hepaCAM and p-mTOR Closely Correlate in Bladder Transitional Cell Carcinoma and hepaCAM Expression Inhibits Proliferation via an AMPK/mTOR Dependent Pathway in Human Bladder Cancer Cells

Panobinostat reverses HepaCAM gene expression and suppresses proliferation by increasing histone acetylation in prostate cancer

Increased expression of histone deacetylases (HDACs) affiliated to the epigenetic regulation is common aberration in prostate cancer (PCa). We have confirmed that hepatocyte cell adhesion molecule (hepaCAM), acting as a tumor suppressor gene, is rarely expressed in PCa previously, However, the mechanisms of which is still unknown. The level of histone acetylation reportedly may involve anti-oncogene transcription and expression. In this study, we investigated the effect of panobinostat, the broad-spectrum histone deacetylases inhibitor, on PCa LNCaP and DU145 cell growth, and observed re-expression of hepaCAM when treated with panobinostat. We demonstrated that intranuclear acetylation of lys9 of histone H3 (Ac-H3K9) were increased, while that of both mRNA and protein of HDAC1, HDAC3, and HDAC4 were decreased when the treating concentration of panobinostat increased. We confirmed the relationship between histone acetylation and the expression of hepaCAM and AR in prostate cancer tissues. We also confirmed that panobinostat could overcome the resistance for androgen deprivation therapy (ADT). Further, we combined panobinostat with Ad-hepaCAM, which resulted in significantly increased antitumor activity and significant attenuation of the proliferation-associated genes CCND1 and PCNA compared to each single treatment. In conclusion, panobinostat may enhance the acetylation of lys9 of histone 3 and reverse the hepaCAM expression through its inhibitory effect on HDACs activity in PCa LNCaP and DU145 cells; Ad-hepaCAM combined with panobinostat may synergistically inhibit the growth of LNCaP and DU145 cells, via a potential mechanism associated with the down-regulation of the expression of CCND1 and PCNA. These findings suggest that this therapeutic strategy should be further developed in clinical trials.

Emerging roles for multifunctional ion channel auxiliary subunits in cancer

Several superfamilies of plasma membrane channels which regulate transmembrane ion flux have also been shown to regulate a multitude of cellular processes, including proliferation and migration. Ion channels are typically multimeric complexes consisting of conducting subunits and auxiliary, non-conducting subunits. Auxiliary subunits modulate the function of conducting subunits and have putative non-conducting roles, further expanding the repertoire of cellular processes governed by ion channel complexes to processes such as transcellular adhesion and gene transcription. Given this expansive influence of ion channels on cellular behaviour it is perhaps no surprise that aberrant ion channel expression is a common occurrence in cancer. This review will focus on the conducting and non-conducting roles of the auxiliary subunits of various Ca2+, K+, Na+ and Cl- channels and the burgeoning evidence linking such auxiliary subunits to cancer. Several subunits are upregulated (e.g. Cavβ, Cavγ) and downregulated (e.g. Kvβ) in cancer, while other subunits have been functionally implicated as oncogenes (e.g. Navβ1, Cavα2δ1) and tumour suppressor genes (e.g. CLCA2, KCNE2, BKγ1) based on in vivo studies. The strengthening link between ion channel auxiliary subunits and cancer has exposed these subunits as potential biomarkers and therapeutic targets. However further mechanistic understanding is required into how these subunits contribute to tumour progression before their therapeutic potential can be fully realised.

HepaCAM inhibits cell proliferation and invasion in prostate cancer by suppressing nuclear translocation of the androgen receptor via its cytoplasmic domain

Hepatocyte cell adhesion molecule (HepaCAM) is a tumour suppressor. However, the mechanism of HepaCAM function in prostate cancer (PCa) remains unknown. In the present study, HepaCAM, androgen receptor (AR) and Ran were analysed in 46 PCa tissue samples using immunohistochemistry. Subsequently, the influence of HepaCAM and its cytoplasmic domain on cell proliferation, migration, and invasion, and associated proteins was examined using MTT, wound healing, Transwell and western blotting assays, respectively. Furthermore, nuclear translocation of AR and Ran was analysed using immunofluorescence and Western blot assays. The results demonstrated that HepaCAM expression was reduced in PCa, and there was an association between downregulation of HepaCAM and changes in the distribution of AR and Ran. Furthermore, HepaCAM, specifically the cytoplasmic domain, was involved in cell proliferation, migration and invasion. Nuclear translocation of AR was dependent on HepaCAM and its cytoplasmic domain. Additionally, HepaCAM suppression of the nuclear translocation of AR occurred via Ran. The results suggest that HepaCAM and its cytoplasmic domain suppress the nuclear translocation of AR via Ran in PCa. The cytoplasmic domain of HepaCAM may serve as a novel target for therapy in PCa.

