The effect of short-course neoadjuvant radiotherapy (5Gy ×5 fractions) on rectal tumor immune microenvironment

Background

Short-course neoadjuvant radiotherapy of 5Gy × 5 fractions is recommended to be a standard treatment for the patients with ressectable stage II/III rectal cancer. While the effect of radiotherapy of 5Gy × 5f on the tumor microenvironment is still unclear. The purpose of this study was to evaluate the interactions between radiotherapy of 5Gy × 5f and the tumor immune microenvironment.

Methods

The changes in the number of immune cells, the changes of P-STAT1, P-STAT3, MICA, KIR, PD-L1 and Gal-1 in tumor before and after radiotherapy were assessed in mouse CT26 rectal cancer model. The effects of radiotherapy of 5Gy × 3f and 5Gy × 5f on HCT116, RKO, SW480,174T, DLD-1 cell lines were also investigated. Furthermore, clinical samples of patients with rectal cancer were analyzed. The changes of T lymphocytes in blood and T lymphocytes and NK cells in tumor before and after radiotherapy were tested. The infiltration of CD8 + T lymphocyte in tumor was studied as well.

Results

In CT26 models, the radiotherapy of 5Gy × 5f promoted CD4 + and CD8 + T lymphocyte infiltration (P

Conclusions

Radiotherapy of 5Gy × 5f could promote the infiltration of CD4 + and CD8 + T lymphocyte in local tumor, and enhance the anti-tumor effect of NK cells and T lymphocytes. Short-course neoadjuvant radiotherapy of 5Gy × 5f have immune stimulatory effects for rectal cancer.

Clinical trial identification

Legal entity responsible for the study

N/A

Funding

Chinese National Natural Science Foundation (NSFC 8120175).

Disclosure

All authors have declared no conflicts of interest.