Phospholipase C epsilon plays a suppressive role in incidence of colorectal cancer

Overarching roles of diacylglycerol signaling in cancer development and antitumor immunity

Diacylglycerol (DAG) is a lipid second messenger that is generated in response to extracellular stimuli and channels intracellular signals that affect mammalian cell proliferation, survival, and motility. DAG exerts a myriad of biological functions through protein kinase C (PKC) and other effectors, such as protein kinase D (PKD) isozymes and small GTPase-regulating proteins (such as RasGRPs). Imbalances in the fine-tuned homeostasis between DAG generation by phospholipase C (PLC) enzymes and termination by DAG kinases (DGKs), as well as dysregulation in the activity or abundance of DAG effectors, have been widely associated with tumor initiation, progression, and metastasis. DAG is also a key orchestrator of T cell function and thus plays a major role in tumor immunosurveillance. In addition, DAG pathways shape the tumor ecosystem by arbitrating the complex, dynamic interaction between cancer cells and the immune landscape, hence representing powerful modifiers of immune checkpoint and adoptive T cell-directed immunotherapy. Exploiting the wide spectrum of DAG signals from an integrated perspective could underscore meaningful advances in targeted cancer therapy.

Dissecting the Mechanism of Action of Spiperone-A Candidate for Drug Repurposing for Colorectal Cancer

Simple Summary

Despite advances in primary and adjuvant treatments, approximately 50% of colorectal cancer (CRC) patients still die from recurrence and metastatic disease. Thus, alternative and more effective therapeutic approaches are expected to be developed. Drug repurposing is increasing interest in cancer therapy, as it represents a cheaper and faster alternative strategy to de novo drug synthesis. Psychiatric medications are promising as a new generation of antitumor drugs. Here, we demonstrate that spiperone—a licensed drug for the treatment of schizophrenia—induces apoptosis in CRC cells. Our data reveal that spiperone’s cytotoxicity in CRC cells is mediated by phospholipase C activation, intracellular calcium homeostasis dysregulation, and irreversible endoplasmic reticulum stress induction, resulting in lipid metabolism alteration and Golgi apparatus damage. By identifying new targetable pathways in CRC cells, our findings represent a promising starting point for the design of novel therapeutic strategies for CRC.

Abstract

Approximately 50% of colorectal cancer (CRC) patients still die from recurrence and metastatic disease, highlighting the need for novel therapeutic strategies. Drug repurposing is attracting increasing attention because, compared to traditional de novo drug discovery processes, it may reduce drug development periods and costs. Epidemiological and preclinical evidence support the antitumor activity of antipsychotic drugs. Herein, we dissect the mechanism of action of the typical antipsychotic spiperone in CRC. Spiperone can reduce the clonogenic potential of stem-like CRC cells (CRC-SCs) and induce cell cycle arrest and apoptosis, in both differentiated and CRC-SCs, at clinically relevant concentrations whose toxicity is negligible for non-neoplastic cells. Analysis of intracellular Ca²⁺ kinetics upon spiperone treatment revealed a massive phospholipase C (PLC)-dependent endoplasmic reticulum (ER) Ca²⁺ release, resulting in ER Ca²⁺ homeostasis disruption. RNA sequencing revealed unfolded protein response (UPR) activation, ER stress, and induction of apoptosis, along with IRE1-dependent decay of mRNA (RIDD) activation. Lipidomic analysis showed a significant alteration of lipid profile and, in particular, of sphingolipids. Damage to the Golgi apparatus was also observed. Our data suggest that spiperone can represent an effective drug in the treatment of CRC, and that ER stress induction, along with lipid metabolism alteration, represents effective druggable pathways in CRC.

Predicting sulforaphane-induced adverse effects in colon cancer patients via in silico investigation

Colorectal cancer (CRC) is a significant global health burden that ranks as the third most diagnosed and second most common cause of cancer related deaths worldwide. New therapeutic strategies include chemoprevention and use of molecules which could prevent, suppress or reverse CRC progression such as sulforaphane (SFN). However, evidences about its safety in CRC patients are still lacking. The aim of this in silico investigation was to predict SFN-induced adverse effects in CRC patients by computational analysis. The study showed that 334 genes were consistently dysregulated in CRC (223 downregulated and 111 upregulated), while 38 were recognized as significant and might be used as predictive biomarkers for overall survival and metastasis (TCGA, GEO, R studio). Among them, SFN interacted with 86 genes, out of which 11 were marked as significant (correlate with overall prognosis and metastasis). Sulforaphane potentiates the overexpression of TIMP1, AURKA, and CEP55, and promotes inhibition of CRYAB, PLCE1, and MMP28, that might lead to the progression of CRC (CTD). Pathway enrichment analysis revealed that SFN stimulated Transcriptional activation of RUNX2, AURKA activation by TPX2, IL-10 signaling, while inhibited Differentiation of White and Brown Adipocyte process, an underlying pathway which inactivation led to obesity (Cytoscape ClueGo + CluePedia, DAVID). Thus, genome signature of CRC patients could serve as important factor when addressing the risk-to-benefit profile of SFN. Patients with colon cancer and increased expression of TIMP1, CCL20, SPP1, AURKA, CEP55, NEK2, SOX9 and CDK1, or downregulation of CRYAB, PLCE1, MMP28, BMP2 and PLAC8 may not be ideal candidates for SFN chemoprevention.

A novel NF-κB regulator encoded by circPLCE1 inhibits colorectal carcinoma progression by promoting RPS3 ubiquitin-dependent degradation

BACKGROUND

Constitutive activation of nuclear factor-κB (NF-κB) signaling plays a key role in the development and progression of colorectal carcinoma (CRC). However, the underlying mechanisms of excessive activation of NF-κB signaling remain largely unknown.

METHODS

We used high throughput RNA sequencing to identify differentially expressed circular RNAs (circRNAs) between normal human intestinal epithelial cell lines and CRC cell lines. The identification of protein encoded by circPLCE1 was performed using LC-MS. The function of novel protein was validated in vitro and in vivo by gain or loss of function assays. Mechanistic results were concluded by immunoprecipitation analyses.

RESULTS

A novel protein circPLCE1-411 encoded by circular RNA circPLCE1 was identified as a crucial player in the NF-κB activation of CRC. Mechanistically, circPLCE1-411 promoted the ubiquitin-dependent degradation of the critical NF-κB regulator RPS3 via directly binding the HSP90α/RPS3 complex to facilitate the dissociation of RPS3 from the complex, thereby reducing NF-κB nuclear translocation in CRC cells. Functionally, circPLCE1 inhibited tumor proliferation and metastasis in CRC cells, as well as patient-derived xenograft and orthotopic xenograft tumor models. Clinically, circPLCE1 was downregulated in CRC tissues and correlated with advanced clinical stages and poor survival.

CONCLUSIONS

circPLCE1 presents an epigenetic mechanism which disrupts NF-κB nuclear translocation and serves as a novel and promising therapeutic target and prognostic marker.

CircPLCE1 facilitates the malignant progression of colorectal cancer by repressing the SRSF2-dependent PLCE1 pre-RNA splicing

Studies have demonstrated that circular RNAs (circRNAs) play important roles in various types of cancer; however, the mechanisms of circRNAs located in the nucleus have rarely been explored. Here, we report a novel circular RNA circPLCE1 (hsa_circ_0019230) that facilitates the malignant progression of colorectal cancer (CRC) by repressing serine/arginine‐rich splicing factor 2 (SRSF2)‐dependent phospholipase C epsilon 1 (PLCE1) pre‐RNA splicing. Quantitative real‐time polymerase chain reaction was used to determine the expression of circPLCE1 in CRC tissues and cells. Cell Counting Kit‐8, Transwell and flow cytometric assays were used to assess the role of circPLE1 in CRC cell proliferation, migration and apoptosis, respectively. An animal study was conducted to test the role of circPLCE1 in vivo. Furthermore, catRAPID and RPISeq were used to predict the possible binding proteins of circPLCE1. RNA fractionation and RNA immunoprecipitation assays were used to confirm the RNA‐protein interaction. In this study, we found that circPLCE1 was more significantly down‐regulated in CRC tissues compared with that in adjacent normal tissues. However, circPLCE1 knockdown suppressed CRC cell proliferation, migration and invasion and increased apoptosis. Nude mouse experiments showed that ectopic expression of circPLCE1 dramatically increased tumour growth in vivo. Mechanistically, circPLCE1 directly bound to the SRSF2 protein, repressing SRSF2‐dependent PLCE1 pre‐RNA splicing, resulting in the progression of CRC. Individually mutating the binding sites of circPLCE1 abolished the inhibition of PLCE1 mRNA production. Our study revealed a novel molecular mechanism in the regulation of PLCE1 and suggested a new function of circular RNA.

