An immunophenotyping analysis was performed in peripheral blood samples from seven patients with lung cancer unfit for surgery treated with stereotactic body radiotherapy (SBRT). The objective was to characterize the effect of SBRT on the host immune system. Four patients received 60 Gy (7.5 Gy × 8) and three 50 Gy (12.5 Gy × 4). Analyses were performed before SBRT, 72 h after SBRT, and at one, three, and six months after the end of SBRT. Of note, there was a specific increase of the immunoactive component of the immune system, with elevation of CD56^+highCD16+ natural killer (NK) cells (0.95% at baseline to 1.38% at six months), and a decrease of the immunosuppressive component of the immune system, with decreases of CD4+CD25+Foxp3+CDA5RA− regulatory T cells (4.97% at baseline to 4.46% at six months), granulocytic myeloid-derived suppressor cells (G-MDSCs) (from 66.1% at baseline to 62.6% at six months) and monocytic (Mo-MDSCs) (8.2% at baseline to 6.2% at six months). These changes were already apparent at 72 h and persisted over six months. SBRT showed an effect on systemic immune cell populations, which is a relevant finding for supporting future combinations of SBRT with immunotherapy for treating lung cancer patients.

A detailed understanding of the interactions and the best dose-fractionation scheme of radiation to maximize antitumor immunity have not been fully established. In this study, the effect on the host immune system of a single dose of 20 Gy through intraoperative radiation therapy (IORT) on the surgical bed in low-risk breast cancer patients undergoing conserving breast cancer has been assessed. Peripheral blood samples from 13 patients were collected preoperatively and at 48 h and 3 and 10 weeks after the administration of radiation. We performed a flow cytometry analysis for lymphocyte subpopulations, natural killer cells (NK), regulatory T cells (Treg) and myeloid-derived suppressor cells (MDSCs). We observed that the subpopulation of NK CD56^+high CD16⁺ increased significantly at 3 weeks after IORT (0.30–0.42%, P < 0.001), while no changes were found in immunosuppressive profile, CD4⁺CD25⁺Foxp3⁺Helios⁺ Treg cells, granulocytic MDSCs (G-MDSCs) and monocytic MDSCs (Mo-MDSCs). A single dose of IORT may be an effective approach to improve antitumor immunity based on the increase in NK cells and the non-stimulation of immunosuppressive cells involved in immune escape. These findings support future combinations of IORT with immunotherapy, if they are confirmed in a large cohort of breast cancer patients.

Purpose: Loss of TGFβ signaling increases error-prone alternative end-joining (alt-EJ) DNA repair. We previously translated this mechanistic relationship as TGFβ and alt-EJ gene expression signatures, which we showed are anticorrelated across cancer types. A score representing anticorrelation, βAlt, predicts patient outcome in response to genotoxic therapy. Here we sought to verify this biology in live specimens and additional datasets. Experimental Design: Human head and neck squamous carcinoma (HNSC) explants were treated in vitro to test whether the signatures report TGFβ signaling, indicated by SMAD2 phosphorylation, and unrepaired DNA damage, indicated by persistent 53BP1 foci after irradiation or olaparib. A custom NanoString assay was implemented to analyze the signatures’ expression in explants. Each signature gene was then weighted by its association with functional responses to define a modified score, βAltw, that was retested for association with response to genotoxic therapies in independent datasets. Results: Most genes in each signature were positively correlated with the expected biological response in tumor explants. Anticorrelation of TGFβ and alt-EJ signatures measured by NanoString was confirmed in explants. βAltw was significantly (P < 0.001) better than βAlt in predicting overall survival in response to genotoxic therapy in The Cancer Genome Atlas (TCGA) pancancer patients and in independent HNSC and ovarian cancer patient datasets. Conclusions: Association of the TGFβ and alt-EJ signatures with their biological response validates TGFβ competency as a key mediator of DNA repair that can be readily assayed by gene expression. The predictive value of βAltw supports its development to assist in clinical decision making.