Secreted phospholipases A₂are differentially expressed and epigenetically silenced in human breast cancer cells

Calcein release from DPPC liposomes by phospholipase A2 activity: Effect of cholesterol and amphipathic copolymers

In this study, we evaluated the impact of incorporating diblock and triblock amphiphilic copolymers, as well as cholesterol into DPPC liposomes on the release of a model molecule, calcein, mediated by exogenous phospholipase A2 activity. Our findings show that calcein release slows down in the presence of copolymers at low concentration, while at high concentration, the calcein release profile resembles that of the DPPC control. Additionally, calcein release mediated by exogenous PLA2 decreases as the amount of solubilized cholesterol increases, with a maximum between 18 mol% and 20 mol%. At concentrations higher than 24 mol%, no calcein release was observed. Studies conducted on HEK-293 and HeLa cells revealed that DPPC liposomes reduced viability by only 5% and 12%, respectively, after 3 hours of incubation, while DPPC liposome in presence of 33 mol% of Cholesterol reduced viability by approximately 11% and 23%, respectively, during the same incubation period. For formulations containing copolymers at low and high concentrations, cell viability decreased by approximately 20% and 40%, respectively, after 3 hours of incubation. Based on these preliminary results, we can conclude that the presence of amphiphilic copolymers at low concentration can be used in the design of new DPPC liposomes, and together with cholesterol, they can modulate liposome stabilization. The new formulations showed low cytotoxicity in HEK-293 cells, and it was observed that calcein release depended entirely on PLA2 activity and the presence of calcium ions.

An evolutionary learning-based method for identifying a circulating miRNA signature for breast cancer diagnosis prediction

Breast cancer (BC) is one of the most commonly diagnosed cancers worldwide. As key regulatory molecules in several biological processes, microRNAs (miRNAs) are potential biomarkers for cancer. Understanding the miRNA markers that can detect BC may improve survival rates and develop new targeted therapeutic strategies. To identify a circulating miRNA signature for diagnostic prediction in patients with BC, we developed an evolutionary learning-based method called BSig. BSig established a compact set of miRNAs as potential markers from 1280 patients with BC and 2686 healthy controls retrieved from the serum miRNA expression profiles for the diagnostic prediction. BSig demonstrated outstanding prediction performance, with an independent test accuracy and area under the receiver operating characteristic curve were 99.90% and 0.99, respectively. We identified 12 miRNAs, including hsa-miR-3185, hsa-miR-3648, hsa-miR-4530, hsa-miR-4763-5p, hsa-miR-5100, hsa-miR-5698, hsa-miR-6124, hsa-miR-6768-5p, hsa-miR-6800-5p, hsa-miR-6807-5p, hsa-miR-642a-3p, and hsa-miR-6836-3p, which significantly contributed towards diagnostic prediction in BC. Moreover, through bioinformatics analysis, this study identified 65 miRNA-target genes specific to BC cell lines. A comprehensive gene-set enrichment analysis was also performed to understand the underlying mechanisms of these target genes. BSig, a tool capable of BC detection and facilitating therapeutic selection, is publicly available at https://github.com/mingjutsai/BSig.

A Review of Rattlesnake Venoms

Venom components are invaluable in biomedical research owing to their specificity and potency. Many of these components exist in two genera of rattlesnakes, Crotalus and Sistrurus, with high toxicity and proteolytic activity variation. This review focuses on venom components within rattlesnakes, and offers a comparison and itemized list of factors dictating venom composition, as well as presenting their known characteristics, activities, and significant applications in biosciences. There are 64 families and subfamilies of proteins present in Crotalus and Sistrurus venom. Snake venom serine proteases (SVSP), snake venom metalloproteases (SVMP), and phospholipases A2 (PLA2) are the standard components in Crotalus and Sistrurus venom. Through this review, we highlight gaps in the knowledge of rattlesnake venom; there needs to be more information on the venom composition of three Crotalus species and one Sistrurus subspecies. We discuss the activity and importance of both major and minor components in biomedical research and drug development.