Recent advances in MDS mutation landscape: Splicing and signalling

Recurrent cytogenetic aberrations, genetic mutations and variable gene expression have been consistently recognized in solid cancers and in leukaemia, including in Myelodysplastic Syndromes (MDS). Besides conventional cytogenetics, the growing accessibility of new techniques has led to a deeper analysis of the molecular significance of genetic variations. Indeed, gene mutations affecting splicing genes, as well as genes implicated in essential signalling pathways, play a pivotal role in MDS physiology and pathophysiology, representing potential new molecular targets for innovative therapeutic strategies.

PLCε regulates prostate cancer mitochondrial oxidative metabolism and migration via upregulation of Twist1

Background

Metabolic rewiring is a common feature of many cancer types, including prostate cancer (PCa). Alterations in master genes lead to mitochondrial metabolic rewiring and provide an appealing target to inhibit cancer progression and improve survival. Phospholipase C (PLC)ε is a regulator of tumor generation and progression. However, its role in mitochondrial metabolism remains unclear.

Methods

The GEO, The Cancer Genome Atlas, and the GTEx databases were used to determine Twist1 mRNA levels in tumors and their non-tumor counterparts. Fifty-five PCa and 48 benign prostatic hypertrophy tissue samples were tested for the presence of PLCε and Twist1 immunohistochemically. An association between PLCε and Twist1 was determined by Pearson’s correlation analysis. PLCε was knocked down with a lentiviral short hairpin RNA. Mitochondrial activity was assessed by measuring the oxygen consumption rate. Western blotting analyses were used to measure levels of PPARβ, Twist1, phosphorylated (p)-Twist1, p-MEK, p-ERK, p-P38, and p-c-Jun N-terminal kinase (JNK). Cells were treated with inhibitors of MEK, JNK, and P38 MAPK, and an agonist and inhibitor of peroxisome proliferator activated receptor (PPAR) β, to evaluate which signaling pathways were involved in PLCε-mediated Twist1 expression. The stability of Twist1 was determined after blocking protein synthesis with cycloheximide. Reporter assays utilized E-cadherin or N-cadherin luciferase reporters under depletion of PLCε or Twist1. Transwell assays assessed cell migration. Finally, a nude mouse tumor xenograft assay was conducted to verify the role of PLCε in tumor formation.

Results

Our findings revealed that the expression of PLCε was positively associated with Twist1 in clinical PCa samples. PLCε knockdown promoted mitochondrial oxidative metabolism in PCa cells. Mechanistically, PLCε increased phosphorylation of Twist1 and stabilized the Twist1 protein through MAPK signaling. The transcriptional activity of Twist1, and the Twist1-mediated epithelial-to-mesenchymal transition, cell migration, and transcription regulation, were suppressed by PLCε knockdown and by blocking PPARβ nuclear translocation. The tumor xenograft assay demonstrated that PLCε depletion diminished PCa cell tumorigenesis.

Conclusions

These findings reveal an undiscovered physiological role for PLCε in the suppression of mitochondrial oxidative metabolism that has significant implications for understanding PCa occurrence and migration.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1323-8) contains supplementary material, which is available to authorized users.

Single Nucleotide Polymorphisms in PLCE1 for Cancer Risk of Different Types: A Meta-Analysis

Background: Recent studies have investigated the relationships between PLCE1 polymorphisms and cancer susceptibility. However, some findings lack consistency.

Objectives: In the current study, we conducted a meta-analysis to more accurately evaluate the relationships between PLCE1 (rs2274223, rs3765524, rs753724, rs11187842, and rs7922612) single nucleotide polymorphisms (SNPs) and risk for different types of cancer.

Methods: We performed a comprehensive search strategy in PubMed, Web of Science, Medline, EMbase, and Scopus for articles available until 19 March 2018. A total of 54 case-control studies comprising 17,955 cases and 20,400 controls were included in the current meta-analysis, which together comprised a total of 32 publications. The pooled odds ratios (ORs) with 95% confidence intervals (CIs) were used to evaluate relationships between the PLCE1 polymorphisms and cancer susceptibility. All statistical analyses were performed using Stata 11 software.

Results: Results of the meta-analysis demonstrated that the rs2274223 polymorphism showed a significant correlation with increased overall cancer susceptibility (AG vs. AA: OR 1.168, 95% CI 1.084–1.259; GG vs. AA: OR 1.351, 95% CI 1.163–1.570; AG+GG vs. AA: OR 1.193, 95% CI 1.103–1.290; GG vs. AA+AG: OR 1.262, 95% CI 1.102–1.446; G vs. A: OR 1.163, 95% CI 1.089–1.242). Results of subgroup analysis showed that the rs2274223 polymorphism was associated with higher risk for esophageal cancer and gastric cancer relative to colorectal cancer and head and neck cancer. In addition, the rs2274223 polymorphism was found to be associated with increased cancer risk, especially among the subgroups comprising Asians, studies with population-based controls, studies employing the TaqMan genotyping method, and studies consistent with Hardy-Weinberg equilibrium (HWE). The association between the rs3765524 polymorphism and reduced overall cancer risk was detected in one specific genetic model (CT vs. CC: OR 0.681, 95% CI 0.523–0.886). Results of subgroup analysis showed that the rs3765524 polymorphism was associated with cancer risk in a specific genetic model among the subgroups of colorectal cancer, esophageal cancer, Asians, studies with population-based controls, and studies consistent with HWE. However, relationships among the PLCE1 rs753724, rs11187842, and rs7922612 polymorphisms and tumor risk were not identified.

Conclusions: Results of the current meta-analysis suggested that PLCE1 (rs2274223, rs3765524) polymorphisms are associated with cancer susceptibility.

PLCE1 polymorphisms and expression combined with serum AFP level predicts survival of HBV-related hepatocellular carcinoma patients after hepatectomy

Polymorphisms in the phospholipase C epsilon (PLCE) 1 gene play a crucial role in the development and progression of several types of cancer. The present study investigated the prognostic significance of PLCE1 gene polymorphisms and expression combined with serum α-fetoprotein (AFP) level in hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC). Single nucleotide polymorphisms were genotyped by sequencing DNA isolated from surgically resected tumor samples of 421 HBV-related HCC patients, and expression profiles were generated based on the GSE14520 dataset. A joint-effects analysis of PLCE1 haplotypes (Ars2274223Crs3765524; Grs2274223Trs3765524) with AFP level stratified at 20 ng/ml showed a significant association with overall survival(OS) of HBV-related HCC patients(log-rank P=0.0003). Patients with AC and GT haplotypes with AFP level ≥ 20 ng/ml had an increased risk of death as compared to those with the AC haplotype and AFP level < 20 ng/ml (adjusted P=0.029 and 0.041, respectively). Patients with the GT haplotype and AFP level < 20 ng/ml also had an increased risk of death, although with a non-significant P value (adjusted P=0.092). Joint-effects analysis of PLCE1 mRNA expression with serum AFP level stratified at 300 ng/ml was significantly associated with HBV-related HCC recurrence and OS. Our results demonstrate that PLCE1 haplotypes (including rs2274223 and rs3765524) and expression combined with serum AFP level may predict postoperative outcome of HBV-related HCC patients.

