Expression of insulin-like growth factor-1 receptor in human colorectal cancer

The activation of the insulinlike growth factor 1/IGF-1 receptor system (IG F1/IGF1-R) has recently emerged as critical event in transformation and tum origenicity of several murine and human tumors. Expression of IGF1 and of I GF1-R has been demonstrated in normal and neoplastic intestinal cell lines of rats and humans. However, the modulation of IGF1-R expression during the progression from normal colonic mucosa to adenoma, to carcinoma, and to me tastasis, has not been evaluated. In this retrospective study, we investiga ted the expression of IGF1-R in 12 colonic adenomas (AD), 36 primary colore ctal adenocarcinomas (CA), and in 27 corresponding metastases (MT). Normal colonic mucosa (N) was adjacent to the CA in 34 cases. Formalin-fixed, para ffin-embedded tissues of each case were immunostained using the avidin-biot in-peroxidase method. We used an anti-IGF1-R rabbit polyclonal antibody (Sa nta Cruz Biotechnology, CA; dilution 1:100). Positive staining was quantita ted by CAS-200. Moderate to strong cytoplasmic immunostaining was observed in 34 of 36 CA (96%), and in 25 of 27 MT (93%). In all of the positive MTs, the intensity of die staining was always strong. In 10 of 12 ADs (83%), on ly a faint cytoplasmic stain was identified. Normal mucosa when present was negative. Strong IGF1-R positivity correlated with higher grade and higher -stage tumors (P < .01). These data suggest a role of IGF1-R expression dur ing die progression of colorectal adenoma to carcinoma. An increased number of IGF1-R receptors may favor the metastasis of colorectal cancer. Copyrig ht (C) 1999 by W.B. Saunders Company.