The clinical role of phospholipase A2 isoforms in advanced-stage ovarian carcinoma

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.

Stimuli-Responsive Hybrid Metal Nanocomposite - A Promising Technology for Effective Anticancer Therapy

Cancer is one of the most challenging, life-threatening illnesses to cure, with over 10 million new cases diagnosed each year globally. Improved diagnostic cum treatment with common side-effects are warranting for successful therapy. Nanomaterials are recognized to improve early diagnosis, imaging, and treatment. Recently, multifunctional nanocomposites attracted considerable interest due to their low-cost production, and ideal thermal and chemical stability, and will be beneficial in future diagnostics and customized treatment capacity. Stimuli-Responsive Hybrid Metal Nanocomposites (SRHMNs) based nanocomposite materials pose the on/off delivery of bioactive compounds such as medications, genes, RNA, and DNA to specific tissue or organs and reduce toxicity. They simultaneously serve as sophisticated imaging and diagnostic tools when certain stimuli (e.g., temperature, pH, redox, ultrasound, or enzymes) activate the nanocomposite, resulting in the imaging-guided transport of the payload at defined sites. This review in detail addresses the recent advancements in the design and mechanism of internal breakdown processes of the functional moiety from stimuli-responsive systems in response to a range of stimuli coupled with metal nanoparticles. Also, it provides a thorough understanding of SRHMNs, enabling non-invasive interventional therapy by resolving several difficulties in cancer theranostics.

Exploration of Potential Ewing Sarcoma Drugs from FDA-Approved Pharmaceuticals through Computational Drug Repositioning, Pharmacogenomics, Molecular Docking, and MD Simulation Studies

Novel drug development is a time-consuming process with relatively high debilitating costs. To overcome this problem, computational drug repositioning approaches are being used to predict the possible therapeutic scaffolds against different diseases. In the current study, computational drug repositioning approaches were employed to fetch the promising drugs from the pool of FDA-approved drugs against Ewing sarcoma. The binding interaction patterns and conformational behaviors of screened drugs within the active region of Ewing sarcoma protein (EWS) were confirmed through molecular docking profiles. Furthermore, pharmacogenomics analysis was employed to check the possible associations of selected drugs with Ewing sarcoma genes. Moreover, the stability behavior of selected docked complexes (drugs-EWS) was checked by molecular dynamics simulations. Taken together, astemizole, sulfinpyrazone, and pranlukast exhibited a result comparable to pazopanib and can be used as a possible therapeutic agent in the treatment of Ewing sarcoma.

Malignancy-associated membranous nephropathy with PLA2R double-positive for glomeruli and carcinoma

Phospholipase A2 receptor (PLA2R) is the most common primary target antigen of idiopathic membranous nephropathy (MN) although PLA2R antibodies are also reported to be present in malignancy-associated MN. However, a case of PLA2R-positive MN secondary to PLA2R-positive carcinoma has not been reported. A 26-year-old Japanese woman presented with general fatigue, fever, and nonproductive cough. Computed tomography demonstrated a left kidney mass with pathologic diagnosis of Xp11.2 translocation renal cell carcinoma (RCC). After the second time of administration with Sunitinib, the patients exhibited significant proteinuria and hypoalbuminemia. Renal biopsy revealed a diagnosis of diffuse MN secondary to RCC. Immunofluorescence staining showed granular patterns positive for immunoglobulin (Ig) G, IgA, and C3c. PLA2R and IgG1-3 were positive, while IgG4 was negative. For the treatment of severe nephrotic syndrome, we attempted steroid therapy without any clinical improvement. Open nephrectomy was performed and surprisingly, RCC was stained for PLA2R with polarity for the basal side. At outpatient follow-up, 4 months after the operation, urinary protein had still persisted, although serum albumin was slightly increased. We report a case of PLA2R-positive MN secondary to PLA2R-positive RCC.

