Exosomal PD-L1 expression and dynamic changes of immune response associated cytokines as predictive biomarkers for immune checkpoint blockage with PD-1/PD-L1 inhibitors in advanced/metastatic non-small cell lung cancer

During the last two decades the therapeutic landscape of advanced non-small cell lung cancer (NSCLC) has profoundly changed due to an improved knowledge of the molecular mechanisms underlying lung carcinogenesis and the subsequent development of novel effective systemic therapies. This led to a dramatic therapeutic shift, moving from the old concept “one size fits all” to a histology-based approach and finally to the advent of personalized medicine. Recently, the development of immune checkpoint inhibitors (ICIs) further revolutionized the therapeutic algorithm of advanced NSCLC with unprecedented results in terms of overall survival in multiple clinical settings. Four different ICIs have been approved to date for the treatment of advanced/metastatic NSCLC either as monotherapy in previously treated patients (nivolumab, pembrolizumab, and atezolizumab) or in chemotherapy-naïve patients with strong PD-L1 (programed death ligand 1) expression (tumor proportion score ≥50%) (pembrolizumab) or as consolidation therapy in inoperable locally advanced NSCLC following chemo-radiotherapy (durvalumab). Furthermore, different chemo-immunotherapy combinations have proved significant survival benefit in chemo-naïve NSCLC, regardless of PD-L1 status, and their approval/reimbursement in Italy is eagerly awaited. Despite these positive results, to date, the only reliable predictive biomarker in clinical practice is the immunohistochemical (IHC) expression of PD-L1. Unfortunately, this is an imperfect biomarker and responses to ICIs can be across all PD-L1 IHC levels, although a tumor proportion score (TPS) ≥50% seems to enrich patients with higher probability of response. Furthermore, despite a more favorable safety profile compared with chemotherapy, some patients can experience treatment-related adverse events that are intrinsically connected to the peculiar mechanism of action of these agents and are therefore known as immune-related adverse events (irAEs). In the vast majority of the cases, irAEs are of low/mild intensity, especially using ICIs targeting the PD-1/PD-L1 axis, but occasionally can be severe or even life threatening. Moreover, another not entirely negligible aspect is the increasing financial burden associated with these novel effective drugs. The identification of new predictive biomarkers is a largely unmet medical need and it is a highly active research field in lung cancer. Recently, liquid biopsy has emerged as a novel powerful tool for molecular profiling of NSCLC and cell free DNA (cfDNA) genotyping has already entered clinical practice for biomarker selection and identification of resistance mutations in oncogene-addicted patients. This minimally invasive diagnostic assay holds promise as a viable alternative to tissue biopsy and has been evaluated for multiple potential clinical uses, including early cancer detection, biomarker identification, patient selection for treatment, and drug resistance monitoring. Besides cfDNA, the liquid biopsy family comprises many other components that can be evaluated in body fluids, as circulating tumor cells (CTCs), exosomes, platelets, microRNA and long non-coding RNA. The aim of the research project was to evaluate the potential role of minimally invasive biomarkes, such as cytokines and exosomal PD-L1 expression in patients with advanced/metastatic NSCLC treated with ICIs targeting the PD-1/PD-L1 axis. In addition we evaluated the role of some systemic markers of inflammation, such as the neutrophil-to-lymphocyte ratio (NLR) that we and other groups demonstrated to be a strong independent prognostic factor. In the following chapter we will provide a comprehensive overview of the rapidly evolving therapeutic scenario of advanced NSCLC, focusing on the immunotherapy revolution. Then we will evaluate the new therapeutic and diagnostic challenges posed by this new class of anticancer agents, such as the concomitant use of medication that can affect the efficacy and safety of ICIs as well as the treatment of special populations, including HIV-infected patients, and finally the potential impact of liquid biopsy and systemic markers of inflammation. In the last chapter we will provide the preliminary data of a retrospective study evaluating the role of exosomal PD-L1 expression and the dynamic changes of some cytokines associated with anticancer immune response and PD-L1 expression, such as interferon-γ (IFN-γ), interleukin-6 (IL-6) and transforming growth factor β (TGF-β) in predicting the outcome of ICI-treated advanced/metastatic NSCLC patients from two different cohorts of patients. In addition, we will evaluate also the role of some known prognostic markers, such as NLR levels, and the potential existence of racial differences in the immune response to ICIs between Caucasian (Italian cohort) and Latin American (Colombian cohort) patients. The project is still ongoing and will further explore the potential of exosomes in the prediction of ICB efficacy through the evaluation of additional components of these tumor vesicles, such exosomal microRNAs (exo miRNAs) and proteomics.