Fas and Fas Ligand Expression In Children with Acute Lymphoblastic Leukemia, Benign Hematological Diseases and Solid Tumors

Abstract

AbstractAbstract 4853Fas/FasL is a key pathway of cellular apoptosis. Fas receptor is expressed on membranes of both normal and neoplastic cells while, Fas ligand (FasL) mainly on activated T-lymphocytes. Fas-FasL abnormalities have been detected in malignancies and autoimmune diseases and implicated in resistance to treatment. The aim of the study was the determination of the levels of Fas, FasL and their coexpression in bone marrow cells of children with acute lymphoblastic leukaemia (ALL) at diagnosis, during the course of treatment and the comparison with relevant levels in other hematological and neoplastic diseases. Expression levels of Fas and FasL were determined with flow cytometry in children with ALL at diagnosis (ALLd, n=13), on day 15 of treatment (d15, n=6), on day33 (ALLd33, n=6), during consolidation (ALLhr, n=12) and at the end of therapy (ALLet, n=7) as well as in children with Langerhans Histiocytosis (LCH, n=4), cytopenias (Cytp, n=8) and solid tumors without bone marrow infiltration at diagnosis (STd, n=5) and on therapy (STther, n=6). Results:The lowest levels of Fas expression were detected at diagnosis of ALL and were gradually statistical significantly increased until remission of day 33 (ALLd vs ALLd33: 8.02±1.94 vs 24.04±6.11, p=0.035). At consolidation Fas levels were found to be decreased compared to day33 (16.1±4.18) and were again increased at the end of therapy (ALLd vs ALLet: 8.02±1.94 vs 24.96±7.95, p=0.024). On the contrary, FasL levels were gradually decreased and finally increased to similar to diagnosis levels at the end of treatment (ALLd: 4.59±1.41, ALLet: 5.89±1.99). In solid tumors at diagnosis Fas levels were similar to the ones while on chemotherapy (STd vs STth:16.04±2.2 vs 15.19±6.4). The highest FasL levels were detected in the group of STd with the relevant levels on treatment being lower in comparison (STd vs STther: 10.91±3.32 vs 2.92±0.79, p=0.052). In LCH both Fas and FasL levels were found to be as low as at ALL diagnosis. In cytopenias no significant difference was observed between groups for either Fas (11.05±4.49) or FasL (3.01±0.62). As for Fas+FasL+ coexpression no difference was evident between ALLd, ALLet and STd or STther [ALLd (0.73±0.38), ALLet (0.64±0.17), STd (0.68±0.095), STther (0.66±0.38)]. The lowest coexpreesion levels were observed in the group of cytopenias with statistical significant difference compared to STd (0.68±0.095 vs 0.26±0.08, p=0.031). In conclusion, at diagnosis of ALL Fas levels were expressed in lowest levels that were found to be gradually increased at remission and at the end of treatment. This finding probably correlates with the apoptotic process of the leukemia clone and possibly with response to treatment. Disclosures:No relevant conflicts of interest to declare.