Regulation of periostin expression by Notch signaling in hepatocytes and liver cancer cell lines.

Notch signaling is involved in both differentiation of hepatocyte progenitors and hepatocellular carcinoma (HCC). The mechanism whereby Notch signaling regulates cellular transformation in hepatocytes is still controversial. This study investigated the impact of overexpressing truncated intracellular Notch1 (NICD1) on transcriptomic profiles of immortalized human hepatocytes. RNA sequencing and gene ontology enrichment analysis revealed that extracellular matrix organization and hyaluronan biosynthesis process gene sets are among those affected by Notch hyperactivation. The relationship between Notch signaling and periostin, an extracellular matrix protein highly expressed in HCC, were further studied. Modulating Notch signaling through NICD1 overexpression or treatment with a gamma secretase inhibitor resulted in increased or decreased periostin expression, respectively, in HCC and liver bile duct carcinoma cell lines. Based on The Cancer Genome Atlas database, mRNA levels of NOTCH1 and POSTN are positively correlated in tumor tissues but not in nontumor tissues. Two consensus RBPJ binding motifs were identified in the -3932/-3921 and + 2522/+2533 bp of POSTN regulatory regions, and NOTCH1 is associated with these binding sites in a liver bile duct carcinoma cell line. Taken together, these results indicate that Notch signaling directly regulates transcription of POSTN in hepatocytes and liver cancer cell lines and may be a candidate for drug targeting in liver cancer.