Background: Endoscopic therapy is the preferred approach for the management of Barrett's esophagus (BE) patients with high-grade dysplasia (HGD) and intramucosal carcinoma (IMC). Little is known about outcome differences in patients with HGD versus IMC.Objective: To determine and compare the rate of recurrent dysplasia or neoplasia in patients with HGD or IMC undergoing endoscopic therapy.Design: Retrospective cohort study.Patients: A total of 246 BE patients with either HGD or IMC referred for endoscopic therapy.Intervention: Patients underwent EMR and/or ablation therapy with the goal of complete eradication of all dysplasia/neoplasia and intestinal metaplasia (CE-IM). Patients were assigned to either the HGD or IMC group based on highest pathology grade at the start of therapy.Main Outcome Measurements: Complete eradication and recurrence of IM and/or HGD/neoplasia were assessed among patients with HGD versus IMC. Only patients with CE-IM (documented eradication of all dysplasia/neoplasia and IM on a single endoscopy) were included for analysis of recurrence rates and risk factors.Results: CE-IM was achieved in 113 of 135 patients (83.7%) with HGD and in 84 of 111 patients (75.7%) with IMC (P = . 16). Overall recurrence rates of dysplasia or neoplasia after CE-IM were similar in both groups (HGD, 8.0% vs IMC, 9.5%; P = . 44; relative risk, 1.2; 95% confidence interval, 0.5-3.0) and remained similar in patients with 5 years of surveillance after CE-IM (HGD, 13.5% vs IMC, 11.4%; P = . 53; relative risk, 0.85; 95% confidence interval, 0.3-2.7).Limitations: Retrospective, observational study and evolution of endoscopic modalities and experience.Conclusion: Endoluminal therapy can successfully achieve eradication of IM and dysplasia or neoplasia in BE patients with HGD and IMC at comparable rates. There were no differences in the rates of recurrent HGD/IMC in the 2 groups.

The central transcriptional response to hypoxia is mediated by the prolyl hydroxylase domain protein (PHD):hypoxia inducible factor (HIF) pathway. In this pathway, PHD prolyl hydroxylates and thereby negatively regulates the α-subunit of the transcription factor HIF (HIF-α). An important HIF target gene is that for erythropoietin (EPO), which controls red cell mass. Recent studies have identified PHD2 as the critical PHD isoform regulating the EPO gene. Other studies have shown that the inducibility of the HIF pathway diminishes as a function of age. Thus, an important question is whether the PHD2:EPO pathway is altered in the aging. Here, we employed a mouse line with a globally-inducible Phd2 conditional knockout allele to examine the integrity of the Phd2:Epo axis in young (six to eight months old) and aging (sixteen to twenty months old) mice. We find that acute global deletion of Phd2 results in a robust erythrocytosis in both young and aging mice, with both age groups showing marked extramedullary hematopoiesis in the spleen. Epo mRNA is dramatically upregulated in the kidney, but not in the liver, in both age groups. Conversely, other Hif targets, including Vegf, Pgk1, and Phd3 are upregulated in the liver but not in the kidney in both age groups. These findings have implications for targeting this pathway in the aging.

The ERYTHROPOIETIN (EPO) gene is regulated by the transcription factor Hypoxia Inducible Factor-α (HIF-α). In this pathway, Prolyl Hydroxylase Domain protein 2 (PHD2) hydroxylates two prolyl residues in HIF-α, which in turn promotes HIF-α degradation by the von Hippel Lindau (VHL) protein. Evidence that HIF-2α is the important isoform for EPO regulation in humans comes from the recent observation that mutations in the HIF2A gene are associated with cases of erythrocytosis. We report here a new erythrocytosis-associated mutation, p.Asp539Glu, in the HIF2A gene. Similar to all reported cases, the affected residue is in close vicinity and C-terminal to the primary hydroxylation site in HIF-2α, Pro531. This mutation, however, is notable in producing a rather subtle amino acid substitution. Nonetheless, we find that this mutation compromises binding of HIF-2α to both PHD2 and VHL, and we propose that this mutation is the cause of erythrocytosis in this individual.

A classic physiologic response to hypoxia in humans is the up-regulation of the ERYTHROPOIETIN (EPO) gene, which is the central regulator of red blood cell mass. The EPO gene, in turn, is activated by hypoxia inducible factor (HIF). HIF is a transcription factor consisting of an alpha subunit (HIF-alpha) and a beta subunit (HIF-beta). Under normoxic conditions, prolyl hydroxylase domain protein (PHD, also known as HIF prolyl hydroxylase and egg laying-defective nine protein) site specifically hydroxylates HIF-alpha in a conserved LXXLAP motif (where underlining indicates the hydroxylacceptor proline). This provides a recognition motif for the von Hippel Lindau protein, a component of an E3 ubiquitin ligase complex that targets hydroxylated HIF-alpha for degradation. Under hypoxic conditions, this inherently oxygen-dependent modification is arrested, thereby stabilizing HIF-alpha and allowing it to activate the EPO gene. We previously identified and characterized an erythrocytosis-associated HIF2A mutation, G537W. More recently, we reported two additional erythrocytosis-associated HIF2A mutations, G537R and M535V. Here, we describe the functional characterization of these two mutants as well as a third novel erythrocytosis-associated mutation, P534L. These mutations affect residues C-terminal to the LXXLAP motif. We find that all result in impaired degradation and thus aberrant stabilization of HIF-2 alpha. However, each exhibits a distinct profile with respect to their effects on PHD2 binding and von Hippel Lindau interaction. These findings reinforce the importance of HIF-2 alpha in human EPO regulation, demonstrate heterogeneity of functional defects arising from these mutations, and point to a critical role for residues C-terminal to the LXXLAP motif in HIF-alpha.

Transcriptionally erythropoietin (Epo) synthesis is tightly regulated by the hypoxia inducible factor (HIF), which is composed of one alpha and one beta subunit that are constitutively expressed. The beta subunit is non-variable, but three different alpha subunits give rise to three isoforms of HIF. The alpha subunit is proteasomally regulated in the presence of oxygen by hydroxylation of the proline in the LXXLAP motif of the oxygen dependent degradation (ODD) domain of HIFalpha, catalysed by members of the prolyl hydroxylase domain (PHD) family of enzymes. This allows the von Hippel Lindau (VHL) protein to associate with the alpha subunit, which is subsequently tagged with ubiquitin and degraded by the proteasome. Any defect in the oxygen sensing pathway that allows the alpha subunit to escape proteasomal regulation leads to elevated expression of HIF target genes.