Fig. 2: Inhibition of the STAT3 target SGK1 sensitizes DLBCL cells to AKT inhibitors.

a STAT3 is recruited to regulatory regions of SGK1. TMD8 DMSO controls or activated B cell samples in red, AZD1480-treated TMD8 samples or activated B cell input samples in green. b RNA-seq FPKM shows a reduction in SGK1 expression after knockdown of STAT3 in TMD8 and OCI-Ly10 cells (Data from GSE106844). c Real-time PCR shows elevated SGK1 expression in naive B cells upon anti-IgM (10 μg/ml) stimulation. Error bars represent mean ± of SE of triplicates. d Immunoblot shows reduced SGK1 protein levels in U2932 cells treated with AZD1480 (4 μM, 12 h). e Immunoblot analysis of indicated proteins in OCI-Ly19 and SUDHL4 after 2 days of retroviral expression of the constitutively activated STAT3 (STAT3-C), combined with or without 4 h treatment of the proteasome inhibitor PS-341 (250 nM). f SGK1 expression is positively correlated with STAT3 expression in 498 patient samples. Data were generated from R2: Genomics Analysis and Visualization Platform (https://hgserver1.amc.nl/cgi-bin/r2/main.cgi). g Immunoblot analysis of SGK1 protein levels in naive B cells, ABC, and GCB DLBCL cell lines. β-actin served as a loading control. h Immunoblot analysis of pAKT protein levels in TMD8, HBL, OCI-Ly1, and OCI-Ly7 cells after 24 h treatment of the AKT inhibitor AKTi-V (20 μM). i CellTiter-Glo™ Luminescent Cell Viability Assay of TMD8, HBL1, OCI-Ly1, and OCI-Ly7 cells after 6 days induction with SGK1 knockdown (shSGK1#2) or 6 days treatment of AKTi-V (2 μM), or both. Data indicate mean ± SE of triplicates. *p < 0.05; **p < 0.01. j CellTiter-Glo™ Luminescent Cell Viability Assay of TMD8, HBL1, OCI-Ly1, and OCI-Ly7 cells after 6 days treatment of the indicated concentrations of AKTi-V or the SGK1 inhibitor GSK650394, or both. Data indicate mean ± SE of triplicates. Combination index (CI) was calculated with CompuSyn software. CI < 1 indicates synergy