RESUMO
PRKAR1A (R1A)-retinoic acid receptor-alpha (R1A-RARalpha) is the sixth RARalpha-containing fusion protein in acute promyelocytic leukemia (APL). Using the murine bone-marrow retroviral transduction/transformation assay, we showed that R1A-RARalpha fusion protein could transform bone-marrow progenitor/stem cells. In gel-shift assays, R1A-RARalpha was able to bind to a panel of retinoic acid response elements both as a homodimer and as a heterodimer with RXRalpha, and demonstrated distinct DNA-binding characteristics compared with wild-type RARalpha/RXRalpha or other X-RARalpha chimeric proteins. The ratio of R1A-RARalpha to RXRalpha proteins affected the retinoic acid response element interaction pattern of R1A-RARalpha/RXRalpha complexes. Studies comparing R1A-RARalpha with R1A-RARalpha(DeltaRIIa) demonstrated that the RIIa protein interaction domain located within R1A was responsible for R1A-RARalpha homodimeric DNA binding and interaction with wild-type R1A protein. However, the RIIa domain was not required for R1A-RARalpha-mediated transformation because its deletion in R1A-RARalpha(DeltaRIIa) did not compromise its transformation capability. In contrast, introduction of point mutations within the RARalpha portion of either R1A-RARalpha or R1A-RARalpha(DeltaRIIa), previously demonstrated to eliminate RXRalpha interaction or treatment of transduced cells with RXRalpha shRNA or a RXRalpha agonist, reduced transformation capability. Thus, leukemic transformation by APL fusion protein PRKAR1A-RARalpha is critically dependent on RXRalpha, which suggests RXRalpha is a promising target for APL.
Assuntos
Transformação Celular Neoplásica/metabolismo , Subunidade RIalfa da Proteína Quinase Dependente de AMP Cíclico/metabolismo , Leucemia Promielocítica Aguda/metabolismo , Receptores do Ácido Retinoico/metabolismo , Receptor X Retinoide alfa/metabolismo , Animais , Proliferação de Células , Transformação Celular Neoplásica/genética , Células Cultivadas , Subunidade RIalfa da Proteína Quinase Dependente de AMP Cíclico/genética , Regulação Leucêmica da Expressão Gênica , Células HeLa , Células-Tronco Hematopoéticas/patologia , Humanos , Leucemia Promielocítica Aguda/genética , Leucemia Promielocítica Aguda/patologia , Camundongos , Camundongos Endogâmicos C57BL , Proteínas de Fusão Oncogênica/genética , Proteínas de Fusão Oncogênica/metabolismo , Ligação Proteica/fisiologia , Receptores do Ácido Retinoico/genética , Receptor alfa de Ácido Retinoico , Receptor X Retinoide alfa/fisiologiaRESUMO
Mutations of isocitrate dehydrogenase 1 (IDH1) are frequently found in certain cancers such as glioma. Different from the wild-type (WT) IDH1, the mutant enzymes catalyze the reduction of α-ketoglutaric acid to d-2-hydroxyglutaric acid (D2HG), leading to cancer initiation. Several 1-hydroxypyridin-2-one compounds were identified to be inhibitors of IDH1(R132H). A total of 61 derivatives were synthesized, and their structure-activity relationships were investigated. Potent IDH1(R132H) inhibitors were identified with Ki values as low as 140 nM, while they possess weak or no activity against WT IDH1. Activities of selected compounds against IDH1(R132C) were found to be correlated with their inhibitory activities against IDH1(R132H), as well as cellular production of D2HG, with R(2) of 0.83 and 0.73, respectively. Several inhibitors were found to be permeable through the blood-brain barrier in a cell-based model assay and exhibit potent and selective activity (EC50 = 0.26-1.8 µM) against glioma cells with the IDH1 R132H mutation.