BAMBI overexpression together with β-sitosterol ameliorates NSCLC via inhibiting autophagy and inactivating TGF-β/Smad2/3 pathway

Non-small cell lung cancer (NSCLC) has the highest mortality rate among all solid tumors with a poor prognosis. The BMP and activin receptor membrane bound inhibitor (BAMBI) has been identified as a hallmark of NSCLC and beta-sitosterol possesses antitumor potentiality. This study explores the effect of BAMBI overexpression and beta-sitosterol in the context of NSCLC. The results revealed that the transfection of pcDNA-BAMBI and beta-sitosterol treatment significantly reduced the levels of autophagy markers light chain 3 (LC3) II and Beclin 1, whereas the levels of LC3 I and p62 were promoted. The reduced punctate accumulations of GFP-LC3 were detected in pcDNA-BAMBI and beta-sitosterol groups, especially in pcDNA-BAMBI + beta-sitosterol group. BAMBI overexpression and beta-sitosterol induced G0/G1 cell cycle arrest and inhibted cell proliferation in A549 cells. In addition, the levels of transforming growth factor-beta (TGF-beta)/p-Smad2/3/c-Myc pathway proteins were decreased. The TGF-beta overexpression further confirmed that BAMBI overexpression and beta-sitosterol treatment suppressed autohagy and viability of A549 cells was through TGF-beta/Smad2/3/c-Myc pathway. Finally, the tumor growth was suppressed in NSCLC xenografts, and the inhibitory effect was stronger under treatment of pcDNA-BAMBI together with beta-sitosterol. These results indicate that BAMBI overexpression and beta-sitosterol may serve as novel targets for the treatment of NSCLC.