Human papilloma virus (HPV)-associated oropharyngeal squamous cell cancer (OPSCC) is a distinct clinical entity with a much better prognosis after (chemo)radiotherapy than HPV-negative OPSCC. We hypothesize that the virally-derived E6 and E7 antigens make HPV-associated OPSCC highly visible to the immune system, unleashing a strong antitumor response. To understand the constitution of an optimal antitumor response we have unraveled the immune contexture of OPSCC.
A comprehensive analysis by mass cytometry (CyTOF), flow cytometry and immunohistochemistry was performed on fresh and archived tissue of a cohort of 97 patients. In addition, the RNA-sequencing data of a cohort of 75 HPV16+ OPSCC patients present in the publicly available cancer genomic atlas (TCGA) database was used to analyze the tumor microenvironment by an analytical strategy to estimate subpopulations of tumor-infiltrating immune cells.
CD4+ T cells formed the major component in OPSCC. Gene set enrichment analysis (GSEA) of the TCGA data in HPV16+ OPSCC with a high vs low CD4 gene expression revealed the enrichment of activated and effector memory CD4+ and CD8+ T cells as well as activated DC in HPV16+ OPSCC with a high expression of CD4. Indeed, flow- and mass-cytometry confirmed an increased percentage of DCs and highly activated effector memory CD4+ and CD8+ T cells in HPV16+ OPSCC. Furthermore, immunohistochemistry showed that these T cells were likely to produce interferon-gamma. Interestingly, the T-cell infiltrate of HPV16+ OPSCC comprised a population of cells expressing a specific C-type lectin receptor. The expression of this receptor strongly correlated to the overall survival of patients with HPV16+ OPSCC and was expressed on type 1 T cells recognizing the HPV oncoproteins E6 and E7.
OPSCC are infiltrated with HPV-specific T cells expressing a C-type lectin receptor that is also expressed by CD4+ T-cells dominating inflammatory diseases such as rejections during graft versus host disease, hence a similar role may be expected in cancer and would be advantageous for tumor control.