Sphingolipids in Cancer Biology and Therapy

While DNA damaging agents such as Doxorubicin (Dox) are highly effective anticancer drugs, their use is often associated with harmful side effects (e.g. cardiotoxicity and myelosuppression). This leads to their administration in suboptimal doses, undermining their ability to effectively kill cancer cells. Our P01 group has also found that sub lethal doses of Dox can actually increase migration of breast cancer (BC) cells, making them more aggressive. Therefore, the goal of our studies is to maximize the antitumor efficacy of low doses of DNA damaging agents by sensitizing their cytotoxic potential and minimizing their promigratory effect. Studies from this P01 and others have linked regulation of individual sphingolipids (SLs) and/or SL enzymes to actions of Dox in BC cells. Considering that the SL pathway builds on highly interconnected reactions, the current fragmented and incomplete picture is not conducive to actionable therapeutic decisions. By applying a global integrative approach that studies metabolism and regulation of the whole pathway, we are linking distinct SL patterns (both enzyme expression/activity and lipid levels) with cytostatic low (LDox) or cytotoxic high (HDox) doses of Dox. This approach has allowed us to discover novel nodes of Dox regulation (e.g., DES1, CERT) and to implicate several modulated SL proteins (nSMase2, ACER2, CERT and SK2) in biologies elicited by either low or high Dox. Most importantly, targeted modulation of key SL nodes identified by our approach is able to ‘convert’ the cytostatic LDox response to that of the cytotoxic HDox response. Based on these compelling data, we propose the hypothesis that identifying and targeting critical nodes of SL metabolism to mimic the SL response observed with cytotoxic Dox doses will sensitize BC cells to low Dox doses, while also overcoming dangerous prometastatic functions. To test this hypothesis, we will pursue 3 aims: Aim 1. Establish integrative approaches to probe global regulation of the SL network in response to chemotherapy in BC cells (by developing state-of-the-art methodologies for measurements of SL metabolism and its regulation). Aim 2. Based on predictions built from the changes in the SL network gathered in Aim 1, target specific SL nodes to sensitize BC cells to low dose chemotherapy while curbing prometastatic functions. Aim 3. Determine and advance the preclinical efficacy of inhibition of select critical SL nodes to LDox in vivo, focusing initially on SK2. Successful completion of these studies will establish, for the first time, a holistic approach to studying SL metabolism and will identify the most effective biochemical intervention to maximize the antitumor efficacy of Dox in BC cells. This will serve as a solid platform for the future study of biological SL responses while continuing to advance cutting-edge-methodologies and approaches for the entire SL field.