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Insulin-like Growth Factor I Rapidly Induces Tyrosine Phosphorylation of a M_r 150,000 and a M_r 160,000 Protein in Highly Metastatic Mouse Colon Carcinoma 26 NL-17 Cells¹

Cancer Chemotherapy Center, Japanese Foundation for Cancer Research, 1-37-1, Kami-Ikebukuro, Toshima-ku [T. Y., Y. I., Y. T., S. N., A. Y., T. Ts.]; Hoshi University, 2-4-41, Ebara, Shinagawa-ku [Y. I.]; Mitsubishi Kasei Institute of Life Sciences, 11, Minamiooya, Machida-shi, [S. I.]; and Institute of Applied Science for Microbiology, University of Tokyo, 1-1-1, Yayoi, Bunkyo-ku [T. Ta., T. Ts.], Tokyo, Japan

Insulin-like growth factor I (IGF-I) stimulates the proliferation of highly metastatic NL-17 cells to a greater extent than poorly metastatic NL-44 cells, both of which are derived from mouse colon carcinoma 26. The NL-17 cells have been compared with NL-44 cells for the signal transduction pathway of IGF-I. IGF-I receptors of both cell types were identified by affinity labeling, and there was no significant difference between the two cell types in the amount or the autophosphorylation activity of the IGF-I receptors. However, when IGF-I-dependent tyrosine phosphorylation of cellular components was examined, remarkable tyrosine phosphorylation of proteins with molecular weights of 150,000 (pp150) and 160,000 (pp160) was found in NL-17 cells. In contrast, this phosphorylation stayed at significantly lower levels in NL-44 cells than in NL-17 cells. The phosphorylation of pp150 and pp160 was induced within 10 s after the addition of IGF-I and reached its maximal level by 30 s. After the removal of IGF-I, the phosphorylation of pp150 and pp160 was reduced to the basal level within 30 min. This phosphorylation was not induced by platelet-derived or epidermal growth factor. The pp150 and pp160 were not absorbed by wheat germ agglutinin-agarose. They were found in the soluble fraction of cytoplasm but not in the membrane or the cytoskeleton. The pp150 and pp160 might be endogenous substrates of IGF-I receptor kinase. These results suggest that tyrosine phosphorylation of pp150 and pp160 mediates the higher proliferative response of NL-17 cells to IGF-I.

¹ This work was supported in part by grants-in-aid from the Ministry of Education, Science and Culture of Japan; Foundation for Promotion of Cancer Research; Haraguchi Memorial Cancer Research Fund; and Uehara Memorial Foundation.

² To whom requests for reprints should be addressed, at Cancer Chemotherapy Center, Japanese Foundation for Cancer Research, 1-37-1, Kami-Ikebukuro, Toshima-ku, Tokyo 170, Japan.

Received 5/23/91. Accepted 8/23/91.

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