Rhomboid domain containing 1 promotes the growth of non-small cell lung cancer through the activation of EGFR and regulation of the BIK-mediated apoptosis

Zhe-Yuan Xu, Xu Li, Rui-Hong Yao, Li-Min Yang, Hao Peng, Wen-Jun Ren, Hong Lu,  Ping Wang

Abstract:

RHBDD1 overexpression is found in various malignancies, including non-small cell lung cancer (NSCLC), and it is correlated with NSCLC patients’ poor overall survival. This study aims to explore the function of RHBDD1 in regulating the progression of NSCLC and its potential molecular basis. qPCR, immunohistochemistry, and/or western blotting were used to evaluate the expression of RHBDD1 in NSCLC tissues and cell lines. RHBDD1 knockdown and overexpression were performed, CCK-8 assay and cell clone formation were applied to study the function of RHBDD1 in cell proliferation in vitro. Flow cytometry and immunofluorescence tests were employed to determine the regulation of apoptosis, cell cycle, and endoplasmic reticulum stress by RHBDD1. As a result, RHBDD1 was found significantly upregulated in NSCLC tissues and cells and associated with pathological tumor staging. RHBDD1 knockdown inhibited the proliferation of NSCLC cells both in vitro and in vivo, promoted their apoptosis, caused cell cycle arrest at G0/G1 phase, characterized with reduced CDK2, suppressed TGF-α secretion, and inhibited the EGFR/Raf/MEK/ERK signaling pathway. In contrast, RHBDD1 overexpression showed the opposite effects. These effects of the manipulated expression of RHBDD1 on NSCLC were restored by EGFR or MEK inhibitor. Additionally, RHBDD1 knockdown and overexpression resulted in decreased and increased BIK cleavage, respectively, but the effects could be blocked by a proteasome inhibitor. In conclusion, our research shows that RHBDD1 promotes the progression of NSCLC through enhancement of proliferation and induction of apoptosis by regulating the EGFR/Raf/MEK/ERK signaling pathway and the level of BIK protein level.