MURINE SQUAMOUS-CELL CARCINOMA CELL-LINES PRODUCED BY A COMPLETE CARCINOGENESIS PROTOCOL WITH BENZO[A]PYRENE EXHIBIT CHARACTERISTIC P53 MUTATIONS AND THE ABSENCE OF H-RAS AND CYL-1 CYCLIN D1 ABNORMALITIES

In this report, we describe the isolation and characterization of six murine squamous cell carcinoma cell lines (BPCC) derived from carcinom as produced by a complete carcinogenesis protocol with benzo[a]pyrene (B[a]P). All six cell lines were tumorigenic to varying degrees in nud e mice, and several were spontaneously metastatic to the lungs. The in vivo invasive potential of each BPCC cell line was determined using d e-epithelialized tracheal xenotransplants into which cells were inocul ated. This assay revealed positive association of tumor grade with in vivo invasiveness, yet no clear relationship to the spontaneous metast atic potential of the cell lines, suggestive that invasive potential i s only one determinant of the overall metastatic phenotype. At the mol ecular level, all six BPCC cell lines revealed the absence of mutation s in the H-ras oncogene and no amplification or rearrangement in the c yl 1/cyclin D1 putative oncogene. Analysis of the p53 tumor suppressor gene revealed a direct correlation between positive nuclear immunohis tochemical staining of the p53 protein in four BPCC cell lines and the presence of p53 mutations identified by direct sequence analysis. The localization of mutations to exons 7 and 8 of the p53 gene and the de tection of G to T transversions in two of the four cell lines bearing p53 mutations are in agreement with previous analyses of a large serie s of primary B[a]P-induced murine skin tumors, In addition, frameshift mutations were identified in two cell lines. The correlation of the b iological and molecular properties of these BPCC cell lines with the k nown characteristics of primary squamous cell carcinomas induced by B[ a]P indicates that these cell lines could be useful tools in elucidati ng the mechanisms of tumorigenesis of this important chemical carcinog en.