Integrative Analysis Identifies a Novel AXL–PI3 Kinase–PD-L1 Signaling Axis Associated with Radiation Resistance in Head and Neck Cancer

Abstract

Purpose The primary cause of death due to head and neck squamous cell carcinoma (HNSCC) is local treatment failure. The goal of this study was to examine this phenomenon using an unbiased approach. Experimental design We utilized HPV-negative cell lines rendered radiation resistant (RR) via repeated exposure to radiation, a panel of HPV-negative HNSCC cell lines and three cohorts of HPV-negative HNSCC tumors (n=68, 97, & 114) from patients treated with radiotherapy and subjected to genomic, transcriptomic and proteomic analysis. Results RR cell lines exhibited up-regulation of several proteins compared to controls, including increased activation of Axl and PI3 kinase signaling as well as increased expression of PD-L1. Additionally, inhibition of either Axl or PI3 kinase led to decreased PD-L1 expression. When clinical samples were subjected to RPPA and mRNA expression analysis in separate cohorts, PD-L1 was correlated with both Axl and PI3K signaling as well as dramatically associated with local failure following radiotherapy. This finding was confirmed examining a third cohort using immunohistochemistry. Indeed, tumors with high expression of PD-L1 had failure rates following radiotherapy of 60%, 70% and 50% compared to 20%, 25% and 20% in the PD-L1 low expression group (p=0.01, 1.9×10−3 and 9×10−4 respectively). This finding remained significant on multivariate analysis in all groups. Additionally, those patients with PD-L1 low/CD8+TILs high had no local failure or death due to disease (p=5×10−4 and p=4×10−4 respectively). Conclusions Taken together, our data point to a targetable Axl-PI3 kinase-PD-L1 axis that is highly associated with radiation resistance.

Sequential therapy of neoadjuvant biochemotherapy with cetuximab, paclitaxel, and cisplatin followed by cetuximab‐based concurrent bioradiotherapy in high‐risk locally advanced oral squamous cell carcinoma: Final analysis of a phase 2 clinical trial

“…23 Nevertheless, latest investigation in patient samples further showed increased AXL-PI3K-PD-L1 signaling to radiation resistance in HPV-negative HNC, suggesting the biomarker to be related to treatment failure. 48 In addition, the expression of PD-L1 was also associated to HIF-1alpha and tumor necrosis, implying the aggressive behavior in these tumor cells. 49 Our post hoc analysis supportively showed a trend of lower Neo-BioCT response rate in patients with initial CPS of more than 5% comparing to those equal or less than 5% (28.6% vs 66.7%, respectively, Supporting Information Supplementary Data 2).…”

“…This remains to be a controversy in HNC, however, because of inconclusive and contradictory clinical evidences to support the theory . Nevertheless, latest investigation in patient samples further showed increased AXL‐PI3K‐PD‐L1 signaling to radiation resistance in HPV‐negative HNC, suggesting the biomarker to be related to treatment failure . In addition, the expression of PD‐L1 was also associated to HIF‐1alpha and tumor necrosis, implying the aggressive behavior in these tumor cells .…”

Immunomodulation by ionizing radiation—impact for design of radio‐immunotherapies and for treatment of inflammatory diseases

“…The impact of RT on damage in these cases is currently investigated by our group as well as the immunological consequences including the dynamics of the macrophage phenotype following RIT. Just recently, Skinner and colleagues showed that PD‐L1 expression is a biomarker for RT‐treatment failure in HPV‐negative head and neck cancer . Knowledge on the immunological basis for that in concerted view with modulations of the phenotype of tumor‐infiltrating immune cells might further advance therapy concepts in the future.…”

“…Just recently, Skinner and colleagues showed that PD-L1 expression is a biomarker for RT-treatment failure in HPV-negative head and neck cancer. 208 Besides all, one has never to forget that a radiation oncologist is always in the dilemma to assure secure local tumor control by additionally aiming to induce systemic and specific anti-tumor immune responses. Whether it is ethical to change well-established radiation protocols that have been developed over years for best local tumor control has to be discussed for every individual case.…”

BAP1 Is a Novel Target in HPV-Negative Head and Neck Cancer

“…Recently, our group used proteomic and transcriptomic analysis to screen for potential targets associated with poor outcome following radiation in human papillomavirus (HPV)-negative HNSCC clinical samples (4). One novel candidate identified on reverse-phase protein array analysis (RPPA) screening was the BRCA1-associated protein-1 (BAP1), a nuclear deubiquitinating enzyme consisting of 729 amino acids.…”