Fig. 5

Chemosensitization of patient-derived glioblastoma propagating cells (GPCs) with standard-of-care temozolomide treatment. Patient cell lines were treated with increasing doses of temozolomide. a The addition of signal transducers and activators of transcription 3 (STAT3) inhibitor AZD1480 to temozolomide treatment demonstrated enhanced chemosensitivity as observed in tumor cell viability. Consistent with bioinformatics prediction, STAT3-high cell lines (NNI-21 and NNI-24) displayed enhanced chemosensitivity to AZD1480 treatment with temozolomide, when compared to STAT3-low cell lines (NNI-20 and NNI-23). *p < 0.05; **p < 0.01; ***p < 0.001 compared to absence of temozolomide. b Combination index (CI)-fraction affected (Fa, indicating fraction of cell viability affected) plots of glioblastoma (GBM) cell lines treated with increasing doses of temozolomide in the presence of 0.5 μM AZD1480. STAT3-high cell lines (NNI-21 and NNI-24) displayed a synergistic, cytotoxic effect (CI < 1) with larger Fa, while STAT3-low cell lines (NNI-20 and NNI-23) showed marginally reduced Fa values. c–f Chemosensitization of STAT3-low cell lines (NNI-20 and NNI-23) was observed with temozolomide as demonstrated in the c, d viability and e, f CI plot with e dual treatment (AZD1480 and Linsitinib) or f upon mechanistic gene IGFBP2 knockdown in combination with 0.5 μM AZD1480. ***p < 0.001 shIGFBP2 compared to non-targeting control (NTC). In the CI plots, dashed line at CI = 1 indicates an additive effect between two compounds; values above and below indicate antagonism or synergism, respectively. Error bars represent standard deviation of the mean. For statistical analysis, two-sided Student’s t test was used. g Ranking of LINCS compounds (N = 1679) based on their concordance with temozolomide consensus signature. Compounds with a high x axis value have a signature concordant with temozolomide, and compounds with a high y axis value have a signature discordant with the STAT3-high GBM disease signature. STAT3 inhibitors, Ruxolitinib and AZD1480, demonstrated low concordance with temozolomide (0.011 and 0, respectively) and high discordance with the STAT3-high GBM disease signature (1 and 0.3125, respectively). List of top ranked synergistic compounds able to reverse the STAT3-high GBM disease signature is provided in Supplementary Table 4