title: Methylation-mediated repression of GADD45alpha in prostate cancer and its role as a potential therapeutic target.
abstract: Defects in apoptotic pathway contribute to uncontrolled proliferation of cancer cells and confer resistance to chemotherapy. Growth arrest and DNA damage inducible, alpha (GADD45alpha) is up-regulated on docetaxel treatment and may contribute to docetaxel-mediated cytotoxicity. We examined the mechanism of regulation of GADD45alpha in prostate cancer cells and the effect of its up-regulation on sensitivity to docetaxel chemotherapy. Expression of GADD45alpha in PC3 cells was higher than that in Du145 and LNCaP cells (17- and 12-fold, respectively; P < 0.05). Although the proximal promoter region was unmethylated in all three cell lines, methylation of a 4 CpG region upstream of the proximal promoter correlated inversely with gene expression levels. Methylation was reversed by treatment of Du145 and LNCaP cells with DNA methyltransferase inhibitors, leading to reactivation of GADD45alpha expression in these cells. The 5' 4 CpG region was also frequently methylated in prostate cancer tissues. Methylation of this region correlated inversely with gene expression in prostate cancer and benign prostate tissues. The methyl binding protein MeCP2 was associated with the methylated 4 CpGs in Du145 cells, and knockdown of MeCP2 in these cells (Du145 MeCP2(-)) led to a significantly increased expression of GADD45alpha (3-fold; P = 0.035) without affecting the methylation status of the gene. Enhanced sensitivity to docetaxel was observed by up-regulation of GADD45alpha in Du145 cells by recombinant expression of GADD45alpha or pretreatment with 5-azacytidine. Our results show that GADD45alpha is epigenetically repressed and is a potential target for treatment of prostate cancer.
authors.affiliation: Sylvester Comprehensive Cancer Center, University of Miami, Miami, Florida 33136, USA.
authors.forename: Kavitha
authors.initials: K
authors.lastname: Ramachandran
authors.forename: Gopal
authors.initials: G
authors.lastname: Gopisetty
authors.forename: Edna
authors.initials: E
authors.lastname: Gordian
authors.forename: Loida
authors.initials: L
authors.lastname: Navarro
authors.forename: Christiane
authors.initials: C
authors.lastname: Hader
authors.forename: Isildinha M
authors.initials: IM
authors.lastname: Reis
authors.forename: Wolfgang A
authors.initials: WA
authors.lastname: Schulz
authors.forename: Rakesh
authors.initials: R
authors.lastname: Singal
mesh_terms: D000970:Antineoplastic Agents / Q000627:therapeutic use*; D001374:Azacitidine / Q000627:therapeutic use; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors / Q000235:genetics*; D045744:Cell Line, Tumor; D019175:DNA Methylation; D017931:DNA Primers; D004273:DNA, Neoplasm / Q000235:genetics; D000077143:Docetaxel; D015972:Gene Expression Regulation, Neoplastic; D016678:Genome; D006801:Humans; D008297:Male; D008745:Methylation; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors / Q000235:genetics*; D011471:Prostatic Neoplasms / Q000188:drug therapy / Q000473:pathology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D043823:Taxoids / Q000627:therapeutic use*; D015854:Up-Regulation; D000097642:GADD45 Proteins
chemical_list: D000970:Antineoplastic Agents; D001374:Azacitidine; D018797:Cell Cycle Proteins; D017931:DNA Primers; D004273:DNA, Neoplasm; D000077143:Docetaxel; D009687:Nuclear Proteins; D043823:Taxoids; C439070:GADD45A protein, human; D000097642:GADD45 Proteins