Alcohol dehydrogenase expression patterns in normal prostate, benign prostatic hyperplasia, and prostatic adenocarcinoma in African American and Caucasian men

BACKGROUND

In situ metabolism of ethanol by alcohol dehydrogenases (ADHs) contributes to oxidative damage of cells and DNA and has been linked to carcinogenesis in numerous epithelial tissues. The goal of this study was to determine expression patterns of ADH1 and ADH7 isozymes in normal, hyperplastic (benign prostatic hyperplasia [BPH]) and neoplastic (prostate cancer [PCa]) prostate. Furthermore, racial differences in ADH expression between African Americans and Caucasians were investigated.

METHODS

ADH expression patterns were characterized by density analysis of ADH immunohistochemistry (n = 21) and real-time RT-PCR of total RNAs by laser-capture microdissection (n = 10) and whole tissue formalin-fixed paraffin embedded prostate biopsies (n = 63).

RESULTS

ADH protein is found in normal prostate and is primarily associated with glandular epithelium. Transcripts of ADH1B are suppressed in PCa compared to BPH (p = 0.0095). Racial differences in ADH7 transcripts exist between African American and Caucasian men. A total of 57.6% of biopsies from African American prostates have detectable ADH7 messenger RNA (mRNA) transcripts compared to the 13.3% of Caucasian prostate biopsies with detectable transcripts (p = 0.0005). This increased frequency of detection contributes to higher mean ADH7 mRNA transcript levels in African Americans (p = 0.001).

CONCLUSIONS

To our knowledge this study is the first to report downregulation of ADH1B in neoplastic prostate at the transcriptional level, suggesting protective regulatory functions. ADH7 transcripts were not detectable in all samples and was found in higher frequency and amount in our African American samples. Racial differences in ADH7 within the prostate is a novel finding and should be investigated further.

Abstract 111: Regulation of alcohol dehydrogenase 1B by DNA methylation and histone modification in epithelial breast cell lines

Homeostasis of normal breast epithelium requires maintenance of a gene expression profile that is, in part, dependent on DNA methylation and histone modification. Tumorgenesis is marked by a disturbance of this profile, as the bulk of the tumor genome is hypomethylated with the exception of tumor suppressor genes that are typically hypermethylated. The hypermethylation interacts with histone modifications to suppress gene expression. Our previous research demonstrated that alcohol dehydrogenase (ADH) isozymes are expressed in normal breast tissue and down-regulated in breast cancer. In this study, qRT-PCR analysis of RNA extracted from normal breast epithelium reveals that ADH1B accounts for 95.8% of total ADH isozyme expression. Expression of ADH1B in RNA extracts from breast tumor is significantly down-regulated to 5.4% of normal expression (p < 0.0001). Similar findings have been identified in lung and colon epithelium. The consistent down-regulation of ADH1B in epithelial cancers suggests that it plays an important role in epithelial maintenance and may act as a tumor suppressor. In addition to its role in oxidation of alcohols, ADH1B participates in a variety of major biochemical processes important to tissue homeostasis such as lipid peroxidation and the oxidation of retinol. Epigenetic modifications that may participate in the observed abrogation of ADH1B expression in breast cancer were investigated. Using qRT-PCR, the expression profile of ADH1B was determined for 3 epithelial breast cell lines: MCF-10A, MCF-10AT, and HS-578T. Neither MCF-10A nor MCF-10AT express ADH1B. HS-578T cells express less than 1% of the ADH1B found in RNA extracted from normal breast epithelium. These results are consistent with observed ADH1B expression in breast tumor samples. Chromatin immunoprecipitation assays were performed on cell lysates from untreated cells and cells treated with 5-Aza-2′-Deoxycytidine (5-aza-2dC) or Trichostatin A (TSA) alone or in combination. 5-aza-2dC inhibits methylation by forming a covalent bond with DNA methyltransferase and TSA is a reversible histone deacetylase inhibitor. Interaction between ADH1B and RNA Pol II increased six fold in cells treated with TSA (p < 0.05). ADH1B expression significantly increased in these cells and further increased in cells treated with a combination of 5-aza-2dC and TSA (p < 0.0001). However, no significant difference was found in cells treated with 5-aza-2dC alone. These results suggest that histone deacetylation plays an important role in the down-regulation of ADH1B expression in these breast cell lines. The methylation state of the promoter region may also interact with histone acetylation to down-regulate ADH1B expression. The down-regulation of ADH1B observed in breast cancer may result from similar changes in epigenetic modifications and the availability of key transcription factors during carcinogenesis.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 111. doi:10.1158/1538-7445.AM2011-111