Immunological Responses Associated With Neoadjuvant Therapy in the Tumor Microenvironment of Esophageal Squamous Cell Carcinoma

Background/Aim: Development of multidisciplinary therapies including immune checkpoint inhibitors for esophageal squamous cell carcinoma (ESCC) requires a clear understanding of immunological responses induced by chemotherapy with/without radiotherapy in the tumor microenvironment. Patients and Methods: This is a retrospective analysis of paired pretreatment biopsy samples and surgically resected tumor samples of 49 patients who underwent radical surgery for ESCC with/without neoadjuvant therapy at Fukushima Medical University Hospital. The cohort included 30 patients treated with neoadjuvant chemotherapy (NAC), 11 treated with neoadjuvant chemoradiotherapy (NACRT), and eight who underwent surgery alone and did not receive neoadjuvant antitumor therapy. Chemotherapy included fluoropyrimidine-and platinum-based agents in all treated patients, and radiotherapy included 40 or 42 Gy administered in 20 or 21 fractions. Expression of CD8, human leukocyte antigen (HLA) class I-ABC, PD-L1, PD-L2, CEACAM-1, LSECtin, and p-STAT1, were determined using immunohisto-chemistry. Results: The frequency of tumor-infiltrating CD8+ T cells was significantly increased by NAC (p<0.05), and the expression of HLA class I-ABC on tumor cells was significantly increased by NAC and NACRT (p<0.05). Furthermore, the ESCC cells expressed PD-L1, PD-L2, and CEACAM-1, whereas the expression of PD-L1 on ESCC cells was significantly correlated with the expression of p-STAT1 in ESCC cells (p<0.05). Conclusion: NAC and NACRT induced both positive and negative immunological responses in patients with ESCC. These results may be a part of basis for multidisciplinary therapy including immune checkpoint inhibitors for patients with advanced ESCC.