Phospholipase A2 superfamily in cancer

Phospholipase A2 enzymes (PLA₂s) comprise a superfamily that is generally divided into six subfamilies known as cytosolic PLA₂s (cPLA₂s), calcium-independent PLA₂s (iPLA₂s), secreted PLA₂s (sPLA₂s), lysosomal PLA₂s, platelet-activating factor (PAF) acetylhydrolases, and adipose specific PLA₂s. Each subfamily consists of several isozymes that possess PLA₂ activity. The first three PLA₂ subfamilies play important roles in inflammation-related diseases and cancer. In this review, the roles of well-studied enzymes sPLA₂-IIA, cPLA₂α and iPLA₂β in carcinogenesis and cancer development were discussed. sPLA₂-IIA seems to play conflicting roles and can act as a tumor suppressor or a tumor promoter according to the cancer type, but cPLA₂α and iPLA₂β play protumorigenic role in most cancers. The mechanisms of PLA₂-mediated signal transduction and crosstalk between cancer cells and endothelial cells in the tumor microenvironment are described. Moreover, the mechanisms by which PLA₂s mediate lipid reprogramming and glycerophospholipid remodeling in cancer cells are illustrated. PLA₂s as the upstream regulators of the arachidonic acid cascade are generally high expressed and activated in various cancers. Therefore, they can be considered as potential pharmacological targets and biomarkers in cancer. The detailed information summarized in this review may aid in understanding the roles of PLA₂s in cancer, and provide new clues for the development of novel agents and strategies for tumor prevention and treatment.

Current insights into functions of phospholipase A2 receptor in normal and cancer cells: More questions than answers

Lipid signaling network was proposed as a potential target for cancer prevention and treatment. Several recent studies revealed that phospholipid metabolising enzyme, phospholipase A2 (PLA₂), is a critical regulator of cancer accelerating pathologies and apoptosis in several types of cancers. In addition to functioning as an enzyme, PLA₂ can activate a phospholipase A2 receptor (PLA2R1) in plasma membrane. While the list of PLA₂ targets extends to glucose homeostasis, intracellular energy balance, adipocyte development, and hepatic lipogenesis, the PLA2R1 downstream effectors are few and scarcely investigated. Among the most addressed PLA2R1 effects are regulation of pro-inflammatory signaling, autoimmunity, apoptosis, and senescence. Localized in glomeruli podocytes, the receptor can be identified by circulating anti-PLA2R1 autoantibodies leading to development of membranous nephropathy, a strong autoimmune inflammatory cascade. PLA2R1 was shown to induce activation of Janus-kinase 2 (JAK2) and estrogen-related receptor α (ERRα)-controlled mitochondrial proteins, as well as increasing the accumulation of reactive oxygen species, thus leading to apoptosis and senescence. These findings indicate the potential role of PLA2R1 as tumor suppressor. Epigenetic investigations addressed the role of DNA methylation, histone modifications, and specific microRNAs in the regulation of PLA2R1 expression. However, involvement of PLA2R1 in suppression of malignant growth and metastasis remains controversial. In this review, we summarize the recent findings that highlight the role of PLA2R1 in the regulation of carcinogenesis-related intracellular signaling.

Current progress in the inflammatory background of angiogenesis in gynecological cancers

A tumor growth depends on the potency of the tumor to support itself with nutrients and oxygen. The development of a vascular network within the tumor is key to its survival. The permanent contest between the tumor and its host involves tumor cells on one side and an immunological system and tissue stroma on the other. The angiogenesis is not only a specialty of the tumor, but it also depends on this complex multidirectional interaction. The most common gynecological cancers, cervical, endometrial and ovarian carcinoma are good examples for studying this problem. In this review, we aim to show that an inflammatory response against a tumor can be reverted into an undesirable process leading to the development of a vascular network within the tumor and, subsequently, further growth of the tumor and progression of a disease. Therefore, a key for tumor management should be searched within the immunological system, rather than focused on cell cycle and anti-angiogenic treatment only.