Comprehensive bioinformation analysis of the miRNA of PLCE1 knockdown in esophageal squamous cell carcinoma

Phospholipase C epsilon 1 (PLCE1) has been recognized as a novel susceptibility marker for esophageal squamous cell carcinoma (ESCC). The purpose of our study is to investigate its effect on the regulation of miRNA expression so as to translating the data into a novel strategy in control of ESCC. In this study, PLCE1 siRNA and vector-only plasmid were stably transfected into Eca109 and EC9706 cells and then subjected to miRNA array analysis, and quantitative real-time PCR was applied to validate miRNA array data. Then bioinformatic analyses, such as GO and pathway software, were conducted to obtain data on these differentially expressed miRNAs-targeted genes (DEGs) and clarify their function and pathway. The results showed that 36 miRNAs were found to be differentially expressed in PLCE1 siRNA-transfected cells compared with the control cells. In particular, 28 miRNAs were upregulated while 8 miRNAs were downregulated. Gene Ontology analysis showed that the function of the DEGs included cell cycle arrest, cell-matrix adhesion, apoptosis, etc. After this, the major pathways associated with the DEGs were regulation of actin cytoskeleton, TGF-beta signaling pathway, Notch signaling pathway and so on. Taken together, these results showed that the knockdown of PLCE1 may play a vital role in the control of ESCC. Further investigation will reveal and verify the function and pathway of the DEGs for the development of novel treatment strategy for the better control of ESCC.

Decreased MALL expression negatively impacts colorectal cancer patient survival

The aim of the present study was to determine whether MALL expression is associated with colon cancer progression and patient survival. MALL mRNA expression was reduced in the tumor tissues of 70% of the colon cancer patients and 75% of the rectal cancer patients as compared to their normal tissues. MALL protein was also significantly reduced in the tumor tissues of colon cancer patients (P < 0.001). Increased LOH and methylation of MALL was observed in tumor tissues as compared to normal tissues. Reduced MALL expression was associated with vessin invasion, disease recurrence and metastasis or death (P ≤ 0.027). Furthermore, patients with MALL-negative tumors had significantly decreased overall survival (OS) and disease-free survival (DFS) (P < 0.008 and P < 0.011, respectively). Univariate analysis indicated that MALL expression was significantly associated with OS and DFS. Finally, overexpression of MALL suppressed HCT116 and SW480 cell proliferation and inhibited HCT116 migration. MALL may play a role in colorectal cancer progression as suppression of its expression in tumor tissues negatively impacts colorectal cancer patient survival. Further analyses are required to determine if reduced MALL expression is due to LOH and/or methylation.

Comprehensive bioinformatics analysis of the mRNA profile of PLCE1 knockdown in esophageal squamous cell carcinoma

The authors previously reported that Phospholipase C epsilon 1 (PLCE1) exacerbated esophageal squamous cell carcinoma (ESCC), however, the underlying mechanism remains to be fully elucidated. The present study aimed to identify key differentially expressed genes (DEGs) and signaling pathways regulated by PLCE1 in ESCC. EC9706 and Eca109 cell lines were transfected with the specific small interfering (si) RNA of PLCE1, reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) and western blotting were performed to detect the expression levels of PLCE1, and subsequently, mRNA array and multiple bioinformatics analysis were conducted. RT‑qPCR was used to verify gene expression array results. The findings of the present study indicated that PLCE1 mRNA and protein expression were significantly suppressed (P<0.05) in the PLCE1 siRNA‑transfected cells. In addition, a total of 223 DEGs with >2‑fold alterations were screened between the PLCE1 siRNA‑treated cells, including 168 upregulated and 53 downregulated DEGs. In particular, inflammation or immune‑associated molecules, including Toll‑like receptor (TLR)‑4 interleukin‑6, ‑8 and chemokine C‑X‑C motif ligand 2 were significantly increased following PLCE1 knockdown. Furthermore, Gene Ontology enrichment revealed terms associated with cell proliferation, differentiation, apoptosis, signal transduction, invasion and metastasis, which may potentially be associated with PLCE1 function. Kyoto Encyclopedia of Genes and Genomes pathway analysis demonstrated 46 pathways were disturbed by DEGs, including focal adhesion, mitogen activated protein kinase, TLR, p53 and janus kinase/signal transducer and activator of transcription signaling pathways. The RT‑qPCR results for validation of the selected DEGs were consistent with that of the microarray data. Overall, the results of the multiple bioinformatic analysis contributes to a systematic understanding of the roles of PLCE1 in ESCC.

MicroRNA-34a functions as a tumor suppressor by directly targeting oncogenic PLCE1 in Kazakh esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is one of the frequent malignant tumors with poor prognosis worldwide. Identifying the prognostic biomarkers and potential mechanisms of such tumors has attracted increasing interest in esophageal cancer biology. Our previous study showed that phospholipase C elipson 1 (PLCE1) expression is up-regulated and associated with disease progression in esophageal carcinoma. MicroRNAs (miRNAs) play vital roles in regulating its target gene expression. However, studies on miRNA-regulated PLCE1 expression and its cellular function are still very few. We found that miR-34a is significantly expressed lower in ESCC tissues. We further showed that PLCE1 is a direct functional target gene of miR-34a, and the functional roles of miR-34a in ESCC cell lines in vitro were also determined through gain- and loss-of-function analyses. Results revealed that miR-34a functions as a tumor suppressor by inhibiting the proliferation, migration, and EMT phenotype, as well as promoting apoptosis of ESCC cell lines. Moreover, PLCE1 is overexpressed in ESCC tumors and promotes tumorigenicity in vivo and vitro. PLCE1 expression is negatively correlated with miR-34a profiles in ESCC tissues. Our data suggest that miR-34a exerts its anti-cancer function by suppressing PLCE1. The newly identified miR-34a/PLCE1 axis partially illustrates the molecular mechanism of ESCC metastasis and represents a new candidate therapeutic target for ESCC treatment.

The controversial role of phospholipase C epsilon (PLCε) in cancer development and progression

The phospholipase C (PLC) enzymes are important regulators of membrane phospholipid metabolism. PLC proteins can be activated by the receptor tyrosine kinases (RTK) or G-protein coupled receptors (GPCR) in response to the different extracellular stimuli including hormones and growth factors. Activated PLC enzymes hydrolyze phosphoinositides to increase the intracellular level of Ca²⁺ and produce diacylglycerol, which are important mediators of the intracellular signaling transduction. PLC family includes 13 isozymes belonging to 6 subfamilies according to their domain structures and functions. Although importance of PLC enzymes for key cellular functions is well established, the PLC proteins belonging to the ε, ζ and η subfamilies were identified and characterized only during the last decade. As a largest known PLC protein, PLCε is involved in a variety of signaling pathways and controls different cellular properties. Nevertheless, its role in carcinogenesis remains elusive.

The aim of this review is to provide a comprehensive and up-to-date overview of the experimental and clinical data about the role of PLCε in the development and progression of the different types of human and experimental tumors.

Low PLCE1 levels are correlated with poor prognosis in hepatocellular carcinoma

Background

Previous reports show that phospholipase C epsilon-1 (PLCE1) expression is positively correlated with esophageal squamous cell carcinoma and gastric cardia adenocarcinomas; however, the expression of PLCE1 in hepatocellular carcinoma (HCC) and its correlation with clinical outcome still remain unclear. The aim of this study was to explore the expression of PLCE1 in HCC tissue and to determine whether PLCE1 was a prognostic factor for HCC patients.

Materials and methods

PLCE1 levels in 20 paired HCC tissues and corresponding paracarcinomatous tissues was investigated by quantitative real-time polymerase chain reaction and Western blot assays. In addition, protein levels of PLCE1 in one normal liver epithelial cell and four HCC cell lines were examined using Western blot assay. Moreover, immunohistochemistry was applied to determine the expression of PLCE1 in HCC and corresponding surrounding tissues from 90 patients. Statistical analyses were used to examine the association between PLCE1 levels and clinicopathological features.

