Profiling Circulating T cells and Tumor Landscape for Predicting Responses to PD-1 blockade in Patients with Non-Small Cell Lung Cancer

Abstract

Immune checkpoint blockade (ICB) has significantly improved outcomes in non-small cell lung cancer (NSCLC), yet only a subset of patients achieves durable responses. This underscores the need for effective methods to assess ICB efficacy. This thesis investigates the response to PD-1 blockade in NSCLC patients across stages I to IV, utilizing blood and tissue samples. In stage III and IV patients, we analyzed circulating immune cell subsets in blood and tumor biopsies. Flow cytometry revealed that changes in activated memory CD8+ T cells, coupled with mutations tumor-specific genes, differentiate responders from non-responders to ICB. The immune infiltration to the tumor analysed via immunohistochemistry (IHC) staining further identified that the presence of CD4+ and CD8+ effector T cells, along with FOXP3+ regulatory T cells, that were associated with clinical response. The findings indicate that tumor biopsies can be useful to evaluate the genetic features of the tumor and infiltration of various immune cell subsets, aiding in the identification of ICB responders. Phenotypic and transcriptomic analysis of circulating CD8+ T cells indicated that responders show upregulation of immune checkpoint receptors such as TIGIT and PD-1. Notably, long-term responders exhibited an increase in TCF-1+PD-1+ CD8+ T cells post-treatment. In stage III and IV patients, early changes in T cells detectable at baseline and over time may contribute to the development of more precise biomarkers for response. Integrating these blood-based findings with next-generation sequencing (NGS) and IHC of tumor biopsies could enhance the biomarker specificity. In stages I and II NSCLC patients that undergo surgery followed by adjuvant treatment, we have developed a co-culture model with normal and tumor tissue with peripheral blood mononuclear cells (PBMCs) to assess the T cell reactivity in individual patients. In this model, the CD8 T cells were activated in response to tissue antigens and maintained effector functions. Overall, our findings can contribute to improving patient-specific prediction of ICB response for achieving better clinical outcomes.