We have established a human gastric scirrhous carcinoma cell line (designated as HSC-43) in a serum-free chemically defined medium (CDM) without any polypeptide growth factor, from a primary tumor of a 56-year-old male patient. HSC-43 cells grew in vitro in adherence with a population doubling time of 55 hr, and had the cytological properties of mucinous epithelial tumor cells. Cytogenetic analysis of the cells revealed pseudo-tetraploidy, with structural abnormalities of deletion at chromosome Iq25 and with 3 marker chromosomes. Some cells had retained features of signet-ring cells and caused fibroblastic proliferation when transplanted into athymic nude mice. The possible involvement of transforming growth factor-α(TGF-α), and its receptor, the epidermal-growth-factor receptor (EGFR), on the growth of HSC-43 cells was studied. Synthesis and secretion of TGF-α by HSC-43 cells were confirmed by biological assay and enzyme-linked immunosorbent assay. Radioreceptor analysis showed the presence of receptors for EGF in HSC-43 cells. Proliferation of HSC-43 cells was inhibited by antibodies against TGF-α and/or the EGFR. However, neither TGF-α nor epidermal growth factor (EGF) was effective in stimulating the cell growth of HSC-43 cells, irrespective of the cell density when supplemented exogenously. Our data suggest that TGF-α and EGFR play a role in the autocrine growth of HSC-43 cells. This may be another example of growth regulation of gastric carcinoma.