Abstract 2678: All-trans-retinoic acid as a new therapeutic approach to target isocitrate dehydrogenase mutations in acute myeloid leukemia
Authors: Boutzen Helena , Toni Fabienne D. , Saland Estelle , Delabesse Eric , mas Véronique De , Demur Cécile , Castelli Florence , Gales Lara , Penard-lacronique Virginie , Botton Stéphane De , Portais Jean-Charles , Junot Christophe , Manenti Stéphane , Récher Christian , Sarry Jean-emmanuel 
Published: May 2015

Abstract
Mutations of isocitrate dehydrogenases 1 and 2 (IDH1/2) occur in about 15% of acute myeloid leukemia (AML) patients, and lead to the production of an oncometabolite, the 2-hydroxyglutarate (2-HG). Importantly, many clinical studies demonstrated that IDH1/2 mutations are systematically conserved at relapse, suggesting that this mutated enzyme could contribute to early leukemogenesis.
In an effort to identify therapy specifically targeting IDH1 R132H mutated blasts, we developed an AML cell line model carrying IDH1 R132H mutation. We first stably transduced HL60 cell line to establish clones carrying either empty vector, IDH1 WT gene or IDH1-R132H mutated gene. We then characterized these clones with different features including 2-HG production.
Since demethylation of many genes involved in the retinol metabolism is impaired by IDH1-R132H mutation and because all-trans retinoic acid (ATRA), a retinol metabolite, is already used in clinic, we studied its effects on IDH1-R132H mutated AML cells.
Here, we showed on our transduced models as well as on primary AML patient samples (n=6), that AML blasts harboring IDH1-R132H mutation were highly sensitive to low doses of ATRA, compared to the IDH1 WT. In fact, IDH1-R132H mutation sensitized to ATRA-induced differentiation, as shown by increased expression of the differentiation marker CD11b and morphological changes evidenced with May-Grünwald-Giemsa staining. This was followed by changes of CD14 and CD15 expression, as well as granulocytic enzymatic activity measured with the nitroblue tetrazolium reduction assay. This terminal granulocytic differentiation came with the reduction of proliferation and colony formation, and then, quickly led to apoptosis of IDH1 R132H mutated AML cells.
Moreover, we showed that the level of differentiation of IDH1 R132H mutated models was correlated to the magnitude of IDH1-R132H protein expression and thus to the 2-HG production. We further demonstrated that treatment with a cell-permeable form of 2-HG sensitized empty construct to ATRA-induced differentiation, whereas the inhibition of IDH1-R132H activity reduced its ATRA-sensitivity in IDH1-R132H mutant.
Altogether, our results show that IDH1-R132H mutation sensitizes to ATRA-induced granulocytic terminal differentiation in a 2-HG concentration-dependent manner and that it leads to their apoptosis. Since serum 2-HG concentration of IDH mutated patients is approximately 100 fold higher than for non mutated patient, we could expect a high and specific effect of ATRA treatment on IDH1 mutated AML patients. Furthermore, as this mutation could contribute to relapse, this might be a promising therapeutic strategy to achieve a long-term remission in AML with IDH1 mutations.
Citation Format: Helena Boutzen, Fabienne De Toni, Estelle Saland, Eric Delabesse, Véronique De mas, Cécile Demur, Florence Castelli, Lara Gales, Virginie Penard-lacronique, Stéphane De Botton, Jean-Charles Portais, Christophe Junot, Stéphane Manenti, Christian Récher, Jean-emmanuel Sarry. All-trans-retinoic acid as a new therapeutic approach to target isocitrate dehydrogenase mutations in acute myeloid leukemia. [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 2678. doi:10.1158/1538-7445.AM2014-2678