Identification of differentially methylated genes in normal prostate tissues from African American and Caucasian men.
OBJECTIVE
Aberrant DNA methylation changes are common somatic alterations in prostate carcinogenesis. We examined the methylation status of six genes in prostate tissue specimens from African American (AA) and Caucasian (Cau) males.


METHODS
We used pyrosequencing to quantitatively measure the methylation status of GSTP1, AR, RARbeta2, SPARC, TIMP3, and NKX2-5. Real-time PCR was used to determine gene expression, and gene reactivation was analyzed by 5-aza-2'-deoxycytidine and/or trichostatin A treatment.


RESULTS
Statistical analysis showed significantly higher methylation in the prostate cancer tissue samples in comparison with matched normal samples for GSTP1 (P = 0.0001 for AA; P = 0.0008 for Cau), RARbeta2 (P < 0.001 for AA and Cau), SPARC (P < 0.0001 for AA and Cau), TIMP3 (P < 0.0001 for AA and Cau), and NKX2-5 (P < 0.0001 for AA; P = 0.003 for Cau). Overall, we observed significant differences (P < 0.05) in the methylation level for all genes, except GSTP1, in the AA samples in comparison with the Cau samples. Furthermore, regression analysis revealed significantly higher methylation for NKX2-5 (P = 0.008) and TIMP3 (P = 0.039) in normal prostate tissue samples from AA in comparison with Cau, and a statistically significant association of methylation with age for NKX2-5 (P = 0.03) after adjusting for race.


CONCLUSIONS
Our findings show higher methylation of several genes in prostate tissue samples from AA in comparison with Cau and may potentially contribute to the racial differences that are observed in prostate cancer pathogenesis.
Kwabi-Addo
Bernard
B
Department of Medicine, Cancer Center, Howard University College of Medicine, Washington, District of Columbia 20060, USA. bkwabiaddo@howard.edu
Wang
Songping
S
Chung
Woonbok
W
Jelinek
Jaroslav
J
Patierno
Steven R
SR
Wang
Bi-Dar
BD
Andrawis
Ramez
R
Lee
Norman H
NH
Apprey
Victor
V
Issa
Jean-Pierre
JP
Ittmann
Michael
M
D001741:Black or African American / Q000235:genetics*; D000368:Aged; D045744:Cell Line, Tumor; D019175:DNA Methylation; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism; D005796:Genes; D051549:Glutathione S-Transferase pi / Q000235:genetics; D006262:Health; D000072576:Homeobox Protein Nkx-2.5; D018398:Homeodomain Proteins / Q000235:genetics*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015676:Osteonectin / Q000235:genetics; D011467:Prostate / Q000166:cytology / Q000378:metabolism*; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D011944:Receptors, Androgen / Q000235:genetics; D018168:Receptors, Retinoic Acid / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D019717:Tissue Inhibitor of Metalloproteinase-3 / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics*; D044465:White People / Q000235:genetics*
D000072576:Homeobox Protein Nkx-2.5; D018398:Homeodomain Proteins; C095552:NKX2-5 protein, human; D015676:Osteonectin; D011944:Receptors, Androgen; D018168:Receptors, Retinoic Acid; C088390:TIMP3 protein, human; D019717:Tissue Inhibitor of Metalloproteinase-3; D014157:Transcription Factors; C540966:retinoic acid receptor, beta2, human; C496556:GSTP1 protein, human; D051549:Glutathione S-Transferase pi