Results

We found that the expression of PLCE1 in tumor tissues was significantly lower than those in paracarcinomatous tissues at both mRNA and protein levels (P<0.05). We also determined that PLCE1 protein expression levels were lower in HCC cell lines than normal liver epithelial cells (P<0.05). Notably, immunohistochemical assay showed that PLCE1 expression was significantly low in HCC tissues compared with the adjacent normal liver tissues (40% vs 18.9%; P<0.05). Besides, PLCE1 levels were negatively correlated with tumor capsulae, vascular invasion, Edmondson grade, alpha-fetoprotein, and tumor-node-metastasis stage (P<0.05). Univariate analysis revealed that lower level expression of PLCE1 was significantly associated with poorer overall survival (OS) rate (P<0.001) and disease-free survival rate (P<0.001). Multivariate analysis revealed that low PLCE1 level was an independent poor prognostic factor of OS and recurrence-free survival (P<0.001 and P=0.003, respectively).

Conclusion

In brief, our results revealed that decreased PLCE1 expression was associated with tumor progression in HCC and may function as a promising biomarker for HCC prognosis.

Targeting oncogenic PLCE1 by miR-145 impairs tumor proliferation and metastasis of esophageal squamous cell carcinoma

Phospholipase C epsilon 1 (PLCE1) is a susceptibility gene in esophageal squamous cell carcinoma (ESCC). Nevertheless, the role of PLCE1 in ESCC tumorigenesis has not been elucidated. In this study, we determined the function of PLCE1 and its regulatory microRNA (miRNA) in ESCC. PLCE1 protein was excessively expressed in ESCC and precancerous lesions compared with that in normal tissues. High PLCE1 expression levels in ESCC were significantly linked with poor overall survival. Knockdown of PLCE1 promoted the apoptosis, cytokine-induced apoptosis, and sensitivity of cancer cells to chemotherapeutic drugs but abrogated the proliferation and EMT phenotype of ESCC in vitro. Notably, miR-145 was newly identified as a potent repressor of PLCE1 expression by directly targeting the 3′UTR of PLCE1. MiR-145 also inhibited cell proliferation, migration, and metastasis, as well as controlled the cytoskeleton dynamics of esophageal cancer. Moreover, miR-145 was expressed at low levels in a large cohort of patients with ESCC and was inversely correlated with PLCE1 protein expression in cancer cells and tissues. These findings demonstrate that PLCE1 functions as tumor promoter in ESCC and can be suppressed by miR-145 through inhibition of PLCE1 translation. Hence, delivery of PLCE1-targeting miR-145 is a potential therapeutic approach for esophageal cancer.

Genetic Variations in Phospholipase C-epsilon 1 (PLCE1) and Susceptibility to Colorectal Cancer Risk

Colorectal cancer (CRC) is the third most common cause of cancer-related mortality and causes almost a million deaths worldwide each year. Genetic and environmental factors have gained importance in CRC as well as other types of cancer due to contribution to development of malignancies. Phosholipase C-epsilon 1 PLCE1 is one of the phospholipase family of enzymes and controls cellular responses leading to cell growth, differentiation and gene expression. Therefore, it was evaluated the effects of PLCE1 variations on developing CRC. Rs2274223 was significantly associated with CRC risk (OR = 2.018) while rs3765524 did not significantly differ (p > 0.05). The findings are the first results of PLCE1 profiles in the Turkish and could provide an understanding of aetiology in CRC.

MiR-328 suppresses the survival of esophageal cancer cells by targeting PLCE1

Esophageal cancer (EC) is the sixth leading cause of death worldwide. Recent studies have highlighted the vital role of microRNAs (miRNAs) in EC development and diagnosis. In our study, qPCR analysis showed that miRNA-328 was expressed at significantly low levels in EC109 and EC9706 cells. The results also showed that overexpression of miR-328 by lentivirus-mediated gene transfer markedly inhibited cell proliferation and invasion, and enhanced apoptosis; whereas, inhibition of miR-328 significantly promoted cell proliferation and invasion, and suppressed apoptosis in EC109 and EC9706 cells. Dual-luciferase reporter assay confirmed that miR-328 directly targeted phospholipase C epsilon 1 (PLCE1) by binding to target sequences in the 3'-UTR. qPCR and Western blot analysis showed that the PLCE1 was overexpressed in EC109 and EC9706 cells. Additionally, we found that miR-328 overexpression decreased PLCE1 mRNA and protein levels, while miR-328 inhibition enhanced the PLCE1 expression. Further analysis showed that PLCE1 overexpression rescued the inhibitory effect of miR-328 on cell proliferation and invasion, and repressed the promotive effect of miR-328 on cell apoptosis. In conclusion, our results suggest that miR-328 suppresses the survival of EC cells by regulating PLCE1 expression, which might be a potential therapeutic method for EC.

Phosphoinositide-specific phospholipase C in health and disease

Phospholipases are widely occurring and can be found in several different organisms, including bacteria, yeast, plants, animals, and viruses. Phospholipase C (PLC) is a class of phospholipases that cleaves phospholipids on the diacylglycerol (DAG) side of the phosphodiester bond producing DAGs and phosphomonoesters. Among PLCs, phosphoinositide-specific PLC (PI-PLC) constitutes an important step in the inositide signaling pathways. The structures of PI-PLC isozymes show conserved domains as well as regulatory specific domains. This is important, as most PI-PLCs share a common mechanism, but each of them has a peculiar role and can have a specific cell distribution that is linked to a specific function. More importantly, the regulation of PLC isozymes is fundamental in health and disease, as there are several PLC-dependent molecular mechanisms that are associated with the activation or inhibition of important physiopathological processes. Moreover, PI-PLC alternative splicing variants can play important roles in complex signaling networks, not only in cancer but also in other diseases. That is why PI-PLC isozymes are now considered as important molecules that are essential for better understanding the molecular mechanisms underlying both physiology and pathogenesis, and are also potential molecular targets useful for the development of innovative therapeutic strategies.

Dysfunction of phospholipase Cγ in immune disorders and cancer

The surge in genetic and genomic investigations over the past 5 years has resulted in many discoveries of causative variants relevant to disease pathophysiology. Although phospholipase C (PLC) enzymes have long been recognized as important components in intracellular signal transmission, it is only recently that this approach highlighted their role in disease development through gain-of-function mutations. In this review we describe the new findings that link the PLCγ family to immune disorders and cancer, and illustrate further efforts to elucidate the molecular mechanisms that underpin their dysfunction.

Phospholipase Cδ1 induces E-cadherin expression and suppresses malignancy in colorectal cancer cells

Colorectal cancer (CRC) is one of the most common causes of cancer-related deaths worldwide, and Kirsten rat sarcoma viral oncogene homolog (KRAS) mutations in CRC predict the ineffectiveness of EGF receptor-targeted therapy. Previous transcriptional microarray analysis suggests the association between phospholipase Cδ1 (PLCδ1) expression and KRAS mutation status in CRC. However, both the roles and the regulatory mechanisms of PLCδ1 in CRC are not known. Here, we found that the expression of PLCδ1, one of the most basal PLCs, is down-regulated in CRC specimens compared with normal colon epithelium by immunohistochemistry. Furthermore, we examined the roles of PLCδ1 in CRC cell lines that harbor an activating KRAS mutation. Ectopic expression of PLCδ1 in CRC cells induced the expression of E-cadherin, whereas knockdown of PLCδ1 repressed the expression of E-cadherin. Moreover, the overexpression of PLCδ1 suppressed the expression of several mesenchymal genes and reduced cell motility, invasiveness, and in vivo tumorigenicity of SW620 CRC cells. We also showed that PLCδ1 expression is repressed by the KRAS/mitogen-activated protein kinase kinase (MEK) pathway. Furthermore, PLCδ1 suppressed the phosphorylation of extracellular signal-regulated kinase (ERK)1/2 through E-cadherin induction in CRC cells, suggesting the presence of a negative regulatory loop between KRAS/MEK/ERK signaling and PLCδ1. These data indicate that PLCδ1 has tumor-suppressive functions in CRC through E-cadherin induction and KRAS/MEK/ERK signal attenuation.

