DNA Hypermethylation Involves in the Down-Regulation of Chloride Intracellular Channel 4 (CLIC4) Induced by Photodynamic Therapy.

Pei-Chi Chiang,Pei-Tzu Li,Chin-Tin Chen,Ming-Jen Lee

doi:10.3390/biomedicines9080927

Abstract

The altered expression of chloride intracellular channel 4 (CLIC4) was reported to correlate with tumor progression. Previously, we have shown that the reduced cellular invasion induced by photodynamic therapy (PDT) is associated with suppression of CLIC4 expression in PDT-treated cells. Herein, we attempted to decipher the regulatory mechanisms involved in PDT-mediated CLIC4 suppression in A375 and MDA-MB-231 cells in vitro. We found that PDT can increase the expression and enzymatic activity of DNA methyltransferase 1 (DNMT1). Bisulfite sequencing PCR further revealed that PDT can induce hypermethylation in the CLIC4 promoter region. Silencing DNMT1 rescues the PDT-induced CLIC4 suppression and inhibits hypermethylation in its promoter. Furthermore, we found tumor suppressor p53 involves in the increased DNMT1 expression of PDT-treated cells. Finally, by comparing CLIC4 expression in lung malignant cells and normal lung fibroblasts, the extent of methylation in CLIC4 promoter was found to be inversely proportional to its expression. Taken together, our results indicate that CLIC4 suppression induced by PDT is modulated by DNMT1-mediated hypermethylation and depends on the status of p53, which provides a possible mechanistic basis for regulating CLIC4 expression in tumorigenesis.

Highlights

Photodynamic therapy (PDT) has been developed as an alternative approach for cancer treatment [1]
We further investigated the regulatory mechanisms involved in PDT-mediated chloride intracellular channel 4 (CLIC4) suppression
In this study, we found that the reduced CLIC4 after PDT was not affected by histone deacetylase (HDAC) inhibitor, which indicated that the reduced CLIC4 expression does not relate to the histone acetylation

Summary

Introduction

Photodynamic therapy (PDT) has been developed as an alternative approach for cancer treatment [1]. The tumoricidal action of PDT involves the cancer cell killing, disruption of tumor vasculature with the following local inflammation. There are many studies conducted to investigate the molecular mechanisms involved in PDT-mediated cell death [3,4,5]. In addition to cell death, a few other studies reported that the primary tumor treated by PDT exhibits a decreased incidence of distant metastasis [6,7,8]. Our previous findings further revealed that the reduced invasiveness of PDT-treated cells relates to the decreased expression of chloride intracellular channel 4 (CLIC4) [9]. The molecular mechanisms involved in regulating the expression of CLIC4 by PDT-induced oxidative stress remain elusive

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Results

Conclusion