NOXA/MCL-1 axis determines cell-death decision between apoptosis and pyroptosis and the inflammatory secretome of breast cancer cells treated with anti-mitotics.

Understanding how the malignant cells respond to chemotherapy is essential to prevent the development of resistance and to improve the efficiency of anti-cancer drugs. Recently, we established that, by intrinsic and paracrine mechanisms, taxol treatment in breast tumor cells increases NOXA a pro-apoptotic protein functioning as an endogenous inhibitor of survival protein MCL-1, thereby enhancing cytotoxic load on the compensatory survival protein BCL-xL. We herein sought to define the contribution of NOXA/MCL-1 to the modality of cell death secretome composition upon anti-mitotic treatment associated with a BCL-xL antagonist. We observed that genetic inactivation of NOXA (enforcing MCL-1 pro-survival activity) in cancer cells not only delays their death when exposed to taxol in combination with the BCL-xL antagonist A1331852, but also alters its morphological characteristics with the apparition of features evoking pyroptosis. We identified the Caspase3-GSDME axis as regulating pyroptotic-like features suggesting that NOXA may act as a negative regulator of this cell death process (and MCL-1 as a positive regulator for it). Furthermore, comparative analysis of secretomes from the NOXA proficient or deficient cancer cells treated by taxol reveals variations in inflammatory cytokine production including those of IL-1{beta} and IL-18. Thus, our results show that anti-mitotic treatments are able to induce death by apoptosis and/or pyroptosis depending on BCL-2 family balance in breast cancer cells. Furthermore, NOXA/MCL-1 ratio appears to control the communication between these two types of cell death and their associated extracellular inflammatory signals in coordination with the pore-forming gasdermin GSDME.