Smart nanoparticles for cancer therapy

Smart nanoparticles, which can respond to biological cues or be guided by them, are emerging as a promising drug delivery platform for precise cancer treatment. The field of oncology, nanotechnology, and biomedicine has witnessed rapid progress, leading to innovative developments in smart nanoparticles for safer and more effective cancer therapy. In this review, we will highlight recent advancements in smart nanoparticles, including polymeric nanoparticles, dendrimers, micelles, liposomes, protein nanoparticles, cell membrane nanoparticles, mesoporous silica nanoparticles, gold nanoparticles, iron oxide nanoparticles, quantum dots, carbon nanotubes, black phosphorus, MOF nanoparticles, and others. We will focus on their classification, structures, synthesis, and intelligent features. These smart nanoparticles possess the ability to respond to various external and internal stimuli, such as enzymes, pH, temperature, optics, and magnetism, making them intelligent systems. Additionally, this review will explore the latest studies on tumor targeting by functionalizing the surfaces of smart nanoparticles with tumor-specific ligands like antibodies, peptides, transferrin, and folic acid. We will also summarize different types of drug delivery options, including small molecules, peptides, proteins, nucleic acids, and even living cells, for their potential use in cancer therapy. While the potential of smart nanoparticles is promising, we will also acknowledge the challenges and clinical prospects associated with their use. Finally, we will propose a blueprint that involves the use of artificial intelligence-powered nanoparticles in cancer treatment applications. By harnessing the potential of smart nanoparticles, this review aims to usher in a new era of precise and personalized cancer therapy, providing patients with individualized treatment options.

Lipid droplets control mitogenic lipid mediator production in human cancer cells

OBJECTIVES

Polyunsaturated fatty acids (PUFAs) are structural components of membrane phospholipids and precursors of oxygenated lipid mediators with diverse functions, including the control of cell growth, inflammation and tumourigenesis. However, the molecular pathways that control the availability of PUFAs for lipid mediator production are not well understood. Here, we investigated the crosstalk of three pathways in the provision of PUFAs for lipid mediator production: (i) secreted group X phospholipase A2 (GX sPLA2) and (ii) cytosolic group IVA PLA2 (cPLA2α), both mobilizing PUFAs from membrane phospholipids, and (iii) adipose triglyceride lipase (ATGL), which mediates the degradation of triacylglycerols (TAGs) stored in cytosolic lipid droplets (LDs).

METHODS

We combined lipidomic and functional analyses in cancer cell line models to dissect the trafficking of PUFAs between membrane phospholipids and LDs and determine the role of these pathways in lipid mediator production, cancer cell proliferation and tumour growth in vivo.

RESULTS

We demonstrate that lipid mediator production strongly depends on TAG turnover. GX sPLA2 directs ω-3 and ω-6 PUFAs from membrane phospholipids into TAG stores, whereas ATGL is required for their entry into lipid mediator biosynthetic pathways. ATGL controls the release of PUFAs from LD stores and their conversion into cyclooxygenase- and lipoxygenase-derived lipid mediators under conditions of nutrient sufficiency and during serum starvation. In starving cells, ATGL also promotes the incorporation of LD-derived PUFAs into phospholipids, representing substrates for cPLA2α. Furthermore, we demonstrate that the built-up of TAG stores by acyl-CoA:diacylglycerol acyltransferase 1 (DGAT1) is required for the production of mitogenic lipid signals that promote cancer cell proliferation and tumour growth.

CONCLUSION

This study shifts the paradigm of PLA2-driven lipid mediator signalling and identifies LDs as central lipid mediator production hubs. Targeting DGAT1-mediated LD biogenesis is a promising strategy to restrict lipid mediator production and tumour growth.

The Phospholipase A2 Superfamily: Structure, Isozymes, Catalysis, Physiologic and Pathologic Roles

The phospholipase A2 (PLA2) superfamily of phospholipase enzymes hydrolyzes the ester bond at the sn-2 position of the phospholipids, generating a free fatty acid and a lysophospholipid. The PLA2s are amphiphilic in nature and work only at the water/lipid interface, acting on phospholipid assemblies rather than on isolated single phospholipids. The superfamily of PLA2 comprises at least six big families of isoenzymes, based on their structure, location, substrate specificity and physiologic roles. We are reviewing the secreted PLA2 (sPLA2), cytosolic PLA2 (cPLA2), Ca²⁺-independent PLA2 (iPLA2), lipoprotein-associated PLA2 (LpPLA2), lysosomal PLA2 (LPLA2) and adipose-tissue-specific PLA2 (AdPLA2), focusing on the differences in their structure, mechanism of action, substrate specificity, interfacial kinetics and tissue distribution. The PLA2s play important roles both physiologically and pathologically, with their expression increasing significantly in diseases such as sepsis, inflammation, different cancers, glaucoma, obesity and Alzheimer's disease, which are also detailed in this review.

