ASH 2025 | CXCL10-CXCR3 signaling as a pro-survival pathway and prognostic biomarker in CNS lymphoma

So this is a study that I think is quite interesting from the biological point of view of primary and secondary CNS lymphoma and it builds upon prior work we have done with BTK and IRAK core targeting agents using patient-derived xenografts of primary and secondary CNS lymphomas which we apply in the setting of intracranial models of these diseases. And we’ve shown in collaboration with a novel IRAK-4 inhibitor called AZ-1495, generated by AstraZeneca, that this agent has single agent activity, it penetrates the brain, antagonizes NF-kappa-B phosphorylation of the T65C rel, and in combination with ibrutinib, can potentiate survival. But nevertheless, all the mice ultimately get resistance and succumb to their intracranial xenografts. To elucidate transcriptional targets of these agents, we’ve done RNA sequence analysis, looking at the transcriptional targets of Ibrutinib, PDX models, AZ-1495, monotherapy, and the combination. And the exciting finding we found was that the top gene antagonized by the combination of the two agents in which we see survival prolongation is the chemokine CXCL10, a known NF-kappa B target gene, which is exciting and interesting, provocative, but what was more exciting was the concomitant we found that the receptor for CXCL10 is actually induced in this setting. It’s upregulated in these patient-derived cells, suggestive of a potential autocrine pathway. Subsequently, we went on to discover that CXCL10 is indeed expressed in patients with primary and secondary CNS lymphoma in the spinal fluid and by immunohistochemistry and diagnostic specimens in abundance. And we’ve shown by in situ hybridization that its expression is co-localized with brain microglia, consistent with a neuroinflammatory process, as well as infiltrating macrophages, as well as auto-production by lymphoma cells themselves with concomitant expression of the receptor CXCR3, which we discovered to be commonly expressed in CNS lymphoma cases by immunohistochemistry as well as by in-situ hybridization. So with that information, we went on to evaluate the functional properties of CXCL10 and CXCR3 in clonal lymphoma cell lines that can grow in vitro, which have the appropriate mutational status, such as the LY10 cell line, as well as LY7 and LY3, and HBL1 cells. We’ve shown that targeting, in particular by CRISPR, deletion of CXCL10 and CXCR3 in LY10 cells leads to attenuated growth in lower serum conditions consistent with a pro-survival pathway. They need this autocrine pathway in order to survive low serum, which may translate to a requirement to grow physiologically in aggressive tumors that use up a lot of oxygen and growth factors, which are depleted of growth factors in oxygen. Subsequently, we were shown that that depletion of CXCL10 or CXCR3, partial knockdown by CRISPR, at least attenuated P65 phosphorylation. It disrupts NF-kappa-B activation as well as P65 total protein levels, which are reduced in low serum within 48 hours. It’s consistent with the discovery that this is a novel NF-kappa-B pro-survival pathway in CNS lymphomas, and what’s provocative is that the brain microenvironment makes the ligand, which promotes activation of this pathway, CXCL10, as shown by in situ hybridization, and in vitro we’ve shown that microglia also makes CXCL10 under pro-inflammatory conditions. We also have some emerging evidence that attenuation of CXCR3 and probably CXCL10 may potentiate the cytotoxicity of chemotherapy drugs such as methotrexate.

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