Mutational and functional analyses reveal that ST7 is a highly conserved tumor-suppressor gene on human chromosome 7q31

Loss of heterozygosity (LOH) of markers on human chromosome 7q31 is frequen tly encountered in a variety of human neoplasias, indicating the presence o f a tumor-suppressor gene (TSC). By a combination of microcell-fusion and d eletion-mapping studies, we previously established that this TSG resides wi thin a critical region flanked by the genetic markers D7S522 and D7S677. Us ing a positional cloning strategy and aided by the availability of near-com plete sequence of this genomic interval, we have identified a TSG within 7q 31, named ST7 (for suppression of tumorigenicity 7; this same gene was rece ntly reported in another context and called RAY1). ST7 is ubiquitously expr essed in human tissues. Analysis of a series of cell lines derived from bre ast tumors and primary colon carcinomas revealed the presence of mutations in ST7. Introduction of the ST7 cDNA into the prostate-cancer-derived cell line PC3 had no effect on the in vitro proliferation of the cells, but abro gated their in vivo tumorigenicity. Our data indicate that ST7 is a TSG wit hin chromosome 7q31 and may have an important role in the development of so me types of human cancer.