Pml nuclear body disruption cooperates in APL pathogenesis and impairs DNA damage repair pathways in mice

Abstract

A hallmark of acute promyelocytic leukemia (APL) is altered nuclear architecture, with disruption of promyelocytic leukemia (PML) nuclear bodies (NBs) mediated by the PML-retinoic acid receptor α (RARα) oncoprotein. To address whether this phenomenon plays a role in disease pathogenesis, we generated a knock-in mouse model with NB disruption mediated by 2 point mutations (C62A/C65A) in the Pml RING domain. Although no leukemias developed in Pml mice, these transgenic mice also expressing RARα linked to a dimerization domain (p50-RARα model) exhibited a doubling in the rate of leukemia, with a reduced latency period. Additionally, we found that response to targeted therapy with all- retinoic acid in vivo was dependent on NB integrity. PML-RARα is recognized to be insufficient for development of APL, requiring acquisition of cooperating mutations. We therefore investigated whether NB disruption might be mutagenic. Compared with wild-type cells, primary Pml cells exhibited increased sister-chromatid exchange and chromosome abnormalities. Moreover, functional assays showed impaired homologous recombination (HR) and nonhomologous end-joining (NHEJ) repair pathways, with defective localization of Brca1 and Rad51 to sites of DNA damage. These data directly demonstrate that Pml NBs are critical for DNA damage responses, and suggest that Pml NB disruption is a central contributor to APL pathogenesis.

Are DNA damage response kinases a target for the differentiation treatment of acute myeloid leukemia?

“…In AML, the expression of leukemia‐associated oncofusion proteins, besides conferring self‐renewal activity and activating a leukemogenic program in the hematopoietic progeny, has been largely associated with defects in the DNA repair pathways and in the accumulation of DNA damage, which can act as an oncogenic driver AML onset . Indeed, a defective DNA damage response (DDR) heightens the accumulation of oncogenic mutations and genomic instability .…”

“…In turn, these events play a role in the pathogenesis and progression of APL. Noteworthy, the ATRA‐induced reformation of PML‐NBs and PML‐RARα oncoprotein degradation, two events contributing to its therapeutic effect in APL, is tightly correlated with the restoration of the DDR in APL cells, both in vitro and in vivo .…”

“…Consequently, cells are more prone to enter into mitosis with high levels of DNA damage or under‐replicated DNA and undergo a process called “mitotic catastrophe” that leads to apoptosis . A number of studies support the notion that cancer cells are more sensitive to the loss of DDR functions compared to normal tissues .…”

PML2‐mediated thread‐like nuclear bodies mark late senescence in Hutchinson–Gilford progeria syndrome

“…Furthermore, several studies have corroborated that PML is involved in homologous recombination (HR) (Boichuk, Hu, Makielski, Pandolfi, & Gjoerup, 2011; Yeung et al, 2012). Increased sister‐chromatid exchange (SCE) was observed in PML −/− cells and PML C52A/C65A cells with disrupted NBs (Voisset et al, 2018; Zhong et al, 1999). In addition to DNA repair, PML NBs regulate gene transcription either via direct interactions with specific genome loci or by recruiting transcription factors (Aoto, Saitoh, Ichimura, Niwa, & Nakao, 2006; Ching, Ahmed, Boutros, Penn, & Bazett‐Jones, 2013; Ching et al, 2005; Ulbricht et al, 2012; Zhong, Salomoni, & Pandolfi, 2000).…”

Acute Promyelocytic Leukemia: Update on the Mechanisms of Leukemogenesis, Resistance and on Innovative Treatment Strategies

“…Notably two of the most active drugs in APL therapy, ATRA and ATO, allow the reformation of PML NBs as the result of PML-RARα degradation [16,17].PML-NBs also have an important role in the mechanisms of DNA damage response (DDR) via both NHEJ and HR repair pathways. Its disruption by PML-RARα strongly affects ATM activation, as well as CHK2 and NBN phosphorylation [18,19]. ATM kinases are clients of the HSP90α chaperone, whose inhibition leads to the destabilization of these important components of the DNA damage response [20].…”