EFFECT OF SPHINGOSINE KINASE INHIBITORS (SPHKS) SKI-II AND ABC294640 ON LEUKEMIC CELLS AND NON-LEUKEMIC LYMPHOCYTES: RATIONAL TO USE THE COMBINATION OF SPHKS INHIBITORS AND ABT-199 (VENETOCLAX) IN CHRONIC LYMPHOCYTIC LEUKEMIA (CLL)

MARICEF VERGARA RUBIO; ESTEBAN ELIAS; CORDINI, GREGORIO; COLADO, ANA; SARAPURA MARTÍNEZ, VALERIA; MORANDE, PABLO E; BEZARES, FERNANDO; SANTIAGO CRANCO; JULIO CÉSAR SÁNCHEZ AVALOS

Virtual (por la pandemia)

Congreso; REUNIÓN DE SOCIEDADES DE BIOCILXVIII REUNIÓN ANUAL DE LA SOCIEDAD ARGENTINA DE INMUNOLOGÍA (SAI); 2020

Sociedad Argentina de Inmunologia

Sphingosinekinases (SphK1 and SphK2) are therapeutic targets for cancer because theyregulate the balance between proapoptotic ceramides andsphingosine-1-phosphate. We found that the SKI-II sphingosine kinase inhibitornot only acts on the leukemic clone, it also affects the survival ofnon-leukemic lymphocytes affecting tumoral microenvironment, mechanism mediatedby both sphingosine kinases. Previously, we reported that autologous activationof T cells induces CLL drugs resistance. In this study we evaluated the effect ofSphKs inhibitors on the activation and proliferation of leukemic microenvironment.Peripheral blood mononuclear cells (PBMC) from CLL patients were cultured withdifferent doses of SKI-II or ABC294640 (SphK2-selective inhibitor). PBMCs ofCLL patients were cultured on immobilized anti-CD3 moAbs (αCD3) to induce activationand proliferation of T cells, or in the presence of a TLR-9 agonist: CpG toinduce the activation of B cells. We found that the plasma concentration of 15μM for both inhibitors reduces the expression of activation markers (CD69 andCD25) of activated T cells (n=20 p<0.0001), and also reduces proliferation(n=15, p<0.0001) by CFSE dilution assay. As for B activation, CD69downregulation was only affected by treatment with ABC294640 (n=20, p=0.0016). Simultaneousanalysis of leukemic B cells demonstrates a correlation between increasedsurvival in response to inhibitor therapy and the worst prognostic clinicalprofile, Binet B-C (n=30, p<0.0001). Finally, we tested generation of CLLresistance to ABT-199 (venetoclax), induced by T cells activation, cultivatingPBMCs in presence of one or the other SphKs inhibitors and managing to reversethis resistance (n=8, p<0.0001). We found that the inhibitors affected the activationof the T cells that can give signals of survival to leukemic cells. Our resultsencourage the use of the combination of selective SphKs inhibitors togetherwith venetoclax in CLL treatment.