ESTRO meets Asia 2024 Congress Report

Uterine cervical cancer is one of the most common malignancies in developing countries, where it is recognised as a major public health problem. Incidence is increasing and girls are being diagnosed with it at younger ages than previously. Approximately 70-80% of cervical cancers are squamous cell carcinomas. Radiotherapy plays a crucial role in the treatment of cervical cancer because its use improves local control effectively and reduces the development of distant metastases, according to the encouraging results of several randomised trials. Unfortunately, nearly 50% of patients with cervical cancer do not respond to standard radiotherapy treatment due to tumour radioresistance. Acquired radioresistance during irradiation is considered one of the most important reasons for local tumour recurrence or treatment failure.

Fragments of transfer RNA (tRFs) are an emerging category of small non-coding RNAs that are generated from the cleavage of mature transfer RNAs (tRNAs) or tRNA precursors. The advance in high-throughput sequencing has contributed to the identification of increasing numbers of tRFs with critical functions in distinct physiological and pathophysiological processes. These tRFs can regulate cell viability, differentiation and homeostasis through multiple mechanisms and are thus considered critical regulators of human diseases, including cancer.

Through our research, we intended to confirm the biological role of tRFs in the acquisition of radioresistance and reveal potential ways to improve radiosensitivity in cervical squamous cell carcinoma. We screened and cultivated a radioresistant cell model (SiHa-RR) that was based on a human cervical squamous cell carcinoma cell line, SiHa, which had been irradiated with a sub-lethal radiation dose of 6Gy.

The radiosensitivity of the SiHa-RR cells was significantly reduced compared with SiHa cells, according to the fit of the cell survival curve for a "multi-target single hit model". Next, we detected the differential expression of tRFs between SiHa and SiHa-RR cells through RNA sequencing and tRF expression profiling. Label-free whole proteomic quantitative sequencing was performed on the SiHa-RR and SiHa, and Gene Ontology enrichment analysis was performed on differentially expressed proteins. It was found that differential expression was enriched mainly in the direction of redox-activity regulation and metal-ion regulation, which indicated that regulation of iron ions and antioxidant stress-related pathways played an important role in the creation of radioresistance in cervical squamous cell carcinoma cells. During examination of the main differentially expressed genes, it was found that many ferroptosis-related genes, including NRF2 and its downstream associates such as FTH1 and NQO1, were significantly upregulated in radioresistant cell lines. The protein interaction network showed that FTH1 and FTL were the key position genes, indicating that the iron metabolism regulation status of cervical squamous cell carcinoma had changed after radiotherapy.

We believe that the upregulation of anti-ferroptosis genes in cervical cancer cells after radiotherapy is the result of an adaptive response to the treatment, and that ferroptosis may be an important way in which radiotherapy kills tumour cells. Based on the expression profile analysis of tRFs, the relative expression level was verified through the use of real-time quantitative polymerase chain reaction, and the fragment known as AS-tDR-001098, which had a large differential expression fold consistent with the sequencing result trend, was selected for subsequent research. A regulation relationship between tRFs and the ferroptosis-related gene has been preliminarily confirmed. The differentially expressed tRFs may be involved in  the regulation of the development of radioresistance in cervical squamous cell carcinoma that is mediated by ferroptosis.

Professor Ning Wu, PhD, chief physician

Department of Radiation Oncology

China-Japan Union Hospital of Jilin University

Changchun, China

wuning@jlu.edu.cn