Peripheral PD-1 and Tim-3 percentages are associated with primary sites and pathological types of peritoneal neoplasms
Authors: Hu Huihui , Zhao Jin , Yuan Judong , Zhang Man 
Published: March 2023

Abstract
Purpose
Programmed death-1 (PD-1) and T cell immunoglobulin and mucin-domain-containing molecule 3(Tim-3) may be used as the biomarkers for the therapy in patients with peritoneal neoplasms. In the current study, the differential percentages of peripheral PD-1 and Tim-3 are explored to investigate whether to associate with primary sites and pathological types of patients with peritoneal neoplasms or not. We also investigated the frequencies of PD-1 and Tim-3 on circulating Lymphocytes, CD3 + T cells, CD3 + CD4 + T cells and CD3 + CD8 + T cells if would correlate with the progression-free survival of peritoneal neoplasms patients.

Methods
115 patients with peritoneal neoplasms were recruited, subjected to multicolor flow cytometric analyses of the percentages of PD-1 and Tim-3 receptors of circulating Lymphocytes, CD3 + T cells, CD3 + CD4 + T cells and CD3 + CD8 + T cells. The peritoneal neoplasms patients were divided into primary group and secondary group depending on whether the tumor had primary focus and limited to peritoneal tumor or not. Then all the patients were regrouped by the pathological types of neoplasms (adenocarcinoma, mesothelioma, and pseudomyxoma). The secondary peritoneal neoplasms group was divided into the different primary site groups (colon, gastric, gynecology). This study also enrolled 38 cases of normal volunteers. The above markers were explored by flow cytometer, to find the differential levels in peritoneal neoplasms patients compared with normal group in peripheral blood.

Results
Higher levels of CD4 + T lymphocytes, CD8 + T lymphocytes, CD45 + PD-1 + lymphocytes, CD3 + PD-1 + T cells, CD3 + CD4 + PD-1 + T cells, CD3 + CD8 + PD-1 + T cells and CD45 + Tim-3 + lymphocytes were found in peritoneal neoplasms group than normal control (the p value was respectively 0.004, 0.047, 0.046, 0.044, 0.014, 0.038 and 0.017). Compared with primary peritoneal neoplasms group, the percentages of CD45 + PD-1 + lymphocytes, CD3 + PD-1 + T cells, and CD3 + CD4 + PD-1 + T cells were increased in the secondary peritoneal neoplasms group (the p value was respectively 0.010, 0.044, and 0.040), while PD-1 did not correlate with the primary sites in secondary group (P > 0.05). Tim-3 had no statistical differences in primary peritoneal neoplasms group compared with secondary group (p > 0.05), but CD45 + Tim-3+% lymphocytes, CD3 + Tim-3+%T cells, and CD3 + CD4 + Tim-3 + T cells were associated with different secondary sites of peritoneal neoplasms (p < 0.05). In the different pathological type groups, the percentages of CD45 + PD-1 + lymphocytes, CD3 + PD-1 + T cells presented the higher levels in adenocarcinoma group compared with mesothelioma group (p = 0.048, p = 0.045). The frequencies of CD45 + PD-1 + lymphocytes and CD3 + PD-1 + T cells in peripheral blood were associated with progression-free survival (PFS).

Conclusions
Our work uncovers peripheral PD-1 and Tim-3 percentages are associated with primary sites and pathological types of peritoneal neoplasms. Those findings might provide important assessment to predict peritoneal neoplasms patients’ immunotherapy responses.