Cd15(+) Tumor Infiltrating Granulocytic Cells Can Predict Recurrence And Their Depletion Is Accompanied By Good Responses To S-1 With Oral Cancer

Background 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.Methods 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.Results 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.Conclusion Preoperative S-1 chemotherapy can potentially improve prognosis by reducing CD15(+) cells in the tumor microenvironment.