Ferroptosis and triple-negative breast cancer: Potential therapeutic targets

Purpose

Triple-negative breast cancer (TNBC) is an aggressive tumor with poor prognosis, it has higher recurrence and metastatic rates than other breast cancer subtypes. This study aims to investigate biomarkers and potential targets for TNBC related to ferroptosis through data mining and bioinformatics analysis. The findings may provide new insights for treating TNBC.

Methods

The TNBC patients' data from the Cancer Genome Atlas (TCGA) database were extracted for differential expression and prognosis analysis. Consensus genes obtained by intersecting differential expressed and ferroptosis-related genes was used to establish the prognostic model by the univariate and multivariate Cox analyses. Besides, TNBC data from the Gene Expression Omnibus (GEO) database was used to confirm the reliability of the prognosis model. Moreover, clinical information was analyzed by multifactorial independent analysis to identify independent prognostic factors. The expression of genes constituting the prognostic model was further validated using the Human Protein Atlas (HPA) database. Finally, the Comparative Toxicogenomic Data (CTD) database was used to explore possible treatment drugs for TNBC.

Results

We obtained 13,245 differential expressed genes, and 177 consensus genes. 98 genes with prognostic implication were obtained by univariable Cox. Then, a prognostic model including 12 ferroptosis-related genes was constructed by multivariable Cox. The area under curve (AUC) value of the prognostic model for TNBC was 0.82. The GEO database validated that the model (AUC = 0.77) could predict the patient outcomes. The staining results of 10 out of 12 prognostic model genes in HPA database showed that their expression was consistent with our predictions. Clinical risk analysis indicated that risk score of patients could act as an independent prognostic factor. Finally, six drugs that may have interaction with 12 ferroptosis-related genes were obtained using the CTD database.

Conclusion

The prognostic model composed of 12 ferroptosis-related genes could predict the prognosis of TNBC patients, and seven genes (ASNS, LAMP2, CAV1, DPP4, HELLS, TF, ZFP69B) could be potential new therapeutic targets for TNBC, and two drugs (1-methyl-3-isobutylxanthine, rosiglitazone) could act as potential therapeutic drugs for the treatment of TNBC.

Phospholipase Signaling in Breast Cancer

Breast cancer progression results from subversion of multiple intra- or intercellular signaling pathways in normal mammary tissues and their microenvironment, which have an impact on cell differentiation, proliferation, migration, and angiogenesis. Phospholipases (PLC, PLD and PLA) are essential mediators of intra- and intercellular signaling. They hydrolyze phospholipids, which are major components of cell membrane that can generate many bioactive lipid mediators, such as diacylglycerol, phosphatidic acid, lysophosphatidic acid, and arachidonic acid. Enzymatic processing of phospholipids by phospholipases converts these molecules into lipid mediators that regulate multiple cellular processes, which in turn can promote breast cancer progression. Thus, dysregulation of phospholipases contributes to a number of human diseases, including cancer. This review describes how phospholipases regulate multiple cancer-associated cellular processes, and the interplay among different phospholipases in breast cancer. A thorough understanding of the breast cancer-associated signaling networks of phospholipases is necessary to determine whether these enzymes are potential targets for innovative therapeutic strategies.

The Metabolic Mechanisms of Breast Cancer Metastasis

Breast cancer is one of the most common malignancy among women worldwide. Metastasis is mainly responsible for treatment failure and is the cause of most breast cancer deaths. The role of metabolism in the progression and metastasis of breast cancer is gradually being emphasized. However, the regulatory mechanisms that conduce to cancer metastasis by metabolic reprogramming in breast cancer have not been expounded. Breast cancer cells exhibit different metabolic phenotypes depending on their molecular subtypes and metastatic sites. Both intrinsic factors, such as MYC amplification, PIK3CA, and TP53 mutations, and extrinsic factors, such as hypoxia, oxidative stress, and acidosis, contribute to different metabolic reprogramming phenotypes in metastatic breast cancers. Understanding the metabolic mechanisms underlying breast cancer metastasis will provide important clues to develop novel therapeutic approaches for treatment of metastatic breast cancer.

