Genome-scale CRISPR screening uncovers SRSF6 as a target to sensitize hepatocellular carcinoma to radiotherapy

Radiotherapy confers clinical benefits to patients with hepatocellular carcinoma (HCC) across all stages, yet its clinical efficacy is limited by radioresistance. This study aimed to identify key regulators of HCC radiosensitivity through genome-wide functional screening.

A genome-wide CRISPR-Cas9 screen in Huh7 cells identified radiosensitivity regulators, with SRSF6 validated by siRNA knockdown and γ-H2AX assessment. Stable shRNA-mediated SRSF6 knockdown was established in Huh7 and HepG2 cells, followed by clonogenic, EdU incorporation, apoptosis, micronucleus, and comet assays. Mechanistically, RNA-seq, Western blotting, mRNA stability assays, RIP-qPCR, and RAD51 overexpression rescue assays were performed. The therapeutic potential of the SRSF6 inhibitor indacaterol was evaluated using MTS assays, HCC xenograft mouse models (BALB/c-nu/nu, n = 28), and HCC patient-derived organoids (PDOs) (n = 3). In addition, SRSF6 expression and its correlation with patient survival were analyzed using data from The Cancer Genome Atlas and a tissue microarray (n = 14 HCC and 14 paired adjacent non-tumorous liver samples).

We identified the RNA-binding protein SRSF6 as a driver of HCC radioresistance. SRSF6 depletion enhanced the radiosensitivity of HCC cells (p <0.05-0.0001) by post-transcriptionally destabilizing the mRNAs of critical DNA repair genes (p <0.05-0.0001), thereby impairing radiation-induced DNA damage repair. The radiosensitizing effect of SRSF6 depletion was partially abrogated by ectopic overexpression of the core DNA repair protein RAD51 (p <0.05-0.001). Indacaterol exhibited cytotoxic effects on HCC cells (p <0.05-0.0001) and enhanced the antitumor efficacy of radiation in vivo (p <0.05-0.0001), as further validated across multiple HCC patient-derived organoids (p <0.05-0.0001).

SRSF6 is a key regulator of HCC radioresistance through its post-transcriptional control of DNA repair capacity, and represents a novel therapeutic target to sensitize HCC to radiotherapy.

In this study, we performed a genome-wide CRISPR-Cas9 knockout library screen to dissect the molecular determinants governing HCC radiosensitivity, and identified RNA-binding protein SRSF6 as a driver of HCC radioresistance. We demonstrate that SRSF6 depletion disrupts the post-transcriptional stability of key DNA repair gene mRNAs and enhances HCC radiosensitivity. These findings are important for radiation oncologists and translational researchers, as they identify SRSF6-dependent RNA regulation as a critical determinant of radiotherapy response in HCC. Practically, we show that the clinically approved bronchodilator indacaterol suppresses SRSF6 function and enhances the antitumor efficacy of radiotherapy, offering a readily repurposable pharmacological strategy to overcome radioresistance. These implications are based on preclinical evidence across multiple models; however, future clinical trials are needed to validate the safety and efficacy of indacaterol-based radiosensitization in patients with HCC.