Cancer cells metabolically "fertilize" the tumor microenvironment with hydrogen peroxid... - 0 views
www.ncbi.nlm.nih.gov/...PMC3180189
cancer reverse warburg effect warburg effect NF-kapppB HIF-1alpha Cav-1 H2O2
shared by Nathan Goodyear on 12 Nov 14
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reducing oxidative stress with powerful antioxidants, is an important strategy for cancer prevention, as it would suppress one of the key early initiating steps where DNA damage and tumor-stroma metabolic-coupling begins. This would prevent cancer cells from acting as metabolic “parasites
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Oxidative stress in cancer-associated fibroblasts triggers autophagy and mitophagy, resulting in compartmentalized cellular catabolism, loss of mitochondrial function, and the onset of aerobic glycolysis, in the tumor stroma. As such, cancer-associated fibroblasts produce high-energy nutrients (such as lactate and ketones) that fuel mitochondrial biogenesis and oxidative metabolism in cancer cells. We have termed this new energy-transfer mechanism the “reverse Warburg effect.
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Then, oxidative stress, in cancer-associated fibroblasts, triggers the activation of two main transcription factors, NFκB and HIF-1α, leading to the onset of inflammation, autophagy, mitophagy and aerobic glycolysis in the tumor microenvironment
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oxidative stress and ROS, produced in cancer-associated fibroblasts, has a “bystander effect” on adjacent cancer cells, leading to DNA damage, genomic instability and aneuploidy, which appears to be driving tumor-stroma co-evolution
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tumor cells produce and secrete hydrogen peroxide, thereby “fertilizing” the tumor microenvironment and driving the “reverse Warburg effect.”
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This type of stromal metabolism then produces high-energy nutrients (lactate, ketones and glutamine), as well as recycled chemical building blocks (nucleotides, amino acids, fatty acids), to literally “feed” cancer cells
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loss of stromal caveolin (Cav-1) is sufficient to drive mitochondrial dysfunction with increased glucose uptake in fibroblasts, mimicking the glycolytic phenotype of cancer-associated fibroblasts.
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oxidative stress initiated in tumor cells is transferred to cancer-associated fibroblasts.
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Then, cancer-associated fibroblasts show quantitative reductions in mitochondrial activity and compensatory increases in glucose uptake, as well as high ROS production
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These findings may explain the prognostic value of a loss of stromal Cav-1 as a marker of a “lethal” tumor microenvironment
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aerobic glycolysis takes place in cancer-associated fibroblasts, rather than in tumor cells, as previously suspected.
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our results may also explain the “field effect” in cancer biology,5 as hydrogen peroxide secreted by cancer cells, and the propagation of ROS production, from cancer cells to fibroblasts, would create an increasing “mutagenic field” of ROS production, due to the resulting DNA damage
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Interruption of this process, by addition of catalase (an enzyme that detoxifies hydrogen peroxide) to the tissue culture media, blocks ROS activity in cancer cells and leads to apoptotic cell death in cancer cells
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In this new paradigm, cancer cells induce oxidative stress in neighboring cancer-associated fibroblasts
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cancer-associated fibroblasts have the largest increases in glucose uptake
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cancer cells secrete hydrogen peroxide, which induces ROS production in cancer-associated fibroblasts
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Then, oxidative stress in cancer-associated fibroblast leads to decreases in functional mitochondrial activity, and a corresponding increase in glucose uptake, to fuel aerobic glycolysis
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cancer cells show significant increases in mitochondrial activity, and decreases in glucose uptake
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fibroblasts and cancer cells in co-culture become metabolically coupled, resulting in the development of a “symbiotic” or “parasitic” relationship.
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cancer-associated fibroblasts undergo aerobic glycolysis (producing lactate), while cancer cells use oxidative mitochondrial metabolism.
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We have previously shown that oxidative stress in cancer-associated fibroblasts drives a loss of stromal Cav-1, due to its destruction via autophagy/lysosomal degradation
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a loss of stromal Cav-1 is sufficient to induce further oxidative stress, DNA damage and autophagy, essentially mimicking pseudo-hypoxia and driving mitochondrial dysfunction
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loss of stromal Cav-1 is a powerful biomarker for identifying breast cancer patients with early tumor recurrence, lymph-node metastasis, drug-resistance and poor clinical outcome
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this type of metabolism (aerobic glycolysis and autophagy in the tumor stroma) is characteristic of a lethal tumor micro-environment, as it fuels anabolic growth in cancer cells, via the production of high-energy nutrients (such as lactate, ketones and glutamine) and other chemical building blocks
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the upstream tumor-initiating event appears to be the secretion of hydrogen peroxide
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one such enzymatically-active protein anti-oxidant that may be of therapeutic use is catalase, as it detoxifies hydrogen peroxide to water
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numerous studies show that “catalase therapy” in pre-clinical animal models is indeed sufficient to almost completely block tumor recurrence and metastasis
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by eliminating oxidative stress in cancer cells and the tumor microenvironment,55 we may be able to effectively cut off the tumor's fuel supply, by blocking stromal autophagy and aerobic glycolysis
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breast cancer patients show systemic evidence of increased oxidative stress and a decreased anti-oxidant defense, which increases with aging and tumor progression.68–70 Chemotherapy and radiation therapy then promote further oxidative stress.69 Unfortunately, “sub-lethal” doses of oxidative stress during cancer therapy may contribute to tumor recurrence and metastasis, via the activation of myofibroblasts.
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a loss of stromal Cav-1 is associated with the increased expression of gene profiles associated with normal aging, oxidative stress, DNA damage, HIF1/hypoxia, NFκB/inflammation, glycolysis and mitochondrial dysfunction
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cancer-associated fibroblasts show the largest increases in glucose uptake, while cancer cells show corresponding decreases in glucose uptake, under identical co-culture conditions
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Thus, increased PET glucose avidity may actually be a surrogate marker for a loss of stromal Cav-1 in human tumors, allowing the rapid detection of a lethal tumor microenvironment.
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it appears that astrocytes are actually the cell type responsible for the glucose avidity.
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In the brain, astrocytes are glycolytic and undergo aerobic glycolysis. Thus, astrocytes take up and metabolically process glucose to lactate.7
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Then, lactate is secreted via a mono-carboxylate transporter, namely MCT4. As a consequence, neurons use lactate as their preferred energy substrate
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both astrocytes and cancer-associated fibroblasts express MCT4 (which extrudes lactate) and MCT4 is upregulated by oxidative stress in stromal fibroblasts.34
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In accordance with the idea that cancer-associated fibroblasts take up the bulk of glucose, PET glucose avidity is also now routinely used to measure the extent of fibrosis in a number of human diseases, including interstitial pulmonary fibrosis, postsurgical scars, keloids, arthritis and a variety of collagen-vascular diseases.
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PET glucose avidity and elevated serum inflammatory markers both correlate with poor prognosis in breast cancers.
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PET signal over-estimates the actual anatomical size of the tumor, consistent with the idea that PET glucose avidity is really measuring fibrosis and inflammation in the tumor microenvironment.
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human breast and lung cancer patients can be positively identified by examining their exhaled breath for the presence of hydrogen peroxide.
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tumor cell production of hydrogen peroxide drives NFκB-activation in adjacent normal cells in culture6 and during metastasis,103 directly implicating the use of antioxidants, NFκB-inhibitors and anti-inflammatory agents, in the treatment of aggressive human cancers.
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Good description of the communication between cancer cells and fibroblasts. This theory is termed the "reverse Warburg effect".
