This program studies oncogenes and papillomaviruses. Oncogene studies have involved ras and EGFR. Some ras experiments are directed towards determining how ras proteins are stimulated to become biologically active and to identify their cellular target(s). Mutations that have been found previously not to affect cell transformation by a highly oncogenic ras gene have been engineered into a proto-oncogene version of ras. Some of these mutations have a significant effect on the ability of the proto-oncogene to induce cellular transformation. In vivo studies with Harvey murine sarcoma virus variants indicate that the target cell for tumor formation is determined, at least in part, by the transforming activity of ras in the virus. Experiments with a full-length EGF receptor proto-oncogene placed in a retrovirus vector have shown that established mouse cells transfected with the viral DNA or infected with a corresponding retrovirus, developed a fully transformed phenotype in vitro that required functional EGFR expression and presence of EGF in the growth medium. These results demonstrate that increased numbers of EGF receptors can contribute to the transformed phenotype. In papillomavirus studies, the E2 open reading frame has been shown to bind to a specific motif present several times in BPV and others PVs. This motif is an enhancer whose activity depends upon E2. Enhancement requires two or more copies of the motif. Anti-E2 sera have detected two E2 protein products in BPV transformed cells. The smaller form of E2, which may competiviely inhibit enhancement by the full-length E2 product, contains the DNA binding activity but lacks enhancer activity. In HPV studies, E6 protein has been identified in human cervical carcinoma cell lines known to express HPV 16 RNA and in mouse cells morphologically transformed by HPV 16 DNA. These results support the hypothesis that E6 can contribute to the transformed phenotype in human cervical cancers.
