, GSSG is recycled back to GSH by glutathione disulfide reductase using reducing equivalents from NADPH. However, under conditions of increased H2O2 flux, this recycling mechanism may become overwhelmed leading to a depletion of intracellular GSH (27, 28).

ascorbate radiosensitization can create an overwhelming oxidative stress to pancreatic cancer cells resulting in oxidation/depletion of the GSH intracellular redox buffer, resulting in cell death.

Treatment with the combination of ascorbate + IR significantly delayed tumor growth compared to controls or ascorbate alone

Ascorbate + IR also significantly increased overall survival compared to controls, IR alone or ascorbate alone

54% of mice treated with the combination of IR + ascorbate had no measurable tumors

Glutathione is a measurable marker indicative of the oxidation state of the thiol redox buffer in cells. In severe systemic oxidative stress, the GSSG/2GSH couple may become oxidized, i.e. the concentration of GSH decreases and GSSG may increase because the capacity to recycle GSSG to GSH becomes rate-limiting

This suggests that the very high levels of pharmacological ascorbate in these experiments may have a pro-oxidant toward red blood cells as seen by a decrease in the capacity of the intracellular redox buffer

These data support the hypothesis that ascorbate radiosensitization does not cause an increase in oxidative damage from lipid-derived aldehydes to other organs.

Our current study demonstrates the potential for pharmacological ascorbate as a radiosensitizer in the treatment of pancreatic cancer.

pharmacological ascorbate enhances IR-induced cell killing and DNA fragmentation leading to induction of apoptosis in HL60 leukemia cells

pharmacological ascorbate significantly decreases clonogenic survival and inhibits the growth of all pancreatic cancer cell lines as a single agent, as well as sensitizes cancer cells to IR

Hurst et al. demonstrated that pharmacological ascorbate combined with IR leads to increased numbers of double-strand DNA breaks and cell cycle arrest when compared to either treatment alone

pharmacological ascorbate could serve as a “pro-drug” for the delivery of H2O2 to tumors

the double-strand breaks induced by H2O2 were more slowly repaired

The combination of ascorbate and IR provide two distinct mechanisms of action: ascorbate-induced toxicity due to extracellular production of H2O2 that then diffuses into cells and causes damage to DNA, protein, and lipids; and radiation-induced toxicity as a result of ROS-induced damage to DNA. In addition, redox metal metals like Fe2+ may play an important role in ascorbate-induced cytotoxicity. By catalyzing the oxidation of ascorbate, labile iron can enhance the rate of formation of H2O2; labile iron can also react with H2O2. Recently our group has demonstrated that pharmacological ascorbate and IR increase the labile iron in tumor homogenates from this murine model of pancreatic cancer

we demonstrated that ascorbate or IR alone decreased tumor growth, but the combination treatment further inhibited tumor growth, indicating that pharmacological ascorbate is an effective radiosensitizer in vivo

data suggest that pharmacological ascorbate may protect the gut locally by decreasing IR-induced damage to the crypt cells, and systemically, by ameliorating increases in TNF-α

PAK1 is essential for the growth of more than 70% of all human cancers, including breast, prostate, pancreatic, colon, gastric, lung, cervical and thyroid cancers, as well as hepatoma, glioma, melanoma, multiple myeloma and for neurofibromatosis tumors

Ivermectin suppresses breast cancer by activating cytostatic autophagy, disrupting cellular signaling in the process, probably by reducing PAK1 expression

Cancer stem cells are a key factor in cancer cells developing resistance to chemotherapies and these results indicate that a combination of chemotherapy agents plus ivermectin could potentially target and kill cancer stem cells, a paramount goal in overcoming cancer

Triple-negative breast cancers, which lack estrogen, progesterone and HER2 receptors, account for 10–20% of breast cancers and are associated with poor prognosis

Ivermectin addition led to transcriptional modulation of genes associated with epithelial–mesenchymal transition and maintenance of a cancer stem cell phenotype in triple-negative breast cancers cells, resulting in impairment of clonogenic self-renewal in vitro and inhibition of tumor growth and metastasis in vivo

Ivermectin-induced cytostatic autophagy also leads to suppression of tumor growth in breast cancer xenografts, causing researchers to believe there is scope for using ivermectin to inhibit breast cancer cell proliferation and that the drug is a potential treatment for breast cancer

ivermectin synergizes with the chemotherapy agents cytarabine and daunorubicin to induce cell death in leukemia cells

Ivermectin inhibits proliferation and increases apoptosis of various human cancers

Activation of WNT-TCF signaling is implicated in multiple diseases, including cancers of the lungs and intestine,

A new screening system has found that ivermectin inhibits the expression of WNT-TCF targets

It represses the levels of C-terminal β-catenin phosphoforms and of cyclin D1 in an okadaic acid-sensitive manner, indicating its action involves protein phosphatases

In vivo, ivermectin selectively inhibits TCF-dependent, but not TCF-independent, xenograft growth without side effects

ivermectin has an exemplary safety record, it could swiftly become a useful tool as a WNT-TCF pathway response blocker to treat WNT-TCF-dependent diseases, encompassing multiple cancers.117

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

of the approximately 108 cannabinoids produced by C. sativa, Δ9-tetrahydrocannabinol (thc) is the most relevant because of its high potency and abundance in plant preparations

