Isolation of DICE1: A gene frequently affected by LOH and downregulated inlung carcinomas

In the development and progression of sporadic tumors multiple tumor suppre ssor genes are inactivated that may be distinct from predisposing cancer ge nes. Previously, a tumor suppressor locus on human chromosome 13q14 that is distinct from the retinoblastoma predisposing gene 1 (RBI) has been identi fied in lung, head and neck, breast, ovarian and prostate tumors, By an app roach that combines genomic difference cloning and positional cloning we is olated the cDNA of a novel gene (DICE1) located at 13q14.12-14.2. The DICE1 gene is highly conserved in evolution and its mRNA is expressed in a nide variety of fetal and adult tissues, The DICE1 cDNA encodes a predicted prot ein of 887 amino acids corresponding to an 100 kD protein that shows 92.9% identity to the carboxy-terminal half of the mouse EGF repeat transmembrane protein DBI-1. The DBI-1 protein interferes with the mitogenic response to insulin-like growth factor 1 (IGF-I) and is presumably involved in anchora ge-dependent growth. When compared to normal lung tissue expression of the DICE1 mRNA aas reduced or undetectable in the majority of non-small cell lu ng carcinomas analysed, The location of the DICE1 gene in the region of all elic loss, its high evolutionary conservation and the downregulation of exp ression in carcinoma cells suggests that DICE1 is a candidate tumor suppres sor gene in non-small cell lung carcinomas and possibly in other sporadic c arcinomas.