HPV status shapes T-cell immunoprofiles in oesophageal adenocarcinoma: high regulatory T cell infiltration predicts poor prognosis.

BACKGROUND: Oesophageal adenocarcinoma (OAC) outcomes remain poor, with a 5-year survival rate of ~20%. Recent evidence suggests that human papillomavirus (HPV) is associated with ~35% of OAC. HPV-positive OAC patients have higher survivorship compared to HPV-negative patients, however current management remains uniform regardless of HPV status. Although the tumour microenvironment (TME), particularly intra-tumoural T-cell infiltration, is associated with improved outcomes in numerous cancers, characterisation of T-cell subsets in HPV-driven and HPV-independent OAC have not been explored. METHODS: Differences in T-cell subsets within OAC biopsies of HPV-positive (n = 15) and HPV-negative (n = 22) were studied by multiplex immunofluorescence microscopy, in a retrospective cross-sectional study. Statistical analyses were conducted to assess differences in T-cell quantification, and to assess the correlation with patient prognosis. RESULTS: Increased densities of FoxP3+ regulatory T-cells (Treg) and reduced CD8+:Treg ratios were evident in HPV-negative OAC compared to HPV-positive OAC. Other CD4+ and CD8+ subset densities were comparable. Univariate analyses demonstrated shorter overall survival (OS) in patients with high Treg proportions and low CD8+:Treg ratios. Multivariate analyses demonstrated a low total CD8+:Treg ratio to be independently associated with poor prognosis (HR 3.06; 95% CI 1.05-10.27; p = 0.050), along with metastasis and absence of HPV infection. CONCLUSION: We report novel evidence of an immunoregulatory TME in HPV-negative OAC, as indicated by high Treg proportions and low CD8+:Treg ratios. Future work may lead to improved risk stratification by the presence or absence of HPV, as well as utilising the CD8+:Treg ratio in the local TME as a predictive biomarker. Additionally, a more in-depth understanding of the TME would assist in the development of novel targeted immunotherapies, for example by modulating Tregs or CD8+ T-cells.