ABSTRACT
Objective: To investigate the effects of maternally expressed gene 3 (MEG3) on endoplasmic reticulum stress-induced colon cancer cell apoptosis and the growth of transplanted human colonic carcinoma in nude mice. Methods:Colon cancer cell lines with the lowest expression level of MEG3 were screened by RT-PCR; negative control cell lines were constructed and stable transfectants were screened. RT-PCR was performed for measuring the lncRNA level of MEG3, cell growth was measured by CCK8, cell apoptosis was determined by Hoechst. Western blot was used to determine the protein levels of Bcl-2, Bax, cleaved Caspase-9, p-PERK, ATF-4, p-EIF2α, CHOP, cleaved Caspase-12, p-AMPK, AMPK, p-mTOR, and mTOR. The expression of CHOP was silenced by si-CHOP, and then cell apoptosis was determined by Hoechst. Transplanted human colonic carcinoma in nude mice was established and tumor volume was measured, tumor growth was measured by IHC Ki67, cell apoptosis was determined by TUNNEL, Western blot was used to determine the protein levels of CHOP, cleaved Caspase-12, and cleaved Caspase-3. Results: The SW480 cell line had the lowest expression level of MEG3 and was used in subsequent experiments. In cytological experiments, compared with those in control group, the cell growth, protein levels of Bcl-2 and ratio of p-mTOR/mTOR were decreased significantly; the apoptosis rate, protein levels of Bax, cleaved Caspase-9, p-PERK, ATF-4, p-eIFα, CHOP and cleaved Caspase-12 and ratio of p-AMPK/AMPK increased notably; the expression of CHOP was silenced; the apoptosis induced by pc-MEG3 could be significantly decreased. In animal experiments, compared with control group, the tumor volume and number of positive cells of Ki67 decreased significantly; the apoptosis rate, protein levels of CHOP, cleaved Caspase-12 and cleaved Caspase-3 increased markedly. Conclusion: MEG3 can promote colon cancer cell apoptosis by endoplasmic reticulum stress, and CHOP may play a crucial role in the process. Furthermore, AMPK/mTOR is also involved in the regulation of apoptosis by MEG3.