Department of Pharmacology, Dartmouth Medical School, Hanover, New Hamsphire 03755, USA.
Cancer Res. 2009 Dec 15;69(24):9360-6. doi: 10.1158/0008-5472.CAN-09-1490.
Testicular germ cell tumors (TGCT) are the most common solid tumors of 15- to 35-year-old men. TGCT patients are frequently cured with cytotoxic cisplatin-based therapy. However, TGCT patients refractory to cisplatin-based chemotherapy have a poor prognosis, as do those having a late relapse. Pluripotent embryonal carcinomas (EC) are the malignant counterparts to embryonic stem cells and are considered the stem cells of TGCTs. Here, we show that human EC cells are highly sensitive to 5-aza-deoxycytidine (5-aza-CdR) compared with somatic solid tumor cells. Decreased proliferation and survival with low nanomolar concentrations of 5-aza-CdR is associated with ATM activation, H2AX phosphorylation, increased expression of p21, and the induction of genes known to be methylated in TGCTs (MGMT, RASSF1A, and HOXA9). Notably, 5-aza-CdR hypersensitivity is associated with markedly abundant expression of the pluripotency-associated DNA methyltransferase 3B (DNMT3B) compared with somatic tumor cells. Knockdown of DNMT3B in EC cells results in substantial resistance to 5-aza-CdR, strongly indicating that 5-aza-CdR sensitivity is mechanistically linked to high levels of DNMT3B. Intriguingly, cisplatin-resistant EC cells retain an exquisite sensitivity to low-dose 5-aza-CdR treatment, and pretreatment of 5-aza-CdR resensitizes these cells to cisplatin-mediated toxicity. This resensitization is also partially dependent on high DNMT3B levels. These novel findings indicate that high expression of DNMT3B, a likely byproduct of their pluripotency and germ cell origin, sensitizes TGCT-derived EC cells to low-dose 5-aza-CdR treatment.
睾丸生殖细胞肿瘤（TGCT）是 15-35 岁男性中最常见的实体肿瘤。TGCT 患者常通过细胞毒性顺铂为基础的治疗治愈。然而，对顺铂为基础的化疗耐药的 TGCT 患者预后不良，晚期复发者也是如此。多能胚胎癌细胞（EC）是胚胎干细胞的恶性对应物，被认为是 TGCT 的干细胞。在这里，我们表明与体细胞实体肿瘤细胞相比，人 EC 细胞对 5-氮杂脱氧胞苷（5-aza-CdR）高度敏感。低纳摩尔浓度的 5-aza-CdR 导致增殖和存活减少，与 ATM 激活、H2AX 磷酸化、p21 表达增加以及已知在 TGCT 中甲基化的基因（MGMT、RASSF1A 和 HOXA9）的诱导有关。值得注意的是，与体细胞肿瘤细胞相比，5-aza-CdR 高度敏感与多能相关的 DNA 甲基转移酶 3B（DNMT3B）的显著丰富表达有关。在 EC 细胞中敲低 DNMT3B 会导致对 5-aza-CdR 的显著耐药，这强烈表明 5-aza-CdR 的敏感性与高水平的 DNMT3B 有机制上的联系。有趣的是，顺铂耐药的 EC 细胞对低剂量 5-aza-CdR 治疗仍保持极高的敏感性，而 5-aza-CdR 的预处理可使这些细胞对顺铂介导的毒性重新敏感。这种再敏化在一定程度上也依赖于高 DNMT3B 水平。这些新发现表明，DNMT3B 的高表达，可能是其多能性和生殖细胞起源的副产品，使 TGCT 衍生的 EC 细胞对低剂量 5-aza-CdR 治疗敏感。