HepaCAM Regulates Warburg Effect of Renal Cell Carcinoma via HIF-1α/NF-κB Signaling Pathway

OBJECTIVE

To investigate how hepatocyte cell adhesion molecule (hepaCAM) regulates cancer energy metabolism through hypoxia-inducible factor (HIF-1α) in renal cell carcinoma (RCC).

MATERIALS AND METHODS

The expression of hepaCAM and HIF-1α in RCC tissue samples was examined by immunohistochemistry. Glucose consumption and lactate production assays were used to detect metabolic activity in RCC cell lines. P65 and IκB kinase (IKKβ) mRNA and protein expression were detected using quantitative real-time polymerase chain reaction and western blotting, respectively. Nuclear translocation of P65 was observed by immunofluorescence staining after re-expressing hepaCAM. The luciferase reporter assay was applied to validate the transcriptional activity of HIF-1α.

RESULTS

HIF-1α expression was elevated and hepaCAM suppressed in RCC compared with adjacent normal tissues. Furthermore, hepaCAM re-expression significantly decreased glycolytic metabolism in RCC cell lines, and reduced HIF-1α, IKKβ, and P65 expression. The expression of HIF-1α, GLUT1, LDHA, and PKM2 were further reduced with combined hepaCAM overexpression and treatment with the NF-κB inhibitor BAY11-7082, compared to hepaCAM overexpression alone. Additionally, hepaCAM decreased the transcriptional activity of HIF-1α and blocked P65 nuclear translocation by the NF-κB pathway.

CONCLUSION

Our data suggest that hepaCAM suppresses the Warburg effect via the HIF-1α/NF-κB pathway in RCC, which is a facilitating factor in hepaCAM-reduced tumorigenesis.

Overexpression of T-cadherin inhibits the proliferation of oral squamous cell carcinoma through the PI3K/AKT/mTOR intracellular signalling pathway

OBJECTIVE

To evaluate T-cadherin gene expression in patients with oral squamous cell carcinoma(OSCC) and explore its effect on the proliferation of OSCC. Additionally, the present study aimed to determine whether the anti-proliferative effect of T-cadherin was associated with the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/mechanistic target of rapamycin (mTOR) signaling pathway.

DESIGN

A reverse transcription-quantitative polymerase chain reaction was performed to detect T-cadherin mRNA expression. A Cell Counting Kit-8 (CCK-8) assay was used to investigate the effect of T-cadherin on cellular proliferation. The survival curves were plotted by Kaplan-Meier method, and the differences between subgroups were determined by log-rank test. The protein expression of phosphorylated (p)-PI3K, total PI3K, p-AKT, total AKT, p-mTOR, total mTOR and cyclin D1was assessed using western blot.

RESULTS

It was revealed that the expression of T-cadherin mRNA was significantly decreased in OSCC samples compared with normal adjacent ones (P = 0.007), and that low T-cadherin expression was correlated with advanced clinical stage (P = 0.0249), higher pathological grade (P = 0.0288) and poor differentiation (P = 0.0295) of OSCC. In addition, T-cadherin negative expression was revealed to be associated with a worse progression‑free survival (PFS) in patients with OSCC. Furthermore, the overexpression of T-cadherin inhibited the proliferation of OSCC cell lines and suppressed the PI3K/AKT/mTOR signaling pathway. Importantly, the combined treatment of T-cadherin with the PI3K inhibitor LY294002 enhanced the inhibitory effect of T-cadherin on cellular proliferation and the PI3K/AKT/mTOR pathway.

CONCLUSIONS

The results of the present study suggested that T-cadherin may function as a tumor suppressor gene in OSCC through suppressing the PI3K/AKT/mTOR pathway, and that it may be a potential therapeutic target for OSCC.