Expression of Secretory Phospholipase A2 Group IIa in Breast Cancer and Correlation to Prognosis in a Cohort of Advanced Breast Cancer Patients

Secreted phospholipase A2 group IIa (sPLA2-IIa) has been shown to promote tumor genesis and cell proliferation. The properties of this group of enzymes are utilized in liposomal drug delivery of chemotherapy. sPLA2-IIa is also under investigation as a possible treatment target in itself, and as a prognostic marker. The expression of sPLA2-IIa in breast cancer has not been examined extensively, and never using immunohistochemistry. We sought to investigate the expression of sPLA2-IIa in a cohort of advanced breast cancer patients with correlation to known clinicopathologic risk factors and survival. Material from 525 breast cancer patients (426 primary tumors and 99 metastases or local recurrences) was examined for sPLA2-IIa expression using immunohistochemistry. Out of these, 262 showed expression of sPLA2-IIa. We found that there was no correlation to clinicopathologic characteristics, and no impact of sPLA2-IIa expression on prognosis. However, we found that a large proportion of patients in our study had high levels of sPLA2-IIa expression, and that sPLA2-IIa was equally expressed in primary tumors and metastases. These findings may be significant in the future development of liposomal drug delivery or targeted sPLA2-IIa treatment.

Liposomes Targeting P21 Activated Kinase-1 (PAK-1) and Selective for Secretory Phospholipase A2 (sPLA2) Decrease Cell Viability and Induce Apoptosis in Metastatic Triple-Negative Breast Cancer Cells

P21 activated kinases (or group I PAKs) are serine/threonine kinases whose expression is altered in prostate and breast cancers. PAK-1 activity is inhibited by the small molecule "Inhibitor targeting PAK-1 activation-3" (IPA-3), which has selectivity for PAK-1 but is metabolically unstable. Secretory Group IIA phospholipase A₂ (sPLA₂) expression correlates to increased metastasis and decreased survival in many cancers. We previously designed novel liposomal formulations targeting both PAK-1 and sPLA_2, called Secretory Phospholipase Responsive liposomes or SPRL-IPA-3, and demonstrated their ability to alter prostate cancer growth. The efficacy of SPRL against other types of cancers is not well understood. We addressed this limitation by determining the ability of SPRL to induce cell death in a diverse panel of cells representing different stages of breast cancer, including the invasive but non-metastatic MCF-7 cells, and metastatic triple-negative breast cancer (TNBC) cells such as MDA-MB-231, MDA-MB-468, and MDA-MB-435. We investigated the role of sPLA₂ in the disposition of these liposomes by comparing the efficacy of SPRL-IPA-3 to IPA-3 encapsulated in sterically stabilized liposomes (SSL-IPA-3), a formulation shown to be less sensitive to sPLA₂. Both SSL-IPA-3 and SPRL-IPA-3 induced time- and dose-dependent decreases in MTT staining in all cell lines tested, but SPRL-IPA-3-induced effects in metastatic TNBC cell lines were superior over SSL-IPA-3. The reduction in MTT staining induced by SPRL-IPA-3 correlated to the expression of Group IIA sPLA₂. sPLA₂ expression also correlated to increased induction of apoptosis in TNBC cell lines by SPRL-IPA-3. These data suggest that SPRL-IPA-3 is selective for metastatic TNBC cells and that the efficacy of SPRL-IPA-3 is mediated, in part, by the expression of Group IIA sPLA₂.

