Immunohistochemical Detection of K-sam Protein in Stomach Cancer1

The K-sam gene, originally isolated as an amplified gene from the stomach cancer cell line KATO-Ill, is characterized by its preferential amplification in the undifferentiated type (diffuse type) of stomach cancer and encodes one of the receptors for heparin-binding growth factors or fibroblast growth factors. The K-sam gene has been isolated by different methods and has been designated BEK, TK14, and Cek2. The receptor for keratinocyte growth factor was also found to be encoded by the same gene. To examine the expression of the K-sam protein in stomach cancer, polycbonal antibody pKl-2 was raised against the extracellular domain of the gene product. This antibody detected K-sam proteins by Western blot and flow cytometry analyses in stomach cancer cell lines KATO-III and HSC39, in which the K-sam gene is amplified and overexpressed. By immunohistochemical analysis, 20 of 38 cases of the undifferentiated type of advanced stomach cancer were K-sam positive, whereas none of 1 1 cases of the differentiated or intestinal type revealed K-sam staining. The K-sam product was observed predominantly in diffusely infiltrative lesions. In one autopsy case, the K-sam protein was detected only focally in the primary tumor, whereas markedly inReceived 1/22/96; revised 4/22/96; accepted 4/25/96. I Supported in part by a Grant-in-Aid for the 2nd Term Comprehensive 10-Year Strategy for Cancer Control from the Ministry of Health and Welfare of Japan; by Grants-in-Aid for Cancer Research from the Ministry of Health and Welfare and from the Ministry of Education. Science, Sports and Culture of Japan; and by the Uehara Memorial Foundation, the Research Foundation for Cancer and Cardiovascular Diseases (Osaka, Japan). and the Bristol-Myers Squibb Foundation. H. It., S. U., and H. Is. were awardees of a Research Resident Fellowship from the Foundation for Promotion of Cancer Research. 2 To whom requests for reprints should be addressed. at Genetics Division, National Cancer Center Research Institute, 1-I, Tsukiji 5-chome. Chuo-ku, Tokyo 104. Japan. Phone: 81-3-3542-251 1. extension 4400; Fax: 81-3-3541-2685. creased staining for the K-sam product was detected diffusely in the metastasized tumor in the lymph node and liver. These results suggest that K-sam overexpression is associated with the malignant phenotype of the undifferentiated type of stomach cancer, such as infiltrative growth and metastasis. INTRODUCTION Although stomach cancer is the most common malignant disease in the world after lung cancer, information on the genetic changes of stomach cancer has just begun to be accumulated (1, 2). Little has been known about the correlation between elinicopathobogical characteristics and genetic information. Stomach cancers are histopathobogically classified into two types: undifferentiated (diffuse type) and differentiated (intestinal type). These two types are also divergent in terms of biological behavior (3). For example, undifferentiated carcinoma is more frequently observed in the younger generation than is the differentiated type, demonstrates diffusely infiltrative growth. readily causes peritoneal dissemination, and is thought to be unfavorable in prognosis (4). From the clinicopathobogical point of view, it is important to clarify the molecular mechanism that determines the biological features of the undifferentiated type of stomach cancer. The K-sam gene was originally identified as an amplified gene in a stomach cancer cell line, KAIO-III, by the in-gel DNA renaturation method (5, 6). This gene is preferentially amplified in the undifferentiated type of stomach cancer, including poorly differentiated adenocarcinoma, signet-ring cell carcinoma, and mucinous adenocarcinoma (6). K-sam is also known to encode one of the heparin-binding growth factor receptors or FGFRs3 (7). The K-sam gene has been isolated by different methods and has been designated BEK, TKI4, and Cek2 (8, 9). The receptor for KGF was also found to be encoded by the same gene (10). The K-sam protein showed selective affinity for KGF or basic FGF by mutually exclusive alternative splicing of exons in the ligand-binding domain (I 1). The K-sam gene is capable of transforming NIH3I3 cells, and the transformed cells are tumorigenic in nude mice (12). Interestingly, truncation of the COOH terminus of the K-sam gene product potentiates transforming activity and is predominantly expressed in stomach cancer cell lines of undifferentiated type (12). In the present paper, we studied the expression of K-sam protein in stomach cancer. We also immunohistoehemicalby examined the presence of the K-sam product in surgical and 3 The abbreviations used are: FGFR, fibroblast growth factor receptor: FGF, fibrobbast growth factor: KGF, keratinocyte growth factor: KGFR. keratinocyte growth factor receptor; AMeX, acetone, methyl benzoate, and xylene. Research. on November 11, 2017. © 1996 American Association for Cancer clincancerres.aacrjournals.org Downloaded from