Docosahexaenoic Acid in the Inhibition of Tumor Cell Growth in Preclinical Models of Ovarian Cancer

The association between oxidized low-density lipoprotein and cancer: An emerging targeted therapeutic approach?

Lipids play an important role in varying vital cellular processes including cell growth and division. Elevated levels of low-density lipoprotein (LDL) and oxidized-LDL (ox-LDL), and overexpression of the corresponding receptors including LDL receptor (LDLR), lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1), and cluster of differentiation 36 (CD36), have shown strong correlations with different facets of carcinogenesis including proliferation, invasion, and angiogenesis. Furthermore, a high serum level of LOX-1 is considered as a poor prognostic factor in many types of cancer including colorectal cancer. Ox-LDL could contribute to cancer progression and metastasis through endothelial-to-mesenchymal transition (EMT) and autophagy. Thus, many studies have shed light on the significant role of ox-LDL as a potential therapeutic target for cancer therapy. In various repurposing approaches, anti-dyslipidemia agents, phytochemicals, autophagy modulators as well as recently developed ldl-like nanoparticles have been investigated as potential tumor therapeutic agents by targeting oxidized-LDL/LOX-1 pathways. Herein, we reviewed the role of oxidized-LDL and LOX-1 in cancer progression, invasion, metastasis, and also cancer-associated angiogenesis. Moreover, we addressed therapeutic utility of several compounds that proved to be capable of targeting the metabolic moieties in cancer. This review provides insights on the potential impact of targeting LDL and ox-LDL in cancer therapy and their future biomedical implementations.

ASC/inflammasome-independent pyroptosis in ovarian cancer cells through translational augmentation of caspase-1

Canonical pyroptosis is type of programmed cell death depending on active caspase-1, and the inflammasome carries out caspase-1 activation. Here, we showed that docosahexaenoic acid (DHA) induced ovarian cancer cell deaths in caspase-1-dependent manner. DHA increased caspase-1 activity and led to interleukin-1β secretion and gasdermin D cleavage while disulfiram inhibited DHA-induced cell death, suggesting that DHA triggered pyroptosis. Intriguingly, ASC, the molecule recruiting caspase-1 to inflammasome for activation, was dispensable for DHA-induced pyroptosis. Instead, we observed remarkable elevation in caspase-1 abundance concurrent with the activation of caspase-1 in DHA-treated cells. As ectopically overexpressing caspase-1 resulted in robust amount of active caspase-1, we reason that DHA activates caspase-1 and pyroptosis through the generation of excessive amount of caspase-1 protein. Mechanistically, DHA increased caspase-1 by specifically accelerating caspase-1 protein synthesis via the p38MAPK/Mnk1 signaling pathway. We have uncovered an unknown pyroptosis mechanism in which caspase-1-dependent pyroptosis can occur without the participation of ASC/inflammasome.

Vitamin D and docosahexaenoic acid inhibit proliferation of the ovarian cancer cell line OVCAR4

BACKGROUND

Ovarian cancer is one of the deadliest cancers in women. Improved preventative, diagnostic, and therapeutic strategies are needed. Certain dietary patterns and nutrients such as vitamin D and omega-3 fatty acids are associated with reduced cancer risk, but their effects on ovarian cancer remain to be fully elucidated, and their combined effects have not been explored.

AIM

To determine the individual and combined effects of the active vitamin D metabolite, calcitriol, and the omega-3 fatty acid, docosahexaenoic acid, on cell growth, and the abundance of the vitamin D receptor (VDR), proteins that modulate cell cycle progression, and apoptotic markers.

METHODS

OVCAR4 cells, a model of ovarian cancer, were treated with calcitriol, and docosahexaenoic acid, either alone or in combination. Effects on cell growth were determined by the sulforhodamine B assay. Changes in VDR, the cell cycle promotor c-Myc, the cell cycle inhibitor p27 and cleaved PARP, were determined by Western blotting.

RESULTS

While OVCAR4 cell growth was inhibited by individual treatment with either calcitriol or docosahexaenoic acid, the combined treatment revealed enhanced growth inhibition as compared to either treatment alone. Furthermore, long-term treatment (12 days) yielded stronger growth inhibition at lower concentrations as compared to short-term treatments (3 days). Accompanying this growth inhibition was a decrease in c-Myc, and an increase in p27.

