Reduced SLIT2 is Associated with Increased Cell Proliferation and Arsenic Trioxide Resistance in Acute Promyelocytic Leukemia

Simple Summary In solid tumors, the altered expression of embryonic genes such as the SLIT-ROBO family has been associated with poor prognosis, while little is known about their role in acute myeloid leukemia (AML). Previous studies reported frequent hypermethylation of SLIT2 mediated by the methyltransferase enzyme EZH2 and more recently the PML protein, which are commonly found to be aberrantly expressed in AML. Here, we aim to assess retrospectively the clinical relevance of the SLIT2 gene in acute promyelocytic leukemia, a homogenous subtype of AML. We demonstrated that reduced SLIT2 expression was associated with high leukocyte counts and reduced overall survival in different APL cohorts. STLI2 treatment decreased APL growth, while SLIT2 knockdown accelerated cell cycle progression and proliferation. Finally, reduced expression of SLIT2 in murine APL blasts resulted in fatal leukemia associated with increased leukocyte counts in vivo. These findings demonstrate that SLIT2 can be considered as a prognostic marker in APL, and a potential candidate for clinical studies of a more heterogeneous disease, such as AML. The SLIT-ROBO axis plays an important role in normal stem-cell biology, with possible repercussions on cancer stem cell emergence. Although the Promyelocytic Leukemia (PML) protein can regulate SLIT2 expression in the central nervous system, little is known about SLIT2 in acute promyelocytic leukemia. Hence, we aimed to investigate the levels of SLIT2 in acute promyelocytic leukemia (APL) and assess its biological activity in vitro and in vivo. Our analysis indicated that blasts with SLIT2(high) transcript levels were associated with cell cycle arrest, while SLIT2(low) APL blasts displayed a more stem-cell like phenotype. In a retrospective analysis using a cohort of patients treated with all-trans retinoic acid (ATRA) and anthracyclines, high SLIT2 expression was correlated with reduced leukocyte count (p = 0.024), and independently associated with improved overall survival (hazard ratio: 0.94; 95% confidence interval: 0.92-0.97; p <0.001). Functionally, SLIT2-knockdown in primary APL blasts and cell lines led to increased cell proliferation and resistance to arsenic trioxide induced apoptosis. Finally, in vivo transplant of Slit2-silenced primary APL blasts promoted increased leukocyte count (p = 0.001) and decreased overall survival (p = 0.002) compared with the control. In summary, our data highlight the tumor suppressive function of SLIT2 in APL and its deteriorating effects on disease progression when downregulated

Reduced SLIT2 is associated with increased cell proliferation and arsenic trioxide resistance in acute promyelocytic Leukemia

The SLIT-ROBO axis plays an important role in normal stem-cell biology, with possible repercussions on cancer stem cell emergence. Although the Promyelocytic Leukemia (PML) protein can regulate SLIT2 expression in the central nervous system, little is known about SLIT2 in acute promyelocytic leukemia. Hence, we aimed to investigate the levels of SLIT2 in acute promyelocytic leukemia (APL) and assess its biological activity in vitro and in vivo. Our analysis indicated that blasts with SLIT2high transcript levels were associated with cell cycle arrest, while SLIT2low APL blasts displayed a more stem-cell like phenotype. In a retrospective analysis using a cohort of patients treated with all-trans retinoic acid (ATRA) and anthracyclines, high SLIT2 expression was correlated with reduced leukocyte count (p = 0.024), and independently associated with improved overall survival (hazard ratio: 0.94; 95% confidence interval: 0.92–0.97; p < 0.001). Functionally, SLIT2-knockdown in primary APL blasts and cell lines led to increased cell proliferation and resistance to arsenic trioxide induced apoptosis. Finally, in vivo transplant of Slit2-silenced primary APL blasts promoted increased leukocyte count (p = 0.001) and decreased overall survival (p = 0.002) compared with the control. In summary, our data highlight the tumor suppressive function of SLIT2 in APL and its deteriorating effects on disease progression when downregulated

Combining gene mutation with gene expression analysis improves outcome prediction in acute promyelocytic leukemia

By combining the analysis of mutations with aberrant expression of genes previously related to poorer prognosis in both acute promyelocytic leukemia (APL) and acute myeloid leukemia, we arrived at an integrative score in APL (ISAPL) and demonstrated its relationship with clinical outcomes of patients treated with all-trans retinoic acid (ATRA) in combination with anthracycline-based chemotherapy. Based on fms-like tyrosine kinase-3-internal tandem duplication mutational status; the Delta Np73/TAp73 expression ratio; and ID1, BAALC, ERG, and KMT2E gene expression levels, we modeled ISAPL in 159 patients (median ISAPL score, 3; range, 0-10). ISAPL modeling identified 2 distinct groups of patients, with significant differences in early mortality (P <.001), remission (P = .004), overall survival (P < .001), cumulative incidence of relapse (P = .028), disease-free survival (P = .03), and event-free survival (P < .001). These data were internally validated by using a bootstrap resampling procedure. At least for patients treated with ATRA and anthracycline-based chemotherapy, ISAPL modeling may identify those who need to be treated differently to maximize their chances for a cure13212951959CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP573754/2008-01998/14247-67th International Symposium on Acute Promyelocytic Leukemi

The experience of the International Consortium on Acute Promyelocytic Leukemia in monitoring minimal residual disease in acute promyelocytic leukaemia

Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)Univ Sao Paulo, Dept Internal Med, Div Haematol, Ribeirao Preto, BrazilUniv Sao Paulo, Dept Internal Med, Div Clin Oncol, Ribeirao Preto, BrazilUniv Sao Paulo, Med Sch Ribeirao Preto, Ctr Cell Based Therapy, Ribeirao Preto, BrazilUniv Fed Pernambuco, Dept Genet, Recife, PE, BrazilSabin Clin Lab, Brasilia, DF, BrazilFdn Hematol & Hemoterapia Pernambuco HEMOPE, Recife, PE, BrazilUniv Fed Rio Grande do Sul, Haematol Serv, Univ Hosp, Porto Alegre, RS, BrazilUniv Fed Parana, Bone Marrow Transplantat Unit, Univ Hosp, Curitiba, Parana, BrazilUniv Estadual Campinas, Hemoctr, Campinas, SP, BrazilUniv Fed Minas Gerais, Haematol Serv, Univ Hosp, Belo Horizonte, MG, BrazilUniv Fed Sao Paulo, Div Haematol, Sao Paulo, BrazilSanta Casa Med Sch, Haematol Serv, Sao Paulo, BrazilUniv Valencia, Hosp Univ & Politecn La Fe, Dept Haematol, Valencia, BrazilUniv Valencia, Dept Med, Valencia, BrazilUniv Tor Vergata, Dept Biomed & Prevent, Rome, ItalySanta Lucia Fdn, Rome, ItalyKings Coll London, Fac Life Sci & Med, Dept Med & Mol Genet, London, EnglandUniv Fed Sao Paulo, Div Haematol, Sao Paulo, BrazilFAPESP: 2013/08135-2FAPESP: 2011/17111-4Web of Scienc