Binding of epidermal growth factor and insulin‐like growth‐factor I in renal carcinoma and adjacent normal kidney tissue

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Abstract
The binding of epidermal growth factor (EGF) and insulinlike growth factor I (IGF‐1) to cell membranes was determined in 14 renal cancers and in 13 normal kidney tissues adjacent to the tumors. The soluble 34K 1GF binding protein (34K IGF‐BP) content and the phosphotyrosyl‐protein phosphatase activity in renal cancer tissue and adjacent normal tissue were also determined. The specific EGF receptor binding in renal cancers was 12.7 ± 2.5% (mean ± SEM) as compared to 2.6 ± 0.2% (mean ± SEM) in normal tissues (p < 0.01). Phosphotyrosyl‐protein phosphatase activity in renal cancer tissue was less than half of that observed in normal renal tissue (p < 0.01). The highest IGF‐1 binding was observed in 5 renal cancers although no consistent differences between IGF‐1 binding to tumor and normal tissues were observed. Both EGF and IGF binding to kidney tissue were higher than binding to gastro‐intestinal tissue irrespective of whether normal or malignant tissues were compared. All normal kidney tissues and 7 of 8 kidney tumors contained measurable amounts of 34K IGF‐BP as determined by RIA and the cross‐linking technique. In 2 tumor tissue samples the 34K IGF‐BP content was increased 8‐ and 15‐fold over that seen in adjacent normal kidney tissue, whereas in the 6 other renal cancers the 34K IGF‐BP was similar to that observed in normal kidney tissue.