br Melanoma cell lines There is suggestive
Melanoma cell lines There is suggestive epidemiological evidence that omega-3 PUFA can be preventative against melanoma, although the mechanisms of this relationship has not been extensively investigated , . A 2014 study demonstrated that DHA inhibited cell proliferation in vitro in A2058, A375, and SK-Mel 3 human skin melanoma cell lines and also revealed that DHA was efficacious in reducing tumor size in vivo, as tumors from animals fed diets enriched with DHA were 69 and 76% smaller in weight and volume, respectively, compared to those from animals fed diets enriched in omega-6 FA from coconut oil . GW9508 significantly reduced proliferation of all three cell lines, however, the authors found only what was described as “negligible” levels of FFA4 transcript in these cells, while FFA1 expression was abundant, suggesting that DHA and GW9508 effects seen here were solely mediated by FFA1. Following their investigation of FFA4 and FFA1 involvement in pancreatic cancer tumorigenicity, Fukushima and colleagues subsequently studied the roles of both FFA4 and FFA1 in A375 and G361 human skin melanoma cell lines . Here, unlike the previous results of Nehra and colleagues , in addition to FFA1, FFA4 transcript was noted to be expressed in A375 atrial natriuretic peptide receptor and G361 cells, the latter of which were not used in the previous study . GW9508 reduced cell proliferation only in G361 cells at the higher concentration used (10 μM) and only inhibited cell migration in G361 cells. Meanwhile, GW9508 in combination with the FFA1 antagonist GW1100 strongly inhibited cell migration in both melanoma cell lines, suggesting that FFA4 modulates anti-invasive properties in these cells . Treatment of both cell lines with tumor promoting agent 12-O-tetradecanolphorbol-13-acetate (TPA) resulted in significantly higher cell migration in A375 and significantly lower migration in G361 cells. Quantitative real-time PCR revealed that acute TPA treatment in A375 cells induced significantly higher FFA1 expression compared to untreated cells, while FFA4 expression did not change. Meanwhile, acute TPA treatment in G361 cells induced significant elevations in both FFA4 and FFA1 transcripts . In A375 cells, knockdown of FFA4 decreased cell proliferation and increased cell migration, which was enhanced by GW9508 treatment. Meanwhile, GW9508 increased migration in TPA-primed cells, and this effect was amplified by FFA4-KD, suggesting that FFA4 regulates inhibitory control over cell proliferation and migration. Additionally, TPA-induced robust MMP-9 activation, which was inhibited by FFA4 KD. Together, these results shown that FFA4 and FFA1 work in opposition to respectively inhibit and enhance TPA-induced migration in melanoma cells.
Breast cancer cell lines Dietary fat intake has been closely related to epidemiological risk of breast cancer development, and higher consumption of dietary omega-3 PUFA from marine sources is associated with a lower incidence of breast cancer , , , , . Additionally, omega-3 PUFAs have been shown to inhibit growth of breast cancer cells in culture and also slow the growth of breast tumor xenografts , , , . Prior to identification of FFA receptors, the mechanisms of omega-3 PUFA on breast cancer cells were thought to include induction of apoptosis and DNA fragmentation, as well as alterations to AKT and NF-κB signaling . These findings were in opposition to those that showed that omega-6 PUFA, such as linoleic acid (LA), induce inflammation, proliferation, EMT, and migration in breast cancer cell lines , , , . Initially, it was reported that both FFA4 and FFA1 are expressed in both tumorigenic MCF-7 breast cancer, as well as non-tumorigenic epithelial MCF10A cell lines , suggesting that these receptors may modulate the activities of PUFA seen in breast tissue. Previous work has also demonstrated that the omega-9 PUFA oleic acid (OA) induced proliferation, ERK1/2 phosphorylation, and activation of the transcription factor AP-1 in MCF-7 cells, but not in MCF10A cells, in a manner that was dependent on transactivation of EGFR and the non-receptor tyrosine-kinase Src . However, this study did not examine the direct role of FFA4 or FFA1 in the effects of OA, and only presumed that one or both of the receptors modulated these activities. Hopkins and colleagues revealed that while FFA1 transcript is present in both MCF-7 and MDA-MB-231 (MDA) cells, FFA4 transcript and protein is only present to a relatively lower degree . Experiments measuring the ability of TUG-891 or GW9508 to inhibit LPA-induced proliferation in breast cancer cells demonstrated that both agents inhibited the LPA-effect in a dose dependent manner. However, TUG-891 produced a shallow dose-response, consistent with activity at a non-uniform population of receptors (i.e., agonism of both FFA1 and FFA4), and also required 100-fold higher concentrations than that seen in DU145 prostate cancer cells to fully inhibit the mitogenic effects of LPA . Meanwhile, GW9508 demonstrated an IC50 of 16 nM at inhibiting the effect of LPA in MDA cells, consistent with its published EC50 of 50 nM. On the contrary to that seen with TUG891, this effect was 100-fold more potent in breast cancer cells as opposed to DU145, and taken together, these data suggest that FFA1, rather than FFA4, plays the major role in inhibition of LPA-induced proliferation of MDA cells. This hypothesis was consistent with observations that GW9508 also fully inhibited LPA-induced migration in MCF-7 cells . Chung and colleagues assessed the in vivo role of FFA4 in mediating dietary PUFA-induced reduction in mammary tumors . This group used orthopic injection of Py230 breast cancer cell lines into ovariectomized immune-component mice in order to stimulate diet- or genetic- induced obesity that promotes inflammation and mammary tumors. While omega-3 PUFA inhibited mammary tumor growth through induction of apoptosis, employing an elegant study design that made use of FFA4+-Py230 tumor injection into FFA−/− mice, the authors reveal that the effects seen were completely independent of FFA4 .