): The gene encoding the transforming growth factor beta 1 type II receptor (TGF-beta1-RII), which mutates at an intragenic microsatellite in genetically unstable primary sporadic colorectal cancers and gastric cancers, is a tumor suppressor gene. TGF-beta1 is secreted in an inactive precursor form, requiring cleavage after binding to the intact insulin-like growth factor II receptor (IGFIIR). Without binding by IGFIIR, latent TGF-beta1 is not activated to its growth-inhibitory state. The applicant's preliminary data suggest that IGFIIR is an important node in the TGF-B1 growth pathway. In a fashion analogous to TGF-beta1RII, mutation of IGFIIR occurs within a coding microsatellite tract in genetically unstable gastrointestinal tumors. The applicant hypothesizes that IGFIIR is inactivated and contributes to the origin or progression or premalignant and frankly malignant gastrointestinal lesions, particularly genetically unstable tumors. The major objectives of this proposal are as follows:
In Aim 1 primary specimens from patients with genetically stable as well as unstable gastrointestinal malignant and premalignant lesions will be analyzed for the prevalence and timing of IGFIIR i n activation during neoplastic development. Premalignant and frankly malignant lesions will be examined, including Barrett's metaplasia, Barrett's-associated dysplasia, esophageal adenocarcinoma, ulcerative colitis-associated dysplasia and cancer, gastric carcinoma, sporadic colorectal carcinoma, and pancreatic carcinoma.
In Aim 2 mechanisms of IGFIIR inactivation will be determined. Coding region microsatellites within IGFIIR will be tested for i n s ertions and deletions; IGFIIR messenger RNA will be studied for quantitative and qualitative abnormalities; methylation studies will be performed on upstream regions of IGFIIR; IGFIIR protein size and amount will be analyzed utilizing Western blotting; and nonsense mutations will be screened for using the in vitro synthesized protein assay, with confirmatory sequencing of any abnormal cDNAs.
In Aim 3, the effects of IGFIIR inactivation on TGF-beta1 function will be studied. Specifically, latent versus active TGFbeta1 expression will be analyzed in neoplastic tissues known t o c ontain mutant or wild-type IGFIIR, using Western blotting and immunohistochemistry; adjacent sections from the same specimens will also be e v a luated for IGFIIR expression.
In Aim 4, to ascertain clinical significance, molecular alterations of IGFIIR will be correlated with survival, interval to death or disease progression, disease-free interval, TNM stage, histologic grade, age, sex, ethnic background, smoking, and family history. The potential value of IGFIIR inactivation as a predictive (early) biomarker, as well as its utility as a prognostic (late) indicator, will be definitively addressed by these correlations.