Despite having been approved as first and second line therapy for non-small cell lung cancer (NSCLC), anti-PD- 1 antibodies still fail in a substantial proportion of lung cancer patients. The mechanism that underlies the failure of anti-PD-1 therapy in the majority of NSCLC patients is not yet fully understood. We have discovered that, in the anti-PD-1-resistant LSL-KrasG12D murine lung adenocarcinoma mouse model, treatment induces a T-cell activation profile that favors Th17/??T17 reinvigoration over CD8+ T cell activation. In contrast, when administered in conjunction with an anti-IL-17 neutralizing antibody, anti-PD-1 treatment results in a dramatic enhancement of CD8+ T-cell cytotoxicity with near-complete eradication of established disease. These findings provide the premise for our central hypothesis that in NSCLC, the failure of anti-PD-1 is, at least in part, due to reinvigoration of PD-1+ type 17 T cells (Th17/??T17), which actively undermine anti-PD-1-mediated restoration of cytotoxic function in CD8+ T-cells. Based on additional murine data, we are also advancing the extended hypothesis that the severity of pre-existing T17 activity in the neoplastic lung is determined by commensal bacteria and that the lung microbiota signature can ultimately predict responsiveness to anti-PD-1 therapy. The goal of this proposal is to demonstrate the relevance of these findings to human prior to initiating an R01 application. Specifically, in Aim 1, we will establish whether intrinsic lung T17/CTL ratio is predictive of anti-PD- 1 responsiveness in NSCLC patients independent of neoantigen burden.
In Aim 2 we will determine whether specific human lung microbiota, individually or in defined combinations, drive the ontogeny of intrinsic T17 immunity and ultimately resistance to ICI therapy. The proposed study is conceptually impactful as it addresses an important clinical conundrum; is mechanistically novel; and has translational relevance since it introduces therapeutic/prognostic approaches that can rapidly move to the clinic.