To ensure the immune system’s balance between the recognition of non-self and the prevention of autoimmunity, the activity of immune cells needs to be strictly controlled. During the process of cancerogenesis, tumor cells try to resist immune responses and work to suppress the cycle of cancer immunity through multiple mechanisms involving regulatory proteins. These proteins—referred to as immune checkpoints—can affect immunoregulatory pathways by either boosting (co-stimulatory) or restricting (co-inhibitory) the immune response. For the majority of these checkpoint markers, soluble isoforms or shed variants that function as immune adjuvants or decoy receptors, have been identified. To date, cancer therapies that use antibodies targeted to the proteins within these immune checkpoint pathways have proven effective. It is also hypothesized that the measurement of the circulating concentration of the soluble forms of the immune checkpoint proteins could potentially correlate with the clinical efficacy of corresponding checkpoint modulator drugs.
To test this hypothesis, we developed two comprehensive multiplexing panels (using Luminex® xMAP® technology) that are specifically designed to detect soluble checkpoint molecules involved in T cell and NK cell regulation. The panels allow the simultaneous detection of immune stimulatory and inhibitory factors, allowing a more holistic picture of the molecular players in cancer immunity. Preliminary results using the Invitrogen™ Immuno-Oncology Checkpoint 14-Plex Human ProcartaPlex™ Panel 1 (Cat. No. EPX14A-15803-901) and the Invitrogen™ Immuno-Oncology Checkpoint 14-Plex Human ProcartaPlex™ Panel 2 (Cat. No. EPX140-15815-901) demonstrate that there are different expression patterns for each that are dependent on both disease state and patient treatment. More in-depth analysis of these soluble biomarkers will hopefully shed more light on the biology of the immune checkpoint pathways and provide a possible tool for monitoring response to therapeutic treatment.