| Background and objective: Recent research has revealed a role for Ambra1, anautophagy-related gene-related (ATG) protein, in the autophagic pro-survival response, andAmbra1has been shown to regulate Beclin1and Beclin1-dependent autophagy inembryonic stem cells. However, whether Ambra1plays an important role in the autophagypathway in colorectal cancer cells is unknown. In this study, we hypothesized that Ambra1is an important regulator of autophagy and apoptosis in CRC cell lines.Methods: To test this hypothesis, we confirmed autophagic activity in serum-starvedSW620CRC cells by assessing endogenous microtubule-associated protein1light chain3(LC3) localization, the presence of autophagosomes (transmission electron microscopy)and LC3protein levels (Western blotting). Ambra1expression was detected by Westernblot in SW620cells treated with staurosporine or etoposide. Calpain and caspase inhibitorswere employed to verify whether calpains and caspases were responsible for Ambra1cleavage. To examine the role of Ambra1in apoptosis, Ambra1knockdown cells weretreated with staurosporine and etoposide. Cell apoptosis and viability were measured byannexin-V and PI staining and MTT assays.Results: We determined that serum deprivation-induced autophagy was associatedwith Ambra1upregulation in colorectal cancer cell lines. Ambra1expression decreasedduring staurosporine-or etoposide-induced apoptosis. Calpains and caspases may beresponsible for Ambra1degradation. When Ambra1expression was reduced by siRNA,SW620cells were more sensitive to staurosporine-or etoposide-induced apoptosis. Inaddition, starvation-induced autophagy decreased.Conclusions: In SW620cell lines, tumor cells use autophagy to resist environmentalpressue, Ambra1promotes autophagy and also have the ability to inhibit apoptois incolorectal cancers. All these above give us a clue that the mechanism of the Ambra1 regulating autophagy and apoptosis may lay the foundation for biotherapy of colorectalcancers. |
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