Periodic Reporting for period 3 - PML-THERAPY (HARNESSING PML NUCLEAR BODIES FOR LEUKAEMIA THERAPY)
Reporting period: 2022-04-01 to 2023-09-30
Apart from surgery, cancers are currently treated with very diverse approaches (chemotherapy, hormonal therapy, targeted therapies, radiotherapies..) How exactly these therapies yield clinical benefit in patients has been a matter of some controversies. Basic science is essential to understand the molecular and cellular bases for therapy response, in particular to optimize it. We are interested in the mechanistic basis of therapy response of acute myeloid leukemia (AML). In a specific form of AML, we previously unravelled (with ERC support) the molecular basis for therapy response. We demonstrated that PML plays a key role in therapy response. Physiologically, PML behaves as an oxidative stress sensor and contributes to redox homeostasis. PML organizes nuclear bodies (NBs), domains that recruit multiple client proteins and may facilitate their post-translational modifications (PTM), particularly conjugation of SUMOs. This controls multiple downstream pathways such as P53, but also RB, HIF1A or interferon (IFN). In APL, NB-disruption blunts P53-driven senescence, contributing to oncogenesis and therapy resistance. PML expression and/or NB-formation are also lost upon many viral infections or during cancer development.
We want to explore the possibility that PML plays a role in response to other therapies in other AMLs. Clearly, unravelling novel molecular mechanisms associated with therapy response will foster novel therapeutic approaches, notably drug combinations, that have immediate societal impact.
Our aim is to mechanistically dissect PML signaling in vivo and therapeutically restore it in malignancies where it is inactivated. We first propose a broad exploration of PML in mice to identify basal and stress-induced PML PTM and identify the repertoire of proteins sumoylated in a PML- dependent manner. We will generate a series of PML knock-in mutant mice and analyze their P53-regulated redox homeostasis. We will mechanistically explore PML-driven senescence in leukemia models where we have evidence for basal or therapy-responsive NB-modulation: acute myeloid leukemia expressing NPMc or IFN-sensitive JAK2-driven leukemias. We will screen chemical libraries for drugs modulating PML expression and/or NB biogenesis. Finally, we will integrate our findings to elaborate innovative therapeutic strategies based on restoration of the PML/P53 checkpoint in leukemia with unmet medical needs
We want to explore the possibility that PML plays a role in response to other therapies in other AMLs. Clearly, unravelling novel molecular mechanisms associated with therapy response will foster novel therapeutic approaches, notably drug combinations, that have immediate societal impact.
Our aim is to mechanistically dissect PML signaling in vivo and therapeutically restore it in malignancies where it is inactivated. We first propose a broad exploration of PML in mice to identify basal and stress-induced PML PTM and identify the repertoire of proteins sumoylated in a PML- dependent manner. We will generate a series of PML knock-in mutant mice and analyze their P53-regulated redox homeostasis. We will mechanistically explore PML-driven senescence in leukemia models where we have evidence for basal or therapy-responsive NB-modulation: acute myeloid leukemia expressing NPMc or IFN-sensitive JAK2-driven leukemias. We will screen chemical libraries for drugs modulating PML expression and/or NB biogenesis. Finally, we will integrate our findings to elaborate innovative therapeutic strategies based on restoration of the PML/P53 checkpoint in leukemia with unmet medical needs
Overall, the project ran well, with excellent support from INSERM. During the first half of this project, despite COVID, a significant number of goals have been met, while most others are in progress. Knock-in alleles of PML targeting critical residues of its functional domains were obtained in mice. Their exploration in response to a broad variety of oxidative stress is ongoing. They are also being used to generate a variety of AML models, so as to decipher their role in therapy response (figure below). The role of PML in controlling stress-induced SUMO2 conjugation was demonstrated in a variety of in vivo or ex vivo settings. Interestingly, PML-dependent, stress-induced SUMO2 conjugation is often followed by proteasome mediated degradation. Proteomic studies identified a number of novel SUMO protein targets regulated by PML and oxidative stress. These proteins, several of which are implicated in transcriptional repression, are key candidates for mediating downstream PML effects in therapy response. We then demonstrated direct implication of PML in pathogenesis and/or therapy response of other AML, fulfilling one of the main goals of this project. We found that NPM1c, an oncoprotein implicated in up to 30% of AMLs, binds PML, impedes NB formation and mitochondria fitness. Actinomycin D directly targets mitochondria to yield reactive oxygen species (ROS) that restore PML NBs, then driving senescence and therapy response. In Jak2-driven myeloproliferative neoplasms (MPN), interferon therapy is greatly potentiated by combination with arsenic. Moreover, this enhanced activity requires PML presence. These two published studies have immediate clinical impact, as they provide a basis for therapeutic trials assessing the efficacy of ActD+Venetoclax associations in AML patients. They also make a strong case for combined IFN/ATO trials in MPN. Mechanistically, they provide an unexpected parallel with APL therapy, stressing the importance of PML in pathogenesis and therapy response of very different types of AMLs.
At the current stage of the project, our studies imply a much broader role for PML in therapy response than anticipated. This justifies the emphasis put on PML biology, as it may yield novel therapeutic approaches.
Our published studies have immediate therapeutic impact and discussions are ongoing with clinical groups and pharmas to implement the new concepts drawn from our work into clinical trials.
We anticipate that our other ongoing studies could similarly yield important concepts with respect to PML biology and novel therapeutic strategies
Our published studies have immediate therapeutic impact and discussions are ongoing with clinical groups and pharmas to implement the new concepts drawn from our work into clinical trials.
We anticipate that our other ongoing studies could similarly yield important concepts with respect to PML biology and novel therapeutic strategies