Role of novel and GWAS originated PLCE1 genetic variants in susceptibility and prognosis of esophageal cancer patients in northern Indian population

Recent genome-wide association studies (GWAS) have identified variants in phospholipase C epsilon1 (PLCE1) as novel susceptibility markers for esophageal squamous cell carcinoma (ESCC) in Chinese population. Although few studies have replicated this findings in other populations, but results are contradictory. So, we aimed to replicate association of two previously reported non-synonymous polymorphisms (rs2274223A>G and rs3765524C>T) from haplotype block 10 and evaluated a novel variant (rs7922612C>T) from haplotype block 2 of PLCE1 with susceptibility and prognosis of ESCC in northern Indian population. The genotyping of PLCE1 variants were performed in 293 histopathologically confirmed incident ESCC cases (including 177 follow-up cases) and 314 age-, gender-, and ethnicity-matched controls using PCR RFLP. All statistical analyses were performed through SPSS version 15.0. Modeling and functional prediction of two non-synonymous variants were carried out using bioinformatics tools. PLCE1 polymorphisms were not associated with susceptibility to ESCC or its clinical phenotypes (tumor location/lymph node metastasis). No interaction with environmental risk factors was found. In silico analysis suggested negligible effect on structure of PLCE1 protein due to PLCE1 rs2274223 (H1927R) and rs3765524 (T1777I) polymorphisms. Survival analysis showed PLCE1 rs7922612CT + TT genotype conferred adverse outcome to ESCC patients. Our study for the first time suggests that GWAS originated PLCE1 variants do not have independent role in susceptibility of ESCC in northern Indian population; however, a novel haplo-tagging SNP rs7922612 may modify survival outcome of ESCC patients.

Association of potentially functional genetic variants of PLCE1 with gallbladder cancer susceptibility in north Indian population

BACKGROUND AND OBJECTIVES

Phospholipase C epsilon 1 (PLCE1) plays crucial roles in carcinogenesis and progression of esophageal and gastric cancers. In the present study, we investigated association of GWAS identified rs2274223 A>G and. rs7922612 T>C polymorphism of PLCE1 with susceptibility to gallbladder cancer (GBC).

METHODS

The study involved genotyping of selected PLCE1 variants in 416 GBC cases and 225 controls. Haplotype analysis was done by SNPStats. In silico analyses were performed using bioinformatic tools.

RESULTS

PLCE1 rs2274223 [AG] and rs7922612 [CC] genotypes were found to be significantly associated with an increased risk of GBC [OR = 1.9, p = 0.002; OR = 2.0, p = 0.04, respectively]. PLCE1 haplotype [Grs2274223-Crs7922612] also showed significant association with GBC [OR = 1.8, p = 0.04]. The association was significant in females and GBC patients with stones and female GBC patients with gallstones [OR = 2.6, p = 0.01; OR = 3.3, p = 0.007], respectively. However, no significant associations with other risk factors such as tobacco usage and age of onset were found. Functional prediction of rs2274223 A>G suggested change in protein coding and splicing regulation.

CONCLUSION

The present study found a significant association of PLCE1 rs2274223 and rs7922612 polymorphisms with susceptibility to GBC probably through gallstone-mediated inflammatory pathway.

PLCE1 mRNA and protein expression and survival of patients with esophageal squamous cell carcinoma and gastric adenocarcinoma

BACKGROUND

Germline genetic variants in PLCE1 (10q23) have demonstrated consistent associations with risk of esophageal squamous cell carcinoma (ESCC) and gastric cancer among Chinese. We evaluated PLCE1 mRNA and protein expression in paired tumor-normal tissues, and their relationship with survival.

METHODS

PLCE1 mRNA was profiled using three probes in the Affymetrix GeneChip U133 for paired tumor-normal tissues of ESCC (n = 132), gastric cardia adenocarcinoma (GCA, n = 62), and gastric noncardia adenocarcinoma (GNCA, n = 72). We used immunohistochemistry to detect PLCE1 protein on slides from tissue microarrays in paired tumor-normal tissues of ESCC (n = 303), and tumors of GCA (n = 298) and GNCA (n = 124).

RESULTS

Compared with normal tissues, PLCE1 mRNA expression was significantly reduced in ESCC tumors (P = 0.03, probe_205112_at), as well as in GCA and GNCA tumors (P < 0.0001, each probe). Protein expression was nonsignificantly reduced in ESCC tumors (P = 0.51). Increased tumor-normal mRNA fold change (probe_205112_at) was associated with longer survival in ESCC (9.6 months for highest vs. lowest quartile; Ptrend = 0.02). Increased mRNA tumor-normal fold change (probe_205111_at) was associated with longer survival for GCA (10.7 months for highest quartile; Ptrend = 0.04), but not for GNCA cases (P = 0.72). Similar to mRNA, elevated tumor-normal fold change for protein in ESCC was also associated with improved survival (8.1 months for highest quartile; Ptrend = 0.04).

CONCLUSIONS

Dysregulated PLCE1 mRNA expression was observed for both ESCC (one probe only) and GCA tumors, and the altered PLCE1 expression seems to be associated with cancer prognosis.

IMPACT

A potential role for PLCE1 in the early detection and/or therapy of ESCC and GCA warrants further investigation.

Tumor suppressor role of phospholipase C epsilon in Ras-triggered cancers

Phospholipase Cε (PLCε) has been characterized as a direct effector of Ras in vitro and in cellular systems; however, the role of PLCε in tumorigenesis and its link to Ras in this context remain unclear. To assess the role of PLCε in Ras-driven cancers, we generated two new mouse strains: one carrying a targeted deletion of Plce (Plce(-/-)) and the other carrying mutant alleles of Plce unable to bind to Ras (Plce(RAm/RAm)). The Plce(-/-) and, to a lesser degree, Plce(RAm/RAm) transgenic mice exhibited increased susceptibility to tumor formation in the two-stage skin carcinogenesis protocol, revealing a tumor suppressor function for this PLC. This result also suggests that in this context Ras binding in part regulates functions of PLCε. Although significant differences were not seen in the LSL-Kras(G12D) nonsmall cell lung carcinoma model, down-regulation of PLCε was found in animal tumors and in cellular systems following expression of the oncogenic Ras. An inhibitory impact of PLCε on cell growth requires intact lipase activity and is likely mediated by protein kinase C enzymes. Further cellular studies suggest involvement of histone deacetylase in the mechanism of PLCε down-regulation. Taken together, our results show a previously unidentified tumor suppressor role for this PLC in animal models and, together with observations of marked down-regulation in colorectal, lung, and skin tumors, suggest its use as a biological marker in cancer.

Identification of Staphylococcus aureus α-hemolysin as a protein drug that is secreted by anticancer bacteria and rapidly kills cancer cells

Targeted bacterial delivery of anticancer proteins has the ability to overcome therapeutic resistance in tumors that limits the efficacy of chemotherapeutics. The ability of bacteria to specifically target tumors allows for delivery of aggressive proteins that directly kill cancer cells and cannot be administered systemically. However, few proteins have been tested for this purpose. To identify effective molecules, we systematically sorted proteins that have been shown to cause mammalian cell death. The genes for five proteins were selected and cloned into Escherichia coli and Salmonella. Supernatant from cultures of the transformed bacteria was applied to flasks of MCF-7 mammary carcinoma cells to identify proteins that (1) were expressed, (2) secreted, and (3) rapidly killed cancer cells. Time-lapse images were taken to visualize mammalian cell morphology. Of the investigated proteins, α-hemolysin from Staphylococcus aureus (SAH) was the most promising because it was secreted, caused trauma to cellular membranes, and induced oncosis in 18 min. After exposure for 6 h, SAH decreased cell viability by 90%. In comparison, the positive control, Pseudomonas aeruginosa exotoxin A (PEA), required 11 days to achieve a similar effect, when administered at 3,000 times its LC50 . The maximum death rate induced by SAH was calculated to be a reduction in cell viability of 7.1% per min, which was 200-fold faster than the PEA control. Two proteins, Dermonecrotic Toxin and Phospholipase C were active when extracted from the bacterial cytoplasm but were not secreted. This investigation revealed for the first time SAH as a potent anticancer drug for delivery by bacteria because of its ability to be secreted in a fully functional form and aggressively kill cancer cells.

