Tumor infiltrating CD103+ tissue residentmemory T cells and CD103-CD8+ T cells in HNSCC are linked to outcome in primary but not metastatic disease.

High numbers of tumor infiltrating lymphocytes (TIL) are linked to better survival in cancer patients. TRM(CD8+CD103+) are recognized as a key player of anti-cancer immune response. To assess TRM in primary, metastatic and recurrent HNSCC we developed a tissue microarray (TMA) and used multiplex immunohistochemistry (MxIHC). 379 HNSCC cases from Southampton Hospitals (2000-2016) with material of primary tumors were retrieved. Of these, 105 cases had lymph node metastases and 82 recurrences. A TMA was generated with triplicate cores for each sample. MxIHC with a stain and strip approach was performed using CD8, CD103, TIM3. Scanned slides were analyzed (digital image analysis) and quality checked (QC). After QC, 194 primary tumors, 76 lymph node metastases and 65 recurrences were evaluable. Alcohol drinking was statistically significantly correlated with a reduction of TRM cells in primary tumors (no drinker vs. heavy drinker: p = 0.0036). The known survival benefit of TRM infiltration in primary tumors was not found for lymph node metastasis. In recurrences a high TRM number led to a favorable outcome after 12 months. The checkpoint molecule TIM3, was expressed significantly higher on TRM and non-TRM cells in the lymph node compared to primary tumors (p < 0.0001), which was also seen in recurrences (p 0.0134, p=0.0007, respectively). We confirm the prognostic impact of TIL in primary tumors and in recurrences. TRM cell density in lymph node metastases was not linked to outcome. The role of TIM3, as a therapeutic target remains to be defined.