17-Allyamino-17-demethoxygeldanamycin and 17-NN-dimethyl ethylene diamine-geldanamycin have cytotoxic activity against multiple gynecologic cancer cell types

HSP90 is a cellular chaperone that is overexpressed in many cancers. HSP90 assists in proper folding of a variety of clients, many of which are oncoproteins. HSP90 has been shown to be elevated in endometrial, ovarian, and breast cancer. Furthermore, HSP90 is known to stabilize the oncoprotein Akt; disruptions of the Akt pathway are common in gynecologic malignancies. We sought to evaluate the effectiveness of HSP90 inhibitors in gynecologic cancer. We tested two HSP90 inhibitors, 17-AAG and 17-DMAG, against gynecologic cancer cell lines (four endometrial, one cervical, one ovarian, and one breast cancer line). We performed Western blots to determine effects of treatment on levels of HSP90 client proteins and PARP cleavage. 3-(4,5-Dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide (MTT) assays were used to assess cell viability, and flow cytometry to quantitate cell-cycle distribution and apoptosis. After treatment with 17-AAG or 17-DMAG, we detected no decrease in HSP90 levels. Levels of other oncoproteins did decrease with treatment: phosphorylated and total Akt, and Met. One cell line underwent G₁ arrest, and five showed G₂ arrest. All showed some level of apoptotic cell death, which was confirmed by detection of PARP cleavage. Sensitivity to the drugs varied among cell lines, ranging from 20% to 90% apoptosis after treatment. Our data suggest that 17-DMAG may be more potent than 17-AAG. HSP90 inhibitors are effective cytotoxic agents in gynecologic cancer cells. Further testing in in vivo model systems is warranted, with the goal of eventual translation to clinical trials in gynecologic oncology patients.