Pepsinogen/Proton Pump Co‐Expression in Barrett's Esophageal Cells Induces Cancer‐Associated Changes

Abstract

At the conclusion of this presentation, participants should better understand the carcinogenic potential of pepsin and proton pump expression in Barrett's esophagus.Objective: Barrett's esophagus (BE) is a well-known risk factor for esophageal adenocarcinoma (EAC). Gastric H + /K + ATPase proton pump and pepsin expression has been demonstrated in some cases of BE; however, the contribution of local pepsin and proton pump expression to carcinogenesis is unknown. In this study, RNA sequencing was used to examine global transcriptomic changes in a BE cell line ectopically expressing pepsinogen and/or gastric H + /K + ATPase proton pumps.Study Design: In vitro translational. Methods: BAR-T, a human BE cell line devoid of expression of pepsinogen or proton pumps, was transduced by lentivirus-encoding pepsinogen (PGA5) and/or gastric proton pump subunits (ATP4A, ATP4B). Changes relative to the parental line were assessed by RNA sequencing.Results: Top canonical pathways associated with protein-coding genes differentially expressed in pepsinogen and/or proton pump expressing BAR-T cells included those involved in the tumor microenvironment and epithelial-mesenchymal transition. Top upstream regulators of coding transcripts included TGFB1 and ERBB2, which are associated with the pathogenesis and prognosis of BE and EAC. Top upstream regulators of noncoding transcripts included p300-CBP, I-BET-151, and CD93, which have previously described associations with EAC or carcinogenesis. The top associated disease of both coding and noncoding transcripts was cancer.Conclusions: These data support the carcinogenic potential of pepsin and proton pump expression in BE and reveal molecular pathways affected by their expression. Further study is warranted to investigate the role of these pathways in carcinogenesis associated with BE.

The Protease Inhibitor Amprenavir Protects against Pepsin-Induced Esophageal Epithelial Barrier Disruption and Cancer-Associated Changes

“…Interestingly, an epidemiologic study demonstrated that long-term PPI therapy has no advantageous effect on COX-2 expression [ 72 ], suggesting that nonacid constituents of refluxate may be responsible for continued dysregulation of COX-2 in patients taking PPIs. Stable ectopic coexpression of pepsinogen and the gastric proton pump in a BE cell line also led to upregulated expression of transcripts associated with BE, EAC, and carcinogenesis including TGFB1 and ERBB2 [ 35 ]; pathway analysis of the global transcriptomic changes identified cancer as the top associated disease, regulation of epithelial–mesenchymal transition by growth factors as a top associated canonical pathway and cell cycle regulation, cell growth/proliferation/death/survival, DNA replication and repair, and lipid metabolism as top associated networks [ 35 ]. In contrast to the hyperproliferative effects of pepsin, acid (pH4) alone has been shown to exert an antiproliferative effect in esophageal cells [ 73 , 74 ].…”

“…Further, the capacity of amprenavir to rescue a pepsin-induced proinvasive cell phenotype characterized by E-cadherin RIP and MMP induction supports its chemopreventive potential. This is particularly intriguing in light of the failure of PPIs to demonstrate chemopreventive benefits for patients with GERD as well as burgeoning evidence that pepsin promotes carcinogenic changes in the esophagus [ 23 , 24 , 30 , 31 , 35 , 53 , 57 , 61 ]. Future in vitro work is warranted to address amprenavir protection against additional pepsin-induced molecular changes harboring a strong correlation with GERD severity and/or EAC, such as IL-8 and PTGS2/COX-2, and cancer-related cellular processes known to be impacted by pepsin such as cell-cycle regulation.…”

“…Instead, studies indicate that PPIs may increase the concentration and toxicity of nonacid constituents of refluxate [ 30 , 32 ]. In the context of weakly to nonacidic refluxate such as that of patients taking PPIs or in extraesophageal reflux, the gastric enzyme pepsin is active up to pH6.5 and stable up to pH8 and can be endocytosed, leading to inflammatory and carcinogenic changes in the aerodigestive tract mucosa, including in the esophagus [ 8 , 33 , 34 , 35 , 36 ].…”

Cancer Risk in Barrett’s Esophagus: A Clinical Review

“…Samuels et al have shown that pepsin exposure to laryngeal squamous epithelium induces cancer-associated changes in these cells [ 124 ]. Other studies have demonstrated that the ectopic expression of proton pumps and/or pepsin in BE cells leads to the genetic and molecular signaling pathway changes associated with EAC [ 125 ].…”

“…The ectopic expression of proton pumps and pepsin in a BE cell line leads to the differential expression of the genes involved in the kinetochore metaphase signaling, tumor microenvironment, and regulation of epithelial-to-mesenchymal (EMT) transition by the growth factors pathways [ 125 ]. Dysfunction of the kinetochore metaphase signaling pathway is associated with polyploidy and aneuploidy in dividing cells; Scott et al have demonstrated the abnormal expression of kinetochore constituents in BE and EAC cells that contributes to chromosome congression failure during mitosis.…”