PurposeAdenocarcinoma, the most common non-small cell lung cancer is a leading cause of death worldwide, with a low overall survival (OS) despite increasing attempts to achieve an early diagnosis and accomplish surgical and multimodality treatment strategies. Cellular retinol binding protein-1 (CRBP-1) regulates retinol bioavailability and cell differentiation, but its role in lung cancerogenesis remains uncertain.
Experimental designCRBP-1 expression, clinical outcome and other prognostic factors were investigated in 167 lung adenocarcinoma patients. CRBP-1 expression was evaluated by immunohistochemistry of tissue microarray sections, gene copy number analysis and tumor methylation specific PCR. Effects of CRBP-1 expression on proliferation/apoptosis gene array, protein and transcripts were investigated in transfected A549 lung adenocarcinoma cells.
ResultsCRBP-1(High) expression was observed in 62.3% of adenocarcinomas and correlated with increased tumor grade and reduced OS as an independent prognostic factor. CRBP-1 gene copy gain also associated with tumor CRBP-1(High) status and dedifferentiation. CRBP-1-transfected (CRBP-1(+)) A549 grew more than CRBP-1(-) A549 cells. At >1?M concentrations, all trans-retinoic acid and retinol reduced viability more in CRBP-1(+) than in CRBP-1(-) A549 cells. CRBP-1(+) A549 cells showed up-regulated RAR?/ RXR? and proliferative and transcriptional genes including pAkt, pEGFR, pErk1/2, creb1 and c-jun, whereas RAR? and p53 were strongly down-regulated; pAkt/pErk/ pEGFR inhibitors counteracted proliferative advantage and increased RAR?/RXR?, c-jun and CD44 expression in CRBP-1(+) A549 cells.
ConclusionCRBP-1(High) expression in lung adenocarcinoma correlated with increased tumor grade and reduced OS, likely through increased Akt/Erk/EGFR-mediated cell proliferation and differentiation. CRBP-1(High) expression can be considered an additional marker of poor prognosis in lung adenocarcinoma patients.
SUBMITTER: Doldo E