s-allylmercaptocysteine and Colonic-Neoplasms

The natural plant-derived product S-allylmercapto-cysteine (SAMC) has been studied in cancer therapy as a single and combination chemotherapeutic agent. The present study was employed to verify the combination use of SAMC and rapamycin that is the mTOR inhibitor with anticancer ability but has limited efficacy due to drug resistance, and to explore the underlying mechanisms. We combined rapamycin and SAMC for colorectal cancer treatment in the HCT‑116 cancer cells and a xenograft murine model. The in vivo study was established by xenografting HCT‑116 cells in BALB/c nude mice. It was found that the combination therapy had enhanced tumor-suppressing ability with the upregulation of the Bax/Bcl-2 ratio as a consequence of activated apoptosis, inhibition of autophagic activity and prevention of Akt phosphorylation. The rapamycin and SAMC combination activated antioxidant transcription expressions of Nrf2 and downstream gene NQO1. Concomitantly, autophagosome cargo p62 was downregulated, indicating that the p62 played a negative-regulatory role between Nrf2 and autophagy. Our results show that the combination of SAMC and rapamycin enhanced the anticancer ability, which could be used for the treatment of colorectal cancer. The underling mechanism of autophagy/p62/Nrf2 pathway discovered may provide a new direction for drug development, especially for traditional Chinese medicines.

Topics: Animals; Antineoplastic Agents; Antioxidants; Apoptosis; Autophagy; Cell Line, Tumor; Cell Proliferation; Colonic Neoplasms; Cysteine; Down-Regulation; Garlic; HCT116 Cells; Humans; Mice; Mice, Inbred BALB C; Mice, Nude; NF-E2-Related Factor 2; Proto-Oncogene Proteins c-akt; Proto-Oncogene Proteins c-bcl-2; RNA-Binding Proteins; Signal Transduction; Sirolimus; Transplantation, Heterologous; Xenograft Model Antitumor Assays

Allyl sulfides are characteristic flavor components obtained from garlic. These sulfides are thought to be responsible for their epidemiologically proven anticancer effect on garlic eaters. This study was aimed at clarifying the molecular basis of this anticancer effect of garlic by using human colon cancer cell lines HCT-15 and DLD-1. The growth of the cells was significantly suppressed by diallyl trisulfide (DATS, HCT-15 IC50 = 11.5 microM, DLD-1 IC50 = 13.3 microM); however, neither diallyl monosulfide nor diallyl disulfide showed such an effect. The proportion of HCT-15 and that of DLD-1 cells residing at the G1 and S phases were decreased by DATS, and their populations at the G2/M phase were markedly increased for up to 12 h. The cells with a sub-G1 DNA content were increased thereafter. Caspase-3 activity was also dramatically increased by DATS. Fluorescence-activated cell sorter analysis performed on the cells arrested at the G1/S boundary revealed cell cycle-dependent induction of apoptosis through the transition of the G2/M phase to the G1 phase by DATS. DATS inhibited tubulin polymerization in an in vitro cell-free system. DATS disrupted microtubule network formation of the cells, and microtubule fragments could be seen at the interphase. Peptide mass mapping by liquid chromatography-tandem mass spectrometry analysis for DATS-treated tubulin demonstrated that there was a specific oxidative modification of cysteine residues Cys-12beta and Cys-354beta to form S-allylmercaptocysteine with a peptide mass increase of 72.1 Da. The potent antitumor activity of DATS was also demonstrated in nude mice bearing HCT-15 xenografts. This is the first paper describing intracellular target molecules directly modified by garlic components.

Topics: Allyl Compounds; Animals; Antineoplastic Agents; Apoptosis; Blotting, Western; Cell Cycle; Cell Line, Tumor; Cell Proliferation; Cell Separation; Cell-Free System; Chromatography, Liquid; Colonic Neoplasms; Cyclin B; Cyclin B1; Cysteine; Cytoplasm; Disulfides; DNA; Flow Cytometry; Fluorescent Antibody Technique, Indirect; Garlic; Humans; Inhibitory Concentration 50; Mice; Mice, Nude; Microtubules; Neoplasm Transplantation; Oxidative Stress; Oxygen; Peptides; Protein Binding; Sulfides; Time Factors; Tubulin

