Mitotic catastrophe cell death induced by heat shock protein 90 inhibitor in BRCA1-deficient breast cancer cell lines.

Heat shock protein 90 (Hsp90) is a molecular chaperone involved in folding, assembly, maturation, and stabilization of the client proteins that regulate survival of malignant cells. As previous reports correlate high Hsp90 expression with decreased survival in breast cancer, Hsp90 may be a favorable target for investigational therapy in breast cancer. In our study, we have examined the response of a panel of both BRCA1-null (UACC 3199, HCC 1937, and MBA-MD-436) and BRCA1-wt breast cancer cell lines (MCF-7, MBA-MD-157, and Hs578T) to determine the proteins governing response to Hsp90 inhibitor 17-allyloamino-17-demethoxy-geldanamycin. On treatment with the drug, cells arrested at G(2)-M phase and entered aberrant mitosis in a BRCA1-dependent manner. Failure to arrest the cells at or before mitosis resulted in formation of micronucleated cells, aberrant segregation of chromosomes, microtubule misalignment, and multicentrosomes, leading in eventual mitotic catastrophe cell death. Our observations show that BRCA1 mediates G(2)-M transition mainly through chek1 on 17-allyloamino-17-demethoxy-geldanamycin treatment.

Expression of CYP3A4 as a predictor of response to chemotherapy in peripheral T-cell lymphomas.

Peripheral T-cell lymphomas (PTCLs) are aggressive tumors in which the current therapy based on multiagent chemotherapy is not successful. Since cytochrome P450 3A subfamily (CYP3A) enzymes are involved in the inactivation of chemotherapy drugs, we hypothesized that CYP3A and P-glycoprotein (MDR1) expression in these lymphomas could result in a poor clinical response. We measured tumoral CYP3A and MDR1 mRNA content in 44 T-cell lymphomas, finding a large variation in CYP3A expression. Multiplex polymerase chain reaction (PCR) analysis and fluorescence in situ hybridization (FISH) analysis showed genomic gains affecting CYP3A and MDR1 genes in T-cell lines and primary tumors, suggesting that this could be the mechanism underlying the tumoral expression variation. To test whether the tumoral expression of CYP3A and/or MDR1 could influence PTCL treatment outcome, their expression levels were compared with the clinical response and survival of the patients, finding that a high tumoral expression of CYP3A4 was significantly associated with a lower complete remission rate. This was further investigated with cell lines stably expressing CYP3A4 that exhibited an increased resistance to doxorubicin and etoposide. In conclusion, a high CYP3A4 tumoral expression could be useful to predict poor response to the standard PTCL chemotherapy; in these cases alternative chemotherapy combinations or doses should be explored.