BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS 243, 503–508 (1998) ARTICLE NO. RC978043 Overexpression and Activation of the Tyrosine Kinase Src in Human Pancreatic Carcinoma Manfred P. Lutz,* I. B. Silke Eßer,* Berenike B. M. Flossmann-Kast,* Roger Vogelmann,* Hardi Lu ¨ hrs,* Helmut Friess,† Markus W. Bu ¨ chler,† and Guido Adler* *Department of Internal Medicine I, University of Ulm, 89070 Ulm, Germany; and †Department of Visceral and Transplantation Surgery, University of Bern, 3010 Bern, Switzerland Received December 19, 1997 kinases which act as receptors for various growth fac- Src family tyrosine kinases participate in the regula- tors and directly modulate substrate proteins by phos- tion of cell adhesion, cell growth and differentiation. phorylation through their catalytic intracellular do- Here, we examine for the first time the potential role main (10). A second group of tyrosine kinases is located of Src for growth regulation of human pancreatic car- within the cytosol and acts as intermediate intracellu- cinoma cells. By immunohistochemical analysis, Src lar signal transducing proteins. Representatives of this was overexpressed in 13/13 pancreatic carcinoma tis- latter category are the Src family tyrosine kinases, sue but not in 6 normal pancreatic tissue specimen. which are enzymes with high structural similarity cou- In Western blots of total cellular extracts, Src protein pling to and transducing signals from growth factor expression was elevated in 14/17 carcinoma cell lines receptors, G protein-coupled receptors and adhesion as compared to normal pancreas or cultured human molecules. At least nine members of this kinase family pancreatic duct cells. Kinase activity was only detect- are known to date and most of them are expressed able in cancer cells and did not correlate with the predominantly in hemopoetic cells. Only the four mem- amount of kinase protein or with the expression of bers Src, Yes, Fyn, and Lyn could be demonstrated in the regulatory kinase Csk, indicating that Src is not other tissues so far (11). In fibroblasts, kinase-activated regulated through protein expression or through ex- pression of Csk. The Src-specific tyrosine kinase inhib- Src-mutants are able to act as transforming oncogene, itor herbimycin A decreased cell growth in a dose-de- indicating the potential of Src for growth regulation pendent manner. We suggest that Src family kinases (12). In addition, infection of rat colon with retroviral participate in growth regulation of pancreatic cancer v-src induces dysplasia, and cotransfection with v-myc cells.  1998 Academic Press induces carcinoma (13). Based in part on this evidence, it has been speculated, that upregulation of the Src kinase is important for growth and transformation of intestinal epithelial cells (14). The potential role of Src Knowledge of pancreatic cancer growth control is still in pancreatic cancer has not been examined. limited although many molecular changes have been Therefore, the purpose of this study was to determine reported which partly explain the aggressive nature of whether the tyrosine kinase Src might play a role in this tumor. These changes include loss of function of pancreatic tumor growth regulation. We now report, the tumor suppressor genes p53, DCC and DPC4, and that Src is overexpressed in human pancreatic carci- activating mutations of the proto-oncogene K-ras in at noma tissue as compared to normal pancreas. In addi- least 70% of pancreatic tumors (1-5). In addition, most tion, Src is activated in many cultured pancreatic carci- of pancreatic cancers examined overexpress a number noma cells and cell growth is inhibited by herbimycin of tyrosine kinase growth factor receptors (6-8). In anal- A, a Src kinase inhibitor, demonstrating the potential ogy to colon cancer or to breast cancer, it has been role of Src in regulation of pancreatic cancer cell prolif- speculated that some of these changes contribute to eration. rapid tumor growth, invasion or metastasis (9). Reversible phosphorylation of signal transducing MATERIAL AND METHODS proteins on tyrosine residues is a well recognized mech- anism of cellular growth control. Tyrosine phosphoryla- Tissue and cell lines. Human pancreatic cancer tissue samples tion events are catalyzed by two major groups of pro- were obtained from thirteen patients undergoing surgical resection for pancreatic adenocarcinoma after written informed consent. Nor- tein tyrosine kinases. One group are transmembrane 0006-291X/98 $25.00 Copyright  1998 by Academic Press All rights of reproduction in any form reserved. 503