Transcriptional factors of the CREB(cAMP Response Element Binding Protein) are involved in the regulation of gene expression in response to a variety of signaling pathways. Proteins produced by the CREB genes play key roles in many physiological processes, including memory and long term potentiation. The retinoic acid receptor (RAR) axis mediates epithelial cell differentiation and proliferation in many tissues including the lung.

The RAR and CREB expression levels were examined in 60 adenocarcinomas and 60 squamous cell carcinomas of the lung using immunohistochemical staining.

1)RAR protein expression was found in 58.3%(35/60) of adenocarcinomas and 36.7%(22/60) of squamous cell carcinomas(P<0.05). 2)RAR protein expression was found in 80%(16/20) of well differentiated adenocarcinomas, 60%(12/20) of moderately differentiated adenocarcinomas, and 35%(7/20) of poorly differentiated adenocarcinomas (P<0.01). 3)RAR protein expression was found in 45%(9/20) of well differentiated squamous cell carcinomas, 35%(7/20) of moderately differentiated squamous cell carcinomas, and 30%(6/20) of poorly differentiated squamous cell carcinomas (P>0.05). 4)CREB expression was found in 61.7%(37/60) of adenocarcinomas and 40%(24/60) of squamous cell carcinomas(P<0.05). 5)CREB expression was found in 85%(17/20) of well differentiated adenocarcinomas, 60%(12/20) of moderately differentiated adenocarcinomas, and 40%(8/20) of poorly differentiated adenocarcinomas (P<0.01). 6)CREB expression was found in 45%(9/20) of well differentiated squamous cell carcinomas, 35%(7/20) of moderately differentiated squamous cell carcinomas, and 35%(8/20) of poorly differentiated squamous cell carcinomas(P>0.05). 7)RAR and CREB expression was found in 68.5% of lung cancers, and there was a significant correlation between them(P<0.05).

RAR and CREB expression can be used to indirectly determine the malignant potentiality of a cell.