Stathmin 1 inhibition amplifies ruxolitinib-induced apoptosis in JAK2V617F cells
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João Agostinho Machado-Neto1, Paula de Melo Campos1, Patricia Favaro1,2, Mariana Lazarini1,2, Adriana da Silva Santos Duarte1, Irene Lorand-Metze1, Fernando Ferreira Costa1, Sara Teresinha Olalla Saad1, Fabiola Traina1,3
1Hematology and Hemotherapy Center, University of Campinas/Hemocentro-Unicamp, Instituto Nacional de Ciência e Tecnologia do Sangue, Campinas, São Paulo, Brazil
2Current address: Department of Biological Sciences, Federal University of São Paulo, Diadema, São Paulo, Brazil
3Current address: Department of Internal Medicine, University of São Paulo at Ribeirão Preto Medical School, Ribeirão Preto, São Paulo, Brazil
Keywords: myeloproliferative neoplasms, STAT3, stathmin 1, ruxolitinib, paclitaxel
Received: February 27, 2015 Accepted: August 11, 2015 Published: August 24, 2015
The JAK/STAT pathway is constitutively activated in myeloproliferative neoplasms and can be inhibited by ruxolitinib, a selective JAK1/2 inhibitor. The JAK2V617F mutation leads to constitutive STAT3 phosphorylation and potentially leads to inhibition of Stathmin 1 activity via STAT3. In support of this hypothesis, we found that, in HEL JAK2V617F cells, ruxolitinib treatment decreased STAT3 and Stathmin 1 association, induced Stathmin 1 activation and microtubule instability. Silencing of Stathmin 1 significantly reduced cell proliferation and clonal growth, and increased apoptosis induced by ruxolitinib. Stathmin 1 silencing also prevented ruxolitinib-induced microtubule instability. To phenocopy the effect of Stathmin 1 inhibition, cells were treated with paclitaxel, a microtubule-stabilizing drug, in association or not with ruxolitinib; combined treatment significantly increased apoptosis, when compared to monotherapy. Notably, Stathmin 1 mRNA levels were highly expressed in CD34+ cells from primary myelofibrosis patients. We then proposed that an undesired effect of ruxolitinib treatment may constitute Stathmin 1 activation and microtubule instability in JAK2V617F cells. Induction of microtubule stability, through Stathmin 1 silencing or paclitaxel treatment, combined with ruxolitinib could be an effective strategy for promoting apoptosis in JAK2V617F cells.
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