Rap-1 Antioncogene in Breast Cancer

摘要

This project aims to devise strategies to antagonize the promitogenic action of Ras and thereby suppress the transforming activity of the Erb2 oncogene found in 70% of human breast adenocarcinomas. We have focused on the identification and characterization of proteins that interact with Rap-1 and Ras through their effector loop in GTP-dependent fashion. We have carried out an extensive two-hybrid screening for proteins that bind to Ras and Rap 1. This has yielded the known Ras-Rap partners and a novel set of noncatalytic polypeptides which have provided the main focus of our efforts. The first of these to be characterized was the polypeptide known as AF-6; this binds more avidly to Rap 1-GTP than to Ras-GTP. Of greater interest is the polypeptide NORE-1, which binds to Ras-GTP at its carboxyterminus and encodes a centrally located zinc finger, and an aminoterminal proline rich domain. High affinity antibodies to NORE-1 cross-react with a family of polypeptides, some of which bind to Ras-GTP in vivo after growth factor stimulation. Recently, a candidate tumor suppressor locus on chromosome 3p21 (frequently deleted in Breast Cancer) was identified as a protein RDA32, a 271AA polypeptide that is 55% identical to NORE1. Ongoing work is focused ca the biologic activation of the NORE-1 family of Ras effectors and their possible role in the negative regulation of cell growth.