Department of Experimental Medicine, Division of Radiotherapy and Radiobiology, University of L'Aquila, Via Vetoio, Coppito 2, 67100 L'Aquila, Italy.
Endocrinology. 2011 Dec;152(12):4550-61. doi: 10.1210/en.2011-1056. Epub 2011 Oct 11.
We hypothesized that hormonal therapy favors the development of the hormone-resistant phenotype through epigenetic mechanisms. Human prostate cancer tissues and in vitro and in vivo models were used to verify this hypothesis. We demonstrated that tumor cells continuously treated with bicalutamide (BCLT) or cultured in androgen-depleted medium progressively acquire higher DNA methyltransferase (DNMT) activity and expression than cells cultured in standard condition. Increased DNMT expression and activity also paralleled the up-regulation of truncated AR isoforms, which favors the development of the hormone-resistant phenotype. After androgen stimulation with 10(-12) m dihydrotestosterone, DNMT activity was significantly reduced in comparison with hormonal therapy. Consistent with these observations, the silencing of DNMT3a and DNMT3b significantly decreased the DNMT activity levels. These findings were also directly correlated with phosphatase and tensin homolog down-regulation and activation of ERK and phosphatidylinositol 3-kinases/AKT8 virus oncogene cellular homolog pathways. The use of a pan-DNMT inhibitor (5-Azacitidine) greatly reduced the development of the hormone-resistant phenotype induced by long-term BCLT treatment, and this finding correlated with low DNMT activity. The regulation of DNMT activity was, in some measure, dependent on the androgen receptor, as small interfering RNA treatment targeting the androgen receptor greatly decreased the modulation of DNMT activity under androgenic and antiandrogenic stimulation. These observations were correlated in vivo in patients, as demonstrated by immunohistochemistry. Patients treated by BCLT before surgery had higher DNMT3a and DNMT3b expression than patients who had not undergone this treatment. Our findings provide evidence of a relationship between the castration-resistant phenotype and DNMT expression and activity in human prostate cancer.
我们假设激素治疗通过表观遗传机制有利于激素抵抗表型的发展。使用人类前列腺癌组织以及体外和体内模型来验证这一假设。我们证明，与在标准条件下培养的细胞相比，连续用比卡鲁胺（BCLT）处理或在雄激素耗尽的培养基中培养的肿瘤细胞具有更高的 DNA 甲基转移酶（DNMT）活性和表达。增加的 DNMT 表达和活性也与截断的 AR 同工型的上调平行，这有利于激素抵抗表型的发展。在用 10(-12) m 二氢睾酮进行雄激素刺激后，与激素治疗相比，DNMT 活性显著降低。与这些观察结果一致，DNMT3a 和 DNMT3b 的沉默显著降低了 DNMT 活性水平。这些发现还与磷酸酶和张力蛋白同系物下调以及 ERK 和磷脂酰肌醇 3-激酶/AKT8 病毒癌基因细胞同系物途径的激活直接相关。泛 DNMT 抑制剂（5-氮杂胞苷）的使用大大降低了由长期 BCLT 治疗诱导的激素抵抗表型的发展，并且这一发现与低 DNMT 活性相关。DNMT 活性的调节在某种程度上依赖于雄激素受体，因为针对雄激素受体的小干扰 RNA 处理大大降低了在雄激素和抗雄激素刺激下 DNMT 活性的调节。这些观察结果在体内与患者相关，如免疫组织化学所示。在手术前接受 BCLT 治疗的患者的 DNMT3a 和 DNMT3b 表达高于未接受这种治疗的患者。我们的研究结果提供了证据表明，在人类前列腺癌中，去势抵抗表型与 DNMT 的表达和活性之间存在关系。
