Abstract B025: Neutrophil depletion enhances the anti-tumor activity of CAR-T cells in an autochthonous model of non-small cell lung cancer
Authors: Ortiz-Espinosa Sergio , Srivastava Shivani 
Published: December 2023

Abstract
CAR-T cell therapy has produced durable clinical responses in hematological malignancies, but efficacy in more common solid tumors is limited in part by poor trafficking of CAR-T cells to tumors. Identifying strategies to improve CAR-T cell trafficking to and persistence within tumors, thus, are needed to improve efficacy against solid tumors. We previously adapted the Kras/p53 (KP) autochthonous model of non-small cell lung cancer (NSCLC) to express the CAR target ROR1 to study the mechanisms limiting the activity of ROR1 CAR-T cells. Similar to what we observed in a phase 1 trial, ROR1 CAR-T cells infiltrated KPROR1 tumors poorly and induced limited tumor control. We showed that using immunogenic chemotherapy to induce the production of T cell-recruiting chemokines significantly improved CAR-T cell infiltration into lung tumors. However, despite improved survival, many tumor nodules remained devoid of CAR-T cells, suggesting that additional mechanisms likely limit CAR-T cell access to tumors. Neutrophils have been shown to inhibit T cell infiltration and function within tumors, and high neutrophil infiltrates in NSCLC patients are associated with poor T cell infiltration and response to immunotherapy. To characterize how neutrophils may impact CAR-T cell localization, we treated KPROR1 mice with ROR1 CAR-T cells or left untreated and analyzed the co-localization of CD8+ T cells and Ly6G+ neutrophils within tumors by multiplex IHC. In untreated mice, neutrophils were primarily found around the perimeters of large tumors (&gt;105 mm2) but were absent from small tumors (&lt;105 mm2). Upon treatment with CAR-Ts, CD8+ T cell frequency increased across all tumors, but intratumoral T cell infiltration was significantly higher in small neutrophil-low tumors than in large neutrophil-high tumors, suggesting that neutrophil-high tumors may be less accessible to CAR-T cells. Interestingly, CAR-T treatment induced a significant increase in neutrophils, with CD8+ T cells in closer proximity to neutrophils, suggesting that CAR-Ts may promote neutrophil recruitment. We hypothesized that this increase in neutrophils might further suppress CAR-T activity. To test this, we pre-treated tumor-bearing KPROR1 mice with anti-Gr1 or a C5aR1 inhibitor, both of which have been shown to reduce neutrophil recruitment to tumors, and injected control or ROR1 CAR-T cells 2 days later. Anti-Gr1 and C5aR1 inhibitor treatments continued for 17 days after CAR-T cell injection. Whereas treatment with CAR-T cells alone had minimal effects, co-treatment with either anti-Gr-1 or C5aR1 inhibitor significantly improved survival. Our findings suggest that neutrophils may limit CAR-T infiltration and/or persistence within tumors and that neutrophil depletion can enhance the anti-tumor activity of CAR-T cells. Future work is aimed at understanding the mechanisms by which neutrophils may limit CAR-T activity. Overall, our results suggest that targeting neutrophils may be a promising strategy to overcome the major challenges in CAR-T therapy for solid tumors.
Citation Format: Sergio Ortiz-Espinosa, Shivani Srivastava. Neutrophil depletion enhances the anti-tumor activity of CAR-T cells in an autochthonous model of non-small cell lung cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor Immunology and Immunotherapy; 2023 Oct 1-4; Toronto, Ontario, Canada. Philadelphia (PA): AACR; Cancer Immunol Res 2023;11(12 Suppl):Abstract nr B025.