Medulloblastoma (MB) is the most common pediatric brain tumour comprising of four distinct molecular subgroups exhibiting high level of intertumoural heterogeneity. The standard multimodal treatment yields a survival rate of 70% but the aggressive treatment affects the long-term sequelae of MB patients. The tumour microenvironment (TME) is a regulator of cancer progression and affects therapeutic efficacy in primary and metastatic brain malignancies. Mechanistic insights into the tumor-promoting role of the individual components of the brain TME will aid in identifying key survival pathways and design of potential therapeutics to combat drug resistance and pathogenesis of the disease. We hypothesize that tumor associated macrophages (TAMs) in the brain TME facilitate drug resistance via the IL-6/STAT3 signalling axis in MB. To understand the role of paracrine signaling resulting from TAMs, a co-culture system was used to evaluate the expression of pSTAT3 and correlated with drug sensitivity and/or resistance in Med8A cell line. When co-cultured with HMC3, a human microglia cell line, the chemosensitive Med8A-S cells exhibited enhanced pSTAT3 expression and acquired drug resistance. Interestingly, Med8A cells lacking expression of IL-6 receptor (IL6R-/-) also exhibited high pSTAT3 levels and drug resistance; suggesting that HMC3 may release soluble factors in addition to IL-6 sufficient to drive chemoresistance in Med8A variants. To assess this, we conditioned cells with stimulatory cytokines belonging to the IL-6 family. We found that oncostatin M (OSM), interleukin-11 (IL-11) and leukemia inhibitory factor (LIF) induced drug resistance and enhanced pSTAT3 levels in IL6R-/- cells. Receptors of the IL-6 family share a common signal transducing beta subunit, glycoprotein (gp130) that transduces the signal intracellularly and phosphorylates janus activated kinases (JAKs) and subsequently STAT3. Our results suggest that paracrine proinflammatory cytokines found in the TME can promote MB drug resistance by signalling through a common signal transducer gp130, hence targeting any one cytokine receptor of the IL-6 family of cytokines may not sufficiently abrogate acquired drug resistance. Currently, we are evaluating the efficacy of agents that target common downstream elements of the IL-6/STAT3 signalling axis, including gp130, JAKs and STAT3, as a potentially improved therapeutic strategy to circumvent acquired drug resistance in medulloblastoma.

Citation Format: Lakshana Sreenivasan, Pascal Leclair, Chinten James Lim. Targetting IL-6/gp130 signalling axis attenuates acquired drug resistance in medulloblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr LB133.