HepaCAM inhibits the malignant behavior of castration-resistant prostate cancer cells by downregulating Notch signaling and PF-3084014 (a γ-secretase inhibitor) partly reverses the resistance of refractory prostate cancer to docetaxel and enzalutamide in vitro

Castration-resistant prostate cancer (CRPC) continues to be a major challenge in the treatment of prostate cancer (PCa). The expression of hepatocyte cell adhesion molecule (HepaCAM), a novel tumor suppressor, is frequently downregulated or lost in PCa. Overactivated Notch signaling is involved in the development and progression of PCa, including CRPC. In this study, we found that the activities of Notch signaling were elevated, while HepaCAM expression was decreased in CRPC tissues compared with matched primary prostate cancer (PPC) tissues. In addition, HepaCAM negativity was found to be associated with a worse progression-free survival (PFS). Furthermore, the overexpression of HepaCAM induced by transfection with a HepaCAM overexpression vector (Ad-HepaCAM) exerted antitumor effects by decreasing the proliferation, and suppressing the invasion and migration of bicalutamide-resistant (Bica-R) cells and enzalutamide-resistant (Enza-R) cells. Importantly, we found that the antitumor effects of HepaCAM on the resistant cells were associated with the downregulation of Notch signaling. Moreover, we revealed that PF-3084014 (a γ-secretase inhibitor) re-sensitized Enza-R cells to enzalutamide, and sequential dual-resistant (E+D-R) cells to docetaxel. Additionally, the findings of this study demonstrated that the use of PF-3084014 alone exerted potent antitumor effect on the resistant cells in vitro. On the whole, this study indicates that HepaCAM potentially represents a therapeutic target and PF-3084014 may prove to a promising agent for use in the treatment of refractory PCa.

Glucocorticoids, genes and brain function

The identification of key genes in transcriptomic data constitutes a huge challenge. Our review of microarray reports revealed 88 genes whose transcription is consistently regulated by glucocorticoids (GCs), such as cortisol, corticosterone and dexamethasone, in the brain. Replicable transcriptomic data were combined with biochemical and physiological data to create an integrated view of the effects induced by GCs. The most frequently reported genes were Errfi1 and Ddit4. Their up-regulation was associated with the altered transcription of genes regulating growth factor and mTORC1 signaling (Gab1, Tsc22d3, Dusp1, Ndrg2, Ppp5c and Sesn1) and progression of the cell cycle (Ccnd1, Cdkn1a and Cables1). The GC-induced reprogramming of cell function involves changes in the mRNA level of genes responsible for the regulation of transcription (Klf9, Bcl6, Klf15, Tle3, Cxxc5, Litaf, Tle4, Jun, Sox4, Sox2, Sox9, Irf1, Sall2, Nfkbia and Id1) and the selective degradation of mRNA (Tob2). Other genes are involved in the regulation of metabolism (Gpd1, Aldoc and Pdk4), actin cytoskeleton (Myh2, Nedd9, Mical2, Rhou, Arl4d, Osbpl3, Arhgef3, Sdc4, Rdx, Wipf3, Chst1 and Hepacam), autophagy (Eva1a and Plekhf1), vesicular transport (Rhob, Ehd3, Vps37b and Scamp2), gap junctions (Gjb6), immune response (Tiparp, Mertk, Lyve1 and Il6r), signaling mediated by thyroid hormones (Thra and Sult1a1), calcium (Calm2), adrenaline/noradrenaline (Adcy9 and Adra1d), neuropeptide Y (Npy1r) and histamine (Hdc). GCs also affected genes involved in the synthesis of polyamines (Azin1) and taurine (Cdo1). The actions of GCs are restrained by feedback mechanisms depending on the transcription of Sgk1, Fkbp5 and Nr3c1. A side effect induced by GCs is increased production of reactive oxygen species. Available data show that the brain's response to GCs is part of an emergency mode characterized by inactivation of non-core activities, restrained inflammation, restriction of investments (growth), improved efficiency of energy production and the removal of unnecessary or malfunctioning cellular components to conserve energy and maintain nutrient supply during the stress response.

