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Insulin‐and insulin‐like growth‐factor‐I receptor tyrosine‐kinase activities in human renal carcinoma
Author(s) -
Kellerer Monika,
von Eye Corleta Helena,
Mühlhöfer Andreas,
Capp Edison,
Mosthaf Luitgard,
Bock Susanne,
Petrides Petro E.,
Häring Hans U.
Publication year - 1995
Publication title -
international journal of cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.475
H-Index - 234
eISSN - 1097-0215
pISSN - 0020-7136
DOI - 10.1002/ijc.2910620502
Subject(s) - insulin receptor , endocrinology , medicine , insulin , irs2 , tyrosine kinase , biology , insulin like growth factor , receptor , insulin like growth factor 1 receptor , insulin receptor substrate , kidney , receptor tyrosine kinase , growth factor , insulin resistance
We studied expression and functional characteristics of the insulin‐ and insulin‐like‐growth‐factor‐1(IGF‐1) receptors in human renal carcinoma. Ligand‐binding properties and tyrosine‐kinase activity of both receptors, as well as the expression of the 2 isoforms of the human insulin receptor (HIR‐A and ‐B) were analyzed in renal carcinoma and normal adjacent kidney tissue of 8 adult patients. Partially purified insulin‐ and IGF‐I receptors from normal and renal cell carcinoma tissue possessed identical affinities for their ligands. Renal cell carcinoma, however, contained 3‐ to 4‐fold more specific insulin‐binding sites and 2‐fold more IGF‐I binding sites than adjacent normal kidney tissue. In addition, we determined the relative content of insulin/IGF‐I receptor hybrids in both tissues. Renal cell carcinoma and adjacent normal tissue revealed similar amounts of insulin/IGF‐l receptor hybrids, i.e., 44 ± 8.2% of tracer IGF‐I binding in normal tissue and 46 ± 12.0% in renal cell carcinoma. When equal amounts of insulin‐ and IGF‐I receptor protein were studied, we found significantly increased receptor autophos‐ phorylation and elevated substrate phosphorylation in carcinoma tissue. To assess whether the differences in insulin‐receptor tyrosine‐kinase activity were caused by an altered pattern of insulin receptor isoform expression, we determined mRNA levels for HIR‐A and ‐B. The 2 insulin receptor isoforms were, however, expressed in highly variable ratios in both normal and tumor tissue. Our experiments show that renal carcinoma expresses an elevated amount of insulin‐ and IGF‐I receptor protein with increased specific autophosphorylation and tyrosine‐kinase activity each. The increase of insulin‐receptor tyrosine‐kinase activity in renal carcinoma cannot be explained by an altered expression pattern of insulin receptor isoforms. © 1995 Wiley‐Liss, Inc.