Phospholipase C-epsilon augments epidermal growth factor-dependent cell growth by inhibiting epidermal growth factor receptor down-regulation

PLCε signaling in cancer

PURPOSE

As one of the members of the PLC family, the phosphoinositide-specific phospholipase Cε (PLCε) has been shown to play pivotal roles in multiple signal pathways and control a variety of cellular functions. A number of studies have shown that aberrant regulation of PLCε was involved in various types of animal and human cancer. However, the role of PLCε in cancer remains elusive. In this review, we provide an overview of the PLCε, especially its roles in multiple signal pathways, and summarize the recent findings that highlight the roles of PLCε in carcinogenesis and cancer progression, making an avenue to provide a novel therapeutic strategy for the treatment of cancer.

METHODS

A literature search mainly paying attention to the network of PLCε involved in tumorigenesis and development was performed in electronic databases.

RESULTS

PLCε plays a key role in medicating the development and progression of human cancers with highest potency to be a target of cancer prevention and treatment.

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.

Nuclear factor-κB signaling pathway is involved in phospholipase Cε-regulated proliferation in human renal cell carcinoma cells

Phospholipase Cε (PLCε), a downstream effector of small GTPase superfamily, has been identified to play a crucial role in tumorigenesis. Previously, our studies have showed that PLCε promotes proliferation of renal cell carcinoma (RCC) cells. However, the molecular mechanisms by which PLCε enhances the survival phenotype of RCC cells are still not fully instructed. In the present study, we first demonstrated that PLCε was highly expressed and had a close correlation with Ki67 protein expression in RCC tissue samples. Further, we found that downregulation of PLCε expression repressed growth and induced apoptosis in RCC cells. In addition, we reported a mechanism by which knockdown of PLCε gene potently suppressed the nuclear factor kappa (NF-κB) signaling pathway through action on inhibitor of κB kinase. Moreover, silencing PLCε gene decreased vascular endothelial growth factor (VEGF) expression, which was a downstream growth factor of NF-κB signaling pathway. Finally, downregulation of VEGF was severely enhanced by treatment cells with NF-κB specific inhibitor BAY11-7028 in PLCε knockdown cells. Taken together, these findings suggest that PLCε promotes RCC cell growth via NF-κB-mediated upregulation of VEGF.

Knockdown of phospholipase C-epsilon by short-hairpin RNA-mediated gene silencing induces apoptosis in human bladder cancer cell lines

Transitional cell carcinoma of bladder (TCCB) is a common malignancy worldwide, and outcomes for patients with advanced bladder cancer remain poor. To study the pathogenesis of TCCB, we investigated roles of Phospholipase C (PLC)ɛ, an effector of Ras and Rap small GTPases. RNA interference was used to knockdown PLCɛ expression in human bladder cancer cell lines (BIU-87 and T24). The expression levels of PLCɛ mRNA and protein were detected by reverse transcriptase-polymerase chain reaction and Western blot, respectively. Flow cytometry (FCM) was used to detect distribution of cell cycle. Cellular apoptosis was reflected by transmission electron microscopy and the expression of bcl-2 and bax. We found that PLCɛ could be efficiently knocked down by shRNA. FCM assay showed that the pGenesil-PLCɛ-transfected cells were arrested at the G0/G1 phase. Silence of PLCɛ might induce apoptosis via modulation of bcl-2 and bax. In conclusion, our results suggest that PLCɛ plays an important role in the pathogenesis of human bladder cancer cells. PLCɛ may be used as a potential target of gene therapy for bladder cancer in future.

A sequence variant in the phospholipase C epsilon C2 domain is associated with esophageal carcinoma and esophagitis

A single-nucleotide polymorphism (rs2274223: A5780G:His1927Arg) in the phospholipase C epsilon gene (PLCϵ) was recently identified as a susceptibility locus for esophageal cancer in Chinese subjects. To determine the underlying mechanisms of PLCϵ and this SNP in esophageal carcinogenesis, we analyzed PLCϵ genotypes, expression, and their correlation in esophageal cancer cell lines, non-transformed esophageal cells, 58 esophageal squamous cell carcinomas and 10,614 non-cancer subjects from China. We found that the G allele (AG or GG) was associated with increased PLCϵ mRNA and protein expression in esophageal cancer tissues and in esophageal cancer cell lines. G allele was also associated with higher enzyme activity, which might be associated with increased protein expression. Quantitative analysis of the C2 domain sequences revealed that A:G allelic imbalance was strongly linked to esophageal malignancy. Moreover, the analysis of 10,614 non-cancer subjects demonstrated that the G allele was strongly associated with moderate to severe esophagitis in the subjects from the high-incidence areas of China (OR 6.03, 95% CI 1.59-22.9 in high-incidence area vs. OR 0.74, 95% CI 0.33-1.64 in low-incidence area; P = 0.008). In conclusion, the PLCϵ gene, particularly the 5780G allele, might play a pivotal role in esophageal carcinogenesis via upregulating PLCϵ mRNA, protein, and enzyme activity, and augmenting inflammatory process in esophageal epithelium. Thus, 5780G allele may constitute a promising biomarker for esophageal squamous cell carcinoma risk stratification, early detection, and progression prediction.

