Search

The growing importance of antitumour immunity by cancer immunotherapy has prompted studies on radiotherapy‑induced immune response. Previous studies have indicated that programmed cell death‑1 ligand (PD‑L1) expression is regulated by DNA damage signalling. However, PD‑L1 up‑regulation after radiotherapy has not been fully investigated at the clinical level, particularly in the context of expression of DNA repair factors. The present study examined the correlation of mRNA expression between PD‑L1 and non‑homologous end joining (NHEJ) factors using The Cancer Genome Atlas database analysis. Among NHEJ factors, Ku80 mRNA expression was negatively correlated with PD‑L1 mRNA expression levels in several types of cancer (colon adenocarcinoma, breast invasive carcinoma, skin cutaneous melanoma, lung adenocarcinoma, head and neck squamous cell carcinoma, uterine corpus endometrial carcinoma, cervical squamous cell carcinoma and endocervical adenocarcinoma). To verify the negative correlation in clinical samples, the present study analysed whether Ku80 expression levels affected PD‑L1 up‑regulation after radiotherapy using cervical squamous cell carcinoma samples. Quantitative evaluation using software analysis of immunohistochemically stained slides revealed that patients with low Ku80 positivity in biopsy specimens demonstrated increased PD‑L1 expression levels after 10 Gy irradiation (Spearman's rank correlation coefficient=‑0.274; P=0.017). Furthermore, PD‑L1 induction levels in tumour cells after 10 Gy of irradiation were significantly inversely correlated with Ku80 expression levels (Spearman's rank correlation coefficient=‑0.379; P

The cell-killing effect of radiotherapy largely depends on unrepaired DNA double-stranded breaks (DSBs) or lethal chromosome aberrations induced by DSBs. Thus, the capability of DSB repair status is critically important in cancer cell-killing effect after ionizing radiation. Here, we investigate the involvement of the DNA damage signaling factors ataxia telangiectasia mutated (ATM) and ring finger protein (RNF) 8 and RNF168 in quiescent G0/G1 cells, which occupy the majority population in tumors, after high-linear-energy-transfer (LET) carbon-ion irradiation. Interestingly, ATM inhibition caused a substantial DSB repair defect after high-LET carbon-ion irradiation. Similarly, RNF8 or RNF168 depletion causes a substantial DSB repair defect. ATM inhibition in RNF8-depleted cells did not have an additive effect, suggesting that ATM and RNF8 function in the same pathway. Importantly, we found that RNF8 RING mutant show similar DSB repair defect, suggesting the requirement of ubiquitin ligase activity in this repair pathway. RNF8 FHA domain, which is required for the interaction with MDC1, is also required for DSB repair in this axis. Furthermore, depletion of p53 binding protein 1 (53BP1), which is an important downstream factor in RNF8-dependent DSB repair, is also required for this repair. Importantly, either ATM inhibition or RNF8 depletion increased the frequency of chromosomal breaks, but reduced dicentric chromosome formation, demonstrating that ATM/RNF8 is required for the rejoining of DSB ends for dicentric chromosome formation. Finally, we show that RNF8 depletion augmented radiosensitivity after high-LET carbon-ion irradiation. Taken together, these results suggest that the inhibition of RNF8 activity or its downstream pathway may augment the efficacy of high-LET carbon-ion therapy.

Radiotherapy induces an immune response in the cancer microenvironment that may influence clinical outcome. The present study aimed to analyse the alteration of CD8+ T‑cell infiltration and programmed death‑ligand 1 (PD‑L1) expression following radiotherapy in clinical samples from patients with uterine cervical squamous cell carcinoma. Additionally, the current study sought to analyse the association between these immune responses and clinical outcomes. A total of 75 patients who received either definitive chemoradiotherapy or radiotherapy were retrospectively analyzed. CD8+ T‑cell infiltration and PD‑L1 expression were determined by immunohistochemistry using biopsy specimens before radiotherapy (pre‑RT) and after 10 Gy radiotherapy (post‑10 Gy). The PD‑L1+ rate was significantly increased from 5% (4/75) pre‑RT to 52% (39/75) post‑10 Gy (P

Radiotherapy is an essential component of cancer therapy. Carbon ion radiotherapy (CIRT) promises to improve outcomes compared with standard of care in many cancers. Nevertheless, clinicians often observe in-field recurrence after CIRT. This indicates the presence of a subset of cancers that harbor intrinsic resistance to CIRT. Thus, the development of methods to identify and sensitize CIRT-resistant cancers is needed. To address this issue, we analyzed a unique donor-matched pair of clinical specimens: a treatment-naïve tumor, and the tumor that recurred locally after CIRT in the same patient. Exon sequencing of 409 cancer-related genes identified enrichment of somatic mutations in and in the recurrent tumor compared with the treatment-naïve tumor, indicating a pivotal role for FGFR signaling in cancer cell survival through CIRT. Inhibition of FGFR using the clinically available pan-FGFR inhibitor LY2874455 sensitized multiple cancer cell lines to carbon ions at 3 Gy (RBE: relative biological effectiveness), the daily dose prescribed to the patient. The sensitizer enhancement ratio was 1.66 ± 0.17, 1.27 ± 0.09, and 1.20 ± 0.18 in A549, H1299, and H1703 cells, respectively. Our data indicate the potential usefulness of the analytical pipeline employed in this pilot study to identify targetable mutations associated with resistance to CIRT, and of LY21874455 as a sensitizer for CIRT-resistant cancers. The results warrant validation in larger cohorts.