Targeting the anaphase promoting complex/cyclosome to induce mitotic arrest in ovarian cancer.

Abstract

Taxanes are a class of chemotherapeutic drug that act to disrupt microtubule function and cause mitotic arrest and cell death. These drugs are commonly used for cancer treatment, however their effectiveness is dependent on the presence of a functioning spindle assembly checkpoint (SAC). As a result, it is possible for cancer cells to become resistant to microtubule disrupting drugs by inactivating the SAC. The anaphase promoting complex/cyclosome (APC/C) is an E3 ubiquitin ligase that acts as the master regulator of cell cycle progression.Inhibition of the APC/C should result in disruption of the cell cycle, resulting in arrest during mitosis and/or pseudo-G1. Previous in silico studies of the APC/C structure identified compounds that potentially bind to the APC/C subunit ANAPC2. Three of these compounds (#8, 10, and 11) were tested on A2780/CP70 and SKOV3 ovarian carcinoma cells and tGM24 telomerase immortalized human fibroblasts. Cell morphology was observed during treatment with the compounds and showed signs of mitotic and apoptotic cells in a dose dependent manner. While all compounds showed the predicted effects, effects were more pronounced with compounds 10 and 11 than compound 8. Mitotic index determinations revealed a significant mitotic delay in both cancer cells and fibroblasts treated with compounds 8, 10, and 11. Compounds 10 and 11 were more potent than compound 8 in inhibition of colony forming ability for all three cell lines. Fibroblasts showed some resistance to compound 8, however fibroblasts exposed to compound 11 showed complete inhibition of cell growth without characteristic morphological signs of apoptosis. All three compounds induced apoptosis in ovarian cancer cells, as indicated by increased caspase 3 activity, but not in fibroblasts. These results indicate that compounds targeting the APC/C can induce mitotic arrest and kill ovarian cancer cells while sparing normal cells.