Arachidonic Acid Induces the Migration of MDA-MB-231 Cells by Activating Raft-associated Leukotriene B4 Receptors

ACSL4-Mediated Membrane Phospholipid Remodeling Induces Integrin β1 Activation to Facilitate Triple-Negative Breast Cancer Metastasis

Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer and has a poor prognosis and a high propensity to metastasize. Lipid metabolism has emerged as a critical regulator of tumor progression and metastasis in other cancer types. Characterization of the lipid metabolic features of TNBC could provide important insights into the drivers of TNBC metastasis. Here, we showed that metastatic TNBC tumors harbor more unsaturated phospholipids, especially long-chain polyunsaturated fatty acids, at the sn-2 position of phosphatidylcholine and phosphatidylethanolamine compared with primary tumors. Metastatic TNBC tumors upregulated ACSL4, a long-chain polyunsaturated acyl-CoA synthetase that drives the preferential incorporation of polyunsaturated fatty acids into phospholipids, resulting in the alteration of membrane phospholipid composition and properties. Moreover, ACSL4-mediated phospholipid remodeling of the cell membrane induced lipid-raft localization and activation of integrin β1 in a CD47-dependent manner, which led to downstream focal adhesion kinase phosphorylation that promoted metastasis. Importantly, pharmacologic inhibition of ACSL4 suppressed tumor growth and metastasis and increased chemosensitivity in TNBC models in vivo. These findings indicate that ACSL4-mediated phospholipid remodeling enables TNBC metastasis and can be inhibited as a potential strategy to improve the efficacy of chemotherapy in TNBC.

SIGNIFICANCE

ACSL4 upregulation in triple-negative breast cancer alters cell membrane phospholipid composition to increase integrin β1 activation and drive metastasis, indicating that targeting ACSL4 could potentially block metastasis and improve patient outcomes.

Mechanism of ferroptosis in breast cancer and research progress of natural compounds regulating ferroptosis

Breast cancer is the most prevalent cancer worldwide and its incidence increases with age, posing a significant threat to women's health globally. Due to the clinical heterogeneity of breast cancer, the majority of patients develop drug resistance and metastasis following treatment. Ferroptosis, a form of programmed cell death dependent on iron, is characterized by the accumulation of lipid peroxides, elevated levels of iron ions and lipid peroxidation. The underlying mechanisms and signalling pathways associated with ferroptosis are intricate and interconnected, involving various proteins and enzymes such as the cystine/glutamate antiporter, glutathione peroxidase 4, ferroptosis inhibitor 1 and dihydroorotate dehydrogenase. Consequently, emerging research suggests that ferroptosis may offer a novel target for breast cancer treatment; however, the mechanisms of ferroptosis in breast cancer urgently require resolution. Additionally, certain natural compounds have been reported to induce ferroptosis, thereby interfering with breast cancer. Therefore, this review not only discusses the molecular mechanisms of multiple signalling pathways that mediate ferroptosis in breast cancer (including metastasis, invasion and proliferation) but also elaborates on the mechanisms by which natural compounds induce ferroptosis in breast cancer. Furthermore, this review summarizes potential compound types that may serve as ferroptosis inducers in future tumour cells, providing lead compounds for the development of ferroptosis-inducing agents. Last, this review proposes the potential synergy of combining natural compounds with traditional breast cancer drugs in the treatment of breast cancer, thereby suggesting future directions and offering new insights.

Narirutin downregulates lipoxygenase-5 expression and induces G0/G1 arrest in triple-negative breast carcinoma cells

BACKGROUND

Triple-negative breast cancer (TNBC) accounts for 20% of breast cancer that does not express HER2, progesterone and estrogen receptors. It is associated with a high mortality rate, morbidity, metastasis, recurrence, poor prognosis and resistance to chemotherapy. Lipoxygenase-5 (LOX-5), cyclooxygenase-2 (COX-2), cathepsin-D (CATD), ornithine decarboxylase (ODC) and dihydrofolate reductase (DHFR) are involved in breast cancer carcinogenesis; hence, there is a pressing need to identify novel chemicals that targets these enzymes. Narirutin, a flavanone glycoside abundantly present in citrus fruits, is reported to have immune-modulatory, anti-allergic and antioxidant potential. Still, the cancer chemopreventive mechanism against TNBC has not been explored.

