A Candidate Tumor Suppressor Gene, H37, from the Human Lung Cancer Tumor Suppressor Locus 3p21.3

Frequent allelic loss and homozygous deletions within chromosome 3p in human lung cancershave suggested that the 3p21.3 (370-kb) region contains a critical tumorsuppressor gene(s) (TSG). With the exact identity/characteristics of such a gene(s) still unconfirmed, a lack of inactivating structural mutations in the expressed genes contained within this region may indicate that the 3p TSG(s) do not fit into the classical “two-mutation” model. This report characterizes a candidate 3p TSG, H37, located within the 370-kb region. Reduced expression of the H37 transcript was found in 9 of 11 (82%) of primary non-small cell lung cancers (NSCLCs) when compared with adjacent normal tissues. Generation of an H37 antibody followed by immunohistochemical analysis of primary NSCLC specimens demonstrated that 46 of 62 (73%) of these cancers contain reduced levels of H37 protein when compared with adjacent normal bronchial cells. Moreover, introduction of the H37 cDNA into human breast cancer cells deleted of 3p21–22 reduced both anchorage-dependent and -independent cell growth in vitro . Subsequent transfection of H37 cDNA into one of the human lung cancer cell lines homozygously deleted in this region resulted in a very low yield of H37-expressing clones. H37 also suppressed anchorage-dependent and -independent growth of A9 mouse fibrosarcoma cells and inhibited tumor formation in nude mice. These data indicate a potential role for H37 as one of the 3p TSGs in human lung cancer.