Abstract 2396: Longitudinal monitoring of stromal stiffness predicts immune escape in preclinical hepatocellular carcinoma

Abstract Background/Objectives: Increased tumor stiffness enhances disease progression and aggressiveness in several cancers. Stiffer extracellular tumor matrix hinders T cell trafficking and promotes immune escape. The interplay between liver tumor mechanical properties and hepatocellular immune cell landscape has not been fully investigated. The aim of our study is to correlate tumor stiffness quantified with shear wave elastography and tumor-infiltrating lymphocyte accumulation using a syngeneic orthotopic rat model of hepatocellular carcinoma (HCC). Methods: Rat hepatoma cell line McA-RH7777 were implanted in the left liver lobe of Buffalo rats. Maximum tumor size and stiffness were evaluated 3 weeks after implantation (baseline) and weekly for 14 days using ultrasound. The maximum tumor size of each rat was evaluated on transverse view of B-mode ultrasound. The elasticity of each rat was evaluated by shear wave elastography (SWE), and SWE measurements were obtained at the maximum tumor size in m/s. A circular region of interest was put manually on the SWE images to calculate tumor stiffness. SWE was performed 3 times for each rat at each time point, and the mean value of tumor stiffness was used for analysis. After 14 days, tumors were harvested for histology and immune cell isolation. Isolated cells were stained with CD3, CD4, CD8, CD25, CD45, CD103, CD161, CD279 (PD-1), FOXP3, IL17A, and INF-g and submitted to spectral cytometry. Results: Shear wave speed at baseline and at 14 days ranged from 1.95 to 3.07 m/s and from 2.25 to 3.26 m/s, respectively. The rate of longitudinal increase or decrease in tumor stiffness measured by SWE is inversely correlated with intratumoral infiltration of CD45+/CD3+, CD3+/CD8+ T cells and IFN-producing CD3+/CD8+ T cells (P=0.015, r=-0.62[-0.857, -0.15], P<0.01, r=-0.74[-0.913, -0.346], P=0.02, r=-0.6[-0.859, -0.107]). Intratumoral CD3+/CD4+ T cells did not significantly correlate with the rate of change in stiffness but did correlate with the rate of change in tumor size measured by B-mode ultrasound (P=0.03, r=-0.58[-0.850, -0.0730]). Conclusion: Our results confirm previous reports of immune escape in stiffer solid tumors in the context of HCC. Findings suggest that longitudinal monitoring of tumor stiffness can be useful for the assessment of immune cell infiltration. Citation Format: Kiyoyuki Minamiguchi, Andrea Cortes, Patricia Da Costa Lopez, Malea Williams, Simone Anfossi, Marites Melancon, Rony Avritscher. Longitudinal monitoring of stromal stiffness predicts immune escape in preclinical hepatocellular carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2396.