Abstract 4273: DNA methyltransferase 3B mediates 5-aza-deoxycytidine hypersensitivity in cisplatin-sensitive and cisplatin-resistant pluripotent embryonal carcinoma cells

Proceedings: AACR 101st Annual Meeting 2010‐‐ Apr 17‐21, 2010; Washington, DC Testicular germ cell tumors (TGCTs) are the most common solid tumors of 15-35 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 carcinoma (EC) are the malignant counterparts to embryonic stem (ES) 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) as compared to a variety of somatic solid tumor cells. This is associated with markedly abundant expression of the pluripotency-associated DNA methyltransferase 3B, DNMT3B, as compared to somatic tumor cells. Knockdown of DNMT3B in EC cells resulted in substantial resistance to 5-aza-CdR, strongly implicating 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 re-sensitizes these cells to cisplatin-mediated toxicity. These findings indicate that high expression of DNMT3B, a likely byproduct of their pluripotent and germ cell nature, sensitizes TGCT-derived EC cells to low dose 5-aza-CdR treatment. 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. Data pertaining to the mechanism of DNMT3B-dependent, 5-aza-CdR hypersensitivity in TGCTs will be presented. Efforts to extend this work to clinical samples are ongoing. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4273.