Diverse effects of phospholipase A2 receptor expression on LNCaP and PC-3 prostate cancer cell growth in vitro and in vivo

Physiological and pathophysiological functions of the phospholipase A2 receptor 1 (PLA2R1) are still not completely understood. To elucidate PLA2R1’s function in prostate carcinoma, the receptor was ectopically overexpressed in LNCaP with silenced PLA2R1, and diminished in PC-3 cells with constitutively increased PLA2R1 expression relative to normal prostate epithelial cells. LNCaP cells were transfected to overexpress PLA2R1 (LNCaP-PLA2R1) and compared to control vector transfected cells (LNCaP-Ctrl). Alternatively, a CRISPR/Cas9-knockdown of PLA2R1 was achieved in PC-3 cells (PC-3 KD) and compared to the corresponding control-transfected cells (PC-3 Ctrl). The impact of PLA2R1 expression on proliferative and metastatic parameters was analysed in vitro. A pilot in vivo study addressed the effects of PLA2R1 in mice xenografted with transfected LNCaP and PC-3 cells. Cell viability/proliferation and motility were significantly increased in LNCaP-PLA2R1 and PC-3 Ctrl compared to LNCaP-Ctrl and PC-3 KD cells, respectively. However, levels of apoptosis, clonogenicity and cell invasion were reduced in LNCaP-PLA2R1 and PC-3 Ctrl cells. Gene expression analysis revealed an up-regulation of fibronectin 1 (FN1), TWIST homolog 1 (TWIST1), and cyclin-dependent kinase 6 (CDK6) in LNCaP-PLA2R1. In LNCaP xenografts, PLA2R1-dependent regulation of clonogenicity appeared to outweigh the receptor’s pro-oncogenic properties, resulting in decreased tumour growth, supporting the tumour-suppressive role of PLA2R1. Alternatively, PC-3 Ctrl xenografts exhibited faster tumour growth compared to PC-3 KD cells, suggesting a pro-oncogenic effect of endogenous PLA2R1 expression. The differential growth-regulatory effects of PLA2R1 may be mediated by FN1, TWIST1, and CDK6 expression, although further investigation is required.

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.

Epigenetic control of phospholipase A2 receptor expression in mammary cancer cells

BACKGROUND

It has recently been proposed that the M-type phospholipase A2 receptor (PLA2R1) acts as a tumour suppressor in certain malignancies including mammary cancer. Considering that DNA methylation is an important regulator of gene transcription during carcinogenesis, in the current study we analyzed the PLA2R1 expression, PLA2R1 promoter methylation, and selected micro RNA (miRNA) levels in normal human mammary epithelial cells (HMEC) and cancer cell lines.

METHODS

Levels of PLA2R1 and DNA methyltransferases (DNMT) specific mRNA were determined using real-time RT-PCR. Methylation specific-high resolution melting (MS-HRM) analysis was utilized to quantify the methylation degree of selected CpG sites localized in the promoter region of the PLA2R1 gene. Expression of miRNA was tested using miScript Primer Assay system.

RESULTS

Nearly complete methylation of the analyzed PLA2R1 promoter region along with PLA2R1 gene silencing was identified in MDA-MB-453 mammary cancer cells. In MCF-7 and BT-474 mammary cancer cell lines, a higher DNA methylation degree and reduced PLA2R1 expression were found in comparison with those in normal HMEC. Synergistic effects of demethylating agent (5-aza-2'-deoxycytidine) and histone deacetylase inhibitor (trichostatin A) on PLA2R1 transcription in MDA-MB-453 cells confirmed the importance of DNA methylation and histone modification in the regulation of the PLA2R1 gene expression in mammary cells. Furthermore, significant positive correlation between the expression of DNMT1 and PLA2R1 gene methylation and negative correlation between the cellular levels of hsa-mir-141, -181b, and -181d-1 and the expression of PLA2R1 were identified in the analyzed cells. Analysis of combined z-score of miR-23b, -154 and -302d demonstrated a strong and significant positive correlation with PLA2R1 expression.

CONCLUSIONS

Our data indicate that (i) PLA2R1 expression in breast cancer cells is controlled by DNA methylation and histone modifications, (ii) hypermethylation of the PLA2R1 promoter region is associated with up-regulation of DNMT1, and (iii) hsa-miR-23b, -154, and -302d, as well as hsa-miR-141, -181b, and -181d-1 are potential candidates for post-transcriptional regulation of PLA2R1 expression in mammary cancer cells.

