DNA Methylation Of Autophagy Gene In Breast Cancer

Breast cancer includes triple-negative and non-triple-negative subtypes,which is the second leading cause of death in women worldwide.Exploring the molecular regulation mechanism is very important for the clinic treatment of breast cancer.Both DNA methylation and autophagy are involved in the initiatition and progression of breast cancer.However,the role of methylation level of autophagy gene in different subtypes of breast cancer and the regulation signal pathway are need further addressed.In this study,we revealed the methylation probability of autophagy gene in triple-negative breast cancer（TNBC）and non-triple-negative breast cancer（non-TNBC）cells,exposed relationship of the key methylation enzyme（DNMT1）and the possible signaling molecules that affect the expression of DNMT1.Firstly,we found the expression of the methylation level of the autophagy marker gene LC3B in TNBC cell lines is down-regulated compared with the non-TNBC cell lines,correspondingly,the expression level of LC3B in TNBC cell lines is increased compared to the non-TNBC cell lines.The results indicate that the methylation modification of LC3B may play a vital role in the occurrence and development of breast cancer.Additionly,we also found that DNA methylation transferases 1（DNMT1）is highly expressed in breast cancer,suggesting that DNMT1 may play a major role in breast cancer DNA methylation modification.Secondly,in order to verify that the expression of autophagy genes are regulated by DNMT1 in breast cancer,we added the exogenous demethylation drug in the medium to culture the breast cancer cell and down-regulated the endogenous mRNA level of DNMT1 with RNAi.The results showed that both treatments can significantly decrease the expression of DNMT1 in TNBC cell lines,accordingly,the expression level of autophagy marker protein LC3B is significantly increased,leading to the proliferation and migration capabilities inhibition of TNBC cell lines.Finally,in order to investigate whether ROS can effect the expression of DNMT1in breast cancer,we stimulated breast cancer cells with H₂O₂ to increase ROS levels.We found the expression of DNMT1 was increased and the expression of autophagy protein LC3B was decreased.The results indicate that ROS may affect the expression of DNMT1 and the ROS may be used as a signal to affect the expression of autophagy proteins via DNMT1.Taken togetother,ROS may influence the expression level of LC3B to affect the autophagy of breast cell through the changing of DNMT1,and it can reduce the proliferation and migration of TNBC cells.Our results also indicated that the regulating ROS and DNA methylation may be used as the potential measure of TNBC clinic treatment.