CD15⁺ tumor infiltrating granulocytic cells can predict recurrence and their depletion is accompanied by good responses to S-1 with oral cancer.

Abstract

It has been reported in oral squamous cell carcinoma (OSCC) that myeloid-derived suppressor cells infiltrate tumor tissues. This study examined whether S-1 chemotherapy changes immune cell populations in the tumor microenvironment. We examined 71 patients with of OSCC, including 51 patients who received preoperative S-1 chemotherapy. Immunohistochemistry for PD-L1, CD8, forkhead box protein 3 (FOXP3), and CD15 was performed using biopsy and resected specimens. The numbers of CD8⁺ , FOXP3⁺ , and CD15⁺ cells in resected specimens were significantly decreased by S-1 chemotherapy. The reduction of the proportion of CD15⁺ cells significantly differed between responders and nonresponders. Most responders were distributed into the group with low PD-L1 expression and a low density of CD8⁺ cells before chemotherapy. Furthermore, many patients with recurrence exhibited a high density of CD15⁺ cells in biopsy specimens. Preoperative S-1 chemotherapy can potentially improve prognosis by reducing CD15⁺ cells in the tumor microenvironment.