PLCE1 rs2274223 A>G polymorphism and cancer risk: a meta-analysis

Phospholipase C epsilon 1 gene (PLCE1) encodes a phospholipase enzyme which regulates various physiological processes (cell growth, differentiation, and apoptosis) and is supposed to play a critical role in carcinogenesis. Recently, a single nucleotide polymorphism (rs2274223 A>G) in PLCE1 was reported as a novel susceptibility locus for esophageal and gastric cancers by genome-wide association studies performed in Chinese population. However, individual association studies replicating this finding showed inconclusive results. Therefore, we performed a meta-analysis of eligible studies to derive precise estimation of the association of PLCE1 rs2274223 A>G polymorphism with cancer risk. We performed pooled analysis of 12 case–control studies including 7,622 cases and 9,555 controls. Odds ratios and 95 % confidence interval were calculated to assess strength of association in overall studies and in subgroup analysis stratified by ethnicity, cancer types, and source of controls. All statistical analyses were performed by MIX 2.0 software. We found that PLCE1 rs2274223 A>G polymorphism was significantly associated with increased risk of cancer in log additive/dominant model and at allele level (GG vs. AA: OR = 1.24, 95 % CI = 1.01–1.53, P = 0.039; AG vs. AA: OR = 1.24, 95 % CI = 1.16–1.32, P < 0.001; AG + GG vs. AA: OR = 1.22, 95 % CI = 1.12–1.34, P < 0.001; and G vs. A allele: OR = 1.15, 95 % CI = 1.05–1.25, P = 0.002). Further, stratified analysis showed elevated risk of only gastric and esophageal tumors. Sub-group analysis based on ethnicity suggests PLCE1 polymorphism conferred significant risk among Asian (Chinese) but not in Caucasian. In conclusion, PLCE1 rs2274223 polymorphism may be used as potential biomarker for cancer susceptibility particularly for esophageal/gastric cancer and for the Chinese population.

Association between phospholipase C epsilon gene (PLCE1) polymorphism and colorectal cancer risk in a Chinese population

OBJECTIVE

To investigate the association between a single nucleotide polymorphism rs2274223 (adenine [A] to guanine [G]) in the phospholipase C epsilon 1 (PLCE1) gene and susceptibility to colorectal cancer (CRC).

METHODS

The PLCE1 rs2274223 polymorphism was genotyped in patients with CRC and age- and sex-matched cancer-free control subjects from a Chinese population in a case-control study. PLCE1 mRNA levels in pair-matched tumour and adjacent noncancerous tissue were evaluated by real-time quantitative reverse transcription-polymerase chain reaction.

RESULTS

A total of 417 patients with CRC and 416 control subjects were enrolled in the study. The AG and GG genotypes of PLCE1 rs2274223 were associated with a significantly increased risk of CRC (for AG + GG versus AA: adjusted odds ratio 1.52, 95% confidence interval 1.15, 2.00). PLCE1 mRNA levels were significantly lower in tumours than in adjacent noncancerous tissue. Lower levels of PLCE1 mRNA were observed in both AG and GG genotype carriers compared with the AA genotype carriers.

CONCLUSIONS

These results indicate that the PLCE1 rs2274223 A > G change might reduce gene expression and that the variant G genotype might contribute to the increased risk of CRC.

Phospholipase C epsilon 1 (PLCE1) haplotypes are associated with increased risk of gastric cancer in Kashmir Valley

BACKGROUND/AIM

Phospholipase C epsilon 1 (PLCE1) plays a crucial role in carcinogenesis and progression of several types of cancers. A single nucleotide polymorphism (SNP, rs2274223) in PLCE1 has been identified as a novel susceptibility locus. The aim of the present study was to investigate the role of three potentially functional SNPs (rs2274223A > G, rs3765524C > T, and rs7922612C > T) of PLCE1 in gastric cancer patients from Kashmir Valley.

PATIENTS AND METHODS

The study was conducted in 108 GC cases and 195 healthy controls from Kashmir Valley. Genotyping was performed by polymerase chain reaction-restriction fragment length polymorphism method. Data were statistically analyzed using c2 test and logistic regression models. A P value of less than 0.05 was regarded as statistically significant.

RESULTS

The frequency of PLCE1 A2274223C3765524T7922612, G2274223C3765524T7922612 , and G2274223T3765524C7922612 haplotypes were higher in patients compared with controls, conferred high risk for GC [odds ratio (OR) =6.29; P = 0.001; Pcorr = 0.003], (OR = 3.23; P = 0.011; Pcorr = 0.033), and (OR = 5.14; P = 0.011; Pcorr = 0.033), respectively. Smoking and salted tea are independent risk factors for GC, but we did not find any significant modulation of cancer risk by PLCE1 variants with smoking or excessive consumption of salted tea.

CONCLUSION

These results suggest that variation in PLCE1 may be associated with GC risk in Kashmir Valley.

Comprehensive genomic analyses of a metastatic colon cancer to the lung by whole exome sequencing and gene expression analysis

We performed whole exome sequencing and gene expression analysis on a metastatic colon cancer to the lung, along with the adjacent normal tissue of the lung. Whole exome sequencing uncovered 71 high-confidence non‑synonymous mutations. We selected 16 mutation candidates, and 13 out of 16 mutations were validated by targeted deep sequencing using the Ion Torrent PGM customized AmpliSeq panel. By integrating mutation, copy number and gene expression microarray data, we identified a JAZF1 mutation with a gain-of-copy, suggesting its oncogenic potential for the lung metastasis from colon cancer. Our pathway analyses showed that the identified mutations closely reflected characteristics of the metastatic site (lung) while mRNA gene expression patterns kept genetic information of its primary tumor (colon). The most significant gene expression network was the 'Colorectal Cancer Metastasis Signaling', containing 6 (ADCY2, ADCY9, APC, GNB5, K-ras and LRP6) out of the 71 mutated genes. Some of these mutated genes (ADCY9, ADCY2, GNB5, K-ras, HDAC6 and ARHGEF17) also belong to the 'Phospholipase C Signaling' network, which suggests that this pathway and its mutated genes may contribute to a lung metastasis from colon cancer.

Increased risk of developing digestive tract cancer in subjects carrying the PLCE1 rs2274223 A>G polymorphism: evidence from a meta-analysis

Background

To date, the association between phospholipase C epsilon 1 (PLCE1) rs2274223 A>G and risk of digestive tract cancer (DTC) remains inconclusive. To derive a more precise estimation of the association, we conducted a meta-analysis on all eligible case–control studies involving 8281 cases and 10,532 controls.

Methods

A comprehensive search was conducted to identify all eligible studies of PLCE1 rs2274223 polymorphism and digestive tract cancer risk. The pooled odds ratio (OR) and the 95% confidence interval (95% CI) were calculated using a fixed or random effect model. Heterogeneity, publication bias, and sensitivity analysis were also explored.

Results

Overall, the PLCE1 rs2274223 A>G polymorphism was associated with risk of DTC in all genetic models (GA vs. AA: OR = 1.21, 95% CI = 1.14–1.29, P<0.001; GG vs. AA: OR = 1.30, 95% CI = 1.06–1.60, P = 0.012; GG/GA vs. AA: OR = 1.20, 95% CI = 1.10–1.32, P<0.001; GG vs. GA/AA: OR = 1.21, 95% CI = 1.01–1.46, P = 0.040). The recessive model did not reach statistically significance when the P values were Bonferroni corrected to 0.0125. In the stratified analysis by cancer type, ethnicity, and source of controls, significantly increased risk was observed for esophagus cancer, Asians in three genetic models (heterozygote comparison, homozygote comparison and dominant model), population-based studies in all genetic models, and for gastric cancer in the heterozygote comparison and dominant model after Bonferroni correction. However, in the subsite of gastric cancer, no significant association was found either in cardia or non-cardia gastric cancer.

Conclusion

Our study indicated that PLCE1 rs2274223 A>G polymorphism was significantly associated with increased risk of DTC, especially among Asian populations. Due to some minor limitations, our findings should be confirmed in further studies.

