Tripartite motif-containing 68-stabilized modulator of apoptosis-1 retards the proliferation and metastasis of lung cancer

Non-small cell lung cancer (NSCLC) is a major global health threat with high incidence and mortality. Modulator of apoptosis-1 (MOAP1), also named MAP-1, belongs to the PNMA gene family and plays a key role in regulating apoptosis and tumor growth. However, its influences on NSCLC are largely unclear, and thus were explored in our present study, particularly the underlying mechanisms. Here, we initially find that MOAP1 expression is significantly decreased in NSCLC patients compared with the normal ones, and negatively correlated with the TNM and pathologic stages among patients. Additionally, MOAP1 low expression predicts a poorer prognosis than that of the NSCLC patients expressing higher MOAP1. Our in vitro studies confirm much lower MOAP1 expression in NSCLC cell lines. Of note, promoting MOAP1 expression strongly reduces the proliferation and induces apoptosis in NSCLC cells, accompanied with cell cycle arrest distributed in G0/G1 phase. Moreover, we find that MOAP1 has a negative correlation with Th2 cells' infiltration, but a positive correlation with the infiltration levels of eosinophils. Epithelial mesenchymal transition (EMT) process is also greatly restrained in NSCLC cells with MOAP1 over-expression, as proved by the reduced migration and invasion of cells. We further identify a positive correlation between MOAP1 and tripartite motif-containing 68 (TRIM68) in patients with NSCLC. Further analysis shows that TRIM68 directly interacts with MOAP1 and stabilizes MOAP1. Importantly, TRIM68 can activate MOAP1 by inducing the K63-linked polyubiquitination of MOAP1. Finally, animal studies verify that promoting MOAP1 efficiently suppresses tumor growth and lung metastasis in the nude mice. Collectively, our results reveal a novel mechanism through which MOAP1 stabilized by TRIM68 inhibits NSCLC development and targeting MOAP1 for its up-regulation may be a promising therapeutic strategy for NSCLC treatment.