Comparative Kinetic and Angiogenic Characterization of Syngeneic Heterotopic Murine Tumors by Using B-Mode and Doppler Ultrasonography

Syngeneic murine tumor models allow evaluating tumor immunity and immunotherapy. This study provides a comparative characterization of two murine syngeneic tumor models, CT26 (colon carcinoma) and F3II (sarcomatoid mammary carcinoma), heterotopically implanted in BALB/c mice and monitored longitudinally through non-invasive Doppler ultrasound imaging. Both models exhibited consistent tumor engraftment but markedly distinct biological patterns: CT26 demonstrated rapid, inoculum-dependent expansion, whereas F3II showed slower kinetics and early plateauing. Linear mixed-effects modeling confirmed that time significantly affected tumor volume, specific growth rate (SGR), and doubling time (DT), revealing a major exponential growth phase around day 20, coinciding with peak vascularity on Doppler assessment. Correlations between SGR, DT, and vascular indices indicated partial coupling between proliferation and angiogenesis. Immunohistochemistry revealed stronger CD3⁺ T-cell infiltration in CT26 and predominant nuclear NF-κB expression in F3II, reflecting divergent immuno-inflammatory microenvironments. These findings validate high-resolution ultrasound as a reliable and ethical tool for dynamic monitoring of tumor kinetics and perfusion in immunocompetent mice, consistent with the 3R principles (Replacement, Reduction, Refinement). Collectively, CT26 and F3II represent complementary biological systems to investigate the interplay between tumor growth, vascular adaptation, and immune regulation, providing a quantitative and translationally relevant framework for preclinical evaluation of anticancer and immunomodulatory therapies.