How is the Immune System Suppressed by Cancer - 1 views
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nitric oxide (NO) released by tumor cells
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Excellent work by Prof de Groot of Essen, indicated by adding exogenous xanthine oxidase ( XO) in hepatoma cells, hydrogen peroxide was produced to destroy the hepatoma cells
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The other important influence of NO is in its inhibition of the proapoptoic caspases cascade. This in turn protects the cells from intracellular preprogrammed death.
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nitric oxide in immune suppression in relation to oxygen radicals is its inhibitory effect on the binding of leukocytes (PMN) at the endothelial surface
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NO from the tumor cells actually suppresses the iNOS, and in addition it reduces oxygen radicals to stop the formation of peroxynitrite in these cells. But NO is not the only inhibitor of iNOS in cancer.
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Prostaglandin E2, released from tumor cells is also an inhibitor of iNOS, as well as suppressing the immune system
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Th-1 subset of T-cells. These cells are responsible for anti-viral and anti-cancer activities, via their cytokine production including Interleukin-2, (IL-2), and Interleukin-12 which stimulates T-killer cell replication and further activation and release of tumor fighting cytokines.
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Th1 cells stimulate NK and other tumor fighting macrophages via IL-2 and IL-12; In contrast, Th2, which is stimulated in allergies and parasitic infections, produce IL-4 and IL-10. IL-4 and IL-10 inhibit TH-1 activation and the histamine released from mast cell degranulation upregulates T suppressor cells to further immune suppression.
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Th-2 subset of lymphocytes, on the other hand are activated in allergies and parasitic infections to release Interleukin-4 and Interleukin-10
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Mast cells contain histamine which when released increases the T suppressor cells, to lower the immune system and also acts directly on many tumor Histamine receptors to stimulate tumor growth
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Tumor cells release IL-10, and this is thought to be one of the important areas of Th-1 suppression in cancer patients
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IL-10 is also a central regulator of cyclooxygenase-2 expression and prostaglandin production in tumor cells stimulating their angiogenesis and NO production
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nitric oxide in tumor cells even prevents the activation of caspases responsible for apoptosis
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early stages of carcinogenesis, which we call tumor promotion, one needs a strong immune system, and fewer oxygen radicals to prevent mutations but still enough to destroy the tumor cells should they develop
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later stages of cancer development, the oxygen radicals are decreased around the tumors and in the tumor cells themselves, and the entire cancer fighting Th-1 cell replication and movement are suppressed. The results are a decrease in direct toxicity and apoptosis, which is prevented by NO, a suppression of the macrophage and leukocyte toxicity and finally, a suppression of the T-cell induced tumor toxicity
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elevated lactic acid which neutralizes the toxicity and activity of Lymphocyte immune response and mobility
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The lactic acid is also feeding fungi around tumors and that leads to elevated histamine which increases T-suppressor cells. Histamine alone stimulates many tumor cells.
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last but not least, the Lactic acid from tumor cells and acidic diets shifts the lymphocyte activity to reduce its efficacy against cancer cells and pathogens in addition to altering the bacteria of the intestinal tract.
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intestinal tract bacteria in cancer cells release sterols that suppress the immune system and down regulate anticancer activity from lymphocytes.
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In addition to the lactic acid, adenosine is also released from tumors. Through IL-10, adenosine and other molecules secreted by regulatory T cells, the CD8+ cells can be inactivated to an anergic state
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Adenosine is a purine nucleoside found within the interstitial fluid of solid tumors at concentrations that are able to inhibit cell-mediated immune responses to tumor cells
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Adenosine appears to up-regulate the PD1 receptor in T-1 Lymphocytes and inhibits the immune system further
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Mast cells with their release of histamine lower the immune system and also stimulate tumor growth and activate the metalloproteinases involved in angiogenesis and metastases
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Cimetidine, an antihistamine has been actually shown to increase in apoptosis in MDSC via a separate mechanism than the antihistamine effect
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In vitro analyses revealed a striking induction of IL-8 expression in CAFs and LFs by tumor necrosis factor-alpha (TNF-alpha)
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these data raise the possibility that the majority of CAFs in CLM originate from resident LFs. TNF-alpha-induced up-regulation of IL-8 via nuclear factor-kappaB in CAFs is an inflammatory pathway, potentially permissive for cancer invasion that may represent a novel therapeutic target