Stinging the Glioma Immune Landscape

Immune therapies such as immune checkpoint inhibitors have had a profound impact on cancer patient survival and quality of life. However, clinical data is now emerging that immune checkpoint inhibitors may only benefit subsets of patients that have high mutational loads, T cell infiltration, PD-L1 expression, defects in DNA mismatch repair, and microsatellite instability. Comprehensive profiling reveals that these favorable predisposing factors are not common within glioblastoma. Glioblastoma represents a prototypical example of an “immunologically cold” tumor. Nonetheless, there are isolated areas in which CD8 T cells are present in the glioblastoma microenvironment but we do not know understand what induces these immune hotspots of reactivity. This proposal will determine what is triggering focal adaptive immune responses. Until now, most studies have focused on immune responses within the tumor. Based on a series of observation of inflammatory responses at the tumor-infiltrative brain edge, we are now focusing on a more detailed evaluation of anti-tumor immune responses at this interface, which likely differs from those in the tumor mass itself. This discrepancy is probably misinforming the scientific community regarding biomarkers of potential response and missing key pathways and mechanisms that are important for antitumor immune surveillance and eradication. In the case of cancer in the CNS, the adjacent brain is “damaged” or stressed, thereby upregulating the expression of immune chemokines. Notably, we are taking this observation several steps further and creating topographical immune atlases of the tumor-CNS interface, in order to more fully understand what controls localized immunological reactivity. Many of the observations that we will potentially make regarding enrichment of immune reactivity within the tumor landscape are likely to hold true for other organ sites, but we also suspect that there will be truly unique CNS-specific observations. Furthermore, in order for us to prioritize available immune therapeutic strategies, this proposal will also be profiling both the innate and adaptive arm of the immune system for common operational mechanisms of immune suppression.