Interleukin 6 induces cell proliferation of clear cell renal cell carcinoma by suppressing hepaCAM via the STAT3-dependent up-regulation of DNMT1 or DNMT3b

Interleukin 6 (IL-6), a tumor promoting cytokine, has been largely implicated in the development of renal cell carcinoma (RCC). Hepatocyte cell adhesion molecule (hepaCAM) is a novel tumor suppressor, which is lost or down-regulated in many cancer types including RCC. In the present study, we intensively investigated the connection between IL-6 and hepaCAM in RCC. Our analysis of RCC tissues, adjacent tissues and paired serum samples from RCC patients revealed that IL-6 was elevated in patient serum and RCC tissue, whereas hepaCAM was completely lost or significantly down-regulated. Furthermore, we observed an association between IL-6 increase and hepaCAM decrease in RCC tissue samples. In the section of cytological researches, we found in RCC cell lines that IL-6 was a direct upstream regulator of hepaCAM, and that hepaCAM down-regulation was involved in IL-6-driven cell proliferation. We also demonstrated that IL-6-mediated promoter hypermethylation largely accounted for the hepaCAM loss in RCC, and it was STAT3-dependent. Additionally, our data showed that DNMT1 up-regulation induced by IL-6/STAT3 signaling was indispensable for IL-6-mediated hepaCAM loss in RCC cell lines ACHN and 769-P, while DNMT3b up-regulation was crucial for hepaCAM loss in A498. Our findings provide a novel signal pathway regulating cell proliferation, potentially representing a therapeutic target for RCC.

Overexpression of HepaCAM inhibits bladder cancer cell proliferation and viability through the AKT/FoxO pathway

PURPOSE

HepaCAM, an N-linked glycoprotein that encodes a member of the immunoglobulin superfamily, has been reported to be a tumor suppressor gene that mediates diverse cellular bio-functions. Recent studies have shown that the FoxO transcription factors play a pivotal role during cancer progression. Here, we explored the correlation between HepaCAM and the FoxO family via regulation of the PI3K/AKT pathway.

METHODS

HepaCAM and FoxO3 expression were detected by immunohistochemistry staining. We detected the effect of HepaCAM on the proliferation and viability of bladder cancer through AKT signaling by colony formation, the MTT assay and Western blotting. We observed the nuclear translocation of FoxO3 by immunofluorescence staining after expressing HepaCAM.

RESULTS

HepaCAM depletion was discovered in bladder cancer tissues compared with adjacent normal tissues, and the decreased level was associated with the degradation of FoxO3. Furthermore, re-expression of HepaCAM significantly disrupted T24 and BIU-87 cell colony formation, as well as reduced p-AKT and p-FoxO protein expression. We found that the combined treatment of HepaCAM-overexpressing adenovirus with the PI3K inhibitor LY294002 enhanced the inhibitory effects on cell proliferation, viability and protein expression. Additionally, overexpressed HepaCAM decreased the activated effect on cell proliferation, viability and protein expression of the AKT activator SC79. Moreover, we observed that HepaCAM induced nuclear translocation of FoxO3.

CONCLUSIONS

Our research implicated that HepaCAM may function as a novel therapeutic target that inhibits the proliferation of bladder cancer via the AKT/FoxO pathway.

HepaCAM associates with connexin 43 and enhances its localization in cellular junctions

HepaCAM (GlialCAM) is frequently deleted in carcinomas, and reintroduction of hepaCAM into transformed cell lines reduces cellular growth and induces senescence. Mutations in HEPACAM give rise to the neurodegenerative disease megalencephalic leukoencephalopathy with subcortical cysts (MLC) since mutated hepaCAM prevents shuttling of MLC1 protein to astrocytic junctions in the plasma membrane. Here we identify that hepaCAM associates with connexin 43, a main component of gap junctions, and enhances connexin 43 localization to the plasma membrane at cellular junctions. HepaCAM also increases the levels of connexin 43, not by enhancing its transcription but by stabilizing connexin 43 protein. In the absence of hepaCAM, connexin 43 undergoes a faster degradation via the lysosomal pathway while proteasomal degradation seems not to be involved. Mutations in hepaCAM that cause MLC, or neutralization of hepaCAM by antibodies disrupt its association with connexin 43 at cellular junctions. By discovering the requirement of hepaCAM for localizing connexin 43, a well-established tumor suppressor, to cellular junctions and stabilizing it there, this study suggests a mechanism by which deletion of hepaCAM may support tumor progression.

