Circulating regulatory T cells of cancer patients receiving radiochemotherapy may be useful to individualize cancer treatment.

Abstract

Dendritic cells (DCs) and regulatory T cells (Treg) play a major role in anti-tumor immune response of cancer patients. We investigated the effect of radiochemotherapy on patients' blood immune cells and their predictive value for tumor response. DCs and Treg of colorectal cancer (CRC) or breast cancer (BC) patients were examined through multicolor flow cytometry before the beginning and after the first week of radiochemotherapy (RCT). DCs were stained for BDCA1 and BDCA2, Treg were stained for CD4, CD25, CD127 and FoxP3. IL-2, IL-10 and TNF-α plasma levels of CRC patients were also determined. We examined the interrelationship between immune cell count alterations, applied dose values, cytokine plasma levels as well as histopathological parameters. DCs were increased in BC and CRC patients compared to healthy control individuals (HC). CRC patients had higher levels of Treg (59.0%) compared to BC patients (31.3%) and HC (27.0%). Treg of CRC (58.7% vs. 41.3% p<0.001) but not BC patients (31.3% vs. 38.8%, p=0.164) decreased distinctly after the first week of radiation therapy. Applied dose values and decrease of Treg correlated positively (r=0.216, p=0.054). We also found a positive correlation of IL-10 plasma levels and Treg levels (r=0.748, p=0.021). CRC patients with favorable tumor stage (<ypT3a) have higher levels of Treg after 5 days of RCT (49.4% vs. 34.0%, p=0.043). Higher Treg levels are associated with favorable tumor stage. We hypothesize that a dramatic decrease of Treg after in vivo irradiation may be a good indicator for necessary dose adjustments in radiation therapy of CRC patients.