Tetrahydrocannabinol exerts a wide variety of biologic effects by mimicking endogenous substances—the endocannabinoids anandamide3 and 2-arachidonoylglycerol4,5—that engage specific cell-surface cannabinoid receptors

the cb2 receptor was initially described to be present in the immune system6, but was more recently shown to also be expressed in cells from other origins

transient receptor potential cation channel subfamily V, member 1

orphan G protein–coupled receptor 55

Most of the effects produced by cannabinoids in the nervous system and in non-neural tissues rely on cb1 receptor activation

two major cannabinoid-specific receptors—cb1 and cb2

cardiovascular tone, energy metabolism, immunity, and reproduction

cannabinoids are well known to exert palliative effects in cancer patients

best-established use is the inhibition of chemotherapy-induced nausea and vomiting

thc and other cannabinoids exhibit antitumour effects in a wide array of animal models of cancer

cannabinoid receptors and their endogenous ligands are both generally upregulated in tumour tissue compared with non-tumour tissue

cb2 promotes her2 (human epidermal growth factor receptor 2) pro-oncogenic signalling in breast cancer

pharmacologic activation of cannabinoid receptors decreases tumour growth

endocannabinoid signalling can also have a tumour-suppressive role

pharmacologic stimulation of cb receptors is, in most cases, antitumourigenic. Nonetheless, a few reports have proposed a tumour-promoting effect of cannabinoids

most prevalent effect is the induction of cancer cell death by apoptosis and the inhibition of cancer cell proliferation

impair tumour angiogenesis and block invasion and metastasis

thc and other cannabinoids induce the apoptotic death of glioma cells by cb1- and cb2-dependent stimulation

Autophagy is primarily a cytoprotective mechanism, although its activation can also lead to cell death

autophagy is important for cannabinoid antineoplastic activity

autophagy is upstream of apoptosis in the mechanism of cannabinoid-induced cell death

the effect of cannabinoids in hormone- dependent tumours might rely, at least in part, on the ability to interfere with the activation of growth factor receptors

glioma cells), pharmacologic blockade of either cb1 or cb2 prevents cannabinoid-induced cell death with similar efficacy

other types of cancer cells (pancreatic48, breast24, or hepatic43 carcinoma cells, for example), antagonists of cb2 but not of cb1 inhibit cannabinoid antitumour actions

thc promotes cancer cell death in a cb1- or cb2-dependent manner (or both) at lower concentrations

cannabidiol (cbd), a phytocannabinoid with a low affinity for cannabinoid receptors15, and other marijuana-derived cannabinoids57 have also been proposed to promote the apoptotic death of cancer cells acting independently of the cb1 and cb2 receptors

In cancer cells, cannabinoids block the activation of the vascular endothelial growth factor (vegf) pathway, an inducer of angiogenesi

In vascular endothelial cells, cannabinoid receptor activation inhibits proliferation and migration, and induces apoptosis

cb1 or cb2 receptor agonists (or both) reduce the formation of distant tumour masses in animal models of both induced and spontaneous metastasis, and inhibit adhesion, migration, and invasiveness of glioma64, breast65,66, lung67,68, and cervical68 cancer cells in culture

the ceramide/p8–regulated pathway plays a general role in the antitumour activity of cannabinoids targeting cb1 and cb2

cbd, by acting independently of the cb1 and cb2 receptors, produces a remarkable anti-tumour effect—including reduction of invasiveness and metastasis

cannabinoids can also enhance immune system–mediated tumour surveillance in some contexts

ability of thc to reduce inflammation75,76, an effect that might prevent certain types of cancer

recent observations suggest that the combined administration of cannabinoids with other anticancer drugs acts synergistically to reduce tumour growth

combined administration of gemcitabine (the benchmark agent for the treatment of pancreatic cancer) and various cannabinoid agonists synergistically reduced the viability of pancreatic cancer cells

Other reports indicated that anandamide and HU-210 might also enhance the anticancer activity of paclitaxel89 and 5-fluorouracil90 respectively

Combined administration of thc and cbd enhances the anticancer activity of thc and reduces the dose of thc needed to induce its tumour growth-inhibiting activity

Preclinical animal models have yielded data indicating that systemic (oral or intraperitoneal) administration of cannabinoids effectively decreases tumour growth

Combinations of cannabinoids with classical chemotherapeutic drugs such as the alkylating agent temozolomide (the benchmark agent for the management of glioblastoma80,84) have been shown to produce a strong anticancer action in animal models

pharmacologic inhibition of egfr, erk83, or akt enhances the cell-death-promoting action of thc in glioma cultures (unpublished observations by the authors), which suggests that targeting egfr and the akt and erk pathways could enhance the antitumour effect of cannabinoids

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

A treatment dose of 4 g ascorbate/kg body weight either once or twice daily did not produce any discernible adverse effects

Xenograft experiments showed that parenteral ascorbate as the only treatment significantly decreased both tumor growth and weight by 41–53%

Peak plasma concentrations of ascorbate approached 30 mM

Pharmacologic concentrations of ascorbate decreased tumor volumes 41–53% in diverse cancer types known for both their aggressive growth and limited treatment options.

Our findings showed that pharmacologic ascorbic acid concentrations were cytotoxic to many types of cancer cells in vitro (Fig. 1A) and significantly impeded tumor progression in vivo without toxicity to normal tissues

The amelioration of ascorbate cytotoxicity in vitro by the addition of catalase was consistent among sensitive cancer cells (Fig. 1B) and points unambiguously to H2O2 generation in the extracellular medium

the current in vivo data support that pharmacologic ascorbate concentrations, which can readily be achieved in humans (Fig. 3E), diminished growth of several aggressive cancer types in mice (Fig. 2) without causing apparent adverse effects.

These intratumoral H2O2 concentrations of >125 μM persisted for >3 h after ascorbate administration