PLCɛ and the RASSF family in tumour suppression and other functions

Not all proteins implicated in direct binding to Ras appear to have a positive role in the generation and progression of tumours; examples include Phospholipase C epsilon (PLCɛ) and some members of the Ras-association domain family (RASSF). The RASSF family comprises of ten members, known as RASSF1 to RASSF10. PLCɛ and RASSF members carry a common Ras-association domain (RA) that can potentially bind Ras oncoproteins and mediate Ras-regulated functions. RASSF1 to RASSF6 also share a common SARAH domain that facilitates protein-protein interactions with other SARAH domain proteins. The majority of the family are frequently downregulated by epigenetic silencing in cancers. They are implicated in various important biological processes including apoptosis, microtubule stabilisation and cell cycle regulation. Recent studies have reinforced the tumour suppressive properties of the RASSF family, with new evidence of emerging pathways and novel functions that suggest a wider role for these proteins. This review will first describe an emerging role of PLCɛ in tumour suppression and then focus on and summarise the new findings on the RASSF family in the last five years to consolidate their well-established functions, and highlight the new regulatory roles of specific RASSF members.

Multiple polymorphisms within the PLCE1 are associated with esophageal cancer via promoting the gene expression in a Chinese Kazakh population

Although recent genome-wide association studies of esophageal squamous cell carcinoma (ESCC) identified a susceptibility locus in phospholipase C epsilon 1 (PLCE1) in Chinese Han populations, few studies further confirmed these findings in pure Kazakh population in which there are higher incidence and mortality of ESCC. Here, we investigated the potential associations between 19 SNPs of PLCE1 and susceptibility to ESCC in 222 cases and 326 controls from a pure ethnic population of Kazakh. Real-time PCR and immunohistochemistry were performed to detect the PLCE1 expression levels and evaluate their association with PLCE1 polymorphism. We found that only 4 SNPs (rs753724, rs11187842, rs2274223, and rs12263737) with moderate linkage disequilibrium (LD) confer significantly increased risk of ESCC, with the ORs ranging from 1.43 to 2.04, and there was a risk allele dose-dependent increase in ESCC risk (P-trend=0.043). Especially, the risk effects of rs2274223 were more evident in poor differentiation and advanced clinical stages of Kazakh ESCC. Additionally, the significantly lowest PLCE1 mRNA expression was found in the KYSE-150 cell line having no risk alleles compared with other three cell lines having risk alleles, and the normal tissues of both homozygous mutant type of PLCE1 rs12263737 and rs2274223 had a higher PLCE1 staining score than that of homozygous wild type. Our findings suggested that genetic variants in PLCE1 might serve as candidate markers for Kazakh ESCC susceptibility, and these LD variants might influence ESCC risk individually and jointly by promoting the messenger RNA and protein expression of the gene.

Overexpression of PLCE1 in Kazakh esophageal squamous cell carcinoma: implications in cancer metastasis and aggressiveness

Three recent large-scale genome-wide association studies (GWAS) in Chinese Han populations have identified an esophageal squamous cell carcinoma (ESCC) susceptibility locus within phospholipase C epsilon 1 (PLCE1) gene, which encodes a phospholipase involved in intracellular signaling. The expressed PLCE1 in ESCC, however, are inconsistent. This study examined PLCE1 expression by immunohistochemistry (IHC) from 110 ethnic Kazakh ESCC patients and 50 from adjacent normal esophageal tissues (NETs). The expressed PLCE1 was localized in cytoplasm, especially in the peripheral layers of cancer cell nests, which was significantly higher in tumors than in NETs (p < 0.001). Increased expression of PLCE1 was correlated with advanced tumor-node-metastasis (TNM) stages (p = 0.015) and lymph node metastasis (p = 0.003) in patients with ESCC. Of the 110 patients, we examined 50 paired ESCC tissues and corresponding NETs by quantitative RT-PCR (polymerase chain reaction) and the mean mRNA level of PLCE1 in ESCC was 1.85-fold higher compared with those in corresponding NETs (p = 0.0012). Meanwhile, 4 of 5 ESCC cell lines also showed elevated expression of PLCE1 mRNA. Furthermore, elevated expression of PLCE1 mRNA in Kazakh ESCC was associated with its immunoreactivity (ρ = 0.297, p = 0.040), lymph node metastasis (p < 0.001), and advanced TNM stages of ESCC (p = 0.013). To our knowledge, this study demonstrates for the first time that PLCE1 overexpression correlates with lymph node metastasis and advanced TNM stages of Kazakh ESCC, implicating a role of PLCE1 in cancer metastasis and aggressiveness in ethnic Kazakh patients with ESCC. Furthermore, the current findings may warrant investigations into whether inhibiting PLCE1 could be a strategy for targeted anticancer therapy particularly for Kazakh ESCC.

Genetic variants at 10q23 are associated with risk of head and neck cancer in a Chinese population

BACKGROUND

A recent genome-wide association study (GWAS) focused on esophageal squamous cell carcinoma (ESCC) has identified several susceptible regions (5q11, 21q22, 6p21 10q23, and 12q24) in Chinese population. We hypothesized that single nucleotide polymorphisms (SNPs) identified in these regions for ESCC were also associated with the risk of head and neck cancer (HNC) which share similar risk factors with ESCC.

METHODS

To test this hypothesis, we genotyped three SNPs (rs2274223, rs2014300 and rs10484761) in a case-control study with 503 HNC cases and 900 cancer-free controls in a Chinese population.

RESULTS

We found that rs2274223 was associated with a significantly increased risk of HNC in our population [GG vs. AA: adjusted odds ratio (OR)=1.86, 95% confidence interval (CI)=1.09-3.16; GG vs. (AG/AA): adjusted OR=1.85, 95% CI=1.09-3.12], and the effect appeared to be more prominent among drinkers (P=0.024) and patients with oral cavity cancer (P=0.019). In contrast, rs2014300 and rs10484761 variant were not observed any significantly association with risk of HNC.

CONCLUSIONS

These results indicate that rs2274223 may be a marker SNP for HNC susceptibility in Chinese population.

Genetic variation in C20orf54, PLCE1 and MUC1 and the risk of upper gastrointestinal cancers in Caucasian populations

Recently, two large genome-wide association studies, conducted in Chinese populations, have reported associations between upper gastrointestinal cancer and the rs2274223, rs13042395 and rs4072037 polymorphisms in PLCE1, C20orf54 and MUC1, respectively. We aimed to determine whether similar associations existed for Caucasian populations. We genotyped two population-based, case-control studies of upper gastrointestinal cancer; the first study included 290 gastric cancer (GC) cases and 376 controls and the second study included 306 GC cases, 107 oesophageal adenocarcinoma cancer cases, 52 oesphageal squamous cell cancer cases and 211 controls. Odds ratios (OR) and 95% confidence intervals (CIs) were computed from logistic models and adjusted for confounding variables. The rs4072037 polymorphism in MUC1 was associated with a reduced risk of GC of intestinal histological type (OR 0.4; 95% CI 0.2-0.9) and a reduced risk of oesophageal squamous cell cancer (OR 0.5; 95% CI 0.2-1.0), but not oesphageal adenocarcinoma. Similarly, rs2274223 in PLCE1 was associated with a reduced risk of oesophageal squamous cell cancer (OR 0.5; 95% CI 0.3-1.0), but not oesphageal adenocarcinoma. We observed no association between rs13042395 in Corf54 and the risk of gastric or oesphageal cancer in either of the two studies. Our findings for rs4072037 and the risk of GC are in agreement with one previous report for a Caucasian population. To the best of our knowledge, this is the first study to report an association between rs2274223 and rs4072037 and the risk of oesophageal squamous cell carcinoma in a Caucasian population.