Mann T, Bastard K, F. Scott K, Church WB. Structural and Functional Aspects of Targeting the Secreted Human Group IIA Phospholipase A2

Human group IIA secretory phospholipase A₂ (hGIIA) promotes the proliferation of cancer cells, making it a compelling therapeutic target, but it is also significant in other inflammatory conditions. Consequently, suitable inhibitors of hGIIA have always been sought. The activation of phospholipases A₂ and the catalysis of glycerophospholipid substrates generally leads to the release of fatty acids such as arachidonic acid (AA) and lysophospholipid, which are then converted to mediator compounds, including prostaglandins, leukotrienes, and the platelet-activating factor. However, this ability of hGIIA to provide AA is not a complete explanation of its biological role in inflammation, as it has now been shown that it also exerts proinflammatory effects by a catalysis-independent mechanism. This mechanism is likely to be highly dependent on key specific molecular interactions, and the full mechanistic descriptions of this remain elusive. The current candidates for the protein partners that may mediate this catalysis-independent mechanism are also introduced in this review. A key discovery has been that selective inhibition of the catalysis-independent activity of hGIIA is achieved with cyclised derivatives of a pentapeptide, FLSYK, derived from the primary sequence of hGIIA. The effects of hGIIA on cell function appear to vary depending on the pathology studied, and so its mechanism of action is complex and context-dependent. This review is comprehensive and covers the most recent developments in the understanding of the many facets of hGIIA function and inhibition and the insight they provide into their clinical application for disease treatment. A cyclic analogue of FLSYK, c2, the most potent analogue known, has now been taken into clinical trials targeting advanced prostate cancer.

Multiplatform Investigation of Plasma and Tissue Lipid Signatures of Breast Cancer Using Mass Spectrometry Tools

Plasma and tissue from breast cancer patients are valuable for diagnostic/prognostic purposes and are accessible by multiple mass spectrometry (MS) tools. Liquid chromatography-mass spectrometry (LC-MS) and ambient mass spectrometry imaging (MSI) were shown to be robust and reproducible technologies for breast cancer diagnosis. Here, we investigated whether there is a correspondence between lipid cancer features observed by desorption electrospray ionization (DESI)-MSI in tissue and those detected by LC-MS in plasma samples. The study included 28 tissues and 20 plasma samples from 24 women with ductal breast carcinomas of both special and no special type (NST) along with 22 plasma samples from healthy women. The comparison of plasma and tissue lipid signatures revealed that each one of the studied matrices (i.e., blood or tumor) has its own specific molecular signature and the full interposition of their discriminant ions is not possible. This comparison also revealed that the molecular indicators of tissue injury, characteristic of the breast cancer tissue profile obtained by DESI-MSI, do not persist as cancer discriminators in peripheral blood even though some of them could be found in plasma samples.

Association of 5'UTR polymorphism of secretory phospholipase A2 group IIA (PLA2G2A) gene with prostate cancer metastasis

Phospholipase A2 (PLA2) enzymes are small lipolytic hydrolases that can regulate immune responses through generation of Arachidonic Acid (AA), a precursor molecule of lipid mediators like prostaglandins, leukotrienes and thromboxanes. One of the family members of PLA2, secretory Phospholipase A2 Group IIA (PLA2G2A), was associated with different types of malignancies including prostate cancer. Elevated serum levels of PLA2G2A was found in prostate cancer (PCa) patients and associated with increased tumor grade in literature. 5'UTR regions have regulatory role in protein expression by controlling the accessibility of factors necessary for the translation initiation. Single nucleotide polymorphisms at 5'UTR regions have the potential to affect mRNA translation efficiency resulting in altered protein levels depending on structure and nucleotide content. Given that the 5'UTR polymorphism in PLA2G2A gene (rs11573156) is associated with increased serum levels of PLA2G2A, the association of this 5'UTR polymorphism with PCa susceptibility and metastasis was investigated in this study. Total of 261 PCa patients and 128 control individuals were genotyped with polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Individuals with heterozygous CG genotype was found to have significantly reduced risk of PCa metastasis with an Odds Ratio (OR) of 0.405 (p = 0.028, 95%CI = 0.181-0.906), compared to the carriers of homozygous CC genotype (p > 0.05) suggesting an anti-metastatic effect for the G allele. No association was found between PCa susceptibility and Gleason score (p > 0.05) in Turkish population.

