IL-1R pathway contributes to the JAK inhibitor treatment sensitivity in pC-ALCL. (A) Chromatin IPs from the indicated antibodies were subjected to real-time PCR analysis for candidate STAT3-binding regions in the IL1R1 and IL1RAP loci in the indicated ALCL lines. (B-C) Indicated ALCL lines were transduced with STAT3, JAK2, or Ctrl sgRNAs, selected, and expression induced, IL1R1 and IL1RAP expressions were measured by real-time PCR. (D) Indicated ALCL lines were treated with the JAK inhibitor ruxolitinib at the indicated concentrations for 24 hours, and IL1R1 and IL1RAP expressions were measured. (E) Viability of indicated cell lines after treatment with AS2444697, ruxolitinib, or both (left). Formal calculation of synergism between AS2444697 and ruxolitinib (right). Positive highest-single-agent (HSA) synergy score values indicate synergy. (F) NSG mice bearing MAC1 xenografts were treated with AS2444697, ruxolitinib, the combination of AS2444697 and ruxolitinib, as well as vehicle controls. Tumor growth was measured as a function of tumor volume. Error bars denote SEM. (G-H) Tumor weight (G) and size (H) at the treatment end point. In panels A-D, error bars denote SEM of triplicates. P was calculated comparing sgCTRL and the indicated sgRNA groups or comparing untreated and treated groups; ∗P < .05; ∗∗P < .01. In panels F-G, error bars denote SEM. ∗P < .05; ∗∗P < .01.