Replication study of PLCE1 and C20orf54 polymorphism and risk of esophageal cancer in a Chinese population

Esophageal cancer is one of the most aggressive cancers in the world. Recent large-scale genome-wide association studies (GWAS) reported that functional genetic variations in the phospholipase C epsilon gene (PLCE1) were strongly associated with risk of esophageal squamous cell carcinoma (ESCC) and gastric cardia adenocarcinoma (GCA) in Chinese population. For C20orf54 rs13042395 genotype and risk of esophageal cancer, the results were inconsistent. We conducted a replication case-control study to evaluate the genetic effects of these two functional single nucleotide polymorphisms (SNPs) on the development of esophageal cancer. A total of 380 cases and 380 controls were recruited for this study. The genotypes were determined by matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-ToF MS). The variant alleles of the functional polymorphism, PLCE1 rs2274223 SNP was associated with the increased risk of esophageal cancer [adjusted odds ratio (OR) = 1.95, 95 % confidence interval (CI) = 1.05-3.59 for PLCE1 rs2274223 GG vs. AA]. However, there was no significant association between the C20orf54 rs13042395 genotype and esophageal cancer risk (adjusted OR = 0.99, 95 % CI = 0.63-1.57 for C20orf54 rs13042395 TT vs. CC). Stratified analyses indicated a significantly increased risk of esophageal cancer associated with the PLCE1 rs2274223 AG genotype was more evident among females, younger patients and never drinkers, compared with the PLCE1 rs2274223 AA genotypes. Stratified analyses also indicated a significantly increased risk of esophageal cancer associated with the PLCE1 rs2274223 GG genotype was more evident among never smokers and never drinkers compared with the PLCE1 rs2274223 AA genotypes. These findings indicated that functional polymorphisms PLCE1 rs2274223 might contribute to esophageal cancer susceptibility.

Association of 10q23 with colorectal cancer in a Chinese population

Recently, a genome-wide association study of gastric cancer (GC) reported the significant association of seven genetic variants (rs4072037 and rs4460629 on 1q22; rs753724, rs11187842, rs3765524, rs2274223, and rs3781264 on 10q23) with GC in a Chinese population. These findings were confirmed in a subsequent independent study. However, it remains unknown whether these loci are associated with an increased risk of colorectal cancer (CRC). This study was to test whether the seven single nucleotide polymorphisms (SNPs) associated with GC were also associated with CRC in a Chinese population. The seven SNPs were genotyped using MassARRAY system. Allelic, genotypic, and haplotypic associations of the SNPs with CRC were investigated using χ(2) tests and logistic regression analysis. The SNPs rs3765524 and rs2274223, located on 10q23, were found to have significant protective effects against CRC, with equal odds ratios per allele. The two SNPs located on 1q22 (rs4072037 and rs4460629) showed a weak association with CRC. No significant association was identified with CRC for the remaining three SNPs located on 10q23 (rs753724, rs11187842, and rs3781264). These results suggest that rs3765524 and rs2274223 on 10q23 are associated with a protective effect against CRC in a Chinese population.

Potentially functional variants of PLCE1 identified by GWASs contribute to gastric adenocarcinoma susceptibility in an eastern Chinese population

BACKGROUND

Recent genome-wide association studies (GWAS) have found a single nucleotide polymorphism (SNP, rs2274223 A>G) in PLCE1 to be associated with risk of gastric adenocarcinoma. In the present study, we validated this finding and also explored the risk associated with another unreported potentially functional SNP (rs11187870 G>C) of PLCE1 in a hospital-based case-control study of 1059 patients with pathologically confirmed gastric adenocarcinoma and 1240 frequency-matched healthy controls.

METHODOLOGY/PRINCIPAL FINDINGS

We determined genotypes of these two SNPs by the Taqman assay and used logistic regression models to estimate odds ratios (ORs) and 95% confidence intervals (95% CI). We found that a significant higher gastric adenocarcinoma risk was associated with rs2274223 variant G allele (adjusted OR = 1.35, 95% CI = 1.14-1.60 for AG+GG vs. AA) and rs11187870 variant C allele (adjusted OR = 1.26, 95% CI = 1.05-1.50 for CG+CC vs. GG). We also found that the number of combined risk alleles (i.e., rs2274223G and rs11187870C) was associated with risk of gastric adenocarcinoma in an allele-dose effect manner (P(trend) = 0.0002). Stratification analysis indicated that the combined effect of rs2274223G and rs11187870C variant alleles was more evident in subgroups of males, non-smokers, non-drinkers and patients with gastric cardia adenocarcinoma. Further real-time PCR results showed that expression levels of PLCE1 mRNA were significantly lower in tumors than in adjacent noncancerous tissues (0.019±0.002 vs. 0.008±0.001, P<0.05).

CONCLUSIONS/SIGNIFICANCES

Our results further confirmed that genetic variations in PLCE1 may contribute to gastric adenocarcinoma risk in an eastern Chinese population.

Putatively functional PLCE1 variants and susceptibility to esophageal squamous cell carcinoma (ESCC): a case-control study in eastern Chinese populations

BACKGROUND

A novel variant rs2274223 located in the phospholipase C epsilon 1 (PLCE1) gene was found to be associated with risk of esophageal squamous cell carcinoma (ESCC) by 2 large-scale genome-wide association studies (GWASs) in Chinese populations. In this study, we aimed to assess such an association in an eastern Chinese population and to address its possibly functional role in the etiology of ESCC.

METHODS

A total of 1061 ESCC cases and 1211 controls were recruited and successfully genotyped for 2 single nucleotide polymorphisms (SNPs) (rs2274223 and rs11187870) of the PLCE1 gene by the TaqMan assay. Real-time PCR and immunohistochemical (IHC) analysis were applied to assess mRNA and protein expression levels, respectively, in a subset of tumor samples.

RESULTS

SNP rs2274223 was independently associated with risk of ESCC (adjusted odds ratio [OR], 1.49; 95% confidence interval [95% CI], 1.03-2.17 for GG vs AA), and SNP rs11187870 was also found to be associated with risk of ESCC assuming a dominant model (adjusted OR, 1.20; 95% CI, 1.00-1.44 for CG/CC vs GG). The Grs2274223Crs11187870 haplotype increased the risk for ESCC by 1.22-fold (95% CI, 1.04-1.42). Further experiments showed that overall PLCE1 mRNA expression was lower in tumor than in paired normal tissues (0.067±0.016 vs 0.264±0.067, P<.05), and the IHC analysis showed the normal tissues of rs2274223 GG genotype had a lower PLCE1 staining score than that of the AG genotype (0.40±0.22 vs 1.33±0.32, P<.05).

CONCLUSIONS

PLCE1 SNP rs2274223 A>G change may reduce gene expression, and the variant G genotypes might contribute to risk of ESCC.

Phospholipase C isozymes are deregulated in colorectal cancer--insights gained from gene set enrichment analysis of the transcriptome

Colorectal cancer (CRC) is one of the most common cancer types in developed countries. To identify molecular networks and biological processes that are deregulated in CRC compared to normal colonic mucosa, we applied Gene Set Enrichment Analysis to two independent transcriptome datasets, including a total of 137 CRC and ten normal colonic mucosa samples. Eighty-two gene sets as described by the Kyoto Encyclopedia of Genes and Genomes database had significantly altered gene expression in both datasets. These included networks associated with cell division, DNA maintenance, and metabolism. Among signaling pathways with known changes in key genes, the “Phosphatidylinositol signaling network”, comprising part of the PI3K pathway, was found deregulated. The downregulated genes in this pathway included several members of the Phospholipase C protein family, and the reduced expression of two of these, PLCD1 and PLCE1, were successfully validated in CRC biopsies (n = 70) and cell lines (n = 19) by quantitative analyses. The repression of both genes was found associated with KRAS mutations (P = 0.005 and 0.006, respectively), and we observed that microsatellite stable carcinomas with reduced PLCD1 expression more frequently had TP53 mutations (P = 0.002). Promoter methylation analyses of PLCD1 and PLCE1 performed in cell lines and tumor biopsies revealed that methylation of PLCD1 can contribute to reduced expression in 40% of the microsatellite instable carcinomas. In conclusion, we have identified significantly deregulated pathways in CRC, and validated repression of PLCD1 and PLCE1 expression. This illustrates that the GSEA approach may guide discovery of novel biomarkers in cancer.