Posted December 9, 2021

Laura Conforti, Ph.D., and Trisha Wise-Draper, M.D., Ph.D., University of Cincinnati
David Hildeman, Ph.D., Cincinnati Children’s Hospital

With an overall 5-year survival rate of less than 50%, head and neck squamous cell carcinoma (HNSCC) is a major health concern, especially to Veterans, with an increased prevalence in Veterans compared to non-Veterans.¹ Immunotherapy is a flourishing treatment strategy that enables the patient’s own immune cells to destroy the cancer. Use of the drug pembrolizumab, an antibody that inhibits the immune checkpoint programmed death 1 (PD1) receptor, shows great promise in treating HNSCC; however, a significant subset of patients do not respond or eventually relapse. With a Fiscal Year 2016 Peer Reviewed Cancer Research Program Translational Team Science Award, Dr. Laura Conforti, Dr. Trisha Wise-Draper, Dr. David Hildeman, and their teams investigated the ionic mechanisms that mediate the response and resistance of HNSCC patients to anti-PD1 therapy.

The research team hypothesized that immunotherapy resistance arises from inhibitory signals emanating from cell surface receptors such as natural killer cell receptor 2B4 (CD244), through inhibitory signal production, and adenosine A2A Receptor (A2AR) via inhibition of T cell migration to the tumor. They postulated that, in responding patients, anti-PD1 therapy increases activity in the calcium (Ca2+) signaling pathway, which in turn strengthens the anti-tumor responses in cytotoxic (CD8+) T-cells. Results from the teams’ study have been published in the Journal for ImmunoTherapy in Cancer.^2,3

The teams investigated avenues of immunotherapy treatments so that future treatments could be more effective. Despite some early setbacks, investigations refocused to determine whether CD244-mediated inhibition of Ca2+ signaling in cytotoxic CD8+ T cells led to anti-PD1 therapy resistance. For these experiments, cells were sampled from both human and murine tissue samples. Peripheral blood mononuclear cells were isolated from healthy and HNSCC patients. Fresh tumor tissue was collected from HNSCC patients at multiple time points before, during, and after anti-PD1 treatment; and splenic CD8+ T cells were isolated from both C57BL/6 murine and human spleens (human splenic cells were collected from spleens destined for transplant). Using flow cytometry to analyze the protein composition of these collected cells, they observed that CD244 was more prevalent in HNSCC CD8+ T cells, which correlated with increased PD1 expression.² Mice with no expression of CD244 (CD244-/-) showed significantly decreased tumor growth and better intervention as compared to wild type mice.² This suggests use of a CD244 inhibitor could be a viable target for new immunotherapeutic drugs for use in combination with pembrolizumab.

The team also studied the molecular effect of pembrolizumab on patient samples from a clinical trial (NCT02641093) to see whether anti-PD1 therapy restored ion channel functionality in CD8+ T cells. Using patch-clamp electrophysiology (a laboratory technique used to study the flow of ions, such as potassium [K+]) on peripheral blood T cells and tumor infiltrating lymphocytes at multiple points before, during, and after treatment, the team found that pembrolizumab enhanced K+ channel activity of cytotoxic CD8+ T cells in HNSCC patients, particularly in “responder” patients.³ Furthermore, by applying a μ-Slide Chemotaxis assay (a method to measure the movement of cells) to study CD8+ T cell’s mobility across a concentration gradient they observed that pembrolizumab treatment increased mobility of these important cancer-fighting CD8+ T cells in responder patients. Overall, responders had heightened cytotoxicity and chemotaxis of CD8+ T cells that was prolonged and persisted after tumor resection.³ This research highlights that a new immunotherapy activating K+ channels could potentially improve CD8+ T cell cytotoxicity and mobility.

The research by Dr. Conforti's team provides a better understanding of how immunotherapy works in patients with HNSCC, which will allow clinicians and researchers to produce strategies to maximize treatment and improve patient outcomes. Dr. Conforti predicts they have set the stage for clinical trials to test new combination therapies. The findings from her team not only have the potential to combat immunotherapy resistance and improve outcomes in HNSCC patients, but could also have broader applications in cancer treatments.

References:

¹ Ferlay J, Soerjomataram I, Dikshit R, et al. 2015. Cancer incidence and mortality worldwide: Sources, methods and major patterns in GLOBOCAN 2012. Int J Cancer 136(5):E359-E386. doi: 10.1002/ijc.29210. Epub 2014 Oct 9. PMCID: 25220842.

² Agresta L, Lehn M, Lampe K, et al. 2020. CD244 represents a new therapeutic target in head and neck squamous cell carcinoma. J Immunother Cancer 8(1):e000245. doi:10.1136/jitc-2019-000245. PubMed PMID:32217758. PubMed Central PMCID:PMC7174077.

³ Newton HS, Gawali VS, Chimote AA, et al. 2020. PD1 blockade enhances K+ channel activity, Ca2+ signaling, and migratory ability in cytotoxic T lymphocytes of patients with head and neck cancer. J Immunother Cancer 8(2):e000844. doi:10.1136/jitc-2020-000844. PMID: 33060146. PMCID:PMC7566435.

Links:

Public and Technical Abstracts: Ionic Mechanisms of Resistance to Immunotherapy in Head and Neck Cancer

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