Karen K. Phillips, Ph.D.

Dissertation research performed under the guidence of Dr. Bernard E. Weissman

ABSTRACT
    Cytogenetic and molecular alterations of chromosomes 6, 11, and 16 often occur in breast tumors, Wilms' tumor, and several other carcinomas, implicating the loss of suppressor gene function. To test this hypothesis, we transferred normal chromosomes 6, 11, 12, and 16 by microcell-mediated chromosome transfer (MMCT) into the G401 Wilms' tumor cell line and/or several breast cancer cell lines and tested the resultant microcell hybrid clones for tumorigenicity and/or metastasis in nude mice. Chromosome 11 microcell hybrids of the MDA-MB-435 breast carcinoma cell line, although not suppressed for tumorigenicity, were >95% suppressed for metastasis, indicating the presence of a metastasis-suppressor gene for breast cancer on this chromosome. To determine which gene might be responsible for the metastasis suppression in the MDA-MB-435 cell line, we examined the role of two known metastasis-suppressor genes on chromosome 11, kai-1 and tapa-1. Although expression of Tapa-1 protein did not correlate with metastatic suppression, the contribution of Kai-1 to these cells remains unclear. Increased Kai-1 protein levels correlated with metastasis suppression, yet kai-1 transfectants were not suppressed for metastasis. However, there may be a threshold level of Kai-1 protein necessary for suppressor function, since the primary tumors of the transfectants had decreased levels of the protein compared to the inoculated cells. Alternatively, primary tumors of the metastasis-suppressed microcell hybrids did not have decreased levels of the Kai-1 protein. Except for a chromosome 11 microcell hybrid, all the G401 hybrid cell lines were tumorigenic when inoculated into kidney capsules, indicating that chromosomes 6 and 12 probably do not contain tumor-suppressor genes for Wilms' tumor.