Abstract

Biomarkers of an effective Antitumor Response to Immune Checkpoint Inhibitor in Head and Neck Cancer

My Mahoney, Associate Professor, Thomas Jefferson University

Head and neck squamous cell carcinoma (HNSCC) is the 6th leading cancer worldwide with common risk factors including chronic alcohol and tobacco use as well as human papillomavirus (HPV) infection. Despite the prevalence, there are no clear clinical biomarkers that could delineate normal homeostasis versus tumorigenic processes, HPV positivity, and response to immune checkpoint inhibitors (ICI). In fact, profiling and validation of any cancer biomarkers have proven so complex that HE4 was the last biomarker approved by the FDA for breast cancer in 2009. Emerging as a potentially reliable source for cancer biomarkers are exosomes or small extracellular vesicles (sEVs), which have been shown to play critical roles in cell-to-cell communication and cancer progression. Here, sEVs were isolated from circulating plasma of HNSCC patients and control volunteers by the immunoaffinity ExoRelease method (Clara Biotech) and subjected to bead-based Multiplex profiling of cancer-specific antigens (Luminex). Results were compared to respective total plasma showing substantial differences between the profiles. Interestingly, higher levels of several cancer biomarkers were detected in HNSCC sEVs, particularly in HPV(-) as compared to HPV(+) patients. Most importantly, HE4 associates with HPV(-). In addition to protein biomarkers, we performed small RNAseq for miRNAs in HNSCC sEVs. Here, in a 4-week window of opportunity trial, HNSCC patients received 2 doses of the ICI anti-PD1 mAb, nivolumab. Patients were stratified according to pathologic treatment response, as demonstrated by reduction in tumor size. sEVs isolated from post-treatment tumor cultured supernatant were analyzed by FACS analysis, which confirmed the downregulation of immune checkpoint receptors in responders. Profiling by miRNAseq and analysis by Weka Explorer revealed that 10 miRNAs were strongly correlated with HPV status and 18 miRNAs with response to ICI treatment. KEGG analysis revealed that their targets were associated with pathways in cancer. While the levels of miRNAs did not change in response to treatment, there was a statistically higher level of anti-inflammatory miRNAs, including tumor suppressor miR-146a, in responders versus non-responders. The results from these studies suggest there are new cancer biomarkers that could contribute to better diagnosis and treatment of HNSCC cancer patients.