ContraNPM1AML provides evidence on the role of specific genes involved in leukemia and on the peculiar activity against NPM1-mutated AML of a series of drugs, approved for other diseases, that therefore have been ‘repurposed’, within the project, in the setting of NPM1-mutated AML. Here we confirm specific actions of arsenic trioxide (ATO) and all-trans-retinoic acid (ATRA) - two drugs used for the treatment of another form of leukemia, named promyelocytic leukemia – in NPM1-mutated AML, where they induce degradation of NPM1 oncoprotein and downregulation of HOX genes, a pathway critical in leukemia renewal, supporting the concept of the essentiality of NPM1 mutant in the leukemia maintenance through HOX genes regulation (Brunetti et al, Cancer Cell 2018). On HOX genes and NPM1 oncoprotein interplay, using the drugs FLT3-inhibitors in FLT3-ITD and NPM1-mutated AML patients we showed for the first time terminal cell differentiation of leukemic cells ‘uncoupled’ from the HOX-related ‘self-renewal signature’ that remained ‘activated’ (up) in presence of sustained NPM1 oncoprotein expression, supporting again its key role in HOX maintenance. These novel data have not been yet published, but were presented at either national or international scientific meetings. The studies on the nucleolar stress inductor drug dactinomycin, that we have previously shown to be clinically active in patients with NPM1-mutated AML, were concluded and showed that expression of NPM1 mutant lowers the threshold for stress-induced cell death, providing an explanation for its clinical activity in NPM1-mutated AML (Gionfriddo et al, Leukemia 2021). Moreover, in collaboration studies, we unveiled a new interplay between NPM1 oncoprotein, the tumour suppressor PML and mitochondria in mediating dactinomycin response and synergistic effect with the bcl2-inhibitor venetoclax (Wu et al, Cancer Discov 2021). Based on our results, dactinomycin is deserving further investigation in larger clinical studies and in combinatorial settings. We also studied the role of omacetaxine mepesuccinate, a drug that inhibits protein synthesis, with the purpose of targeting levels of proteins relevant for leukemia cell survival and, strikingly, we found that it decreased NPM1 oncoprotein levels, besides other relevant players in leukemia, and induced leukemia cell differentiation. Its combination with the bcl-2 inhibitor venetoclax showed unexpected potent and synergic anti-leukemic effects in preclinical studies so that these findings were readly translated from bench to bedside in the first clinical trial stemmed from our ContraNPM1AML ERC-granted research and based on the chemo-free association of these two drugs.
Finally, a substantial effort was placed in two main tasks to discover new targets by identifying essential interactions by high throughput drug library screens and gene targeting in NPM1-mutated AML. To carry out the highly complex drug screening the ERC team was supported by the Horizon 2020-funded CORBEL project, that guaranteed connection with two European research infrastructures, EU-OPENSCREEN (FMP, Berlin) and Euro-BioImaging (EBML, Heidelberg), allowing the access to technologies not available in the PI’s lab and to scale-up screening to a 40.000 compounds library. Despite the COVID-19 pandemic, a lockdown, and constantly-evolving travel restrictions have slowed down cross-border cooperation, the ERC/Corbel team succeeded in completing the chemical screening, leading to the identification of two main classes of drugs that have been chosen for the further investigational studies within the time frame of the project and were proven to be particularly effective in NPM1-mutated AML in the preclinical setting. The screening lead also to the identification of other drugs and even not-annotated compounds that will be the object of future drug development studies.
