Abstract: Objective To investigate the association between Yes⁃associated protein (YAP) signaling activation and the clinical characteristics of patients with hepatocellular carcinoma (HCC), and to analyze the potential molecular mechanism by which YAP signaling promotes HCC progression through extracellular matrix (ECM) remodeling. Methods The tissue samples and clinicopathological data of 116 HCC patients who underwent liver resection at the Guangxi Medical University Cancer Hospital from May 2018 to July 2019 were included. Patients were classified based on a YAP upregulated gene set using gene set variation analysis method. Transcriptomic sequencing was performed to investigate the clinical significance and molecular characteristics of YAP signaling activation, with validation conducted using the HCC cohort from The Cancer Genome Atlas database. Single⁃cell RNA sequencing data from 10 HCC samples were obtained from the Gene Expression Omnibus database, and molecular characteristics of malignant cells with high YAP scores were analyzed, and CellChat algorithm was employed to investigate the interaction mechanism between high YAP malignant cells and fibroblasts. Results The overall survival of patients in the high YAP score group was significantly shorter than that of the low YAP score group (P<0.001). Additionally, the high YAP score group was associated with a higher prevalence of microvascular invasion (P<0.001), advanced Edmondson grading (P=0.005), and advanced Barcelona Clinic Liver Cancer staging (P=0.008). High YAP score was an independent risk factor for overall survival in HCC patients (HR=2.467, 95%CI: 1.121-5.429, P=0.025). Differential gene expression analysis revealed that up⁃regulated genes in the high YAP score group were significantly enriched in ECM⁃related signaling pathways. Single⁃cell analysis revealed that ECM stiffness promoted YAP signaling activation in myofibroblast⁃like cancer⁃associated fibroblasts (myCAF), further enhanced the expression of fibrosis⁃related genes and accelerated ECM deposition and remodeling. Additionally, CellChat analysis demonstrated that myCAF specifically activated YAP signaling in malignant cells via the COL1A1/COL1A2⁃CD44 ligand⁃receptor axis. Conclusions YAP signaling activation was strongly associated with poor prognosis in HCC patients. It induced myCAF to secrete fibrosis⁃related genes, increasing ECM stiffness, which in turn further activated YAP signaling in malignant cells via the COL1A1/COL1A2⁃CD44 axis, forming a positive feedback loop.

Key words: Hepatocellular carcinoma, Extracellular matrix, Yes?associated protein, Stiffness