pp60c-src activation in lung adenocarcinoma

Nine src family members are known including c-Src, c-Yes, c-Lck, c-Fyn, c-Hck, c-Lyn, c-Blk, c-Fgr and c-Yrk. They encode proteins with molecular weights of 55-62 kilodaltons (kDa), which are either cytoplasmic or membrane-associated protein tyrosine kinases. A close correlation exists between an elevated pp60(c-src) tyrosine kinase activity and cell transformation. However, the level of activation of pp60(c-src) in non-small cell lung cancers (NSCLC) remains obscure. The aim of this study was to examine the level of activity of pp60(c-src) in NSCLC. pp60(c-src) expression and in vitro protein tyrosine kinase activity in lung cancer tissue samples were measured by western blotting and in vitro kinase assays and compared with those in the surrounding non-tumour lung tissue from the same patient. pp60(c-src) phosphorylation was assessed by two-dimensional tryptic phosphopeptide mapping. The kinase activity of pp60(c-src) was significantly activated in NSCLC, especially in adenocarcinomas. In addition, the pp60(c-src) kinase activity increased with the size of the adenocarcinoma. Two-dimensional tryptic phosphopeptide mapping showed dephosphorylation of pp60(c-src) at Tyr 530 in adenocarcinomas. The proto-oncogene product, pp60(c-src), was activated in NSCLC, especially in adenocarcinomas, in part through the dephosphorylation of Tyr 530. Our results suggest that activation of pp60(c-src) might play an important role in the progression of lung adenocareinomas. (C) 2003 Elsevier Science Ltd. All rights reserved.