DNA methylation-altered genes in the rat hippocampal neurogenic niche after continuous exposure to amorphous curcumin.

Rat offspring who are exposed to an amorphous formula of curcumin (CUR) from the embryonic stage have anti-anxiety-like behaviors, enhanced fear extinction learning, and increased synaptic plasticity in the hippocampal dentate gyrus (DG). In the present study, we investigated the links between genes with altered methylation status in the neurogenic niche and enhanced neural functions after CUR exposure. We conducted methylation and RNA sequencing analyses of the DG of CUR-exposed rat offspring on day 77 after delivery. Methylation status and transcript levels of candidate genes were validated using methylation-sensitive high-resolution melting and real-time reverse-transcription PCR, respectively. In the CUR group, we confirmed the hypermethylation and downregulation of Gpr150, Mmp23, Rprml, and Pcdh8 as well as the hypomethylation and upregulation of Ppm1j, Fam222a, and Opn3. Immunohistochemically, reprimo-like+ hilar cells and protocadherin-8+ granule cells were decreased and opsin-3+ hilar cells were increased by CUR exposure. Both reprimo-like and opsin-3 were partially expressed on subpopulations of glutamic acid decarboxylase 67+ γ-aminobutyric acid-ergic interneurons. Furthermore, the transcript levels of genes involved in protocadherin-8-mediated N-cadherin endocytosis were altered with CUR exposure; this was accompanied by Ctnnb1 and Syp upregulation and Mapk14, Map2k3, and Grip1 downregulation, suggesting that CUR-induced enhanced synaptic plasticity is associated with cell adhesion. Together, our results indicate that functionally different genes have altered methylation and expression in different neuronal populations of the hippocampal neurogenic niche, thus enhancing synaptic plasticity after CUR exposure.

Comparative distribution of Arcadlin/Protocadherin-8 mRNA in the intact and ischemic brains of adult mice.

The structural plasticity of dendritic spines serves as the adaptive capabilities of the central nervous system to various stimuli. Among these stimuli, cerebral ischemia induces dynamic alterations in neuronal network activity. Arcadlin/Paraxial protocadherin/Protocadherin-8 (Acad), a regulator of dendritic spine density, is strongly induced by activating stimuli to the neurons. However, the detailed distribution of Acad in normal and ischemic adult brains remains unclear. We comprehensively described Acad expression patterns in normal and ischemic adult brains by in situ hybridization histochemistry. We found that intact adult brains expressed Acad in the piriform cortex, dentate gyrus, hippocampal CA3, entorhinal cortex, amygdala, and hypothalamus. Acad expression was dramatically upregulated in the piriform cortex, olfactory area, dentate gyrus, entorhinal cortex, prefrontal cortex, insular cortex, amygdala, and septohippocampal nucleus 4 h after cerebral ischemia. Cerebral ischemia induced widespread neuronal activation, which was required for Acad upregulation. Our data suggested the involvement of Acad in the adaptive plasticity and remodeling of the neuronal network in the limbic and paralimbic systems.

MicroRNA-124-3p inhibited progression of nasopharyngeal carcinoma by interaction with PCDH8 and the inactivation of PI3K/AKT/mTOR pathway.

Nasopharyngeal carcinoma (NPC) is characterised by distinct geographical distribution and is particularly prevalent in Asian countries. But the mechanisms related to the progression of nasopharyngeal carcinoma (NPC) are not completely understood. MiR-124-3p functions as a tumor suppressor in many kinds of human cancers. Here, we explored the effects and mechanism of miR-124-3p on the proliferation and colony formation in NPC. In our study, we reported that miR-124-3p was significantly downregulated in NPC tissues and cell lines. Overexpression miR-124-3p decreased NPC cell proliferation and colony formation abilities. Meanwhile, knockdown miR-124-3p increased proliferation and colony formation abilities. Additionally, dual-luciferase assay showed that miR-124-3p could positively regulated PCDH8 by targeting its 3'-UTR. Overexpression of PCDH8 could partially rescue the proliferation and colony formation role of miR-124-3p inhibitor. Our study indicated that miR-124-3p played a tumor suppressor by directly interacting with PCDH8 and inhibiting the activation of the phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) signaling pathway. Overall, we found that miR-124-3p inhibited the activation of the PI3K/AKT/mTOR signaling pathway in NPC by interacting with PCDH8. Thus, PCDH8 may be a potential molecular target that impeded NPC proliferation and colony formation.

