PPIL1 Drives Hepatocellular Carcinoma Progression and Cancer Stem Cell Self-renewal Through DAAM2-mediated Wnt/β-Catenin Activation.

BACKGROUND/AIM: Hepatocellular carcinoma (HCC) accounts for ~90% of primary liver cancer, which ranks as the third-leading cause of global cancer mortality. Emerging evidence establishes cancer stem cells (CSCs) as central regulators of HCC progression, metastasis, and therapeutic resistance, with stemness-related pathways like Wnt/β-catenin signaling critically maintaining CSC self-renewal. In this study, we aimed to investigate the role of Peptidyl-prolyl isomerase-like 1 (PPIL1) in HCC progression and CSC self-renewal. MATERIALS AND METHODS: PPIL1 expression patterns were systematically analyzed using The Cancer Genome Atlas Liver Hepatocellular Carcinoma (TCGA-LIHC) data and validated in primary HCC specimens via qRT-PCR and western blot. PPIL1 was knocked down in HCC cell lines using shRNAs, and cell viability, migration, and sphere formation were assessed in vitro. Xenograft mouse models were established to evaluate the effects of PPIL1 on tumor growth kinetics and liver CSC-related properties. Transcriptome analysis was performed to identify downstream targets and signaling pathways affected by PPIL1 knockdown. RESULTS: Our analysis revealed significantly elevated PPIL1 expression in HCC tumors and liver CSCs, with its expression level positively correlating with tumor stage and histological grade. PPIL1 knockdown effectively suppressed HCC cell proliferation, migration, and in vivo tumor growth. The essential role of PPIL1 in liver CSC maintenance was demonstrated by impaired sphere-forming capacity and diminished tumor initiation potential. Mechanistic studies identified PPIL1 as a regulator of Wnt/β-catenin signaling through transcriptional up-regulation of dishevelled associated activator of morphogenesis 2 (DAAM2). CONCLUSION: Our findings suggest PPIL1 to be a crucial regulator of HCC progression and liver CSC maintenance via DAAM2-mediated Wnt/β-catenin activation. This positions PPIL1 as a promising molecular target for HCC therapy, with particular relevance for addressing CSC-driven therapeutic resistance.