LAPSER1: a novel candidate tumor suppressor gene from 10q24.3.

Numerous LOH and mutation analysis studies in different tumor tissues, including prostate, indicate that there are multiple tumor suppressor genes (TSGs) present within the human chromosome 8p21-22 and 10q23-24 regions. Recently, we showed that LZTS1 (or FEZ1), a putative TSG located on 8p22, has the potential to function as a cell growth modulator. We report here the cloning, gene organization, cDNA sequence characterization and expression analysis of LAPSER1, an LZTS1-related gene. This gene maps within a subregion of human chromosome 10q24.3 that has been reported to be deleted in various cancers, including prostate tumors, as frequently as the neighboring PTEN locus. The complete LAPSER1 cDNA sequence encodes a predicted protein containing various domains resembling those typically found in transcription factors (P-Box, Q-rich and multiple leucine zippers). LAPSER1 is expressed at the highest levels in normal prostate and testis, where multiple isoforms are seen, some of which are either undetectable or differentially expressed in some prostate tumor tissues and cell lines. Over-expression of LAPSER1 cDNA strongly inhibited cell growth and colony-forming efficiencies of most cancer cells assessed. Together these data suggest that LAPSER1 is another gene involved in the regulation of cell growth whose loss of function may contribute to the development of cancer.