Dataset Information

Promoter Gene Methylation Regulates Clooxygenase-2 Expression in Androgen-Dependent and Independent Prostate Cancer Cells

ABSTRACT:

Background

Clooxygenase-2 (COX-2) expression is overexpressed in human prostate cancer, and aberrant methylation of the COX-2 promoter has also been elucidated. However, how the methylation of CpG islands at COX-2 regulates its expression in prostate cancer is still unclear. We will determine the methylated 5′ CpG island of the COX-2 gene and its role in the expression of COX-2 in prostate androgen-dependent and androgen-independent cancer cells, LNCaP and DU145.

Methods

We used western blotting and quantitative reverse transcription polymerase chain reaction (qRT-PCR) to confirm the COX-2 expression in prostate cancer cell lines, including LNCaP (androgen-dependent) and DU145 (androgen-independent) cells. To investigate whether the COX-2 expression was regulated by the methylation status of the 5′ CpG island, we treated LNCaP and DU145 cells with the DNA methylation inhibitor, 5-aza-2′-deoxycytidine, and determined COX-2 expression in the treated/untreated cells by western blotting and qRT-PCR. Subsequently, bisulfite sequencing was performed to study the methylation sites in the treated/untreated cells. The effects of 5-aza-2′-deoxycytidine to cell proliferation, cell migration and cell cycle process in DU145 and LNCaP cells were determined using Cell Counting Kit-8 (CCK-8) assay, transwell assay and flow cytometry, respectively.

Results

The results revealed that the expression of COX-2 in androgen-dependent LNCaP cells was 5.44-fold (in protein level) and 2.46-fold (in mRNA level) higher than that in androgen-independent DU145 cells. After 5-aza-2′-deoxycytidine treatment, COX-2 expression in DU145 cells was elevated significantly, but no change was found in LNCaP cells. The A and C regions of the COX-2 CpG island exhibited reduced methylation along with that an increased expression of COX-2 was noted in DU145 cell after 5-aza-2′-deoxycytidine treatment. Also, the treatment with 5-aza-2′-deoxycytidine inhibited cell proliferation, cell migration and influenced the cell cycle progression in both DU145 and LNCaP cells.

Conclusions

Our results reveal that androgen receptor (AR)-dependent/independent prostate cancer cell lines exhibit different regulation of methylation in COX-2 that regulate its expression. Additionally, 5-aza-2′-deoxycytidine treatment of DU145 and LNCaP cells inhibits their ability of tumor progression.

SUBMITTER: Liu C

PROVIDER: S-EPMC9239499 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BACKGROUND: Prostate cancer is one of the leading causes of cancer death in men. Androgen ablation, the most commonly-used therapy for progressive prostate cancer, is ineffective once the cancer cells become androgen-independent. The regulatory mechanisms that cause this transition (from androgen-dependent to androgen-independent) remain unknown. In this study, based on the microarray data comparing global gene expression patterns in the prostate tissue between androgen-dependent and -independent prostate cancer patients, we identify a set of transcription factors and microRNAs that potentially cause such difference, using a model-based computational approach. RESULTS: From 335 position weight matrices in the TRANSFAC database and 564 microRNAs in the microRNA registry, our model identify 5 transcription factors and 7 microRNAs to be potentially responsible for the level of androgen dependency. Of these transcription factors and microRNAs, the estimated function of all the 5 transcription factors are predicted to be inhibiting transcription in androgen-independent samples comparing with the dependent ones. Six out of 7 microRNAs, however, demonstrated stimulatory effects. We also find that the expression levels of three predicted transcription factors, including AP-1, STAT3 (signal transducers and activators of transcription 3), and DBP (albumin D-box) are significantly different between androgen-dependent and -independent patients. In addition, microRNA microarray data from other studies confirm that several predicted microRNAs, including miR-21, miR-135a, and miR-135b, demonstrate differential expression in prostate cancer cells, comparing with normal tissues. CONCLUSION: We present a model-based computational approach to identify transcription factors and microRNAs influencing the progression of androgen-dependent prostate cancer to androgen-independent prostate cancer. This result suggests that the capability of transcription factors to initiate transcription and microRNAs to facilitate mRNA degradation are both decreased in androgen-independent prostate cancer. The proposed model-based approach indicates that considering combinatorial effects of transcription factors and microRNAs in a unified model provides additional transcriptional and post-transcriptional regulatory mechanisms on global gene expression in the prostate cancer with different hormone-dependency.