In situ hybridization for high risk HPV E6/E7 mRNA in oropharyngeal squamous cell carcinoma.

OBJECTIVES: To report a single institution's experience using human papillomavirus (HPV) E6/E7 mRNA in-situ hybridization (mRNA ISH) for HPV detection in oropharyngeal squamous cell carcinoma (OPSCC). To review the literature on HPV detection methods. STUDY DESIGN: Retrospective chart review, literature review. SETTING: Tertiary care academic hospital. SUBJECTS AND METHODS: We conducted a retrospective chart review of 122 OPSCC biopsy specimens. mRNA ISH was performed on formalin-fixed paraffin-embedded (FFPE) tissue with a pool of 18 high risk HPV probes using an automated stainer; p16 immunohistochemistry (IHC) was also performed. We conducted a literature review on HPV detection methods including p16 IHC, mRNA ISH, DNA ISH, and PCR. RESULTS: In our cohort, mRNA ISH had a sensitivity and specificity of 100% and 100% with reference to p16 (100% concordance). 2-year OS was 87.5% vs. 94.5% for p16/HPV-negative vs. positive patients. 2-year DFS was 60.0% vs. 84.2%. On literature review, mRNA ISH demonstrated consistently high sensitivity and specificity ranging from 88-98% and 90-100% respectively. In comparison, the specificity of p16 was 85-95%. CONCLUSIONS: Our report supports the use of mRNA ISH for HPV detection in OPSCC and validates its feasibility using automated tissue staining methods on FFPE tissue. Our findings and literature review support that mRNA ISH may have superior specificity and be easier to interpret than p16. Further study on the prognostic value and cost-effectiveness of mRNA ISH is warranted and may establish this HPV detection method as the "gold standard."

OX40+ plasmacytoid dendritic cells in the tumor microenvironment promote antitumor immunity.

Plasmacytoid DCs (pDCs), the major producers of type I interferon, are principally recognized as key mediators of antiviral immunity. However, their role in tumor immunity is less clear. Depending on the context, pDCs can promote or suppress antitumor immune responses. In this study, we identified a naturally occurring pDC subset expressing high levels of OX40 (OX40+ pDC) enriched in the tumor microenvironment (TME) of head and neck squamous cell carcinoma. OX40+ pDCs were distinguished by a distinct immunostimulatory phenotype, cytolytic function, and ability to synergize with conventional DCs (cDCs) in generating potent tumor antigen-specific CD8+ T cell responses. Transcriptomically, we found that they selectively utilized EIF2 signaling and oxidative phosphorylation pathways. Moreover, depletion of pDCs in the murine OX40+ pDC-rich tumor model accelerated tumor growth. Collectively, we present evidence of a pDC subset in the TME that favors antitumor immunity.