Expression of protocadherin8: Function as a tumor suppressor in hypopharyngeal carcinoma.

Protocadherin8 (PCDH8), an integral membrane protein, was reported to be a tumor suppressor involved in tumorigenesis in cancers. We aimed to investigate the expression of PCDH8 and its clinicopathological significance in hypopharyngeal carcinoma. We also examined the possible inactivation mechanism of PCDH8. A total of 80 pairs of hypopharyngeal carcinoma tumor tissues and non-tumor tissues were investigated to examine the immunohistochemical expression of PCDH8. Prognostic value and clinicopathological significance of PCDH8 expression were examined by Kaplan-Meier and log-rank test and Cox's ones. Ten pairs of tumor tissues and non-tumor tissues were analyzed by RT-PCR and 4 pairs by Western blot respectively. Promoter methylation of PCDH8 was observed in 14 pairs of tumor tissues and non-tumor tissues by methylation-specific PCR (MSP). The expression of PCDH8 in tumor tissues was depressed immunohistochemically when compared with non-tumor tissues and was significantly lower in the advanced pathological stage. Meanwhile, the expression of PCDH8 served as an independent prognostic risk factor for overall survival of hypopharyngeal carcinoma. The mRNA and protein levels of PCDH8 in tumor tissues was also down-regulated than in non-tumor tissues. Moreover, aberrant promoter methylation of PCDH8 occurred frequently in tumor tissues, rather than in non-tumor tissues. For the first time, our study demonstrates the tumor-suppressive function of PCDH8 and its epigenetic inactivation by promoter methylation in hypopharyngeal carcinoma. It suggests that PCDH8 may serve as a useful prognostic biomarker and a potential therapeutic target for hypopharyngeal carcinoma patients.

Protocadherin-8 promotes invasion and metastasis via laminin subunit γ2 in gastric cancer.

Growing evidence suggests that protocadherins (PCDH) play crucial roles in pathogenesis and progression of cancers, including gastric cancer (GC). Protocadherin-8 (PCDH8) was previously reported to be involved in metastasis of GC, but functional studies yielded inconsistent results and the molecular mechanism remained unknown. The present study aimed to explore the clinical relevance, function and molecular mechanism of PCDH8 in GC. Data from the GEPIA and Kaplan-Meier plotter databases showed that high expression of PCDH8 was significantly correlated with poorer prognosis in GC. Ectopic expression of PCDH8 in GC cells promoted invasion and migration in vitro and metastasis in vivo, and knockdown of PCDH8 inhibited invasion and migration in vitro. RNA sequencing followed by gene set enrichment analysis found a remarkable enrichment in the extracellular matrix receptor interaction pathway, with the expression of laminin subunit γ2 (LAMC2) being significantly increased in the PCDH8-overexpressing group. High expression of LAMC2 was significantly correlated to poor prognosis in GC in GEPIA database. Upregulation of LAMC2 following PCDH8 overexpression was further confirmed by immunohistochemistry in liver metastatic lesions of nude mice. To our knowledge, this is the first report of the metastasis-enhancing property and molecular mechanism through upregulation of LAMC2 of PCDH8 in cancer. High expression of PCDH8 could be used as a biomarker for poor prognosis in clinical practice.

PCDH8 inhibits glioma cell proliferation by negatively regulating the AKT/GSK3ß/ß-catenin signaling pathway.

Protocadherin-8 (PCDH8), a member of the protocadherin superfamily of proteins, is frequently lost in numerous types of cancer. However, the role that PCDH8 serves in human glioma, and the molecular mechanisms underlying this, remain unclear. Data from the present study demonstrated that the expression levels of PCDH8 mRNA and protein were significantly decreased in human glioma tissue compared with normal brain tissue. This suggested that PCDH8 is associated with the development of glioma. Thus, the role of PCDH8 in glioma cell proliferation was investigated by silencing and overexpressing PCDH8 in U251 glioma cells. Overexpression of PCDH8 significantly inhibited glioma cell proliferation, while silencing of PCDH8 using small interfering RNA promoted glioma cell proliferation. Restoration of PCDH8 decreased phosphorylated (p)-Rac-α serine/threonine-protein kinase (AKT) [Threonine (T)308/Serine (S)473] and p-glycogen synthase kinase-3ß (p-GSK3ß) (S9) protein expression, thereby reducing the level of ß-catenin when compared with the control. By contrast, silencing of PCDH8 increased levels of p-AKT (T308/S473) and p-GSK3ß (S9), thereby increasing the level of ß-catenin. In conclusion, the results of the present study suggested that PCDH8 suppressed glioma cell proliferation, and that the loss of PCDH8 may stimulate the proto-oncogene Wnt/ß-catenin signaling pathway and therefore promote glioma cell proliferation.

