Soy Isoflavones Promote Radioprotection of Normal Lung Tissue by Inhibition of Radiation-Induced Activation of Macrophages and Neutrophils

Neutrophil-lymphocyte ratio and a dosimetric factor for predicting symptomatic radiation pneumonitis in non-small-cell lung cancer patients treated with concurrent chemoradiotherapy

OBJECTIVES

To identify the factors that predict the progression of radiological radiation pneumonitis (RP) to symptomatic RP, and to evaluate the usefulness of the neutrophil-lymphocyte ratio (NLR) as a marker of RP severity and prognosis in stage III non-small cell lung cancer (NSCLC) patients treated with definitive concurrent chemoradiotherapy (CCRT).

MATERIALS AND METHODS

We retrospectively reviewed 61 patients treated between January 2010 and December 2015. Patients' demographic characteristics, clinical data, laboratory findings and treatment parameters were analyzed to determine the predictive factors associated with progression from radiological RP to symptomatic RP.

RESULTS

Forty-seven patients (77%) exhibited radiological RP at a median of 78 days after radiation therapy (RT) completion, and 15 (32%) of these patients developed symptomatic RP. The interval between RT completion and radiological RP presentation was shorter in patients who progressed to symptomatic RP (P = .001); progression was highly probable if this latency period was ≤2 months (P = .002). Stage and RT technique correlated with symptomatic RP development (P = .046 and P = .046, respectively). Among dosimetric factors, a V₂₀ (defined as the lung volume receiving ≥20 Gy) of >30% was the most significant predictor of symptomatic RP (P = .001). The NLR and C-reactive protein level at radiological RP were higher in patients who developed symptomatic RP (P = .067 and P = .012, respectively). On multivariate analysis, a V₂₀ >30% and an NLR at radiological RP >6 were associated with symptomatic RP development.

CONCLUSION

The NLR at radiological RP is a useful biomarker for predicting symptomatic RP development after CCRT in stage III NSCLC patients.

Innate Immune Pathways Associated with Lung Radioprotection by Soy Isoflavones

Introduction

Radiation therapy for lung cancer causes pneumonitis and fibrosis. Soy isoflavones protect against radiation-induced lung injury, but the mediators of radioprotection remain unclear. We investigated the effect of radiation on myeloid-derived suppressor cells (MDSCs) in the lung and their modulation by soy isoflavones for a potential role in protection from radiation-induced lung injury.

Methods

BALB/c mice (5–6 weeks old) received a single 10 Gy dose of thoracic irradiation and soy isoflavones were orally administrated daily before and after radiation at 1 mg/day. Arginase-1 (Arg-1) and nuclear factor κB (NF-κB) p65 were detected in lung tissue by western blot analysis and immunohistochemistry. Lung MDSC subsets and their Arg-1 expression were analyzed by flow cytometry. Cytokine levels in the lungs were measured by ELISA.

Results

At 1 week after radiation, CD11b⁺ cells expressing Arg-1 were decreased by radiation in lung tissue yet maintained in the lungs treated with radiation and soy isoflavones. Arg-1 was predominantly expressed by CD11b⁺Ly6C^lowLy6G⁺ granulocytic MDSCs (gr-MDSCs). Arg-1 expression in gr-MDSCs was reduced by radiation and preserved by supplementation with soy isoflavones. A persistent increase in Arg-1⁺ cells was observed in lung tissue treated with combined radiation and soy isoflavones at early and late time points, compared to radiation alone. The increase in Arg-1 expression mediated by soy isoflavones could be associated with the inhibition of radiation-induced activation of NF-κB and the control of pro-inflammatory cytokine production demonstrated in this study.

Conclusion

A radioprotective mechanism of soy isoflavones may involve the promotion of Arg-1-expressing gr-MDSCs that could play a role in downregulation of inflammation and lung radioprotection.

Radiotherapy and MVA-MUC1-IL-2 vaccine act synergistically for inducing specific immunity to MUC-1 tumor antigen

Background

We previously demonstrated that tumor irradiation potentiates cancer vaccines using genetic modification of tumor cells in murine tumor models. To investigate whether tumor irradiation augments the immune response to MUC1 tumor antigen, we have tested the efficacy of tumor irradiation combined with an MVA-MUC1-IL2 cancer vaccine (Transgene TG4010) for murine renal adenocarcinoma (Renca) cells transfected with MUC1.

Methods

Established subcutaneous Renca-MUC1 tumors were treated with 8 Gy radiation on day 11 and peritumoral injections of MVA-MUC1-IL2 vector on day 12 and 17, or using a reverse sequence of vaccine followed by radiation. Growth delays were monitored by tumor measurements and histological responses were evaluated by immunohistochemistry. Specific immunity was assessed by challenge with Renca-MUC1 cells. Generation of tumor-specific T cells was detected by IFN-γ production from splenocytes stimulated in vitro with tumor lysates using ELISPOT assays.

Results

Tumor growth delays observed by tumor irradiation combined with MVA-MUC1-IL-2 vaccine were significantly more prolonged than those observed by vaccine, radiation, or radiation with MVA empty vector. The sequence of cancer vaccine followed by radiation two days later resulted in 55–58% complete responders and 60% mouse long-term survival. This sequence was more effective than that of radiation followed by vaccine leading to 24–30% complete responders and 30% mouse survival. Responding mice were immune to challenge with Renca-MUC1 cells, indicating the induction of specific tumor immunity. Histology studies of regressing tumors at 1 week after therapy, revealed extensive tumor destruction and a heavy infiltration of CD45⁺ leukocytes including F4/80⁺ macrophages, CD8⁺ cytotoxic T cells and CD4⁺ helper T cells. The generation of tumor-specific T cells by combined therapy was confirmed by IFN-γ secretion in tumor-stimulated splenocytes. An abscopal effect was measured by rejection of an untreated tumor on the contralateral flank to the tumor treated with radiation and vaccine.

Conclusions

These findings suggest that cancer vaccine given prior to local tumor irradiation augments an immune response targeted at tumor antigens that results in specific anti-tumor immunity. These findings support further exploration of the combination of radiotherapy with cancer vaccines for the treatment of cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s40425-016-0204-3) contains supplementary material, which is available to authorized users.

Extraction, purification and anti-radiation activity of persimmon tannin from Diospyros kaki L.f

In this study, persimmon tannin was extracted from Diospyros kaki L.f. using ultrasound-assisted extraction and purified by D101 macroporous resin column chromatography and polysulfone ultrafiltration membrane. The tannin content of the final persimmon tannin extracts was attained to 39.56% calculated as catechin equivalents. Also, the radioprotective effects of persimmon tannin for HEK 293T cells proliferation and apoptosis after Gamma irradiation were investigated by CCK-8, Hoechst 33258 staining, flow cytometry assay and intracellular reactive oxygen species assay (ROS). Persimmon tannin was pre-incubated with HEK 293T cells for 12 h prior to Gamma irradiation. It was found that pretreatment with persimmon tannin increased cell viability and inhibited generation of Gamma-radiation induced ROS in HEK 293T cells exposed to 8 Gy Gamma-radiation. The percentage of apoptotic cells were only 6.7% when the radiation dose was 8 Gy and pretreated with 200 μg/ml of persimmon tannin. All these results indicated that persimmon tannin offered a potent radioprotective effect on cell vitality and cell apoptosis of Gamma-radiation exposure in HEK 293T cells. This study would serve as a pre-clinical evaluation of persimmon tannin for use in people with radiation protection.