Colorectal carcinoma is infiltrated by FOXP3 – positive lymphocytes

Tumor is a complex tissue composed of cancer cells and stromal cells (e.g. endothelial cells, fibroblasts, dendritic and NK cells, macrophages and lymphocytes). Tumor-infiltrating lymphocytes (TIL) are found in a variety of solid cancers and they are a possible prognostic factor as it is thought that TILs execute a host immune response against cancer cells. In colorectal carcinoma (CRC), TILS are particularly numerous in cases associated with microsatellite instability and have more favorable clinical outcome. Generally, cytotoxic T-cells (CD8+) are prognostically favorable, whereas recent discovered subgroup of TILs, regulatory T-cells (T-reg,CD4+CD25+FOXP3+) are not. They inhibit antitumor activity of CD8+ and CD4+ T-cells. The aim of our study was to investigate if the TIL of CRC include T-reg lymphocytes, which was not proved so far. More recent studies have shown that T-reg lymphocytes are unically characterized by expression of transcription factor FOXP3. Therefore we used immunohistochemical staining to detect lymphocytes co-expressing CD4+ and FOXP3+ in 9 cases of CRC primary tumors. All cases of CRC were left-side localized, respecting a different biological behaviour of left/right-side localized CRCs. We used formalinfixed and paraffin-embedded sections and commercially available monoclonal antibodies. Our preliminary results show that TIL in CRC include in cancer stroma a subset of CD4+ CD25+FOXP3+ lymphocytes. Now, we are interested if T-reg lymphocytes can be used as a prognostic marker for CRC and we analyze a group of 20 patients with CRC in I-IV clinical stage. We are also interested if there is a connection between occurrence of T-reg and other stromal cells, especially cytotoxic T-lymphocytes and NK cells.
Acknowledgment: This project is supported by Internal Grant Agency, Ministry of Health, Czech Republic. No.: NR/9076-4.