The role of VIP in cornea

PURPOSE

Exogenous vasoactive intestinal peptide (VIP) down-regulates pro-inflammatory but up-regulates anti-inflammatory cytokines, growth factors (GFs) and Toll-like receptors promoting healing in experimental Pseudomonas aeruginosa (P. aeruginosa) keratitis. Whether VIP is required for GF or GF receptor (R) expression in normal and infected corneas is unknown and is the purpose of this study.

METHODS

VIP knockout ((-/-)) and wild-type (WT) C57BL/6 (B6) mice were infected and tested using PCR array, real-time RT-PCR, ELISA, and immunostaining. VIP antagonist treatment studies also were done using B6 and BALB/c mice.

RESULTS

Infected corneas of VIP(-/-) versus WT B6 mice perforated earlier (2 vs. 5 days postinfection [p.i.]), and array data showed that GFs were differentially changed between groups. RT-PCR revealed that the infected cornea of VIP(-/-) versus WT mice expressed higher mRNA levels of epidermal growth factor (EGF) and hepatocyte growth factor (HGF), reduced FGF, EGFR, and HGFR, with no difference in FGFR; differences between groups were not seen in normal cornea. Immunostaining for GF and GFR in the normal cornea of VIP(-/-) versus WT mice was similar. However, at 1 day p.i., VIP(-/-) versus WT mice had more intense EGF and HGF, similar FGFR, and reduced FGF, EGFR, and HGFR staining. VIP antagonist treatment decreased protein levels for GFR at 5 days p.i. in both B6 and BALB/c mice, with no significant changes in normal cornea.

CONCLUSIONS

The data showed that endogenous VIP is not requisite for GF or GFR expression in the normal cornea but, after infection, its absence or reduction is critical for their regulation.

Involvement of the PLCε/PKCα pathway in human BIU-87 bladder cancer cell proliferation

PLCε (phospholipase Cε), one of effectors belonging to the small GTPase superfamily, has been suggested to play a crucial role in carcinogenesis. However, its bio-function in bladder cancer has never been demonstrated. In our previous study, we found that PLCε mRNA was highly expressed in bladder cancer tissues. In the present study, we silenced the PLCε gene by shRNA (small-hairpin RNA) in the bladder cancer cell line BIU-87. The results showed that it significantly inhibited cell proliferation and arrested the cell cycle at G0/G1-phase. The regulation of cell characteristics has been related to PKCα (protein kinase Cα) activity. Further study showed that knockdown of the PLCε gene down-regulated oncogenes c-fos and c-jun. These results indicate that PLCε plays a crucial role in bladder cancer, and PLCε may be a key molecule regulating the signal pathway of bladder cancer proliferation.

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.

shRNA targeting PLCε inhibits bladder cancer cell growth in vitro and in vivo

OBJECTIVES

To investigate the role of phospholipase Cε (PLCε) by silencing PLCε with short hairpin RNA (shRNA) in human bladder cancer cells BIU-87 in vitro and in vivo.

METHODS

A PLCε shRNA expression vector was transfected into BIU-87 cells, and the expression of PLCε protein was detected by Western blotting. Cell proliferation was determined using the MTT assay, and the cell cycle was detected using flow cytometry. A tumor xenograft experiment was established to evaluate the tumor growth under the condition of PLCε knockdown, and the expression of PLCε, proliferating cell nuclear antigen, and cyclin D1 were detected by Western blotting or immunohistrochemistry.

RESULTS

PLCε shRNA reduced the protein level of PLCε, leading to marked proliferation inhibition and significant cell cycle arrest. Furthermore, PLCε shRNA reduced the tumor xenograft growth implanted with BIU-87 cells. The protein expression of PLCε, proliferating cell nuclear antigen, and cyclin D1 were downregulated in the bladder tumor xenograft.

CONCLUSIONS

The knockdown of PLCε by shRNA could inhibit bladder tumor growth and might be an alternative approach for human bladder cancer therapy.