The correlation between infiltration of FoxP3⁺ Tregs, CD66b⁺ TANs and CD163⁺ TAMs in colorectal cancer

Introduction: The infiltration of immune cells in tumor tissue is affected by the tumor microenvironment. However, the relationship between the infiltration of regulatory T cells (Tregs), tumor-associated neutrophils (TANs) and tumor-associated macrophages (TAMs) in colorectal cancer (CRC) remains unclear.

Material and methods: Tissue microarray and immunohistochemistry were used to detect the infiltration of FoxP3⁺ Tregs, CD66b⁺ TANs and CD163⁺ TAMs in 249 CRC samples (training cohort) and 243 CRC samples (validation cohort). The relationship between two cells was evaluated by Spearman's rank correlation coefficient and comparison between two groups was analyzed by Mann-Whitney U test.

Results: The continuous variable positive cell numbers were non-normally distributed. Spearman correlation analysis showed that CD66b⁺ TAN level in cancer tissues was negatively related to FoxP3⁺ Treg level (correlation coefficient: -0.495, p < 0.05) and CD163⁺ TAM level (correlation coefficient: -0.266, p < 0.05), and FoxP3⁺ Treg level was positively related to CD163⁺ TAM level (correlation coefficient: 0.467, p < 0.05) in the training cohort. The numbers of FoxP3⁺ Tregs were significantly different between low and high CD66b⁺ TAN level groups (p < 0.001), as well as that of CD66b⁺ TANs in low and high CD163⁺ TAM level groups and CD163⁺ TAMs in different FoxP3⁺ Treg level groups. The results of the validation cohort were similar to those of the training cohort.

Conclusions: There is a negative correlation between infiltration of CD66b⁺ TANs and that of FoxP3⁺ Tregs or CD163⁺ TAMs, and a positive correlation between infiltration of FoxP3⁺ Tregs and CD163⁺ TAMs in CRC tissues.