METHODS

In vitro experiments, enzyme activity, expression analysis, molecular docking and MD simulation were carried out.

RESULTS

Narirutin suppressed the growth of MDA-MB-231 and MCF-7 in a dose-proportional manner. The pronounced effect with >50% inhibition was observed in SRB and MTT assays for MDAMB-231 cells. Unexpectedly, narirutin suppressed the proliferation of normal cells (24.51%) at 100 μM. Further, narirutin inhibits the activity of LOX-5 in cell-free (18.18 ± 3.93 μM) and cell-based (48.13 ± 7.04 μM) test systems while moderately affecting COX-2, CATD, ODC and DHFR activity. Moreover, narirutin revealed a down-regulation of LOX-5 expression with a fold change of 1.23. Besides, MD simulation experiments confirm that narirutin binding forms a stable complex with LOX-5 and improves the stability and compactness of LOX-5. In addition, the prediction analysis demonstrates that narirutin could not cross the blood-brain barrier and did not act as an inhibitor of different CYPs.

CONCLUSIONS AND SIGNIFICANCE

Narirutin could be a potent cancer chemopreventive lead for TNBC, further paving the way for synthesizing novel analogues.

MicroRNA miR-1275 coordinately regulates AEA/LPA signals via targeting FAAH in lipid metabolism reprogramming of gastric cancer

Glycerophospholipid signal and fatty acid metabolism are closely related to the occurrence and progression of tumours, and metabolic reprogramming caused by hydrolytic enzymes plays an important role in gastric cancer (GC). Here, we performed whole transcriptome sequencing and combined qRT-PCR to screen out the significantly high expression of fatty acid amide hydrolase (FAAH) in GC tissues, which was further verified in both TCGA and Oncomine databases. Functional tests confirmed that FAAH played an oncogene role in GC, and silencing FAAH could delay tumour growth, inhibit tumour metastasis, and promote cell apoptosis both in vitro and in vivo. FAAH-mediated lipid metabolism reprogramming through coordinated regulation of arachidonoyl ethanolamide (AEA)/lysophosphatidic acid (LPA) signalling and activated the cyclooxygenase-2 (COX-2)/prostaglandin E2 (PGE2) axis to promote GC progression. Luciferase reporter assay and immunofluorescence-fluorescence in situ hybridization (IF-FISH) were applied to validate the interactions of miR-1275/FAAH. Overexpression and knockdown of miR-1275 in vitro could indirectly modulate the above lipid signalling by targeting FAAH, thereby affecting GC progression. Our study indicates that deregulated FAAH is a key lipid signal and the miR-1275/FAAH/AEA/LPA axis can serve as a diagnostic biomarker for GC or as a target for therapy development.

Emerging role of ferroptosis in breast cancer: New dawn for overcoming tumor progression

