A Nonclassic CCAAT Enhancer Element Binding Protein Binding Site Contributes to α-Methylacyl-CoA Racemase Expression in Prostate Cancer

Abstract

A A A-Methylacyl-CoA racemase (AMACR), an enzyme involved in branched-chain fatty acid B B B-oxidation that is normally expressed at high levels in human liver, is specifically and consistently overexpressed at both mRNA and protein levels in human prostate cancer and potentially other cancer types. To characterize the mechanisms underlying transcriptional regulation of AMACR at the genetic and epigenetic levels, we performed a series of methylation and reporter assays in prostate cancer tissues and cell lines. The results ruled out altered methylation patterns as the cause of overexpression in prostate cancer cells. However, promoter deletion analysis identified an 8-bp nonclassic CCAAT enhancer element located f f80 bp upstream of the transcriptional initiation site that is responsible for AMACR expression in both prostate cancer cell lines and cell lines of liver origin. Deletion or mutation of this element completely abolished AMACR promoter activity. Ectopic expression of CCAAT/enhancer binding protein B B B increased luciferase activity driven by a wild-type AMACR promoter sequence but not by the sequence in which the putative CCAAT/enhancer binding protein binding element had been mutated. These results implicate a nonclassic CCAAT enhancer element in the AMACR gene promoter as playing a critical role in the regulation of AMACR gene expression. (Mol Cancer Res 2005;3(2):110 -8)

Deletion Hotspots in AMACR Promoter CpG Island Are cis-Regulatory Elements Controlling the Gene Expression in the Colon

“…Two CGIs were identified flanking the transcription start site (Figure 2A). The first is a novel CGI located upstream of the ATG site (−230 to −60; the position of the translation start site was set as +1) with 18 CG dinucleotides, whereas the second CGI downstream of the ATG site (48 to 357, not shown in Figure 2A) has been reported and shown to not be involved in gene regulation in PCa cells [5]. In concordance, our pilot studies indicated that the downstream CGI exhibited no differences in methylation/deletion/mutation status among the histological entities of the colon (data not shown).…”

“…Since most malignancies increase fatty acid utilization as an energy source to fuel growth [2], it has been suggested that increased β-oxidation of branched-chain fatty acids provides transformed cells with a unique metabolic advantage [3]. This idea is supported by recent findings that knockdown of AMACR transcripts or inhibition of the racemase activity effectively blocked growth of prostate cancer (PCa) cells [4],[5]. In humans, the major sources of phytol-derived, 2-methyl-branched fatty acids are dietary ruminant fats, meat, and dairy products.…”

“…However, the relationship between levels of AMACR expression and the sequence of adenoma-carcinoma progression in the colon [22] has not been fully characterized. Except for a report that identified a non-canonical CCAAT enhancer element in the AMACR promoter [5] and a lack of regulation of this gene by androgen [16],[23], no information is available regarding how the AMACR gene is regulated. Furthermore, although recent studies have identified a few AMACR gene variants to be associated with PCa [24],[25] or CCa [26] risks, a sequence polymorphism in the promoter region of AMACR has not been reported.…”

AMACRAmplification in Myxofibrosarcomas: A Mechanism of Overexpression That Promotes Cell Proliferation with Therapeutic Relevance

“…However, involvement of alterative regulatory mechanisms was likely in a subset of myxofibrosarcomas, because approximately 40% of AMACR-overexpressing myxofibrosarcomas lacked gene amplification. Actually, the expression level of AMACR in common carcinomas is mostly regulated by various transcriptional factors, such as C/EBP family members, Sp1, and ZNF202 (25)(26)(27). In the multivariate analysis of a subset cohort, AMACR overexpression, independent of SKP2, remained as the single adverse prognosticator, with an insignificant trend between two oncoproteins in expression levels.…”

High alpha-methylacyl-CoA racemase (AMACR) is associated with ERG expression and with adverse clinical outcome in patients with localized prostate cancer

“…A number of early studies revealed this to be false, with AMACR expression in prostate cancer being a largely androgen-independent process [50,51]. Recent studies have identified a non-classical C/EBP binding site within the AMACR promoter region [52]. This binding site, located at the −80 bp position, has been shown to be responsible for the observed expression of AMACR in the normal liver and prostatic cancer-derived cell lines.…”