REGULATION OF CELL DEATH BY INHIBITOR OF KAPPA-B KINASE IN TRIPLE NEGATIVE BREAST CANCER CELLS

Purpose: Triple-negative breast cancer (TNBC) is characterized by the lack of estrogen receptor, progesterone receptor, and HER2/neu and hence poses problems for targeted therapy. Thus there is an urgent need to identify suitable molecular targets for the treatment of TNBC. The inhibitor of kappa-B kinase-epsilon (IKK-epsilon) is a breast cancer specific oncogene that is elevated in TNBCs and plays an important role in breast cancer cell survival. Cancer cells often evade death by overcoming apoptosis or type I programmed cell death. However, the role of autophagy or self-digestion in cancer is ambiguous. While a low level of autophagy promotes cell survival under stress, excessive autophagy may lead to type II programmed cell death. The purpose of this project is to determine the mechanism by which IKK-epsilon promotes survival of breast cancer cells. Methods: Triple-negative breast cancer MDA-MB-231 cells were transfected with non-targeting control siRNA or siRNA against appropriate genes. Proteins were separated using SDS-PAGE (sodium dodecyl sulfate-polyacrylamide gel electrophoresis). Western blot analysis and enhanced chemiluminescence were used to study the overall levels of apoptosis and autophagy markers. Results: Knockdown of IKK-epsilon in MDA-MB-231 potentiated tumor necrosis factor-alpha (TNF)-induced apoptosis. IKK-epsilon knockdown also showed a decrease in p62/SQSTM1 and an increase in proteins associated with autophagy induction. Conclusions: The increase in autophagic markers in IKK-epsilon depleted cells suggests that IKK-epsilon protects MDA-MB-231 cells by promoting autophagy. Understanding the specific mechanism of survival of TNBC cells could aid in developing effective therapy.