Abstract 4239: Differentiation and apoptosis induced by all-trans retinoic acid is associated with downregulation of peroxiredoxin 1 in myeloid leukemia cells
All-trans retinoic acid (ATRA) based differentiation therapy with potentially curative outcome in acute promyelocytic leukemia (APL), has limited benefit in non-APL acute myeloid leukemia (AML). Thus, identifying key mediators of ATRA-induced differentiation/apoptosis in AML cells may reveal new putative therapeutic targets. Previously, we reported (Leukemia 20: 1809, 2006) that the therapeutic efficacy of ATRA is enhanced in topoisomerase 2β (TOP2β)-deficient AML cell lines, both APL (HL-60, AP-1060) and non-APL (KG-1), in part due to decreased expression of the antioxidant enzyme, peroxiredoxin (PRDX) 2 and increased accumulation of reactive oxygen species (ROS). Based on preliminary observations that (a) ATRA leads to down-regulation of a related antioxidant protein, PRDX1 (RNA array analysis), and (b) PRDX1 mRNA expression relative to PRDX2 mRNA is significantly higher in HL-60, KG-1, and leukemic blast cells from 20 AML patients (qRT-PCR analysis), we evaluated the role of PRDX1 in sensitizing the apoptotic effects of ATRA. Specifically, we tested the hypothesis that ATRA induced growth arrest/apoptosis is associated with decreased PRDX1 levels and increased ROS, which can be modulated by TOP2β. Accordingly, downregulation of TOP2β can enhance apoptosis by increasing ROS, whereas overexpression of TOP2β can inhibit PRDX1 downregulation by ATRA and attenuate ROS-induced apoptosis. Treatment of HL-60, KG-1 and patient AML blast cells with 1 µM ATRA in the absence or presence of 0.1 µM ICRF193 (TOP2β catalytic inhibitor) led to a 3 to 4-fold decrease in PRDX1 mRNA and protein. No effect of ICRF193, which leads to degradation of TOP2β, was observed on PRDX1 levels. Interestingly, while treatment with ATRA + ICRF 193 did not enhance PRDX1 down regulation compared to ATRA alone, it did lead to significantly (p Citation Format: Eric J. Norris, Yogin C. Patel, Michaela B. Reinhart, Ram N. Ganapathi, Mahrukh K. Ganapathi. Differentiation and apoptosis induced by all-trans retinoic acid is associated with downregulation of peroxiredoxin 1 in myeloid leukemia cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4239. doi:10.1158/1538-7445.AM2014-4239