The Wnt/β-catenin-P2-HNF4α feedback loop facilitates colorectal tumorigenesis and malignancy.

[BACKGROUND] The Wnt/β-catenin signaling pathway is a crucial regulator of colorectal cancer (CRC) development; however, its downstream targets and mechanistic contributions to tumorigenesis remain incompletely understood. Hepatocyte nuclear factor 4 alpha (HNF4α), a transcription factor primarily studied in liver function and hepatocarcinogenesis, has an unclear role in CRC. This study investigates the antagonistic and synergistic effects of HNF4α isoforms driven by the P1 and P2 promoters on Wnt/β-catenin signaling in colorectal cancer.

[METHODS] We assessed P1/P2-HNF4α expression and its regulation by Wnt/β-catenin signaling using bulk RNA sequencing (RNA-seq), single-cell RNA sequencing (scRNA-seq), in vitro and in vivo CRC models, and clinical tumor samples. Chromatin immunoprecipitation sequencing (ChIP-seq) was performed to determine the regulatory effect of TCF7L1 on HNF4α. Clinical correlations between P1/P2-HNF4α levels and Wnt/β-catenin activity were analyzed using immunohistochemistry, RNA sequencing, and Spearman's rank correlation. Statistical significance was determined using Student's t-test and ANOVA.

[RESULTS] P2-HNF4α was significantly overexpressed in CRC tissues compared to normal controls and significantly promoted tumor growth in subcutaneous xenograft models using nude mice. Mechanistically, P2-HNF4α was transcriptionally activated by the Wnt/β-catenin/TCF7L1 axis, creating a positive feedback loop that amplified oncogenic Wnt signaling. Clinically, P2-HNF4α expression strongly correlated with Wnt/β-catenin pathway activation in patient samples (r = 0.58, p < 0.0001). Functionally, P1/P2-HNF4α knockdown suppressed CRC cell proliferation and inhibited Wnt-driven tumorigenesis.

[CONCLUSIONS] This study identifies P2-HNF4α as a novel downstream effector of the Wnt/β-catenin pathway and a critical driver of CRC progression. The Wnt/β-catenin/HNF4α feedback loop identified here provides mechanistic insights into colorectal carcinogenesis and highlights P2-HNF4α as a potential therapeutic target. These findings may inform strategies to disrupt Wnt signaling hyperactivation in CRC.