Abstract 4207: JAK inhibition reverses IL10-mediated resistance to B cell receptor (BCR) pathway inhibition in DLBCL
Authors: Liu Xuesong (Mike) , Favata Margaret , Li Jun , Shin Niu , Wang Kathy He , Wang Qian , Li Yun-Long , Combs Andrew , Xue Chu-Biao , Newton Robert , Vaddi Kris , Scherle Peggy 
Published: May 2015

Abstract
Diffuse large B cell lymphoma (DLBCL) is the most common form of non-Hodgkin's lymphoma, and can be classified into activated B-cell like (ABC) and germinal center B-cell like (GCB) DLBCL according to gene expression profiling. In both subtypes, dysregulation of the B cell receptor (BCR) signaling pathway plays a critical role in tumorigenesis and survival. BCR activation induces phosphorylation of CD79A/B by Src family tyrosine kinases, which leads to the activation of the BTK and PI3Kδ/Akt pathways. Oncogenic mutations have been identified in DLBCL impacting CD79A/B (BCR complex), PTEN (negative regulator of PI3K), CARD11 and MYD88 (NF-kB activating factors) function. The influence of these mutations on the DLBCL phenotype appears to be further modified by aberrant cytokine signaling and JAK/Stat pathway activation. High levels of JAK/Stat-activating cytokines such as IL6 and IL10 are present in DLBCL, and patients with high serum IL10 have been shown to have shorter event-free survival and a higher international Prognostic Index score. Therefore, concurrent inhibition of both the BCR and JAK/Stat pathways may provide an attractive therapeutic approach in DLBCL. We have developed and characterized a potent and selective PI3Kδ inhibitor INCB040093 and have established that DLBCL cells are sensitive to INCB040093 treatment. We demonstrate that IL10 activates the JAK/Stat signaling pathway in DLBCL cells, which renders the cells resistant to INCB040093 in cell proliferation assays. This resistance can be reversed by co-treatment with a JAK1/JAK2 inhibitor. Although INCB040093 induces apoptosis in DLBCL cells, concurrent activation of the JAK/Stat pathway by IL10 prevents INCB040093-induced apoptosis, an effect that can be abrogated by a JAK1/JAK2 inhibitor. Similar resistance to IL-10 is observed with the BTK inhibitor, ibrutinib, which can also be reversed by a JAK1/JAK2 inhibitor. Interestingly, a JAK1 selective inhibitor is as effective as a JAK1/JAK2 inhibitor in reversing the IL10-mediated resistance to PI3Kδ and BTK inhibition. Combination treatment blocks both PI3K/Akt and JAK/Stat signaling pathways and results in the down-regulation of pro-survival proteins, including Pim2 and c-myc. These data illustrate the functional cross-talk that exists in DLBCL between the BCR and JAK/Stat signaling pathways, and support the clinical evaluation of combined BCR and JAK inhibition as a novel approach to targeted therapy.
Citation Format: Xuesong (Mike) Liu, Margaret Favata, Jun Li, Niu Shin, Kathy He Wang, Qian Wang, Yun-Long Li, Andrew Combs, Chu-Biao Xue, Robert Newton, Kris Vaddi, Peggy Scherle. JAK inhibition reverses IL10-mediated resistance to B cell receptor (BCR) pathway inhibition in DLBCL. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4207. doi:10.1158/1538-7445.AM2014-4207