Abstract
Several newly developed drugs including JQ1 (BET inhibitor), ABT199 (BCL2 inhibitor), and bortezomib (proteasome inhibitor) may offer novel therapeutic strategies for aggressive diffuse large B-cell lymphoma (DLBCL). We tested these drugs together with doxorubicin in a series of combinations in 16 DLBCL cell lines including 4 ABC-DLBCL (OCI-Ly3, OCI-Ly10, SUDHL2, RIVA) and 12 GCB-DLBCL lines (OCI-Ly4, OCI-Ly18, BJAB, SUDHL4, SUDHL6, SUDHL10, DB, PR1, VAL, SC1, Karpas-231, Karpas-422). Among these cell lines, ABT199 and doxorubicin, and to a lesser extent JQ1 and bortezomib, showed high variations in their ED50 values. Of the six cell lines showing high ABT199 ED50 values, four (SUDHL10, OCI-Ly4, SUDHL2, and BJAB) had no or little BCL2 expression, and SUDHL6 also displayed a low BCL2 expression. There was no association between the ED50 value of doxorubicin, JQ1 and bortezomib, and TP53/MYC/BCL2 genetic abnormalities or cell of origin subtype. A synergistic effect in all or the majority of drug combinations was seen in 11 cell lines, while an antagonistic effect in a high proportion of drug combinations was observed in the remaining 5 cell lines including the 3 (SUDHL10, OCI-Ly4, and SUDHL2) with little BCL2 expression, and additionally OCI-Ly18 and RIVA. Extensive Western blot analyses revealed high MCL1 expression in SUDHL10 and OCI-Ly4 but no apparent alterations in other cell lines. The molecular mechanism underlying the antagonistic effect of drug combinations in DLBCL is heterogeneous with the altered BCL2 family protein expression (absent BCL2, but high MCL1) in some cell lines.