Rab-like protein 1 A is upregulated by cisplatin treatment and partially inhibits chemoresistance by regulating p53 activity.

Rab-like protein 1 A (RBEL1A), which is a predominant isoform of RBEL1, has been identified to serve an important function in breast tumorigenesis and may be upregulated in breast tumor cells. RBEL1A may block the transcriptional activity of p53, which is important in the induction of cisplatin sensitivity. Previous studies supported the association between the induction of chemoresistance and the inhibition of p53 by RBEL1A. However, the response of RBEL1A to chemotreatment and its interaction with p53 remains to be investigated. The present study revealed that the cisplatin treatment induced the expression of RBEL1A in MCF-7 cells. Consistent with previous studies, the present study demonstrated that cisplatin treatment and RBEL1A overexpression blocked the oligomerization of p53 in MCF-7 cells and led to a decrease of the transcriptional activity of p53 and its downstream target gene p21. Additionally, upregulation of RBEL1A decreased the protein level of p53 by promoting the ubiquitination of p53. A cytotoxicity assay demonstrated that upregulation of RBEL1A partially contributed to chemosensitivity via inhibiting p53 in MCF-7 cells. A pG13L (p53-responsive reporter plasmid) luciferase reporter and co-immunoprecipitation assay revealed that upregulation of RBEL1A led to an inhibition of the transcriptional activity of p53 or its target gene p21. Analysis of cellular proliferation, cell cycle and invasion also confirmed the regulatory activity of RBEL1A on the malignancy of breast cancer cells. Taken together, these results suggest that the induction of RBEL1A following cisplatin treatment may partially inhibit chemosensitivity in a p53-dependent manner.