Introduction

Hepatocellular carcinoma (HCC) is the sixth most common malignancy and the third leading cause of cancer-related deaths globally, with increasing incidence and mortality rates. Most patients are diagnosed at advanced stages, missing the opportunity for radical treatment. Sorafenib, a tyrosine kinase inhibitor, is the first-line treatment for advanced HCC; however, drug resistance typically develops within 6 months. Therefore, elucidating the mechanisms of sorafenib resistance and identifying new therapeutic targets are of significant importance. Our study focuses on the role and mechanism of Ribonucleotide Reductase M2 (RRM2) in sorafenib resistance in HCC.

Aims & Methods

The primary objective of this study is to investigate the role of RRM2 in sorafenib resistance in HCC and explore its underlying mechanisms. We aim to clarify whether RRM2 regulates aerobic glycolysis via the HIF-1α/HK2 pathway, thereby affecting sorafenib sensitivity. Our methods include:

• Analyzing RRM2 expression in HCC tissues and its correlation with clinical outcomes, such as disease-free survival (DFS) and overall survival (OS).
• Establishing sorafenib-resistant HCC cell lines (LM3-SR and SMMC7721-SR) and manipulating RRM2 expression using lentiviral vectors for knockdown and overexpression.
• Conducting in vitro experiments to assess the effects of RRM2 on cell proliferation, apoptosis, glycolysis, and sorafenib sensitivity using assays such as CCK8, flow cytometry, and Seahorse analysis.
• Performing in vivo studies using a nude mouse xenograft model to evaluate the impact of RRM2 knockdown on tumor growth and sorafenib efficacy.
• Utilizing RNA-seq, Western blot, PCR, and other techniques to investigate the molecular mechanisms, including the potential regulation of HIF-1α and HK2 by RRM2.

Results

• Clinical Correlation: RRM2 expression was significantly higher in HCC tissues compared to adjacent normal tissues. Higher RRM2 levels were associated with shorter DFS and OS in HCC patients.
• In Vitro Findings: RRM2 knockdown in sorafenib-resistant HCC cells (LM3-SR and SMMC7721-SR) increased sensitivity to sorafenib, as evidenced by reduced cell viability and increased apoptosis. Additionally, RRM2 knockdown decreased glycolysis, as indicated by reduced lactate production and glucose uptake. Conversely, RRM2 overexpression in HCC cells promoted resistance to sorafenib and enhanced glycolysis.
• Molecular Mechanisms: RRM2 regulated the expression of glycolytic enzymes, particularly HK2, through the HIF-1α pathway. Knockdown of RRM2 reduced HIF-1α and HK2 expression, while overexpression of HIF-1α or HK2 could reverse the effects of RRM2 knockdown on glycolysis and sorafenib sensitivity.
• In Vivo Validation: In a nude mouse xenograft model, RRM2 knockdown enhanced the inhibitory effects of sorafenib on tumor growth, as demonstrated by reduced tumor volume and increased apoptosis.

Conclusion

Our study demonstrates that RRM2 plays a crucial role in sorafenib resistance in HCC by regulating aerobic glycolysis via the HIF-1α/HK2 pathway. Targeting RRM2 or its downstream pathways may represent a promising strategy to overcome sorafenib resistance and improve therapeutic outcomes in HCC patients. Future work will focus on further elucidating the molecular mechanisms and exploring the potential clinical applications of RRM2 as a therapeutic target.

Disclosure

The authors declare that they have no conflict of interest.

Introduction

Colorectal cancer is one of the most prevalent cancers with an estimated 1.8 million newly developed cases and 0.9 million cancer-related deaths in 2020.Resection of adenomatous polyps decreases the incidence and mortality of colorectal cancer. Narrow-band imaging (NBI) and linked color imaging (LCI) are the most predominantly conducted image-enhanced endoscopy using short-wavelength light but their usefulness in screening and surveillance colonoscopy remains controversial.

Aims & Methods

Our aim in this study was to investigate the superiority of LCI over NBI for ADR.
This is an open-label, two-arm, parallel, 1:1, multicenter, randomized, controlled, right-sided colonoscopy study and included patients who underwent colonoscopy at six endoscopy centers in Japan from November 2020 through November 2023. The patients were randomly assigned to undergo a proximal-sided colonoscopy (cecum and ascending colon) with LCI or 2G-NBI followed by WLI. The primary outcome included the ADR and secondary outcomes involved polyp detection rate (PDR), polyp miss rate, and adenoma miss rate. This study was registered on November 4, 2020, in the Japan Registry of Clinical Trials (jRCT1012200007).

Results

During the study period, 1,655 patients were randomly assigned to the LCI group (828 patients, primary LCI followed by secondary WLI) and the 2G-NBI group (827 patients, primary 2G-NBI followed by secondary WLI), and 776 patients in the LCI group and 752 patients in the 2G-NBI groups were finally analyzed. The ADRs were 26.7% and 23.4% and the PDRs were 32.6% and 28.9% in primary LCI and 2G-NBI, respectively, with no statistically significant differences in ADR and PDR between groups (P = 0.14 and P = 0.12). However, multivariate regression analysis revealed primary LCI observation as an independent predictor for reducing PDR in the secondary WLI (Odds ratio [OR]: 0.72, 95% confidence interval [CI]: 0.53−0.97, P = 0.029). Moreover, polyp analysis demonstrated that miss rates of adenomas and polyps were significantly lower in the LCI group than in the NBI group (OR: 0.54, 95% CI: 0.39−0.76 in adenoma; OR: 0.59, 95% CI: 0.44−0.78 in polyp).

Conclusion

LCI is not superior to 2G-NBI in ADR and PDR in a clinical right-sided colonoscopy setting. However, LCI significantly reduced miss rates of adenomas and polyps.

Disclosure

Naohisa Yoshida has received lecture and/or consulting fees from Fujifilm and Olympus; Shoko Ono has received lecture and/or consulting fees from Fujifilm and Olympus; Momoko Tsuda has received lecture and/or consulting fees from Fujifilm; Nobuaki Yagi have received lecture and/or consulting fees from Fujifilm and Olympus; Mototsugu Kato has received lecture and/or consulting fees from Fujifilm. The remaining authors disclose no conflicts.