Vidanes Genevieve M, Paton Vince, Wallen Eric, Peehl Donna M, Navone Nora, Brooks James D
Department of Urology, Stanford University Medical Center, Pasteur Drive, Stanford, California 94305-5118, USA.
Prostate. 2002 Jun 1;51(4):225-30. doi: 10.1002/pros.10093.
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.
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).
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.
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.
谷胱甘肽S-转移酶π（GSTP1）表达缺失是人类前列腺癌中描述的最常见的基因改变，几乎在所有肿瘤中都会出现，无论肿瘤分级或分期如何。在现有的人类前列腺癌细胞系中，只有LNCaP反映了这种表型。我们研究了前列腺癌细胞系MDA PCa 2a和MDA PCa 2b是否具有这种表型。
通过蛋白质免疫印迹法（Western blot）和Northern印迹法评估MDA PCa 2a和MDA PCa 2b细胞系中GSTP1蛋白和mRNA水平。通过用甲基化敏感限制性内切酶BssHII、NotI和SacII消化基因组DNA后的Southern印迹分析评估DNA甲基化。在用DNA甲基转移酶抑制剂5-氮杂胞苷和/或组蛋白脱乙酰酶抑制剂曲古抑菌素A（TSA）处理后，通过逆转录聚合酶链反应（RT-PCR）确定GSTP1的重新表达。
与体内所有人类前列腺癌一样，MDA PCa 2a和2b细胞系均缺乏GSTP1蛋白和mRNA表达。这种表达缺失与GSTP1基因启动子中的甲基化有关。用甲基转移酶抑制剂5-氮杂胞苷处理导致GSTP1重新表达。单独使用TSA不会导致GSTP1重新表达，也不会增强5-氮杂胞苷诱导的表达。
MDA PCa 2a和2b似乎是人类前列腺癌的有用模型，因为它们由于启动子甲基化导致基因沉默而缺乏GSTP1表达。组蛋白乙酰化的抑制似乎不影响GSTP1表达。
