Docosahexaenoic acid enrichment of tumor phospholipid membranes increases tumor necroptosis in mice bearing triple negative breast cancer patient-derived xenografts.

Docosahexaenoic acid (DHA) reduces breast cancer tumor growth in preclinical models. To better understand how DHA amplifies the actions of docetaxel (TXT) chemotherapy, we examined the effects of two doses of dietary DHA on tumor size, membrane DHA content and necroptosis using a drug resistant triple negative breast cancer (TNBC) patient derived xenograft (PDX) model. Female NOD.Cb-PrkdcscidIl2rg mice bearing TNBC PDXs were randomized to one of three nutritionally complete diets (20% w/w fat): control (0% DHA), high DHA (3.8% HDHA), or low DHA (1.6% LDHA) with or without intraperitoneal injections of 5 mg/kg TXT, twice weekly for 6 weeks (n=8 per group). Tumors from mice fed either HDHA+TXT or LDHA+TXT were similar in size to each other, but were 36% and 32% smaller than tumors from mice fed control+TXT, respectively (P<.05). A dose effect of DHA incorporation was observed in plasma total phospholipids and in phosphatidylethanolamine and phosphatidylinositol. Both doses of DHA resulted in similarly increased necrotic tissue and decreased NFκB protein expression compared to control tumors, however only the HDHA+TXT had increased expression of necroptosis related proteins: RIPK1, RIPK3 and MLKL (P<.05). Increased MLKL was observed in the lipid raft portion of HDHA+TXT tumor extracts. This work confirms the efficacy of a combination therapy consisting of DHA supplementation and TXT chemotherapy using two doses of DHA as indicated by reduced tumor growth in a TNBC PDX model. Moreover, the results suggest that decreased growth may occur through increased DHA incorporation into tumor phospholipid membranes and necroptosis.