MCL-1 plays an oncogenic role in breast cancer by modulating chemoresistance and stemness properties by activating Wnt/β-catenin

Abstract Background Breast cancer is the most common malignant tumor and the leading cause of death in women. Chemotherapy is one of the most important treatments for breast cancer. However, the development of chemotherapy resistance is the main cause of 20–30% of breast cancer patients developing metastasis, leading to death. MCL-1, an anti-apoptotic protein, has not been found to contribute to chemotherapy resistance in breast cancer. Methods We used large gene panels to detect pathological sections of tumors in drug-resistant and sensitive patients. We validated protein profiling by IHC in a larger cohort of samples. We performed the function of MCL-1 by knockdown and overexpression in vitro and in vivo. Luciferase assay and CHIP assay were used to prove the regulatory network between MCL-1 and LRP6. Result We found that MCL-1 is more highly expressed in drug-resistant breast cancer tissues than it is in sensitive breast cancer tissues. Functional studies have revealed that MCL-1 plays an important role in drug resistance by regulating apoptosis in breast cancer cells. We found that overexpression of MCL-1 enhances the chemoresistance and stemness of breast cancer cells in vitro and in vivo, while silencing has the opposite effect. Mechanistically, by downregulating and upregulating MCL-1, we show that MCL-1 regulates LRP6 and activates the WNT/β-catenin signaling pathway in breast cancer cells. Finally, we found that a high level of MCL-1 expression predicts a poor prognosis in breast cancer. Conclusion Our work highlights the role of MCL-1 in chemoresistance and stemness. The MCL-1-WNT/β-catenin axis might be used as a new clinical target for breast cancer therapy.