Targeting cytosolic phospholipase A2 α in colorectal cancer cells inhibits constitutively activated protein kinase B (AKT) and cell proliferation

A constitutive activation of protein kinase B (AKT) in a hyper-phosphorylated status at Ser473 is one of the hallmarks of anti-EGFR therapy-resistant colorectal cancer (CRC). The aim of this study was to examine the role of cytosolic phospholipase A2α (cPLA2α) on AKT phosphorylation at Ser473 and cell proliferation in CRC cells with mutation in phosphoinositide 3-kinase (PI3K). AKT phosphorylation at Ser473 was resistant to EGF stimulation in CRC cell lines of DLD-1 (PIK3CAE545K mutation) and HT-29 (PIK3CAP499T mutation). Over-expression of cPLA2α by stable transfection increased basal and EGF-stimulated AKT phosphorylation and proliferation in DLD-1 cells. In contrast, silencing of cPLA2α with siRNA or inhibition with Efipladib decreased basal and EGF-stimulated AKT phosphorylation and proliferation in HT-29. Treating animals transplanted with DLD-1 with Efipladib (10 mg/kg, i.p. daily) over 14 days reduced xenograft growth by >90% with a concomitant decrease in AKT phosphorylation. In human CRC tissue, cPLA2α expression and phosphorylation were increased in 63% (77/120) compared with adjacent normal mucosa determined by immunohistochemistry. We conclude that cPLA2α is required for sustaining AKT phosphorylation at Ser473 and cell proliferation in CRC cells with PI3K mutation, and may serve as a potential therapeutic target for treatment of CRC resistant to anti-EGFR therapy.

Structural analysis of a group III Glu62-phospholipase A2 from the scorpion, Mesobuthus tamulus: Targeting and reversible inhibition by native peptides

Group III phospholipase A(2) enzyme transcript from the Mesobuthus tamulus (Indian red scorpion) codes for three distinct products that include a large enzymatic subunit, a pentameric peptide and a small non-enzymatic subunit. The structures of these two subunits were modeled based on their sequence identity to bee venom PLA(2) and the partial sequence of MU2 adaptin subunit of AP2 clathrin adaptor, respectively. The enzymatic subunit comprises of three helices, the calcium binding loop and a substrate binding hydrophobic channel where the structure is stabilized by four disulfide bonds. The active site of the enzyme shows a catalytic histidine residue. Interestingly, there is a conservative mutation of the conserved aspartic acid, a classical participant of catalysis in this enzyme family, to glutamic acid. However, the side chain oxygen atoms of this glutamate are oriented away from the catalytic histidine implicating the non-participation of this residue in stabilizing the tautomeric conformation of the histidine. The acidic non-enzymatic subunit comprises of extensive hydrophobic residues with a conformation of an anti-parallel β-sheets making it ideal for tissue specific targeting. The native pentapeptide with the sequence Alanine-Arginine-Serine-Alanine-Arginine was docked to the enzymatic subunit. The peptide ligand occupies the hydrophobic cavity and makes a plethora of interactions with the residues in the channel, including a hydrogen bond with the crucial catalytic histidine and coordinate bond with the calcium ion. This ligand has a binding constant (K(D)) of 1.5μM. This makes the ligand a potential reversible inhibitor, ideal to prevent the enzyme from interacting with non-specific molecules enroute to the target. The enzyme-ligand complex also provides a model to understand the stereochemistry required for the design of more potent drug molecules against such enzyme drug targets.

Expression of the peroxisome proliferator-activated receptors-alpha, -beta, and -gamma in ovarian carcinoma effusions is associated with poor chemoresponse and shorter survival