Long non‑coding RNA SLNCR1 regulates non‑small cell lung cancer migration, invasion and stemness through interactions with secretory phospholipase A2

Long non-coding RNA (lncRNA) SRA-like non-coding RNA (SLNCR1; also known as linc00673) is a recently identified oncogenic lncRNA. The role of SLNCR1 in non-small cell lung cancer (NSCLC), a common malignancy, remains poorly understood. The present study aimed to investigate the involvement of long non-coding RNA SLNCR1 in the pathogenesis of NSCLC. Reverse transcription-quantitative PCR (RT-qPCR) and ELISA were performed to measure the levels of lncRNA SLNCR1 and secretory phospholipase A2 (sPLA2) in lung biopsies, respectively. Correlations between expression levels of lncRNA SLNCR1 and sPLA2 were analyzed by Pearson's correlation analysis. Diagnostic value of lncRNA SLNCR1 for NSCLC was evaluated by receiver operating characteristic curve analysis. lncRNA SLNCR1 small interfering (si)RNA and sPLA2 overexpression vector were transfected into NSCLC cells. Cell migration, invasion and stemness were examined by Transwell migration assay, Matrigel invasion assay and flow cytometric assay, respectively. Following transfection, expression of lncRNA SLNCR1 and sPLA2 was detected by RT-qPCR and western blotting, respectively. The results demonstrated that lncRNA SLNCR1 expression levels were upregulated in tumor tissues compared with adjacent healthy tissues of patients with NSCLC. Plasma lncRNA SLNCR1 and sPLA2 expression levels were upregulated in patients with NSCLC compared with healthy controls. Plasma lncRNA SLNCR1 and sPLA2 were positively correlated in patients with NSCLC, but not in healthy controls. lncRNA SLNCR1 siRNA silencing inhibited, whereas sPLA2 overexpression promoted cell migratory and invasive abilities and stemness. lncRNA SLNCR1 siRNA silencing led to downregulated sPLA2 expression, whereas sPLA2 overexpression did not significantly affect lncRNA SLNCR1 expression. sPLA2 overexpression attenuated the inhibitory effects of lncRNA SLNCR1 siRNA silencing on cell migration, invasion and stemness. In conclusion, lncRNA SLNCR1 may regulate cancer cell migration, invasion and stemness in NSCLC through interactions with sPLA2.

Antitumoral effects of γCdcPLI, a PLA2 inhibitor from Crotalus durissus collilineatus via PI3K/Akt pathway on MDA-MB-231 breast cancer cell

Phospholipases A₂(PLA₂s) overexpression is closely associated with the malignant potential of breast cancers. Here, we showed for the first the antitumoral effects of γCdcPLI, a PLA₂ inhibitor from Crotalus durissus collilineatus via PI3K/Akt pathway on MDA-MB-231 cell. Firstly, γCdcPLI was more cytotoxic to MDA-MB-231 breast cancer cells than other cell lines (MCF-7, HeLa, PC3 and A549) and did not affect the viability of non-tumorigenic breast cell (MCF 10A). In addition, γCdcPLI induced modulation of important mediators of apoptosis pathways such as p53, MAPK-ERK, BIRC5 and MDM2. γCdcPLI decreased MDA-MB-231 adhesion, migration and invasion. Interestingly, the γCdcPLI also inhibited the adhesion and migration of endothelial cells and blocked angiogenesis by inhibiting tube formation by HUVECs in vitro and sprouting elongation on aortic ring assay ex vivo. Furthermore, γCdcPLI reduced the production of vascular endothelial growth factor (VEGF). γCdcPLI was also able to decrease PGE2 levels in MDA-MB-231 and inhibited gene and protein expression of the PI3K/Akt pathway. In conclusion, γCdcPLI showed in vitro antitumoral, antimestatatic and anti-angiogenic potential effects and could be an attractive approach for futures studies in cancer therapy.