Epidemiological and experimental carcinogenesis studies provide evidence that components of garlic (Allium sativum) have anticancer activity. We recently reported that the garlic derivative S-allylmercaptocysteine (SAMC) inhibits growth, arrests cells in G(2)-M, and induces apoptosis in human colon cancer cells (Shirin et al., Cancer Res., 61: 725-731, 2001). Because a fraction of the SAMC-treated cells are specifically arrested in mitosis, we examined the mechanism of this effect in the present study. Immunofluorescent microscopy revealed that the treatment of SW480 cells or NIH3T3 fibroblasts with 150 micro M SAMC (the IC(50) concentration) caused rapid microtubule (MT) depolymerization, MT cytoskeleton disruption, centrosome fragmentation and Golgi dispersion in interphase cells. It also induced the formation of monopolar and multipolar spindles in mitotic cells. In vitro turbidity assays indicated that SAMC acted directly on tubulin to cause MT depolymerization, apparently because it interacts with -SH groups on tubulin. To investigate the signaling pathways involved in SAMC-induced apoptosis, we assayed c-Jun NH(2)-terminal kinase (JNK) activity and found that treatment with SAMC caused a rapid and sustained induction of JNK activity. The selective JNK inhibitor SP600125 inhibited the early phase (24 h) but not the late phase (48 h and later) of apoptosis induced by SAMC. Expression of a dominant-negative mutant of JNK1 in SW480 cells inhibited apoptosis induced by SAMC at 24 h but had no protective effect at 48 h. JNK1(-/-) mouse embryonic fibroblasts were resistant to SAMC-induced apoptosis at 24 h but not at 48 h. On the other hand, the inhibition or abrogation of JNK1 activity did not inhibit the G(2)-M arrest induced by SAMC. SAMC also activated caspase-3. The general caspase inhibitor z-VAD-fmk inhibited both early and late phases of apoptosis induced by SAMC. We conclude that the garlic-derived compound SAMC exerts antiproliferative effects by binding directly to tubulin and disrupting the MT assembly, thus arresting cells in mitosis and triggering JNK1 and caspase-3 signaling pathways that lead to apoptosis.

Topics: Animals; Apoptosis; Binding Sites; Caspase 3; Caspases; Cell Cycle; Cell Line, Tumor; Centrosome; Colonic Neoplasms; Cysteine; Enzyme Activation; Enzyme Inhibitors; Golgi Apparatus; Humans; Mice; Microtubules; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Mitogen-Activated Protein Kinase 8; Mitogen-Activated Protein Kinases; Mitosis; NIH 3T3 Cells; p38 Mitogen-Activated Protein Kinases; Tubulin

Growth-inhibitory effects on DS19 mouse erythroleukemia cells were seen in the micromolar concentration range with allicin and S-allylmercaptocysteine and in the millimolar range with allyl butyrate, allyl phenyl sulfone, and S-allyl cysteine. Increased acetylation of histones was induced by incubation of cells with the allyl compounds at concentrations similar to those that resulted in the inhibition of cell proliferation. The induction of histone acetylation by S-allylmercaptocysteine was also observed in Caco-2 human colon cancer cells and T47D human breast cancer cells. In contrast to the effect on histone acetylation, there was a decrease in the incorporation of phosphate into histones when DS19 cells were incubated with 25 microM S-allylmercaptocysteine. Histone deacetylase activity was inhibited by allyl butyrate, but there was little or no effect with the allyl sulfur compounds examined in this study. A similar degree of downregulation of histone deacetylase and histone acetyltransferase was observed when DS19 cells were incubated with S-allylmercaptocysteine or allyl isothiocyanate. The induction of histone acetylation by S-allylmercaptocysteine was not blocked by a proteasome inhibitor. The mechanism by which S-allylmercaptocysteine induces histone acetylation remains to be characterized. It may be related in part to metabolism to allyl mercaptan, which is a more effective inhibitor of histone deacetylase.

Topics: Acetylation; Acetyltransferases; Allyl Compounds; Animals; Antineoplastic Agents; Breast Neoplasms; Colonic Neoplasms; Cysteine; Disulfides; Electrophoresis, Polyacrylamide Gel; Female; Histone Acetyltransferases; Histone Deacetylases; Histones; Humans; Leukemia, Erythroblastic, Acute; Leupeptins; Mice; Saccharomyces cerevisiae Proteins; Sulfinic Acids; Tumor Cells, Cultured