Peroxisome proliferator-activated receptors regulate lipid metabolism, affecting inflammation and cancer. The present study analyzed the anatomical site-related expression and prognostic role of peroxisome proliferator-activated receptors in ovarian carcinoma. Fresh-frozen effusions (n = 79), primary carcinomas (n = 44), and solid metastases (n = 16) were studied for peroxisome proliferator-activated receptor-alpha, -beta, and -gamma messenger RNA expression using reverse transcriptase polymerase chain reaction. Peroxisome proliferator-activated receptor-gamma messenger RNA expression was further assessed in 60 tumors (30 effusions, 20 primary carcinomas, 10 metastases) using in situ hybridization. Peroxisome proliferator-activated receptor-gamma protein expression was immunohistochemically analyzed in 160 effusions. All peroxisome proliferator-activated receptors were expressed in most tumors at all anatomical sites using reverse transcriptase polymerase chain reaction, but peroxisome proliferator-activated receptor-alpha (P = .004) and peroxisome proliferator-activated receptor-beta (P = .002) messenger RNA levels were higher in effusions compared with primary carcinomas and solid metastases. In situ hybridization localized peroxisome proliferator-activated receptor-gamma messenger RNA to carcinoma cells in both effusions and solid lesions. Peroxisome proliferator-activated receptor-gamma protein was detected in carcinoma cells in 102 of 160 (64%) effusions. Higher effusion messenger RNA levels of all peroxisome proliferator-activated receptors were associated with less favorable response to chemotherapy at diagnosis (P = .009). In univariate survival analysis, higher messenger RNA expression of all peroxisome proliferator-activated receptors was associated with poor progression-free (P = .045) and overall (P = .014) survival. Higher peroxisome proliferator-activated receptor-gamma protein expression was similarly associated with poor overall survival for the entire cohort (P = .046) and for patients with disease recurrence effusions (P = .009). Peroxisome proliferator-activated receptors were not independent predictors of survival in Cox multivariate analysis. Peroxisome proliferator-activated receptor members are frequently expressed in ovarian carcinoma, with upregulated expression in effusions. Peroxisome proliferator-activated receptor expression in effusions is associated with poor response to chemotherapy at disease recurrence and poor survival, suggesting a role in tumor biology at this unique microenvironment.

Cytosolic phospholipase A2-alpha: a potential therapeutic target for prostate cancer

PURPOSE

Cytosolic phospholipase A2-alpha (cPLA2-alpha) provides intracellular arachidonic acid to supply both cyclooxygenase and lipoxygenase pathways. We aim to determine the expression and activation of cPLA2-alpha in prostate cancer cell lines and tissue and the effect of targeting cPLA2-alpha in vitro and in vivo.

EXPERIMENTAL DESIGN

The expression of cPLA2-alpha was determined in prostate cancer cells by reverse transcription-PCR, Western blot, and immunocytochemistry. Growth inhibition, apoptosis, and cPLA2-alpha activity were determined after inhibition with cPLA2-alpha small interfering RNA or inhibitor (Wyeth-1). Cytosolic PLA2-alpha inhibitor or vehicle was also administered to prostate cancer xenograft mouse models. Finally, the expression of phosphorylated cPLA2-alpha was determined by immunohistochemistry in human normal, androgen-sensitive and androgen-insensitive prostate cancer specimens.

RESULTS

cPLA2-alpha is present in all prostate cancer cells lines, but increased in androgen-insensitive cells. Inhibition with small interfering RNA or Wyeth-1 results in significant reductions in prostate cancer cell numbers, as a result of reduced proliferation as well as increased apoptosis, and this was also associated with a reduction in cPLA2-alpha activity. Expression of cyclin D1 and phosphorylation of Akt were also observed to decrease. Wyeth-1 inhibited PC3 xenograft growth by approximately 33% and again, also reduced cyclin D1. Immunohistochemistry of human prostate tissue revealed that phosphorylated cPLA2-alpha is increased when hormone refractory is reached.

CONCLUSIONS

Expression and activation of cPLA2-alpha are increased in the androgen-insensitive cancer cell line and tissue. Inhibition of cPLA2-alpha results in cells and xenograft tumor growth inhibition and serves as a potentially effective therapy for hormone refractory prostate cancer.

Involvement of epigenetic mechanisms in the regulation of secreted phospholipase A2 expressions in Jurkat leukemia cells

