Expression of bone morphogenetic proteins in human lung carcinomas

Background. The bone morphogenetic proteins (BMP) are phytogenetically conserved proteins, which are essential for embryonic development. Bone morphogenetic protein-2 (BMP-2) was recently shown to be expressed in a small sample of lung carcinomas. Studies have suggested that BMP-2 may enhance tumor growth. The present study examined which BMP family members are expressed in non-small cell lung carcinomas (NSCLC). Furthermore, the frequency of BMP-2 overexpression and the types of lung carcinomas expressing BMP-2 were determined. Methods. Tissue samples were obtained from the operating room and frozen in liquid nitrogen. Samples included metastatic NSCLC, benign lung tumors, adenocarcinoma, squamous cell carcinoma, bronchioloalveolar, and neuroendocrine carcinomas. Paired normal lung tissues served as the controls. The BMP-2, BMP-4, BMP-6, BMP-7, and growth differentiation factor 5 (GDF-5) expressions were examined by Western blot analysis. Results. The BMP-4, BMP-6, BMP-7, and GDF-5 were infrequently expressed in NSCLC. The BMP-2 was expressed in 41 of 42 NSCLC with minimal expression in normal lung tissue; BMP-2 was expressed 17 fold higher than that of normal lung tissue. The BMP-2 was over-expressed in all subtypes of NSCLC, including neuroendocrine carcinomas. The BMP-2 expression was similar between squamous cell carcinomas and adenocarcinomas; however, bronchioloalveolar carcinomas tended to have a lower level of expression. The BMP-2 was not significantly expressed in benign lung tumors. Conclusions. Bone morphogenetic protein-2 is the predominant family member expressed in NSCLC. The BMP-2 is overexpressed in the majority of human lung carcinomas independent of cell type.