Angio-Phenotype of Pediatric Acute Lymphoblastic Leukemia and Pharmacodynamic Evaluation of the Antiangiogenic Activity of Corticosteroids.

Abstract

Corticosteroids are essential in the treatment of pediatric acute lymphoblastic leukaemia (ALL). Corticosteroid anti-angiogenic activity is postulated but unproven.Objectives: To assess the kinetics of cellular and plasma angiogenic surrogate markers during 7-day prednisone pre-phase/induction therapy in the AIEOP ALL 2000 protocol.Methods: 17 diagnosed common ALL and 12 normal controls were enrolled. Total and viable circulating endothelial cells (CECs) and progenitors (CEPs), vascular endothelial growth factor receptors (VEGFR2, R3), endoglin (CD105), VECadherin (CD144) expression were analyzed by four color flow-cytometry on peripheral blood. Plasma circulating VEGF, VEGFRs and endoglin were analyzed by ELISA. Gene expression of VE-Cadherin, Nanog, RGS5, VEGFR2 and R3 were quantified by Real Time RT-PCR.Results: Total CECs (31 ±8cells/uL), viable CECs (12 ± 5 cells/uL) and CEPs (0.91 ±0.91 cells/uL) were found to be significantly higher in pediatric controls than in adult. At baseline patients demonstrated a statistically higher number of CECs (CD45− CD31+ CD146+ cells) and CEPs (CD133+ cells) p=0.01 and 0.03, compared to controls. CD105, VEGFR-3 and VEGFR-2 expression on leukemic blasts was 91%, 27% and 0% of patients, respectively.After 7 days of prednisone, a statistically significant reduction of total and viable CECs (p= 0.01) and CEPs ( p<0.0001) as well as endothelial cells expressing VEGFR2, R3, and CD105 (p=0.01, p=0.03, p=0.02) was observed. Plasma VEGFR2, VEGFR3, and endoglin showed a trend to decrease at day 8 and 33 but did not reach significance. A statistically significant reduction of blast was also observed.The pro-apototic effect of prednisone was greater on blast compared to lymphocytes.VEGFR-3 gene expression was significantly increased in patients at diagnosis compared to pediatric controls, and significantly reduced on day 8.Conclusions:Increase in CECs, CEPS confirm a pro-angiogenic activity at diagnosis in common ALL. The anti-leukemic effects of prednisone may be linked to its pro-apoptotic and anti-angiogenic activities. Total and viable CECs, CEPs, expression of endoglin and VEGFR3 on blast appear to be suitable angiogenic surrogate biomarkers.