Identification of Biomarkers in Non-Small Cell Lung Cancer Patients Treated with PD-1 Monoclonal Antibody Immunotherapy

Cancer immunotherapy works by taking a patient's existing immune system and priming it to recognize cancer cells in order for immune cells to mount an effective response to the disease. This is a less invasive means of treating cancer for the patient. However current immunotherapy does come with its own unique side effects such as auto immune disorders that manifest in the patients' treatment due to the blocking of essential immune regulatory checkpoints. In this study , patients are treated with drugs nivolumab and pembrolizumab , both of which are PD-1 (Programmed Death Receptor 1) monoclonal antibodies. These antibodies bind to PD-1 and prevent ligand interaction with PD-L1. PD-1 is a receptor expressed on the surface of activated B-cells , macrophages and T-cells. When PD-1 is activated by PD-L1 a signal propagates from the receptor to inside the cell that results in the apoptosis of the cell that expresses PD-1. The activation of PD-1 on activated T-cells ultimately results in a reduction of T-cell proliferation and IFN-[gamma] secretion. An apoptotic signal occurs through the inhibition of the cell survival signal that is propagated through the PI3K pathway. While there is knowledge on how the expression and activation of PD-1 on immune cells regulates the progression of cancer , there is a lack of evidence to suggest biomarkers in non-small cell lung cancer patients for optimizing immunotherapy. This study serves to identify biomarkers in non-small cell lung cancer patients undergoing PD-1 monoclonal antibody immunotherapy. To accomplish this , blood samples were collected from non-small cell lung cancer patients undergoing the immunotherapy treatment and the cell counts were taken. Cell types of interest include cytotoxic T-cells , helper T-cells , B-cells , and granulocytes. Cytotoxic T-cells were identified by CD8 expression , a known marker of cytotoxic T-cells. Helper T-cells were identified by CD4 expression and B-cells were identified by CD19 expression , both of which are known markers of helper T-cells and B-cells , respectively. Secondly , this study investigated the expression levels of known immune regulatory genes and how these changed over the course of the immunotherapy treatment. Known immune regulatory genes included PD-L1 , PD-1 , CTLA4 , CD28 , A2A , CD80 and CD86. The expression levels of the proton sensing family of G-protein coupled receptors (G2A , GPR4 , OGR1 and TDAG8) were also investigated. Thirdly , we investigated how tumor cell expression of PD-1 and PD-L1 was altered when introduced into an acidic environment. Due to the tumor microenvironment being characteristically acidic this would provide insight on how anti PD-1 and anti PD-L1 immunotherapies could potentially be used in various cancers and may also lead to the development of potential future combination therapies. Our study shows that approximately 90% of patients exhibited an increase in cytotoxic T-cell counts with 50% of patients achieving healthy donor cytotoxic T-cell counts after receiving immunotherapy. Additionally 2 patients out of the total 16 patients achieved and sustained cytotoxic T-cell counts above that of healthy donors. There was an observable trend that indicated a possible correlation that PD-1 levels at baseline could predict patient response to the PD-1 monoclonal antibody immunotherapy. In addition to our research into the clinical aspects of PD-1 monoclonal antibody immunotherapy , we also investigated the change in expression of PD-1 and PD-L1 mRNA in several cancer cell lines. We observed that there was a variation in how cancer cells responded to acidosis. PD-1 and PD-L1 mRNA expression was shown to be regulated through several variables such as the acidity of the media , duration of exposure to acidic conditions and cancer cell type. It was also observed that there was PD-1 and PD-L1 expression in these cancer cell lines , at 5 hour and 24 hour treatment times , with a prominent level of PD-L1 mRNA expression in most of these cancer cells