Local cellular immunity in colorectal cancer depending on tumor site.

Abstract

e15613 Background: Colorectal cancer (CRC) is the third most commonly diagnosed cancer. More than 60% of all cases of CRC are colon cancer (CC). The role of individual units of the immune system in the development of this tumor is ambiguous. The purpose of this study was to characterize local populations and subpopulations of immunocompetent cells in colorectal cancer with different tumor locations. Methods: The study included 50 CC (adenocarcinoma) patients aged 35-86 years, women n = 26 (52%). Stage I tumors were registered in 4 patients (8%), stage II 25 (50%), stage III 21 (42%). 20 patients (40%) had right-sided CC (group 1), 9 (18%) left-sided CC (group 2), and 21 (42%) sigmoid CC (group 3). All patients received surgical treatment. Cell suspensions were obtained from tumor (TT) and peritumoral tissues (PT) (1-3 cm from the tumor), and then processed with an antibody panel in accordance with the manufacturer instructions (Becton Dickinson, USA) to identify the main populations and subpopulations of leukocytes and lymphocytes. The relative number of major populations and subpopulations of lymphocytes was determined on the BD FACSCanto flow cytometer. Results: A decrease in lymphocytic infiltration was noted left-sided tumors and sigmoid tumors compared to right-sided CC, by 46% and 51%, respectively. The percentage of CD3+ cells was almost the same regardless of the colon tumor location, and the number of main populations of T lymphocytes differed: in group 3, the content of CD4+ cells was 21% higher, and CD8+ cells were 22% lower compared with group 1, while group 2 had no differences. Group 2 differed in the tumor infiltration with both NK and NKT lymphocytes, which were higher by 25% and 22%, respectively, than in group 1. An increase in NK cells was noted in the sigmoid colon (group 3), and the relative number of NKT lymphocytes decreased. A common feature of TT in groups 2 and 3 was an increase in the content of B lymphocytes by 98% and 133%, respectively. PT of group 2 showed a decrease by 72%, 33%, 66%, and 46% in the relative number of lymphocytes, CD4+, NKT and B lymphocytes compared with group 1, together with an increased content of NK and CD8+ lymphocytes. PT in patients of group 3 had a decrease in the number of total and NK lymphocytes by 46% and 26%, respectively, and a significant increase by 85% in the content of CD8+ cells, with no changes in CD3+, CD4+ cells, B and NKT lymphocytes. Conclusions: The local immune status of CRC patients demonstrated a number of differences: right-sided tumors were characterized by a higher T-lymphocytic infiltration with the same tendency in the perifocal tissues, while left-sided and sigmoid tumors showed higher B-lymphocytic infiltration, which can help in the disease prognosis and choice of treatment strategy.