CDC73 Impairment of MAPK1 Ubiquitination and Activation of the mTOR Signaling Pathway

Abstract

CDC73 has been reported to be upregulated in breast cancer. This study aimed to illuminate the underlying mechanism by which CDC73 mediates breast cancer. Here, a breast cancer tissue microarray and three breast cancer cell lines MDA-MB-231, BT-549 as well as MCF-7 were employed. Using RNAi method, we knocked down CDC73 and MAPK1 in breast cancer cells. CDC73 overexpression plasmids (LV-013) were generated through pMD2.G and pSPAX2 vectors. Cell events related to tumor development were analyzed through Celigo cell counting assay, a cell counting kit, wound healing assay, Transwell assay and flow cytometry analysis. The exploration on the underlying mechanism was based on PrimeView human gene expression array. Xenograft tumor models were constructed to visualize the effects of CDC73/MAPK2 on breast cancer progression. CDC73 was abundantly expressed in breast cancer tissues and cell lines, and the expression of CDC73 was related to poor prognosis of patients. In breast cancer, CDC73 could promote the proliferation and migration of tumor cells, while disrupting apoptosis. Also, we found that CBL, an E3 ubiquitin ligase, could interact with CDC73 and promote MAPK1 ubiquitination and degradation of this protein. In addition, silencing MAPK1 led to a suppression of breast cancer cell growth in vitro and in vivo, and even abolished the promoting effects of CDC73 overexpression. We also found that mTOR pathway played a role in CDC73-mediated breast cancer. mTOR pathway inhibitor reversed cell phenotypes induced by CDC73 overexpression. CDC73 promoted MAPK1 ubiquitination and degradation so that affected MAPK1 level and subsequently led to breast cancer progression, providing a novel therapeutic strategy to combat cancer.