Abstract

Activation of ferroptosis, a recently described mechanism of regulated cell death, dramatically inhibits growth of ovarian cancer cells. Given the importance of lipid metabolism in ferroptosis and the key role of lipids in ovarian cancer, we examined the contribution to ferroptosis of steroyl CoA desaturase (SCD1), an enzyme that catalyzes the rate-limiting step in monounsaturated fatty acid synthesis, in ovarian cancer cells. SCD1 was highly expressed in ovarian cancer tissue, cell lines, and a genetic model of ovarian cancer stem cells. Inhibition of SCD1 induced lipid oxidation and cell death. Conversely, over-expression of SCD1 or exogenous administration of its C16:1 and C18:1 products, palmitoleicic acid or oleate, protected cells from death. Inhibition of SCD1 induced both ferroptosis and apoptosis: inhibition of SCD1 decreased CoQ10, an endogenous membrane antioxidant whose depletion has been linked to ferroptosis, while concomitantly decreasing unsaturated fatty acyl chains in membrane phospholipids and increasing long chain saturated ceramides, changes previously linked to apoptosis. Simultaneous triggering of two death pathways suggests SCD1 inhibition may be an effective component of anti-tumor therapy, since overcoming this dual mechanism of cell death may present a significant barrier to the emergence of drug resistance. Supporting this concept, we observed that inhibition of SCD1 significantly potentiated the anti-tumor effect of ferroptosis inducers in both ovarian cancer cell lines and a mouse orthotopic xenograft model. Our results suggest that the use of combined treatment with SCD1 inhibitors and ferroptosis inducers may provide a new therapeutic strategy for patients with ovarian cancer.