Association between protocadherin 8 promoter hypermethylation and the pathological status of prostate cancer.

Promoter hypermethylation of tumor suppressor genes has been confirmed to serve a pivotal role in tumorigenesis. Protocadherin 8 (PCDH8), a novel tumor suppressor gene, has been reported to be inactivated by promoter hypermethylation a number of cancer types, including bladder cancer and renal cell carcinoma. The aim of the present study was to investigate the occurrence of PCDH8 hypermethylation in prostate cancer and its potential as a novel biomarker of prostate cancer. The transcriptional levels of PCDH8 were examined by quantitative polymerase chain reaction (PCR) in 82 prostate cancer tissues as well as 30 prostate hyperplasia tissues, and verified the protein level by western blot analysis of representative samples. PCDH8 expression levels were found to be reduced to 0.30±0.10 in 70.7% (58/82) of prostate cancer tissues. To identify the possible reason for mRNA downregulation, the methylation status of the PCDH8 promoter was assessed in prostate cancer tissues and prostate hyperplasia tissues by methylation-specific PCR (MSP). A total of 47 prostate cancer patients who exhibited reduced PCDH8 expression (57.3%; 47/82) also showed promoter hypermethylation (47/58). None of the samples (0/30) in the benign prostate hyperplasia group were positive on MSP. Furthermore, the associations between the methylation status of the PCDH8 promoter and various clinicopathological features of prostate cancer were analyzed, revealing that the methylation status of PCDH8 was closely associated with tumor size, tumor shape (papillary/non-papillary), tumor stage and tumor grade (all P<0.05), while there were no correlations with the age of the patients or the number of tumors (P>0.05). Additionally, patients with hypermethylation of the PCDH8 gene promoter had a relapse rate of 36.17% and a mortality rate of 29.79%, which were significantly higher than the hypermethylation-negative patients (P<0.05), indicating a poorer prognosis. Therefore, the methylation status of the PCDH8 gene in prostate cancer may be an important marker for use in the early diagnosis and prediction of prognosis in prostate cancer.

Methylation of PCDH8 in pancreatic carcinoma cell lines / 中华胰腺病杂志

Objective To investigate the methylation status of PCDH8 gene in pancreatic carcinoma.Methods Methylation of PCDH8 gene in 2 samples of normal pancreatic tissues and 6 pancreatic carcinoma cell lines (PANC1, ASPC1, BxPC3, CFPAC, PaTu8988 and SW1990) was detected by the methylationspecific PCR (MSP) method. The expression of PCDH8 mRNA was detected with 5-Aza-2-deoxycytidine (5-Aza-dC) treatment, a kind of DNA methyltransferase (DNMT) inhibitor in 6 pancreatic carcinoma cell lines by real-time-PCR. Results The methylation of PCDH8 gene was not detected in normal tissues, while it was partially methylated in PANC1, BxPC3, CFPAC and it was totally methylated in PaTu8988, ASPC1, SW1990.PCDH8 mRNA was expressed in PANC1, SW1990, PaTu8988 and the relative quantities of mRNA expression (RQ) were 1.576 ± 0.648, 0.013 ± 0.008, 0.002 ± 0.001; PCDH8 mRNA was not expressed in BxPC3,CFPAC, ASPC1. After 5-Aza-dC treatment, PCDH8 mRNA was expressed in PANC1, ASPC1, BxPC3,CFPAC, PaTu8988, SW1990 and the relative quantities of mRNA expression all significantly increased, and they were 7. 463 ± 2.628, 10. 696 ± 1.539, 7.852 ± 2.762,421.815 ± 1.493, 118.595 ± 4.089, 6.690 ±1.884. Conclusions The methylation of PCDH8 gene may be the major mechanism of down-regulated expression of PCDH8 gene in pancreatic carcinoma.