Activation of AMPK α2 inhibits airway smooth muscle cells proliferation

The aims of the present study were to examine the effect of adenosine monophosphate-activated protein kinase (AMPK) activation on airway smooth muscle cells (ASMCs) proliferation and to address its potential mechanisms. Platelet derived growth factor (PDGF) activated phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) signaling pathway, and this in turn up-regulated S-phase kinase-associated protein 2 (Skp2) and consequently reduced cyclin dependent kinase inhibitor 1B (p27) leading to ASMCs proliferation. Pre-incubation of cells with metformin, an AMPK activator, blocked PDGF-induced activation of mTOR and its downstream targets changes of Skp2 and p27 without changing Akt phosphorylation and inhibited ASMCs proliferation. Transfection of ASMCs with AMPK α2-specific small interfering RNA (siRNA) reversed the effect of metformin on mTOR phosphorylation, Skp2 and p27 protein expression and cell proliferation. Our study suggests that activation of AMPK, particularly AMPK α2, negatively regulates mTOR activity to suppress ASMCs proliferation and therefore has a potential value in the prevention and treatment of asthma by negatively modulating airway remodeling.

5-azacytidine inhibits the proliferation of bladder cancer cells via reversal of the aberrant hypermethylation of the hepaCAM gene

Hepatocyte cell adhesion molecule (hepaCAM), a tumor-suppressor gene, is rarely expressed in bladder carcinoma. However, little is known concerning the mechanisms of low hepaCAM expression in bladder cancer. Abnormal hypermethylation in the promoter plays a crucial role in cancer by silencing tumor-suppressor genes, which is catalyzed by DNA methyltransferases (DNMTs). In the present study, a total of 31 bladder cancer and 22 adjacent tissues were assessed by immunohistochemistry to detect DNMT3A/3B and hepaCAM expression. Methylation of hepaCAM was determined by methylation‑specific polymerase chain reaction (MSP). The mRNA and protein levels of DNMT3A/3B and hepaCAM were determined by RT-PCR and western blot analysis after treatment with 5-azacytidine (AZAC). Following AZAC treatment, the proliferation of bladder cancer cells was detected by CCK-8 and colony formation assays. Cell cycle distribution was examined by flow cytometry. To further evaluate the tumor‑suppressive roles of AZAC and the involved mechanisms, the anti-tumorigenicity of AZAC was tested in vivo. The expression of DNMT3A/3B protein was markedly increased in the bladder carcinoma tissues (P<0.05), and had a negative linear correlation with hepaCAM expression in the same patients according to Pearson's analysis (r=-0.7176/-0.7127, P<0.05). The MSP results indicated that the hepaCAM gene was hypermethylated in three bladder cancer cell lines. Furthermore, we found that downregulation of DNMT3A/3B expression, after treatment with AZAC, reversed the hypermethylation and expression of hepaCAM in bladder cancer cells. In addition, AZAC inhibited the proliferation of bladder cancer cells and arrested cells at the G0/G1 phase. The in vivo results showed that expression of DNMT3A/3B and hepaCAM as well as tumor growth of nude mice were markedly altered which corresponded with the in vitro results. Due to the ability to reactivate expression of hepaCAM and inhibit growth of bladder cancer cells, AZAC may represent an effective treatment for bladder cancer.

Expression of hepaCAM inhibits bladder cancer cell proliferation via a Wnt/β-catenin-dependent pathway in vitro and in vivo

We previously established that hepatocyte cell adhesion molecule (hepaCAM), a typical structure of immunoglobulin (Ig)-like adhesion molecules, inhibited the proliferation and the progression of cultured human bladder cancer cells. As increasing evidence reveals that aberrant activation of canonical Wnt pathway is involved in the pathogenesis of bladder cancer, and β-catenin serves as a pivotal molecule of Wnt pathway. Then, we explored whether the anti-proliferation effect of hepaCAM was associated with Wnt/β-catenin pathway in human bladder cancer cells. The negative correlation between hepaCAM and β-catenin in transitional cell carcinoma of bladder (TCCB) was found. Follow by, studied the effect of hepaCAM on the key elements of Wnt pathway. Here, Our researches showed that hepaCAM played a central role in modulating the Wnt/β-catenin signaling pathway by interfering nuclear protein levels of β-catenin, leading to down-regulate transcriptional activity of LEF/TCF and its target genes c-Myc and cyclinD1. Mechanistically, we demonstrated that hepaCAM-activated GSK3β led to elevate the phosphorylation of β-catenin, contributing to the aberrant translocation of β-catenin. In addition, Anti-proliferation and associated molecular mechanisms of hepaCAM were demonstrated by using vivo experiment. In conclusion, our reports uncover that expression of hepaCAM suppresses the proliferation of bladder cancer cells through a Wnt/β-catenin-dependent signaling pathway in vitro and in vivo.

