Carcinogenesis Advance Access originally published online on November 26, 2008
Carcinogenesis 2009 30(2):348-355; doi:10.1093/carcin/bgn266
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Regulation of the leucocyte chemoattractant receptor FPR in glioblastoma cells by cell differentiation
1 Laboratory of Molecular Immunoregulation, Cancer and Inflammation Program, Center for Cancer Research, National Cancer Institute at Frederick, Frederick, MD 21702, USA
2 Department of Pathophysiology, Third Military Medical University, Chongqing 400038, People's Republic of China
3 SuperArray Bioscience Corporation, 7320 Executive Way, Suite 101, Frederick, MD 21704, USA
4 Basic Research Program, SAIC-Frederick, National Cancer Institute at Frederick, Frederick, MD 21702, USA
* To whom correspondence should be addressed. Laboratory of Molecular Immunoregulation, Cancer and Inflammation Program, Center for Cancer Research, National Cancer Institute at Frederick, Building 560, Room 31-76, Frederick, MD 21702-1201, USA. Tel: +1 301 846 6979; Fax: +1 301 846 7042; Email: wangji{at}mail.ncifcrf.gov
The G protein-coupled formylpeptide receptor (FPR), known to mediate phagocytic leucocyte chemotaxis in reponse to bacterial- and host-derived agonists, was expressed by tumor cells in specimens of surgically removed more highly malignant human gliomas. In human glioblastoma cell lines, FPR activation increased cell motility, tumorigenicity and production of angiogenic factors. In studies of the mechanistic basis for the selective expression of FPR in more highly malignant gliomas, we found that the DNA methyltransferase inhibitor 5-Aza-2'-deoxycytidine (Aza), while promoting the differentiation of human glioblastoma cells, downregulated FPR expression. Aza also reduced the global methylation levels in glioblastoma cells and activated the pathway of p53 tumor suppressor. Methylation-specific polymerase chain reaction revealed that Aza treatment of tumor cells reduced the methylation of p53 promoter, which was accompanied by increased expression of p53 gene and protein. In addition, overexpression of p53 in glioblastoma cells mimicked the effect of Aza treatment as shown by increased cell differentiation but reduction in FPR expression, the capacity of tumor sphere formation in soft agar and tumorigenesis in nude mice. Furthermore, Aza treatment or overexpression of the wild-type p53 in glioblastoma cells increased the binding of p53 to FPR promoter region shown by chromatin immunoprecipitation. These results indicate that increased methylation of p53 gene retains human glioblastoma cells at a more poorly differentiated phase associated with the aberrant expression of FPR as a tumor-promoting cell surface receptor.
Abbreviations: Aza, 5-Aza-2'-deoxycytidine; CHIP, chromatin immunoprecipitation; DMEM, Dulbecco’s modified Eagle’s medium; EMSA, electrophoretic mobility shift assay; FCS, fetal calf serum; fMLF, N-formyl-methionyl-leucyl-phenylalanine; FPR, formylpeptide receptor; GFAP, glial fibrillary acidic protein; mRNA, messenger RNA; NF, nuclear factor; PBS, phosphate-buffered saline; PCR, polymerase chain reaction; PRE, p53-responsive element; RT2, real-time reverse transcription; WT, wild-type
Received August 7, 2008; revised October 31, 2008; accepted November 20, 2008.