Correlation between methylation of the E-Cadherin gene and malignancy of prostate cancer

E-Cadherin Downregulation is Mediated by Promoter Methylation in Canine Prostate Cancer

E-cadherin is a transmembrane glycoprotein responsible for cell-to-cell adhesion, and its loss has been associated with metastasis development. Although E-cadherin downregulation was previously reported in canine prostate cancer (PC), the mechanism involved in this process is unclear. It is well established that dogs, besides humans, spontaneously develop PC with high frequency; therefore, canine PC is an interesting model to study human PC. In human PC, CDH1 methylation has been associated with E-cadherin downregulation. However, no previous studies have described the methylation pattern of CDH1 promoter in canine PC. Herein, we evaluated the E-cadherin protein and gene expression in canine PC compared to normal tissues. DNA methylation pattern was investigated as a regulatory mechanism of CDH1 silencing. Our cohort is composed of 20 normal prostates, 20 proliferative inflammatory atrophy (PIA) lesions, 20 PC, and 11 metastases from 60 dogs. The E-cadherin protein expression was assessed by immunohistochemistry and western blotting and gene expression by qPCR. Bisulfite- pyrosequencing assay was performed to investigate the CDH1 promoter methylation pattern. Membranous E-cadherin expression was observed in all prostatic tissues. A higher number of E-cadherin negative cells was detected more frequently in PC compared to normal and PIA samples. High-grade PC showed a diffuse membranous positive immunostaining. Furthermore, PC patients with a higher number of E-cadherin negative cells presented shorter survival time and higher Gleason scores. Western blotting and qPCR assays confirmed the immunohistochemical results, showing lower E-cadherin protein and gene expression levels in PC compared to normal samples. We identified CDH1 promoter hypermethylation in PIA and PC samples. An in vitro assay with two canine prostate cancer cells (PC1 and PC2 cell lines) was performed to confirm the methylation as a regulatory mechanism of E-cadherin expression. PC1 cell line presented CDH1 hypermethylation and after 5-Aza-dC treatment, a decreased CDH1 methylation and increased gene expression levels were observed. Positive E-cadherin cells were massively found in metastases (mean of 90.6%). In conclusion, low levels of E-cadherin protein, gene downregulation and CDH1 hypermethylation was detected in canine PC. However, in metastatic foci occur E-cadherin re-expression confirming its relevance in these processes.

Research on the establishment of a TPM3 monoclonal stable transfected PANC-1 cell line and the experiment of the EMT occurrence in human pancreatic cancer

Background: Pancreatic cancer is one of the most aggressive human malignancies that is associated with early metastasis and chemoresistance. Tropomyosin (TPM) is an indispensable regulatory protein for muscle contraction, Abnormal expressions of TPM gene are closely related to the carcinogenesis and metastasis of malignant tumors.

Purpose: In this experiment, a monoclonal stable transfected cell line was established by the knock-down of TMP3 expression in PANC-1 cells with the lentivirus method, and the impacts of the downregulated TPM3 gene expression on the EMT-related molecules and biological behaviors of PANC-1 cells were explored.

Methods: Based on the TPM3 gene sequence, we designed the RNA interference sequence, constructed and screened out the recombinant plasmid segment TPM3-shRNA with the optimal silencing effect, and carried out lentivirus titer determination and packaging. The recombinant lentiviral interference vector LV-TPM3-shRNA was transfected into PANC-1 cells; the transfection efficiency was then evaluated to screen out the monoclonal stable transfected PANC-1 cell line with downregulated TPM3 expression. The qRT-PCR and Western blot were used to detect the changes in the gene- and protein-levels expressions of EMT-related transcription factors in the target cell line and to respectively test the variations of the invasion and proliferation capacities.

Results: It is shown that the monoclonal stable transfected PANC-1 cell line with downregulated TPM3 expression was successfully established with the recombinant lentiviral vector. After knocking down the expression of TPM3 gene in PANC-1 cells, EMT occurred in the cells; the cell phenotype showed malignant transformation, and the in vitro biological behaviors of the cells (such as proliferation and invasion) were enhanced to different degrees.

Conclusion: It is indicated that the TPM3 gene can be a potential target spot for the treatment of pancreatic cancer.

NDRG2 Regulates the Expression of Genes Involved in Epithelial Mesenchymal Transition of Prostate Cancer Cells

BACKGROUND

Metastasis is the main cause of prostate cancer (PCa) death. The inhibitory effect of N-myc downstream-regulated gene 2 (NDRG2) on the invasiveness properties of PCa cells has been demonstrated previously. However, its underlying mechanisms have not yet been investigated. The present study aimed to investigate the effects of NDRG2 overexpression on the expression of genes involved in epithelial-mesenchymal transition (EMT) including E-cadherin (E-CAD), α- and β-catenins, Slug and Snail, transforming growth factor (TGF)-α and -β, and vascular endothelial growth factor (VEGF).

METHODS

In the present in vitro study, LNCaP cells were divided into three groups, namely NDRG2 group (transfected with PSES-pAdenoVator-PSA-NDRG2-IRES-GFP plasmid), mock group (transfected with mock plasmid), and control group (without transfection). The effect of NDRG2 overexpression on the migration and invasion of LNCaP cells were investigated using the transwell assay. Real-time PCR was used for the evaluation of gene expression. For the statistical analyses, one-way ANOVA, student t test or Mann-Whitney U test were applied using the SPSS software (version 15.0). P values <0.05 were considered statistically significant.

RESULTS

The results demonstrated that the overexpression of NDRG2 reduced the invasion and migration of LNCaP cells compared to the control and mock groups (P<0.001). A decreased expression of TGF-β (P=0.002), VEGF (P=0.014), Slug (P=0.005), and Snail (P=0.012); and an increased expression of E-CAD (P=0.009) were observed following NDRG2 overexpression in LNCaP cells.

CONCLUSION

The results of the present study suggest that NDRG2 inhibits the invasiveness properties of LNCaP cells probably through changes in the expression of genes involved in EMT.