Genetic and Epigenetic SLC18A2 Silencing in Prostate Cancer Is an Independent Adverse Predictor of Biochemical Recurrence after Radical Prostatectomy

Abstract

Purpose: This study investigates SLC18A2 (vesicular monoamine transporter 2) expression in prostate adenocarcinoma and examines its potential as a predictive marker for prostate cancer patient outcome after radical prostatectomy. Experimental Design: Expression and single nucleotide polymorphism microarray analyses identified SLC18A2 as both down-regulated and subject to common loss-of-heterozygosity in prostate cancer. Down-regulated SLC18A2 expression was validated on tissue microarrays containing benign and malignant prostate specimens from an independent patient group (n = 738). Furthermore, SLC18A2 immunoreactivity in radical prostatectomy tumor specimens (n = 506) was correlated to clinicopathologic characteristics and recurrence-free survival. The possibility of SLC18A2 silencing by aberrant DNA methylation in prostate cancer cells was investigated by bisulfite sequencing. Results: Tissue microarray analysis revealed markedly lower cytoplasmic SLC18A2 staining in cancer compared with nonmalignant prostate tissue samples, confirming RNA expression profiling results. Furthermore, multivariate analysis identified cytoplasmic SLC18A2 immunoreactivity as a novel predictor of biochemical recurrence following prostatectomy (hazard ratio, 0.485; 95% confidence interval, 0.333-0.709; P < 0.001) independent of prostate-specific antigen, Gleason score, tumor stage, and surgical margin status. SLC18A2 showed loss-of-heterozygosity in 23% of the tumors and was densely hypermethylated in 15 of 17 (88%) prostate cancer samples plus 6 of 6 prostate cancer cell lines. In contrast, SLC18A2 was unmethylated in 4 of 4 adjacent nonmalignant prostate and 3 of 5 benign prostatic hyperplasia tissue samples, whereas 2 of 5 benign prostatic hyperplasia samples had monoallelic hypermethylation. Methylation and histone deacetylase inhibitory agents rescued SLC18A2 expression in three prostate cancer cell lines. Conclusions: SLC18A2 silencing by DNA hypermethylation and/or allelic loss is a frequent event inprostate cancerandanovelindependent predictorofbiochemicalrecurrenceafterprostatectomy.

Heterogeneous patterns of DNA methylation-based field effects in histologically normal prostate tissue from cancer patients

“…Hence, our results confirm and expand on previous reports of PC-specific hypermethylation of these genes in prostatectomy specimens1820212223. Furthermore, to investigate if epigenetic cancer field effects exist for our eight novel candidate genes, we analysed non-malignant diagnostic needle biopsy samples from 79 patients with/without cancer in other biopsies using qMSP.…”

“…To date, several genes have been identified as common targets for aberrant promoter hypermethylation in PC17, including the extensively studied GSTP1 (Glutathione S-Transferase pi 1) gene that is hypermethylated in more than 90% of all PC tissue samples1819. Moreover, we have previously reported similarly high frequencies of cancer-specific promoter hypermethylation for the eight biomarker candidate genes AOX1 (Aldehyde Oxidase 1), CCDC181 (Coiled-Coil Domain Containing 181, also known as C1orf114 ), GABRE (Gamma-Aminobutyric Acid A Receptor Epsilon), GAS6 (Growth Arrest-Specific 6), HAPLN3 (Hyaluronan and Proteoglycan Link Protein 3), KLF8 (Kruppel-like Factor 8), MOB3B (MOB kinase activator 3B), and SLC18A2 (Solute Carrier Family 18 vesicular monoamine Member 2) in malignant tissue samples from radical prostatectomy (RP) specimens20212223. However, while hypermethylation-based cancer field effects have been demonstrated for GSTP1 in several previous studies of PC242526272829, the existence of such epigenetic field effects remains to be investigated for our eight novel candidate methylation marker genes.…”

Progression-Free Survival in Ovarian Cancer Is Reflected in Epigenetic DNA Methylation Profiles

“…The most significant hypermethylation was observed in (1) transmembrane and coiled-coil domains 5 (p = 1.58 × 10 –6 ), which was linked to cardiovascular disease risk and progression if harboring a single nucleotide polymorphism mutation [36]; (2) protein tyrosine phosphatase receptor type N (p = 1.55 × 10 –5 ), a signaling molecule that regulates a variety of cellular processes including oncogenic transformation that was previously identified as DNA methylation marker for squamous cell lung cancer [37]; (3) solute carrier family 18 (vesicular monoamine) member 2 (p = 2.26 × 10 –5 ) that is silenced by DNA methylation in prostate cancer and serves as a novel predictor of biochemical recurrence after prostatectomy [38], and (4) signaling lymphocyte activation molecule family member 7 (p = 5.35 × 10 –5 ), a member of the CD2 family that is highly expressed in myeloma cells and a potential new therapeutic antibody target for the treatment of multiple myeloma [39]. Further hypermethylated genes include membrane-spanning 4 domains, subfamily A, member 1 (p = 4.91 × 10 –5 ) which was recently positively associated with disease-specific survival in high-grade serous epithelial ovarian cancer [40] and GUCY2C (p = 7.19 × 10 –4 ) being described as a predictive marker of recurrence in node-negative colorectal cancer [41].…”

“…The most significantly hypermethylated CpG sites were associated with these genes found to be predictive markers in squamous lung cancer [37], prostate cancer [38] and ovarian cancer [40]. Further hypermethylated genes include signaling lymphocyte activation molecule family member 7, a potential new therapeutic antibody target for the treatment of multiple myeloma [39].…”

Genetic Association Analysis of 300 Genes Identifies a Risk Haplotype in SLC18A2 for Post-traumatic Stress Disorder in Two Independent Samples

“…SLC18A2, also known as VMAT2, is responsible for transporting monoamine neurotransmitters (serotonin, noradrenaline, dopamine) into synaptic vesicles (Erickson et al, 1996). It has been implicated in several complex disorders including Parkinson's disease (Sala et al, 2010), depression (Christiansen et al, 2007), alcohol, and nicotine dependence (Schwab et al, 2005), prostate cancer (Sorensen et al, 2009), and Tourette's syndrome (Ben-Dor et al, 2007). SLC18A2 is also the target of reserpine and tetrabenazine (Peter et al, 1993), drugs used to treat high blood pressure, agitation, tardive dyskinesia, and involuntary movements of Huntington's disease.…”