Plasma extracts not only from patients with acute gastric mucosal lesion (AGML) but also from rats with AGML induced by HC1-ethanol administration were found to possess growth promoting effects on human gastric carcinoma cell line KATO III as well as on cultured mucosal cells from guinea pig stomach. The growth promoting activities were sequentially purified by hydroxy-apatite gel-chromatography, Sephadex gel chromatography, and Bio-gel chromatography, which resulted in purification of the two distinct growth promoting activities. The smaller one (m. w. 6, 000) was found to be TFG-alhpa by specific radioimmunoassay. The larger one (m. w. 80, 000) was further purified with HPLC and SDS-PAGE followed by application to Peptide sequencer, and it was shown that this activity[Gastric Mucosal Growth Factor (GM-GF) ] has partial amino acid sequence of Phe-Leu-Pro-Glu-Arg-Tyr.
The effects of the purified GM-GF on the growth of not only normal gastric mucosa but also gastric cancer cells were compared with those of gastrin, TGF-alpha, prostaglandin E_2 (PGE_2) and calcitonin. All of these agents enhance the growth of mucosal cells from guinea pig stomach with the potency order of GM-GF>TGF-alpha = gastrin>PGE_2>calcitonin. In contrast, the growth of human gastric carcinoma cell line KATO III were stimulated by only GM-GF, TGF-alpha and gastrin with the potency order of TGF-alpha = gastrin>GM-GF, whereas both PGE_2 and calcitonin had inhibitory effects. On the other hand, both PGE_2 and calcitonin enhance cyclic AMP generation in not only gastric mucosal cells but also KATO III cells, while gastrin enhances inositolphospholipid turnover with resulting elevation of[Ca^<++>]i in both cells. In contrast, GM-GF enhances tyrosine phosphorylation with concomitant increase of [Ca^<++>]i in both normal mucosal cells and cancer cells, although like hepatocyte growth factor, GM-GF appears to be more effective on normal epithelial cells than on cancer cells.