Depleting CBR1 increases chemosensitivity by reducing stemness and quiescence traits in non-small cell lung cancer

Carbonyl reductase 1 (CBR1), a member of the short-chain dehydrogenase/reductase (SDR) superfamily, is implicated in tumor progression and treatment resistance. However, its role in non-small cell lung cancer (NSCLC) remains unclear. This study examined CBR1 expression in NSCLC tissues and cell lines, using gene interference and pharmacological inhibition to assess its impact on stemness, chemosensitivity, and quiescence, and to explore underlying mechanisms. Our findings indicate that CBR1 expression is elevated in NSCLC tissues and cell lines, and further increases in the presence of cisplatin (CDDP). Gene interference reducing CBR1 expression significantly decreased the percentage of cluster of differentiation 133 (CD133)-positive cells and the expression of octamer-binding transcription factor 4 (OCT4) and SRY (sex determining region Y)-box 2 (SOX2), while enhancing CDDP chemosensitivity. The CBR1-specific inhibitor hydroxy-PP-Me (PP-Me) markedly increased CDDP cytotoxicity and reduced stemness. Additionally, CBR1 inhibition via short hairpin RNA (shRNA) CBR1 (sh-CBR1) or PP-Me disrupted NSCLC cell quiescence, as shown by a decrease in G0 phase cells and p27 expression, alongside an increase in cyclin D1 and phospho-retinoblastoma (pRb) expression. Furthermore, SET domain-containing protein 4 (SETD4), which mediates stemness, chemosensitivity, and quiescence in NSCLC cells, was downregulated by sh-CBR1 or PP-Me treatment. The overexpression of SETD4 counteracted the enhanced chemosensitivity resulting from CBR1 inhibition. In A549 xenografts, combined PP-Me and CDDP therapy significantly inhibited tumor growth compared to either treatment alone. In conclusion, CBR1 inhibition enhances CDDP chemosensitivity by suppressing stemness and quiescence in NSCLC.