Profiling the effects of carbonic anhydrase 9/12 inhibition on tumor associated macrophage/microglia polarization in glioma

Abstract Brain tumor microenvironments, including hypoxia and acidic stress, contain a subset of stem-like neoplastic cells termed brain tumor initiating cells (BTICs) that are resistant to chemo- and radiotherapy, providing a reservoir for tumor recurrence and a desirable target for glioma treatments. In prior studies, we have shown that inhibition of carbonic anhydrases 9 and 12 (CA9/12) in combination with chemotherapeutic temozolomide effectively delayed in vivo growth in a BTIC xenograft model. CA9/12 are hypoxia-responsive genes shown to be elevated in tumors that modulate the intra- and extracellular pH in tumor microenvironments. Importantly, downstream effects of hypoxia have shown CSF-1R induction, which can polarize tumor associated macrophages/microglia (TAM) toward an immunosuppressive phenotype and further exacerbate tumor progression. We have profiled CA9/12 inhibitor-treated GBM tumors using integrative omics (kinomics/transcriptomics) and discovered a shift in kinomic activity and gene expression that suggests an immunosuppressive transition in TAMs. Validating this observation, we characterized surface expression of CD11b+ TAMs post-treatment and discovered decreased expression of MHCII (inflammatory) and increased expression of CD206 (immunosuppressive). Together, our data suggest that by understanding the immunophenotypic shift that happens in response to CA9/12 inhibition in glioma, we may be able design a treatment strategy to improve upon the effectiveness of inhibitor therapy.