Silencing of pi-class glutathione S-transferase in MDA PCa 2a and MDA PCa 2b cells.
BACKGROUND
Loss of expression of the glutathione S-transferase-pi (GSTP1) is the most common genetic alteration described in human prostate cancer, occurring in virtually all tumors regardless of grade or stage. Of the available human prostate cancer cell lines, only LNCaP mirrors this phenotype. We investigated whether the prostate cancer cell lines MDA PCa 2a and MDA PCa 2b share this phenotype.


METHODS
GSTP1 protein and mRNA levels were assessed in the MDA PCa 2a and MDA PCa 2b cell lines by Western and Northern blot. DNA methylation was evaluated by Southern blot analysis of genomic DNA digested with the methylation-sensitive restriction enzymes BssHII, NotI, and SacII. Re-expression of GSTP1 was determined by RT-PCR following treatment with 5-azacytidine, a DNA methyltransferase inhibitor, and/or the histone deacetylase inhibitor trichostatin A (TSA).


RESULTS
Like all human prostatic carcinomas in vivo, both the MDA PCa 2a and 2b cell lines lack protein and mRNA expression of GSTP1. This lack of expression is associated with methylation in the GSTP1 gene promoter. Treatment with the methyltransferase inhibitor 5-azacytidine resulted in re-expression of GSTP1. By itself, TSA did not result in re-expression of GSTP1, nor did it augment expression induced by 5-azacytidine.


CONCLUSIONS
MDA PCa 2a and 2b appear to be useful models of human prostatic carcinoma in that they lack expression of GSTP1 due to gene silencing via promoter methylation. Inhibition of histone acetylation does not appear to affect GSTP1 expression.
Vidanes
Genevieve M
GM
Department of Urology, Stanford University Medical Center, Pasteur Drive, Stanford, California 94305-5118, USA.
Paton
Vince
V
Wallen
Eric
E
Peehl
Donna M
DM
Navone
Nora
N
Brooks
James D
JD
D019175:DNA Methylation; D017931:DNA Primers; D004273:DNA, Neoplasm / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic; D051549:Glutathione S-Transferase pi; D005982:Glutathione Transferase / Q000096:biosynthesis* / Q000235:genetics*; D006801:Humans; D007527:Isoenzymes / Q000096:biosynthesis* / Q000235:genetics*; D008297:Male; D010641:Phenotype; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D011471:Prostatic Neoplasms / Q000201:enzymology* / Q000473:pathology; D014407:Tumor Cells, Cultured / Q000502:physiology*
D017931:DNA Primers; D004273:DNA, Neoplasm; D007527:Isoenzymes; C496556:GSTP1 protein, human; D051549:Glutathione S-Transferase pi; D005982:Glutathione Transferase