Key Players in Choline Metabolic Reprograming in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC), defined as lack of estrogen and progesterone receptors in the absence of protein overexpression/gene amplification of human epidermal growth factor receptor 2, is still a clinical challenge despite progress in breast cancer care. ¹H magnetic resonance spectroscopy allows identification and non-invasive monitoring of TNBC metabolic aberrations and elucidation of some key mechanisms underlying tumor progression. Thus, it has the potential to improve in vivo diagnosis and follow-up and also to identify new targets for treatment. Several studies have shown an altered phosphatidylcholine (PtdCho) metabolism in TNBCs, both in patients and in experimental models. Upregulation of choline kinase-alpha, an enzyme of the Kennedy pathway that phosphorylates free choline (Cho) to phosphocholine (PCho), is a major contributor to the increased PCho content detected in TNBCs. Phospholipase-mediated PtdCho headgroup hydrolysis also contributes to the build-up of a PCho pool in TNBC cells. The oncogene-driven PtdCho cycle appears to be fine tuned in TNBC cells in at least three ways: by modulating the choline import, by regulating the activity or expression of specific metabolic enzymes, and by contributing to the rewiring of the entire metabolic network. Thus, only by thoroughly dissecting these mechanisms, it will be possible to effectively translate this basic knowledge into further development and implementation of Cho-based imaging techniques and novel classes of therapeutics.

LncRNAs as new biomarkers to differentiate triple negative breast cancer from non-triple negative breast cancer

Triple negative breast cancer (TNBC) is an aggressive type of breast cancer with high heterogeneity. To date, there is no efficient therapy for TNBC patients and the prognosis is poor. It is urgent to find new biomarkers for the diagnosis of TNBC or efficient therapy targets. As an area of focus in the post-genome period, long non-coding RNAs (lncRNAs) have been found to play critical roles in many cancers, including TNBC. However, there is little information on differentially expressed lncRNAs between TNBC and non-TNBC. We detected the expression levels of lncRNAs in TNBC and non-TNBC tissues separately. Then we analyzed the lncRNA expression signature of TNBC relative to non-TNBC, and found dysregulated lncRNAs participated in important biological processes though Gene Ontology and Pathway analysis. Finally, we validated these lncRNA expression levels in breast cancer tissues and cells, and then confirmed that 4 lncRNAs (RP11-434D9.1, LINC00052, BC016831, and IGKV) were correlated with TNBC occurrence through receiver operating characteristic curve analysis. This study offers helpful information to understand the initiation and development mechanisms of TNBC comprehensively and suggests potential biomarkers for diagnosis or therapy targets for clinical treatment.

Epigenetic control of group V phospholipase A2 expression in human malignant cells

Secreted phospholipases A2 (sPLA2) are suggested to play an important role in inflammation and tumorigenesis. Different mechanisms of epigenetic regulation are involved in the control of group IIA, III and X sPLA2s expression in cancer cells, but group V sPLA2 (GV-PLA2) in this respect has not been studied. Here, we demonstrate the role of epigenetic mechanisms in regulation of GV-PLA2 expression in different cell lines originating from leukaemia and solid cancers. In blood leukocytes from leukaemic patients, levels of GV-PLA2 transcripts were significantly lower in comparison to those from healthy individuals. Similarly, in DU-145 and PC-3 prostate and CAL-51 and MCF-7 mammary cancer cell lines, levels of GV-PLA2 transcripts were significantly lower in relation to those found in normal epithelial cells of prostate or mammary. By sequencing and methylation-specific high-resolution melting (MS-HRM) analyses of bisulphite-modified DNA, distinct CpG sites in the GV-PLA2 promoter region were identified that were differentially methylated in cancer cells in comparison to normal epithelial and endothelial cells. Spearman rank order analysis revealed a significant negative correlation between the methylation degree and the cellular expression of GV-PLA2 (r = -0.697; p = 0.01). The effects of demethylating agent (5-aza-2'-deoxycytidine) and histone deacetylase inhibitor (trichostatin A) on GV-PLA2 transcription in the analysed cells confirmed the importance of DNA methylation and histone modification in the regulation of the GV-PLA2 gene expression in leukaemic, prostate and mammary cancer cell lines. The exposure of tumour cells to human recombinant GV-PLA2 resulted in a reduced colony forming activity of MCF-7, HepG2 and PC-3 cells, but not of DU-145 cells suggesting a cell-type-dependent effect of GV-PLA2 on cell growth. In conclusion, our results suggest that epigenetic mechanisms such as DNA methylation and histone modification play an important role in downregulation of GV-PLA2 expression in cancer cells.

Primary cilium suppression by SREBP1c involves distortion of vesicular trafficking by PLA2G3

The lipogenic transcription factor SREBP1c is often aberrantly activated in cancer cells and suppresses primary cilium formation. PLA2G3 is implicated in the cilium-repressing action of SREBP1c. This involves alterations in vesicular trafficking, which is largely mediated by increased lysophospholipid levels.

