Analysis of insulin-like growth factors and insulin-like growth factor I receptor expression in renal cell carcinoma

The expression of insulin-like growth factors I (IGF-I) and II (IGF-II) and insulin-like growth,factor I receptor (IGF-IR) was studied in 137 clear cell, 23 chromophobe. and 20 papillary renal cell carcinomas (RCCs) using a tissue microarray technique. IGF-I immunoreactivity was detected hi 110 (82. 1%) of 134 clear cell, 8 (36%) of 22 chromophobe, and 3 (15%) of 20 papillary RCCs (P <. 001). IGF-IR immunoreactivity was detected in 39 (29.5%) of 132 clear cell, 9 (41%) of 22 chromophobe, and 19 (95%) of 20papillary RCCs (P <.001). In contrast, all tumors lacked IGF-II expression. Expression of IGF-I and IGFIR was not related to tumor stage, grade, or prognosis. The IGF system is expressed differentially among different tumor types. The expression. of IGF-I together with its receptor, IGF-IR, provides evidence for the existence of an autocrine-paracine loop, of tumor-cell stimulation hi RCC and makes this type of cancer a candidate for therapeutic strategies aimed to interfere with the IGF pathway.