CONCLUSIONS

The observed reduction in cell growth mediated by calcitriol and docosahexaenoic acid highlights the need for further research utilizing these nutrients, alone and especially in combination, to support ovarian cancer prevention and treatment.

Lysophosphatidylcholine-DHA Specifically Induces Cytotoxic Effects of the MDA-MB-231 Human Breast Cancer Cell Line In Vitro-Comparative Effects with Other Lipids Containing DHA

Docosahexaenoic acid (DHA, C22:6 ω-3) is a dietary polyunsaturated fatty acid that has an important role in human health. Epidemiological studies linked a high intake of DHA to a reduced risk of certain cancers. Recently, attention focused on how the lipid carrier in which DHA is delivered, i.e., esterified on acylglycerols, phospholipids, or free, affects its biological effects. However, studies comparing the effects of these different forms for DHA supply to cancer cells in vitro are limited. In this study, the effect of free DHA and five lipids carrying one to three DHA chains (LPC-DHA, PC-DHA, MAG-DHA, DAG-DHA and TAG-DHA) on the viability of the MDA-MB-231 breast cancer cell line was compared. Our results revealed a strong structure-function relationship of DHA-carrying lipids on the viability of MDA-MB-231 cells. Glycerophosphocholine-based lipids are the most effective DHA carriers in reducing the viability of MDA-MB-231 cells, with LPC-DHA being more effective (IC₅₀ = 23.7 µM) than PC-DHA (IC₅₀ = 67 µM). The other tested lipids are less toxic (MAG-DHA, free DHA) or even not toxic (DAG-DHA, TAG-DHA) under our conditions. Investigating the mechanism of cell death induced by LPC-DHA revealed increased oxidative stress and membrane cell damage.

Nutraceutical-Based Nanoformulations for Breast and Ovarian Cancer Treatment

Different strategies have been investigated for a more satisfactory treatment of advanced breast cancer, including the adjuvant use of omega-3 polyunsaturated fatty acids (PUFAs). These nutritional compounds have been shown to possess potent anti-inflammatory and antiangiogenic activities, the capacity to affect transduction pathways/receptors involved in cell growth and to reprogram tumor microenvironment. Omega-3 PUFA-containing nanoformulations designed for drug delivery in breast cancer were shown to potentiate the effects of enclosed drugs, enhance drug delivery to target sites, and minimize drug-induced side effects. We have critically analyzed here the results of the most recent studies investigating the effects of omega-3 PUFA-containing nanoformulations in breast cancer. The anti-neoplastic efficacy of omega-3 PUFAs has also been convincingly demonstrated by using preclinical in vivo models of ovarian cancer. The results obtained are critically analyzed here and seem to provide a sufficient rationale to move to still lacking interventional clinical trials, as well as to evaluate possible advantages of enclosing omega-3 PUFAs to drug-delivery nanosystems for ovarian cancer. Future perspectives in this area are also provided.

Lipid-based regulators of immunity

Lipids constitute a diverse class of molecular regulators with ubiquitous physiological roles in sustaining life. These carbon-rich compounds are primarily sourced from exogenous sources and may be used directly as structural cellular building blocks or as a substrate for generating signaling mediators to regulate cell behavior. In both of these roles, lipids play a key role in both immune activation and suppression, leading to inflammation and resolution, respectively. The simple yet elegant structural properties of lipids encompassing size, hydrophobicity, and molecular weight enable unique biodistribution profiles that facilitate preferential accumulation in target tissues to modulate relevant immune cell subsets. Thus, the structural and functional properties of lipids can be leveraged to generate new materials as pharmacological agents for potently modulating the immune system. Here, we discuss the properties of three classes of lipids: polyunsaturated fatty acids, short-chain fatty acids, and lipid adjuvants. We describe their immunoregulatory functions in modulating disease pathogenesis in preclinical models and in human clinical trials. We conclude with an outlook on harnessing the diverse and potent immune modulating properties of lipids for immunoregulation.