Identification of p63 expression in human lung cancer: analysis by complementary DNA and tissue microarray

Objective: To evaluate p63 expression at mRNA transcripts and protein levels in lung squamous cell cancer (SCC), adenocarcinoma, large cell lung cancer (LCLC) and small cell lung cancer (SCLC) and their matched metastatic tumors. The association between p63 expression and p63 locus at chromosomal 3q27 q29 was also investigated. Methods: p63 mRNA expression levels in a large series of lung cancers including SCC, adenocarcinoma, LCLC, SCLC and their matched metastatic tumors were analyzed by cDNA microarray technology. A tissue microarray from 150 primary lung cancer specimens was constructed and used for immunohistochemical detection of p63 protein expression. Chromosomal imbalances at the p63 locus in 70 primary lung cancers samples were studied by comparative genomic hybridization (CGH) technology. Results: mRNA levels were 10 fold in SCC compared to LCLC, SCLC, and adenocarcinoma. Interestingly, the mRNA expression of p63 in metastatic carcinomas was significantly higher than that in their matched primary tumors ( P <0 001). Immunohistochemistry demonstrated that p63 expression was 94.64% in SCC but only 1 79% in lung adenocarcinoma and 2 of 4 LCLC were positive staining. All the results in of SCLC were negative. There was a statistically significant difference for p63 positivity between pT1 tumors and those of higher stage ( P =0 035). The CGH results indicated that p63 locus at chromosomal 3q27 q29 was overrepresented in SCC. p63 immunopositivity correlated significantly with pronounced gains of the p63 locus at chromosomal 3q27 q29 (P=0.0001), indicating that strong expression of p63 in lung SCC correlated with increased gene amplification. Conclusion: p63 might play an important role not only in squamous differentiation of lung cancer but also in tumor development and progression.