PRMT1-mediated EZH2 methylation promotes breast cancer cell proliferation and tumorigenesis

Protein arginine methyltransferase 1 (PRMT1) is able to promote breast cancer cell proliferation. However, the detailed mechanisms of PRMT1-mediated breast cancer cell proliferation are largely unknown. In this study, we reveal that PRMT1-mediated methylation of EZH2 at the R342 site (meR342-EZH2) has a great effect on PRMT1-induced cell proliferation. We also demonstrate that meR342-EZH2 can accelerate breast cancer cell proliferation in vitro and in vivo. Further, we show that meR342-EZH2 promotes cell cycle progression by repressing P16 and P21 transcription expression. In terms of mechanism, we illustrate that meR342-EZH2 facilitates EZH2 binding with SUZ12 and PRC2 assembly by preventing AMPKα1-mediated phosphorylation of pT311-EZH2, which results in suppression of P16 and P21 transcription by enhancing EZH2 expression and H3K27me3 enrichment at P16 and P21 promoters. Finally, we validate that the expression of PRMT1 and meR342-EZH2 is negatively correlated with pT311-EZH2 expression. Our findings suggest that meR342-EZH2 may become a novel therapeutic target for the treatment of breast cancer.

FAM96A and FAM96B Suppress Breast Cancer Proliferation and Migration via the Wnt/β-Catenin Signaling Pathway

Background: Family with sequence similarity 96 member A and B (FAM96A and FAM96B) are two highly conserved homologous proteins belonging to MIP18 family. Many studies have shown that FAM96A and FAM96B play many different functions mainly through interacting with other different proteins. Recently, several studies show that FAM96A and FAM96B are significantly down-regulated compared in human gastrointestinal stromal tumors, colon cancer, liver cancer and gastric cancer with corresponding normal tissues. However, the molecular regulatory mechanisms of FAM96A and FAM96B in breast cancer development and metastasis are still unclear. In this work, we aimed to explore the molecular mechanisms of FAM96A and FAM96B in breast cancer progression.Methods: We used specific siRNAs to down-regulate FAM96A and FAM96B expression, and used recombinant plasmids to up-regulate FAM96A and FAM96B expression in breast cancer cells. Cell proliferation was measured using MTT and colony formation assays. Cell cycle and apoptosis were detected by flow cytometry analysis. Wound healing and transwell assays were used to examine cell migration and invasion abilities. The relationships among FAM96A/B, EMT and Wnt/β-catenin signaling pathway were determined by analyzing the expression changes of classical markers and biological functional changes after XAV-939 inhibitor treatment. Results: We found that FAM96A and FAM96B expression in breast cancer was down-regulated. FAM96A/B overexpression suppressed breast cancer cell proliferation, invasion and migration, induced cell apoptosis and led to cell cycle arrested in G0/G1 phase. Conversely, FAM96A/B knockdown exhibited the opposite effects on breast cancer cells. Moreover, our data demonstrated that FAM96A/B overexpression suppressed EMT and Wnt/β-catenin signaling pathway, while FAM96A/B knockdown showed the promoting effects on EMT and Wnt/β-catenin signaling pathway in breast cancer cells. Furthermore, a Wnt pathway inhibitor, XAV-939 treatment reversed the promoting effects of FAM96A and FAM96B knockdown on breast cancer cell proliferation, invasion and migration.Conclusions: Our findings revealed that FAM96A and FAM96B may act as tumor suppressor genes and inhibit breast cancer progression via modulating the Wnt/β-catenin pathway, which can provide the potential markers for the diagnosis and treatment of breast cancer.

p53–GSDME Elevation: A Path for CDK7 Inhibition to Suppress Breast Cancer Cell Survival

Higher cyclin-dependent kinase (CDK7) expression is a character of breast cancer and indicates poor prognosis. Inhibiting CDK7 exhibited effective cancer cell suppression which implies the potential of CDK7 inhibition to be a method for anti-cancer treatment. Our study aimed to explore a novel mechanism of CDK7 inhibition for suppressing breast cancer cell survival. Here, we proved inhibiting CDK7 repressed breast cancer cell proliferation and colony formation and increased the apoptotic cell rate, with p53 and GSDME protein level elevation. When p53 was suppressed in MCF-7 cells, the decline of GSDME expression and associated stronger proliferation and colony formation could be observed. Since downregulation of GSDME was of benefit to breast cancer cells, p53 inhibition blocked the elevation of GSDME induced by CDK7 inhibition and retrieved cells from the tumor suppressive effect of CDK7 inhibition. Therefore, CDK7 inhibition exerted a negative effect on breast cancer cell proliferation and colony formation in a p53–GSDME dependent manner. These results revealed the CDK7–p53–GSDME axis could be a pathway affecting breast cancer cell survival.