Expression of non-homologous end joining factor, Ku80, is negatively correlated with PD-L1 expression in cancer cells after X-ray irradiation

Takuya Kumazawa; Yasumasa Mori; Hiro Sato; Tiara Bunga Mayang Permata; Yuki Uchihara; Shin-Ei Noda; Kohei Okada; Sangeeta Kakoti; Keiji Suzuki; Hayato Ikota; Hideaki Yokoo; Soehartati Gondhowiardjo; Takashi Nakano; Tatsuya Ohno; Atsushi Shibata

doi:10.3892/ol.2021.13147

Expression of non-homologous end joining factor, Ku80, is negatively correlated with PD-L1 expression in cancer cells after X-ray irradiation

Oncol Lett. 2022 Jan;23(1):29. doi: 10.3892/ol.2021.13147. Epub 2021 Nov 23.

Authors

Takuya Kumazawa^{1

2}, Yasumasa Mori^{1

3}, Hiro Sato¹, Tiara Bunga Mayang Permata⁴, Yuki Uchihara⁵, Shin-Ei Noda⁶, Kohei Okada¹, Sangeeta Kakoti^{1

5

7}, Keiji Suzuki⁸, Hayato Ikota⁹, Hideaki Yokoo¹⁰, Soehartati Gondhowiardjo⁴, Takashi Nakano³, Tatsuya Ohno¹, Atsushi Shibata⁵

Affiliations

¹ Department of Radiation Oncology, Graduate School of Medicine, Gunma University, Maebashi, Gunma 3718511, Japan.
² Department of Radiation Oncology, Saku Central Hospital Advanced Care Center, Saku, Nagano 3850051, Japan.
³ National Institute of Radiological Sciences, National Institute for Quantum and Radiological Science and Technology, Chiba 2638555, Japan.
⁴ Department of Radiation Oncology, Faculty of Medicine Universitas Indonesia, Dr Cipto Mangunkusumo National General Hospital, Jakarta 10430, Indonesia.
⁵ Signal Transduction Program, Gunma University Initiative for Advanced Research, Gunma University, Maebashi, Gunma 3718511, Japan.
⁶ Department of Radiation Oncology, Comprehensive Cancer Centre, International Medical Centre, Saitama Medical University, Saitama 3501298, Japan.
⁷ Department of Radiation Oncology, Tata Memorial Centre, Homi Bhabha National Institute, Mumbai, Maharashtra 400012, India.
⁸ Department of Radiation Medical Sciences, Atomic Bomb Disease Institute, Nagasaki University, Nagasaki 852-8523, Japan.
⁹ Clinical Department of Pathology, Gunma University Hospital, Maebashi, Gunma 3718511, Japan.
¹⁰ Department of Human Pathology, Gunma University Graduate School of Medicine, Maebashi, Gunma 3718511, Japan.

Abstract

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<0.001). The present study also confirmed that short interfering RNA-mediated Ku80 depletion was associated with greater X-ray-induced PD-L1 up-regulation in HeLa cells. These results indicated that radiotherapy could enhance PD-L1 induction in tumour cells with low Ku80 expression in a clinical setting. Furthermore, these data highlighted Ku80 as a potential predictive biomarker for immune checkpoint therapy combined with radiotherapy.

Keywords: DNA damage response; Ku80; biomarker; immunotherapy; programmed death-1 ligand; radiotherapy.

Grants and funding

This study was supported by JSPS KAKENHI (grant nos. JP17H04713 and JP19K08195), the Takeda Science Foundation, the Uehara Memorial Foundation, the Astellas Foundation for Research on Metabolic Disorders, The Kanae Foundation for the Promotion of Medical Science, the Yasuda Memorial Medicine Foundation and the Nakajima Foundation. This study was also supported by the Program of the Network-Type Joint Usage/Research Centre for Radiation Disaster Medical Science of Hiroshima University, Nagasaki University and Fukushima Medical University and the Grants-in-Aid from the Ministry of Education, Culture, Sports, Science and Technology of Japan for programmes for Leading Graduate Schools, Cultivating Global Leaders in Heavy Ion Therapeutics and Engineering.