The synergistic effect of spindle assembly checkpoint activity and inhibition of mitotic exit in reducing mitotic slippage

The treatment of cancer, chemotherapy is an important part of a patient’s regimen. Anti-microtubule agents, such as vinca alkaloids and taxanes are anti-mitotic drugs function by activating the Spindle Assembly Checkpoint (SAC) arresting the cell in mitosis. Unfortunately these types of chemotherapeutic agents are broad acting, less effective and they allow cancer cells to slip out of mitosis before apoptosis can occur.  Due to this mitotic slippage, these treatments aren’t as effective against more aggressive forms of cancer, including “triple negative” breast cancer. It is now believed that blocking mitotic exit downstream of the SAC is a better strategy for reduction of mitotic slippage. We hypothesize that tumor cells adapt to the inactivation of the SAC, making them more sensitive to reactivation, or prevention of mitotic exit.  We aim to show that arresting cells downstream of the SAC by inhibition of the Anaphase Promoting Complex (APC), mitotic slippage will be decreased in Drosophila S2 cells. We will examine the change in rate of mitotic slippage in Drosophila S2 cells by RNAi-mediated inhibition of proteins that function in late mitotic events, focusing on components of the APC.  We will also measure the cumulative effects of inactivation of the SAC and mitotic exit inhibition on mitotic progression and apoptosis. Drosophila eye clones, employing the FLP/FRT Recombinase system, will be used to examine mitotic slippage more physically. This will be used to create a functional model for examination of mitotic slippage with over-expression or suppression of certain late mitotic genes and drug addition.