TREAT-NPM1-AML Project – Improving therapy of NPM1-mutated AML

Acute myeloid leukemia (AML) is the most common acute leukemia in adults accounting for approximately  15,000 new cases/year in Europe and 20,000 new cases/year in US. Currently, about 40-50% of AML patients (age 18-60 years) can be cured using conventional chemotherapy. However, AML is curable only in a small percentage (5-10%) of older patients (age >60 years) whose number is increasing exponentially. Thus, the therapy of this disease still remains an urgent medical need that might be addressed with the development of molecular therapies aimed to target new identified genetic lesions that can induce leukemogenesis, or with the use of immunotherapic approaches.

Even though about 50% of adult patients diagnosed with AML show normal cytogenetics (CN-AML), the unceasing work of Dr. Falini and other investigators has broadened the mutational landscape of the AML genome by identifying 23 recurrent mutations, including those affecting the nucleophosmin (NPM1), fms related tyrosine kinase 3 (FLT3) and DNA methyltransferase 3 alpha (DNMT3A) genes, paving the way for new targeted therapies for AML cases induced by these genetic lesions. In particular, the P.I., using immunohistochemical techniques, discovered the NPM1 mutations in 2005 and found that they represent the most frequent genetic lesions in AML (about 30% of all AML and 60% of CN-AML). The NPM1 gene encodes for a multifunctional protein with shuttling and chaperone properties that is localized in the nucleolus. The P.I. discovered that all NPM1 mutations (more than 50 so far identified) cause the same change at the C-terminus level of the NPM1 protein, i.e. the  loss of the nucleolar binding domain and the generation of an additional nuclear export signal (NES) motif that are responsible for the aberrant dislocation of both mutated and wild-type NPM1 proteins in the cytoplasm of the leukemic cells. This event appears to be critical for the leukemogenic activity.

Prof. Falini played a critical role in all steps of this discovery process from the bench to the bedside. Over the past 10 years, his initial findings have been extensively validated by numerous investigators in thousands of leukemic patients, such that NPM1-mutated AML is now recognized as a disease entity in the WHO-2016 classification of lympho-hematopoietic neoplasms and evaluation of the mutational status of NPM1 (in combination with that of FLT3 gene) is now recommended as mandatory in the prognostic stratification of AML (European LeukemiaNet, 2017). Search for NPM1 mutations is also a valuable tool for monitoring of minimal residual disease in AML patients, with major impact on treatment decisions.

Although it still remains unclear how the NPM1 mutants promote leukemia, the high frequency of NPM1 mutations in AML and their specificity for this disease, as well as their association with  unique gene expression profile and microRNA signature, make them an appealing target for the development of new molecular tailored therapies.

The ERC research project TREAT-NPM1-AML is focused on improving the therapy of NPM1-mutated AML through the repositioning of old drugs (e.g. actinomycin D) in the light of the genetic lesion  and by identifying protein interactors that co-localize with NPM1 (in the nucleus and/or in the cytoplasm) and may represent novel therapeutic targets. These studies, which will be conducted both in primary AML cells from patients and in mice models, are also expected to highlight new biological mechanism through which the NPM1 mutants can induce leukemia, opening the door to novel therapeutic approaches. In conclusion, the objectives that we want to address in the course of the ERC project are: