TRIM68 regulates ubiquitinated degradation of Rabex-5 and plays a role in progression of breast cancer through Rab5-Rac1.

TRIM family proteins are widely involved in tumorigenesis and progression, while TIRM68 is less explored in breast cancer. The expression of TRIM68 in breast cancer was explored in two public databases (GEPIA and UALCAN), and the survival was tested on Kaplan-Meier plotter database. The expression of TRIM68 in local breast cancer and corresponding para-carcinoma tissues were determined using qRT-PCR and immunohistochemistry. The gain- and loss-of function of TRIM68 were carried in breast cancer cells by knockdown or overexpression, the migration and invasion of breast cancer cells were examined by trasnwell, epithelial-mesenchymal transition (EMT) was determined by western blot, cell morphology was observed under light microscope. The activation of Rab5-Rac1 was determined using GST-pull down assay. The ubiquitination of Rabex-5 was determined using in vitro ubiquitination assay. The lower expression of TRIM68 in breast cancer tissues compared to the non-tumor tissues, both in public data and our local clinic samples. Also, lower TRIM68 expression was in breast cancer cells. TRIM68 overexpression impaired, but TRIM68 knockdown facilitated the migration, invasion and EMT in breast cancer cells. TRIM68 regulates the activation of Rab5-Rac1 signaling, and Rabex-5 was identified to be mediated by TRIM68 in a ubiquitination-dependent degradation manner. Furthermore, Rabex-5 knockdown completely abrogated the pro-tumor effects of TRIM68 knockdown in breast cancer cells. Our study first uncovered the crucial role of TRIM68 in malignant behaviors of breast cancer cells, through Rabex-5-mediated Rac5 activation, and shed new light on the development of the diagnostic and therapeutic strategies of breast cancer.