Cell Death Mechanisms and Response to Immune Checkpoint Inhibitors in Lung Cancer

Abstract

Lung cancer is the leading cause of cancer-related deaths worldwide and immunotherapies are emerging as promising therapeutic options for this group of patients. A number of monoclonal antibodies targeting the programmed death-1 receptor (PD-1) and its ligand, programmed death-1 ligand (PD-L1) have already been approved by the United States Food and Drug Administration (FDA) and are routinely used as treatment options for lung cancer patients. However, identifying biomarkers which are able to predict response to these targeted treatments remains a major challenge in oncology. The objective of this work is to explore whether tumor-associated immunogenic cell death mechanisms (necroptosis and pyroptosis) and non-immunogenic cell death mechanisms (autophagy and apoptosis) modulate response to immunotherapy in lung cancer patients. In response to different threats, cells have the ability to activate distinct signal transduction pathways and cell death mechanisms. These mechanisms are intertwined with immune activation as programmed cell death (PCD) and can regulate a host inflammatory response. However, the ability of different PCD to elicit immune and inflammatory responses varies from mechanism to mechanism. For example, necroptosis and pyroptosis lead to the release of intracellular material into the extracellular space. Thus, these two cell death mechanisms can stimulate an innate and adaptive immune response. Apoptosis and autophagy, on the other hand, are less immunogenic and have a smaller effect on immune activation and inflammatory response. As such, cancer-associated cell death mechanisms may shape immune response and potentially render susceptibility to immune-checkpoint inhibitors. To explore whether cancer-associated cell death mechanisms modulate response to antibody-based immune-checkpoint inhibitors, we used 56 pre-treated surgical samples and core needle biopsies collected from non-small cell lung cancer (NSCLC) patients that underwent treatment with anti-PD-1 inhibitors: Nivolumab (OPDIVO) or Pembrolizumab (KEYTRUDA). Pure tumor epithelia were isolated from the surrounding cells using Laser Capture Microdissection (LCM). The Reverse Phase Protein Microarray (RPPA), a high throughout antibody-based immunoassay was then used to capture expression and activation levels of 37 proteins involved in two immunogenic (necroptosis and pyroptosis) and two less immunogenic PCD pathways (apoptosis and autophagy). Cell death associated signal transduction events were compared between patients that benefited from treatment and those that did not. By unveiling novel predictive markers of response to treatment, this work has the potential to fill and important gap in the field of cancer immunotherapy and precision medicine.