Distortion of primary cilium formation is increasingly recognized as a key event in many human pathologies. One of the underlying mechanisms involves aberrant activation of the lipogenic transcription factor sterol regulatory element–binding protein 1c (SREBP1c), as observed in cancer cells. To gain more insight into the molecular pathways by which SREBP1c suppresses primary ciliogenesis, we searched for overlap between known ciliogenesis regulators and targets of SREBP1. One of the candidate genes that was consistently up-regulated in cellular models of SREBP1c-induced cilium repression was phospholipase A2 group III (PLA2G3), a phospholipase that hydrolyzes the sn-2 position of glycerophospholipids. Use of RNA interference and a chemical inhibitor of PLA2G3 rescued SREBP1c-induced cilium repression. Cilium repression by SREBP1c and PLA2G3 involved alterations in endosomal recycling and vesicular transport toward the cilium, as revealed by aberrant transferrin and Rab11 localization, and was largely mediated by an increase in lysophosphatidylcholine and lysophosphatidylethanolamine levels. Together these findings indicate that aberrant activation of SREBP1c suppresses primary ciliogenesis by PLA2G3-mediated distortion of vesicular trafficking and suggest that PLA2G3 is a novel potential target to normalize ciliogenesis in SREBP1c-overexpressing cells, including cancer cells.

Differential expression of lipid metabolism-related proteins in different breast cancer subtypes

PURPOSE

This study aimed to determine the expression and clinical significance of proteins that are involved in lipid metabolism in human breast tumors.

METHODS

Tumors from 476 breast cancer patients were used to construct tissue microarrays. Then, immunohistochemistry (IHC) for hormone-sensitive lipase (HSL), Perilipin 1 (PLIN1), fatty acid binding protein 4 (FABP4), carnitine palmitoyltransferase IA (CPT-1A), acyl-CoA oxidase 1 (ACOX-1), and fatty acid synthase (FASN) was performed on these microarrays.

RESULTS

Breast tumors were classified into 4 subtypes: luminal A (n = 242; 50.8%), luminal B (n = 134; 28.2%), human epidermal growth factor receptor 2 (HER2) (n = 50; 10.5%), and triple negative breast cancer (TNBC) (n = 50; 10.5%). The expression of PLIN1 (p < 0.001), FABP4 (p = 0.029), CPT-1A (p = 0.001), ACOX-1 (p < 0.001), and FASN (p < 0.001) differed significantly among these tumor subtypes. Notably, PLIN1, CPT-1A, and FASN expression was highest in HER2 tumors and lowest in TNBC tumors. Similarly, the expression of FABP4 and ACOX-1 was highest in HER2 tumors and lowest in luminal A tumors. In addition, ACOX-1 positivity was associated with significantly shorter overall survival (p = 0.018). When tumor subtype was considered, FABP4 positivity was associated with significantly shorter disease-free survival (p = 0.005) and overall survival (p = 0.041) in TNBC.

CONCLUSION

Lipid metabolism-related proteins are differentially expressed in different IHC subtypes of breast cancer and some are associated with decreased survival rates.

New targeted therapies for breast cancer: A focus on tumor microenvironmental signals and chemoresistant breast cancers

Breast cancer is the most frequent female malignancy worldwide. Current strategies in breast cancer therapy, including classical chemotherapy, hormone therapy, and targeted therapies, are usually associated with chemoresistance and serious adverse effects. Advances in our understanding of changes affecting the interactome in advanced and chemoresistant breast tumors have provided novel therapeutic targets, including, cyclin dependent kinases, mammalian target of rapamycin, Notch, Wnt and Shh. Inhibitors of these molecules recently entered clinical trials in mono- and combination therapy in metastatic and chemo-resistant breast cancers. Anticancer epigenetic drugs, mainly histone deacetylase inhibitors and DNA methyltransferase inhibitors, also entered clinical trials. Because of the complexity and heterogeneity of breast cancer, the future in therapy lies in the application of individualized tailored regimens. Emerging therapeutic targets and the implications for personalized-based therapy development in breast cancer are herein discussed.