Breast cancer has become a serious threat to women's health. Cancer progression is mainly derived from resistance to apoptosis induced by procedures or therapies. Therefore, new drugs or models that can overcome apoptosis resistance should be identified. Ferroptosis is a recently identified mode of cell death characterized by excess reactive oxygen species-induced lipid peroxidation. Since ferroptosis is distinct from apoptosis, necrosis and autophagy, its induction successfully eliminates cancer cells that are resistant to other modes of cell death. Therefore, ferroptosis may become a new direction around which to design breast cancer treatment. Unfortunately, the complete appearance of ferroptosis in breast cancer has not yet been fully elucidated. Furthermore, whether ferroptosis inducers can be used in combination with traditional anti- breast cancer drugs is still unknown. Moreover, a summary of ferroptosis in breast cancer progression and therapy is currently not available. In this review, we discuss the roles of ferroptosis-associated modulators glutathione, glutathione peroxidase 4, iron, nuclear factor erythroid-2 related factor-2, superoxide dismutases, lipoxygenase and coenzyme Q in breast cancer. Furthermore, we provide evidence that traditional drugs against breast cancer induce ferroptosis, and that ferroptosis inducers eliminate breast cancer cells. Finally, we put forward prospect of using ferroptosis inducers in breast cancer therapy, and predict possible obstacles and corresponding solutions. This review will deepen our understanding of the relationship between ferroptosis and breast cancer, and provide new insights into breast cancer-related therapeutic strategies.

Sex Differences in Pulmonary Eicosanoids and Specialized Pro-Resolving Mediators in Response to Ozone Exposure

Ozone (O3) is a criteria air pollutant known to increase the morbidity and mortality of cardiopulmonary diseases. This occurs through a pulmonary inflammatory response characterized by increased recruitment of immune cells into the airspace, pro-inflammatory cytokines, and pro-inflammatory lipid mediators. Recent evidence has demonstrated sex-dependent differences in the O3-induced pulmonary inflammatory response. However, it is unknown if this dimorphic response is evident in pulmonary lipid mediator metabolism. We hypothesized that there are sex-dependent differences in lipid mediator production following acute O3 exposure. Male and female C57BL/6J mice were exposed to 1 part per million O3 for 3 hours and were necropsied at 6 or 24 hours following exposure. Lung lavage was collected for cell differential and total protein analysis, and lung tissue was collected for mRNA analysis, metabololipidomics, and immunohistochemistry. Compared to males, O3-exposed female mice had increases in airspace neutrophilia, neutrophil chemokine mRNA, pro-inflammatory eicosanoids such as prostaglandin E2, and specialized pro-resolving mediators (SPMs) such as resolvin D5 in lung tissue. Likewise, precursor fatty acids (arachidonic and docosahexaenoic acid; DHA) were increased in female lung tissue following O3 exposure compared to males. Experiments with ovariectomized females revealed that loss of ovarian hormones exacerbates pulmonary inflammation and injury. However, eicosanoid and SPM production were not altered by ovariectomy despite depleted pulmonary DHA concentrations. Taken together, these data indicate that O3 drives an increased pulmonary inflammatory and bioactive lipid mediator response in females. Furthermore, ovariectomy increases susceptibility to O3-induced pulmonary inflammation and injury, as well as decreases pulmonary DHA concentrations.

Arachidonic Acid Attenuates Cell Proliferation, Migration and Viability by a Mechanism Independent on Calcium Entry

Arachidonic acid (AA) is a phospholipase A2 metabolite that has been reported to mediate a plethora of cellular mechanisms involved in healthy and pathological states such as platelet aggregation, lymphocyte activation, and tissue inflammation. AA has been described to activate Ca²⁺ entry through the arachidonate-regulated Ca²⁺-selective channels (ARC channels). Here, the analysis of the changes in the intracellular Ca²⁺ homeostasis revealed that, despite MDA-MB-231 cells expressing the ARC channel components Orai1, Orai3, and STIM1, AA does not evoke Ca²⁺ entry in these cells. We observed that AA evokes Ca²⁺ entry in MDA-MB-231 cells transiently expressing ARC channels. Nevertheless, MDA-MB-231 cell treatment with AA reduces cell proliferation and migration while inducing cell death through apoptosis. The latter mostly likely occurs via mitochondria membrane depolarization and the activation of caspases-3, -8, and -9. Altogether, our results indicate that AA exerts anti-tumoral effects on MDA-MB-231 cells, without having any effect on non-tumoral breast epithelial cells, by a mechanism that is independent on the activation of Ca²⁺ influx via ARC channels.