This is extensively reported in medical research that anti-cancer properties of garlic-derived organosulfur compounds (OSCs) can kill cancer cells. OSCs activate stress kinases and cause apoptosis in malignant neuroblastoma by stimulating the mitochondrial pathway. That results in cell cycle arrest, and generation of reactive oxygen species and removal of free radicals from blood.
Anti-tumor effect of garlic
Many in vitro and in vivo studies have suggested possible cancer-preventive effects of garlic preparations and their respective constituents. Garlic has been found to contain a large number of potent bioactive compounds with anticancer properties, largely allylsulfide derivatives. Different garlic derivatives have been reported to modulate an increasing number of molecular mechanisms in carcinogenesis, such as DNA adduct formation, mutagenesis, scavenging of free radicals, cell proliferation and differentiation as well as angiogenesis. The growth rate of cancer cells is reduced by garlic, with cell cycle blockade that occurs in the G2/M phase (Capasso, 2013 ▶). In 1990, the U.S. National Cancer Institute initiated the Designer Food Program to determine which foods played an important role in cancer prevention (Dahanukar and Thatte, 1997 ▶). They concluded that garlic may be the most potent food having cancer preventive properties. Garlic has a variety of anti-tumor effects, including tumor cell growth inhibition and chemopreventive effects. In rodents, garlic and its constituents have been reported to inhibit the development of chemically induced tumors in the liver (Kweon et al., 2003 ▶), colon (Knowles and Milner, 2003 ▶), prostate (Hsing et al., 2002 ▶), bladder (Lau et al., 1986 ▶), mammary gland (Amagase and Milner, 1993 ▶), esophagus (Wargovich et al., 1988 ▶), lung (Sparnins et al., 1986 ▶), skin (Nishino et al., 1989 ▶), and stomach (Wattenberg et al., 1989 ▶) in both rodent and human studies. Diallyl trisulfide (DATS), an organosulfur compound isolated from garlic, has been shown anticancer activity both in in vitro and in vivo investigations. The cytotoxicity of DATS toward prostate epithelial cells reduced as opposed to PC-3 cancer cells (Borkowska, 2013 ▶).
Possible anticarcinogenic mechanisms of garlic and its constituents may include the inhibition of carcinogen activation (Amagase and Milne, 1993 ▶), the enhancement of detoxification (Sumiyoshi and Wargovich, 1990 ▶), excretion (Tadi et al., 1991a ▶), and the protection of DNA from activated carcinogens (Tadi et al., 1991b ▶). Furthermore, DATS reduced tumor mass and number of mitotic cells within tumors. DATS reduced mitosis in tumors, decreased histone deacetylase activity, increased acetylation of H3 and H4, inhibited cell cycle progression, and decreased pro-tumor markers (survivin, Bcl-2, c-Myc, mTOR, EGFR, VEGF) (Wallace et al., 2013 ▶). Garlic components have been found to block covalent binding of carcinogens to DNA, enhance degradation of carcinogens, have anti-oxidative and free radical scavenging properties, and regulate cell proliferation, apoptosis, and immune responses. Ajoene, a garlic stable oil soluble sulfur rich compound and garlic-derived natural compound, have been shown to induce apoptosis in leukemic cells in addition to the other blood cells of leukemic patients. Ajoene induced apoptosis in human leukemic cells via stimulation of peroxide production, activation of caspase-3-like and caspase-8 activity. Garlic synergizes the effect of eicosapentaenoic acid, a breast cancer suppressor, and antagonizes the effect of linoleic acid, a breast cancer enhancer (Tsubura et al., 2011 ▶).
Anti-proliferative activity of ajoene was demonstrated against a panel of human tumor cell lines (Li et al., 2002 ▶). Furthermore, allicin inhibits proliferation of human mammary endometrial and colon cancer cells. Growth inhibition is accompanied by an accumulation of the cells in WIG1 and G2lM phase of the cell cycle. Thus allicin is also responsible for the anti-proliferative effect of garlic derivatives. Diallyl sulfide and diallyl disulfide, inhibit arylamine N-acetyltransferase activity and 2-aminofluorene-DNA in human promyelocytic leukemia cells (Lin et al., 2002 ▶). Reduction of the risk of some malignancies by consumption of selenium-enriched plants, such as garlic was suggested (Finley, 2003 ▶). DATS inhibited cell growth of human melanoma A375 cells and basal cell carcinoma cells by enhancement of the levels of intracellular reactive oxygen species and DNA damage and by inducing endoplasmic reticulum stress and mitochondria-mediated apoptosis (Wang et al., 2012 ▶).
Bayan L, Koulivand PH, Gorji A. Garlic: a review of potential therapeutic effects. Avicenna J Phytomed. 2014;4(1):1-14.
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