The role of AGR2 and AGR3 in cancer: similar but not identical

In the past decades, highly related members of the protein disulphide isomerase family, anterior gradient protein AGR2 and AGR3, attracted researchers' attention due to their putative involvement in developmental processes and carcinogenesis. While AGR2 has been widely demonstrated as a metastasis-related protein whose elevated expression predicts worse patient outcome, little is known about AGR3's role in tumour biology. Thus, we aim to confront the issue of AGR3 function in physiology and pathology in the following review by comparing this protein with the better-described homologue AGR2. Relying on available data and in silico analyses, we show that AGR proteins are co-expressed or uncoupled in context-dependent manners in diverse carcinomas and healthy tissues. Further, we discuss plausible roles of both proteins in tumour-associated processes such as differentiation, proliferation, migration, invasion and metastasis. This work brings new hints and stimulates further thoughts on hitherto unresolved conundrum of anterior gradient protein function.

Down-regulation of mechanisms involved in cell transport and maintenance of mucosal integrity in pigs infected with Lawsonia intracellularis

Lawsonia intracellularis is an obligate intracellular bacterium, responsible for the disease complex known as proliferative enteropathy (PE). L. intracellularis is associated with intestinal crypt epithelial cell proliferation but the mechanisms responsible are yet to be defined. Microarray analysis was used to investigate the host-pathogen interaction in experimentally infected pigs to identify pathways that may be involved. Ileal samples originating from twenty-eight weaner pigs experimentally challenged with a pure culture of L. intracellularis (strain LR189/5/83) were subjected to microarray analysis. Microarray transcriptional signatures were validated using immunohistochemistry and quantitative real time PCR of selected genes at various time points post challenge. At peak of infection (14 days post challenge) 86% of altered transcripts were down regulated, particularly those involved in maintenance of mucosal integrity and regulation of cell transport. Among the up-regulated transcripts, CD163 and CDK1 were novel findings and considered to be important, due to their respective roles in innate immunity and cellular proliferation. Overall, targeted cellular mechanisms included those that are important in epithelial restitution, migration and protection; maintenance of stable inter-epithelial cell relationships; cell transport of nutrients and electrolytes; innate immunity; and cell cycle.

HepaCAM inhibits clear cell renal carcinoma 786-0 cell proliferation via blocking PKCε translocation from cytoplasm to plasma membrane

Hepatocyte cell adhesion molecule (HepaCAM) plays a crucial role in tumor progression and has been recognized as a novel tumor suppressor gene. The high protein expression level of protein kinase Cε (PKCε) has been discovered in many tumor types. In the present study, we determined HepaCAM and PKCε protein levels in human clear cell renal cell carcinoma (ccRCC) tissues and analyzed the correlation between them. We observed an inverse relationship in the expression of HepaCAM and PKCε in ccRCC and adjacent normal tissues. In ccRCC tissue, HepaCAM expression was undetectable while PKCε expression was high; the opposite was found in the adjacent normal tissue. Western blot analysis demonstrated that PKCε cytosolic protein levels increased while plasma membrane protein levels decreased without any change in total protein following infection of the ccRCC cell line 786-0 with adenovirus-GFP-HepaCAM (Ad-GFP-HepaCAM). Moreover, the application of Ad-GFP-HepaCAM combined with a PKCε-specific translocation inhibitor (εV1-2) effectively inhibited 786-0 cell growth. Ad-mediated expression of HepaCAM in 786-0 cells reduced the levels of phosphorylated AKT and cyclin D1 and inhibited cell proliferation. In summary, our studies point to interesting connections between HepaCAM and PKCε in tissues and in vitro. HepaCAM may prevent the translocation of PKCε from cytosolic to particulate fractions, resulting in the inhibition of 786-0 cell proliferation. Therapeutic manipulation of these novel protein targets may provide new ways of treating ccRCC.

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.