Cancer stem cells possess the ability of self-renewal, unlimited proliferation,and non-sensitivity to physical and chemical factors, which is regarded to be a cause of ovarian cancer recurrence, but the mechanism is currently unclear. We found that the expression of STON2 was significantly lower in ovarian cancer-stem like cells by LC-MS/MS-based label free quantitative proteomics approach and western blot validation. STON2 knockdown upregulated the expression of the CSC-related markers in protein level, increased the spheroids number and CD44+CD24proportion. Besides, in vivo xenograft experiments, the volume of tumors from the shSton2 group were much bigger compared with the shNC group. Moreover, STON2 overexpression decreased the CSC-related markers and inhibited the spheroids number compared with the control group. Transcriptome sequencing data showed that MUC1 is negative correlation with STON2, which were verificated by RT-PCR and western blot analysis. Subsequently, we found that MUC1 mediated the role of STON2 in regulation of stem-like properties in ovarian cancer. MUC1 knockdown resulted in a significant decrease in the sphere-forming ability, CSC-related markers and CD44+CD24proportion. In addition, MUC1 overexpression caused an increment of CSC-related markers expression and CD44+CD24proportion. Furthermore, we found that the reducing of sphere-forming ability caused by STON2 overexpression was rescued by MUC1 overexpression. As MUC1 can be regulated through epigenetic mechanisms, we found that DNA methylation inhibitor Azacitidine was able to rescue the upregulation of MUC1 by STON2. The DNA methylation levels of MUC1 in one CpG-rich region were then evaluated with pyrosequencing, and the data displayed that the siSton2 group is lower than the control group. Furthermore, we found that the DNMT1 as a member of the DNA methyltransferase family decreased following with STON2 knockdown in protein level, rather than in mRNA level. We thus knock down DNMT1 using specific siRNA, and found that MUC1 overexpression both in mRNA level and protein level. In this study, we focused primarily on STON2 repression leading to DNMT1 downregulation and MUC1 activation is a main mechanism underlying the maintenance of stem-like properties in ovarian cancer.

Citation Format: Shanshan Xu. Ston2 knockdown promotes stem-like properties via dnmt1-mediated muc1 upregulation in ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 164.