Epigenetic changes provide a frequent mechanism for transcriptional silencing of genes in cancer cells. We previously established that epigenetic mechanisms are important for control of group IIA phospholipase A(2) (PLA2G2A) gene transcription in human DU-145 prostate cells. In this study, we analyzed the involvement of such mechanisms in the regulation of five sPLA(2) isozymes and the M-type receptor of sPLA(2) (sPLA(2)-R) in human leukemic Jurkat cells. These cells constitutively expressed sPLA(2)-IB, sPLA(2)-III, sPLA(2)-X, and sPLA(2)-R but not sPLA(2)-IIA and sPLA(2)-V. Transcription of sPLA(2)-IIA and sPLA(2)-V was, however, detected after exposure of cells to the DNA demethylating agent, 5-aza-2'-deoxycytidine (5-aza-dC). Expression of sPLA(2)-IIA was further enhanced by additional exposure to interferon-gamma and blocked by inhibitors of specificity protein 1, nuclear factor kappaB, and Janus kinase/signal transducer and activator of transcription-dependent pathways. Sequence analysis and methylation-specific polymerase chain reaction of bisulfite-modified genomic DNA revealed two 5'-CpG sites (-111 and -82) in the sPLA(2)-IIA proximal promoter that were demethylated after 5-aza-dC treatment. These sites may be involved in the DNA binding of specificity protein 1 and other transcription factors. Similar findings after treatment of human U937 leukemia cells with 5-aza-dC indicate that this mechanism of PLA2G2A gene silencing is not restricted to Jurkat and DU-145 cells. These data establish that regulation of sPLA(2)-IIA and sPLA(2)-V in Jurkat and other cells involves epigenetic silencing by DNA hypermethylation.

Differential expression of secretory phospholipases A2 in normal and malignant prostate cell lines: regulation by cytokines, cell signaling pathways, and epigenetic mechanisms

Upregulation of group IIA phospholipase A(2) (sPLA(2)-IIA) correlates with prostate tumor progression suggesting prooncogenic properties of this protein. Here, we report data on expression of three different sPLA(2) isozymes (groups IIA, V, and X) in normal (PrEC) and malignant (DU-145, PC-3, and LNCaP) human prostate cell lines. All studied cell lines constitutively expressed sPLA(2)-X, whereas sPLA(2)-V transcripts were identified only in malignant cells. In contrast, no expression of sPLA(2)-IIA was found in PrEC and DU-145 cells, but it was constitutively expressed by IFN-gamma in LNCaP and PC-3 cells. Expression of sPLA(2)-IIA is upregulated in PC-3 and in PrEC cell in a signal transducer and activator of transcription-1-dependent manner, but not in LNCaP cell. Additional signaling pathways regulating sPLA(2)-IIA expression include cAMP/protein kinase A, p38 mitogen-activated protein kinase, protein kinase C, Rho-kinase, and mitogen-activated/extracellular response protein kinase / extracellular signal-regulated kinase. No deletions were revealed in the sPLA(2)-IIA gene from DU-145 cells lacking the expression of sPLA(2)-IIA. Reexpression of sPLA(2)-IIA was induced by 5-aza-2'-deoxycytidine demonstrating that DNA methylation is implicated in the regulation of sPLA(2)-II. Together, these data suggest that sPLA(2)-IIA and sPLA(2)-V, but not sPLA(2)-X, are differentially expressed in normal and malignant prostate cells under the control of proinflammatory cytokines; epigenetic mechanisms appear involved in the regulation of sPLA(2)-IIA expression, at least in DU-145 cells.

Distinct expression pattern of the full set of secreted phospholipases A2 in human colorectal adenocarcinomas: sPLA2-III as a biomarker candidate

Recent studies suggest that secreted phospholipases A₂ (sPLA₂s) represent attractive potential tumour biomarkers and therapeutic targets for various cancers. As a first step to address this issue in human colorectal cancer, we examined the expression of the full set of sPLA₂s in sporadic adenocarcinomas and normal matched mucosa from 21 patients by quantitative PCR and immunohistochemistry. In normal colon, PLA2G2A and PLA2G12A were expressed at high levels, PLA2G2D, PLA2G5, PLA2G10 and PLA2G12B at moderate levels, and PLA2G1B, PLA2G2F and PLA2G3 at low levels. In adenocarcinomas from left and right colon, the expression of PLA2G3 was increased by up to 40-fold, while that of PLA2G2D and PLA2G5 was decreased by up to 23- and 14-fold. The variations of expression for sPLA₂-IID, sPLA₂-III and sPLA₂-V were confirmed at the protein level. The expression pattern of these sPLA₂s appeared to be linked respectively to the overexpression of interleukin-8, defensin α6, survivin and matrilysin, and downregulation of SFRP-1 and RLPA-1, all these genes being associated to colon cancer. This original sPLA₂ profile observed in adenocarcinomas highlights the potential role of certain sPLA₂s in colon cancer and suggests that sPLA₂-III might be a good candidate as a novel biomarker for both left and right colon cancers.