THE TUMOR MICROENVIRONMENT IN CHRONIC LYMPHOCYTIC LEUKEMIA (CLL): VENETOCLAX RESISTANCE INDUCED BY T CELLS.

SARAPURA MARTINEZ VALERIA JUDITH; BUONINCONTRO BRENDA; CASSARINO CHIARA; BERNATOWIEZ J; COLADO ANA; CORDINI, GREGORIO; CUSTIDIANO, MARÍA DEL ROSARIO; MAHUAD CAROLINA; PAVLOVSKY, MIGUEL A.; PEREZ PAULA ; OSTROWSKY MATIAS ; VERMEULEN MÓNICA; BORGE MERCEDES; GIORDANO MIRTA; GAMBERALE ROMINA

Mar del Plata

Congreso; Reunión Anual de Sociedades de Biociencias; 2022

Reunión Anual de Sociedades de Biociencias, Buenos Aires 16-19 Noviembre 2022.

CLL cells survive and proliferate in lymphoid tissues surroundedby activated T cells, myeloid cells and stroma.Venetoclax (VEN) is a BCL-2 inhibitor used for CLL treatment.We have previously reported that autologous activatedT cells (aaT cells) generate VEN-resistant (VEN-r)CLL cells and that sphingosine kinases (SphKs) are involvedin CLL cell survival. We aimed to characterize thefactors involved in the generation of VEN resistance andto evaluate whether SphK inhibitors, SKI-II and opaganib,can reduce it. VEN-r cells were generated with PBMCfrom CLL patients cultured for 48h with anti-CD3 (aCD3)and then with VEN for 24h. SphK inhibitors were presentduring all the culture or once VEN-r cells were generated.Purified CLL cells (pCLL) were cultured for 48hwith supernatants from aCD3-stimulated PBMC cultures,activated purified CD4 + T cells (pCD4 +) or extracellularvesicles (EVs) produced by pCD4 + cells, and thenwith VEN. The survival and activation of CLL (CD86,PD1 expression) and T cells (CD40L, CD69 expression)were evaluated by flow cytometry and the expression ofSphKs by western blot in viable pCLL. We found that aaTcells generate VEN-r CLL cells through secreted factorsand by direct cell contact (p˂0.05, n= 6). Activated pCD4+ T cells and EVs produced by pCD4+ T cells generateVEN resistance (p<0,01, n=7) and EVs increase CD86(p<0,001, n=10) and PD1 expression on leukemic cells(p<0,05, n=8). AaT cells enhance SphK2 expression inCLL cells (p<0,01, n=9), which is higher in VEN-r cells(p<0,05, n=9). SphK inhibitors reduce T cell and CLL activation(p<0,05, n=8), impair the generation of VEN resistance(p<0,001, n=20) and, in combination with VEN,favor VEN-r CLL cell death (p<0,05, n=3). Conclusion:CD4 + T cells participate in the generation of VEN-r CLLcells by cell contact and secreted factors, including EVs.Given that SphK inhibitors reduce VEN resistance, acombined therapy may be a promising treatment optionfor CLL patients in the future.