Docosahexanoic acid (DHA) and eicosapentanoic acid (EPA) have been shown to possess anti-carcinogenic properties in mammary cancers, both in vitro and in vivo. The objective of this study was to investigate the effect of treating three different breast cancer cell lines with DHA or EPA on cellular growth, chemotherapy efficacy, and CD95 expression and localization in the cell. MDA-MB-231, MCF-7 and SKBr-3 cells were incubated with EPA or DHA with or without chemotherapy agents [doxorubicin (dox), Herceptin]. Cell growth was assessed by WST-1 assay and CD95 expression was investigated using flow cytometry, Western blotting and confocal microscopy. DHA and EPA inhibited the growth of all three breast cancer cell lines in a dose-dependent fashion (P < 0.05). DHA, and to a lesser extent EPA, induced the movement and raft clustering of CD95 in the cell membrane (via confocal microscopy) and the surface expression (via flow cytometry) in MDA-MB-231 cells. Neither fatty acid altered the growth/metabolic activity of the non-transformed MCF-12A breast cell line. Pre-treatment with DHA, but not EPA, improved the efficacy of dox in estrogen receptor negative MDA-MB-231 cells (P < 0.05), but not in the other two cell lines. Pre-treating cells with DHA increased CD95 surface expression (threefold) and the plasma membrane raft content of CD95 (2fold) and FADD (>4-fold) after dox treatment, compared to dox treatment alone (P < 0.05). This study demonstrated that pre-treatment of estrogen receptor negative MDA-MB-231 cells with DHA increased the anti-cancer effects of dox and presents evidence to suggest that this may be mediated in part by CD95-induced apoptosis.

Globally, there were 14.1 million new cancer diagnoses and 8.2 million cancer deaths in 2012. For many cancers, conventional therapies are limited in their successes and an improved understanding of disease progression is needed in conjunction with exploration of alternative therapies. The long chain polyunsaturated fatty acid, docosahexaenoic acid (DHA), has been shown to enhance many cellular responses that reduce cancer cell viability and decrease proliferation both in vitro and in vivo. A small number of studies suggest that DHA improves chemotherapy outcomes in cancer patients. It is readily incorporated into cancer cell membranes and, as a result there has been considerable research regarding cell membrane initiated events. For example, DHA has been shown to mediate the induction of apoptosis/reduction of proliferation in vitro and in vivo. However, there is limited research into the effect of DHA on cell cycle regulation in cancer cells and the mechanism(s) by which DHA acts are not fully understood. The purpose of the current review is to provide a critical examination of the literature investigating the ability of DHA to stall progression during different cell cycle phases in cancer cells, as well as the consequences that these changes may have on tumour growth, independently and in conjunction with chemotherapy.

Background Docosahexaenoic acid (DHA) has been shown to reduce growth of breast cancer cells in vitro and in vivo; it may also benefit the action of cytotoxic cancer drugs. The mechanisms for these observations are not completely understood. Objectives We sought to explore how pretreatment of MDA-MB-231 breast cancer cells with DHA alters gene expression with doxorubicin (DOX) treatment and confirm that feeding DHA to tumor-bearing nu/nu mice improves the efficacy of DOX. Methods MDA-MB-231 cells were subjected to 4 conditions: a control mixture of 40 μM linoleic and 40 μM oleic acid (OALA), DHA (60 μM plus OALA), OALA DOX (0.41 μM), or DHA DOX (plus OALA) and assessed for effects on viability and function. Female nu/nu mice (6 wk old) bearing MDA-MB-231 tumors were randomly assigned to a nutritionally complete diet (20 g ± 2.8 g DHA/100 g diet) containing a polyunsaturated:saturated fat ratio of 0.5, with or without injections 2 times/wk of 5 mg DOX/kg for 4 wk. Results Microarray and protein analysis indicated that DHA DOX cells, compared with OALA DOX, had upregulated expression of apoptosis genes, Caspase-10 (1.3-fold), Caspase-9 (1.4-fold), and Receptor (TNFRSF)-interacting serine-threonine kinase 1 (RIPK1) (1.2-fold), while downregulating cell cycle genes, Cyclin B1 (−2.1-fold), WEE1 (−1.6-fold), and cell division cycle 25 homolog C (CDC25C) (−1.8-fold) (P < 0.05). DHA DOX–treated mice had 50% smaller tumors than control mice (P < 0.05). Analysis of proapoptotic proteins from tumors of DHA DOX mice showed increased Caspase-10 (by 68%) and BH3 interacting domain death agonist (Bid) (by 50%), decreased B-cell CLL/lymphoma 2 (BCL2) (by 24%), and decreased cell cycle proteins Cyclin B1 and Cdc25c (both by 42%), compared with control mice (P < 0.05). Conclusions Supplementation with DHA facilitates the action of DOX in MDA-MB-231 cells and in nu/nu mice, which may occur via amplification of the effect of DOX on apoptosis and cell cycle genes.

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To better understand how docosahexaenoic acid (DHA) improves the effects of doxorubicin (DOX), we examined DHA AE DOX on changes in whole cell and lipid raft phospholipids (PL) of MDA-MB-231 and MCF-7 breast cancer cells. We sought to confirm whether the relative changes in PL DHA content of MDA-MB-231 cells could be extended to PL from MDA-MB-231 tumors grown in mice fed a DHA supplemented diet AEDOX. Treatment with DHA did not change PL composition yet DOX increased the proportion of phosphatidylserine in MCF-7 cell lipid rafts by twofold (p < 0.001). Regardless of DOX, the relative percent incorporation of DHA was higher in MDA-MB-231 cells compared to MCF-7 cells in phosphatidylserine, phosphatidylethanolamine, and phosphatidylcholine (whole cell and lipid rafts); and higher in phosphatidylethanolamine vs. phosphatidylcholine (4.4-fold in MCF-7 and 6-fold in MDA-MB-231 cells respectively). DHA treatment increased eicosapentaenoic acid and docosapentaenoic acid in MDA-MB-231 cells but not MCF-7 cells. Increased DHA content in MDA-MB-231 cells, MCF-7 cells, and MDA-MB-231 tumors in all PL moieties (except sphingomyelin) corresponded with reduced arachidonic acid (p < 0.05). Feeding mice 2.8% (w/w of fat) DHA AE DOX increased tumor necrotic regions