NR1H4

Overview

NR1H4 (nuclear receptor subfamily 1 group H member 4), commonly known as FXR (farnesoid X receptor), is a bile acid-activated nuclear receptor that regulates bile acid homeostasis, lipid metabolism, and intestinal barrier integrity. FXR is the master transcriptional regulator of bile acid synthesis and transport in the liver and intestine. Downregulation of FXR in cholangiocarcinoma allows accumulation of toxic bile acids and unleashes oncogenic signaling via STAT3 and BCL2L1 (Bcl-xL).

Alterations observed in the corpus

  • NR1H4 (FXR) is downregulated in primary cholangiocarcinoma (CCA); FXR activation by CDCA or GW4064 suppresses CCA proliferation via SHP-mediated STAT3 inhibition and downregulation of BCL2L1 (Bcl-xL). Heterogeneous expression across CCA subtypes (pCCA/dCCA H-score <120) suggests DNMT-inhibitor combinations are needed for effective reactivation. PMID:25608663

Cancer types (linked)

  • CHOL / IHCH / EHCH / PHCH: FXR downregulation is a recurrent feature of CCA across subtypes; loss of FXR activity unleashes STAT3 phosphorylation and BCL2L1-mediated survival signaling. FXR agonist obeticholic acid (OCA/INT-747) and synthetic agonist GW4064 are under preclinical and early clinical evaluation. PMID:25608663

Co-occurrence and mutual exclusivity

  • FXR (NR1H4) loss-of-function cooperates with GPBAR1 (TGR5) and S1PR2 bile acid receptor dysregulation in the gut-liver axis oncogenic cascade; STAT3 and BCL2L1 are downstream effectors. PMID:25608663

Therapeutic relevance

  • Obeticholic-acid (OCA/INT-747): FXR agonist that reactivates SHP/LRH-1 to suppress CCA proliferation and migration; heterogeneous FXR expression across subtypes suggests DNMT inhibitor combination needed. PMID:25608663

Open questions

  • FXR systemic loss vs tissue-specific activation carries opposing oncogenic risks (β-catenin-driven GI tumorigenesis on hyperactivation), requiring long-term safety studies. Whether CpG methylation of NR1H4 promoter is the dominant mechanism of FXR silencing in CCA is unresolved. PMID:25608663

Sources

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