PILOT--ONCOGENES IN ORAL SQUAMOUS CELL CARCINOMA

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Identification of growth regulatory genes that are altered by mutation, gene amplification, or rearrangement is a major focus of cancer research. For the majority of human tumors, no such oncogene alteration has been found. That unidentified genes are activated is strongly suggested by cytogenetic and chromosome hybridization studies. For squamous cell carcinoma of the head and neck (SCCHN), up to eight new loci seem especially likely to harbor new oncogenes. Although many known oncogenes fail to transform NIH3T3 cells, the development of new assays has been hindered by the inability to efficiently transfect other cell types. Adenovirus-polylysine conjugate was found efficient for stable transfection of rat cells in vitro, facilitating several alternate screening strategies. In the initial screen we isolated breast cancer cDNAs that transform adenovirus E1a-immortalized rat kidney cells. One of these, named TAB (transforming gene amplified in breast cancer), was found amplified about 10-fold in breast cancer MCF-7 cells, and 2-5 fold in several primary breast cancers. Comparison of the full-length, about 400 amino acid open reading frame with sequences in the database failed to detect related genes or functional motifs. TAB was localized to chromosome 3p14.1-2 using somatic cell hybrid lines. The gene was further localized to a 100- 200kb interval in 3p14.1 using a complete YAC contig of 3p14. TAB maps within a region of 8Mb that represents the minimal region of loss of heterozygosity in renal cell carcinoma. The same region is lost from SCCHN and numerous other tumors. We propose to apply this new assay to SCCHN. A plasmid-based, cDNA expression library will be constructed using mRNA from SCCHN cell lines. The library will be introduced into adenovirus E1a-immortalized cells and transforming human cDNAs will be rescued from resulting transformed cell lines. These will be partially sequenced, and novel genes will be mapped to specific human chromosomes. Genes that map to loci previously implicated in SCCHN will be further characterized. These studies aim to isolate at least one new gene that undergoes somatic alteration in SCCHN. We propose to test primary SCCHN tumors for gene amplification of TAB. Since TAB represents a candidate gene relevant to allelic loss at 3p14, we propose to test for sequence alterations at the TAB locus in SCCHN tumors with loss of chromosome 3p.