Publication

Abstract : Syngeneic orthotopic tumor models offer an optimal functional tumor–immune interface for hepatocellular carcinoma research. Yet, unpredictable growth kinetics and spontaneous regression pose major obstacles. Efficient induction protocols and continuous monitoring are therefore essential. Routine exploratory surgeries are ethically untenable, making non-invasive imaging modalities attractive alternatives. High-resolution magnetic resonance imaging and microcomputed tomography deliver detailed insights but incur substantial equipment costs, radiation risks, time demands, and require specialized expertise—challenges that limit their routine use. In contrast, ultrasound (US) imaging emerges as a cost-effective, radiation-free, and rapid approach, facilitating practical and ethical longitudinal assessment of tumor progression in preclinical studies. AIM To optimize the orthotopic hepatocellular carcinoma model and evaluate the potential of US imaging for accurate and cost-effective tumor monitoring. METHODS Hepatocellular carcinoma was induced in 28 Sprague Dawley rats by implanting 5 × 106 N1S1 cells into the left lateral hepatic lobe. Tumor progression was monitored weekly via US. Upon reaching 100-150 mm³, an experimental group (n = 14) received Sorafenib (40 mg/kg) orally on alternate days for 28 days; efficacy was compared to untreated controls. US accuracy was validated against micro-computed tomography, gross caliper measurements and histopathological analysis. Reliability and operator proficiency in US assessment were also evaluated. RESULTS US images procured 7-day post-surgery revealed a well-defined hypoechoic nodule at the left liver lobe tip, confirming successful tumor induction (mean volume 130 ± 39 mm³). Only three animals exhibited spontaneous regression by week 2, underscoring the model’s stability. Sorafenib treatment elicited a marked tumor reduction (678 ± 103 mm³) vs untreated control (6005 ± 1760 mm³). US assessment demonstrated robust intra and interobserver reproducibility with high sensitivity and specificity for tumor detection. Moreover, US derived volumes correlated strongly with gross caliper measurements, histopathological analysis, and microcomputed tomography imaging, validating its reliability as a non-invasive monitoring tool in preclinical hepatocellular carcinoma studies. CONCLUSION The results demonstrate that US imaging is a reliable, cost-effective, and animal sparing approach with an easy to-master protocol, enabling monitoring of tumor progression and therapeutic response in orthotopic liver tumor models.