Origins of cancer: ain't it just mature cells misbehaving?

A pervasive view is that undifferentiated stem cells are alone responsible for generating all other cells and are the origins of cancer. However, emerging evidence demonstrates fully differentiated cells are plastic, can be coaxed to proliferate, and also play essential roles in tissue maintenance, regeneration, and tumorigenesis. Here, we review the mechanisms governing how differentiated cells become cancer cells. First, we examine the unique characteristics of differentiated cell division, focusing on why differentiated cells are more susceptible than stem cells to accumulating mutations. Next, we investigate why the evolution of multicellularity in animals likely required plastic differentiated cells that maintain the capacity to return to the cell cycle and required the tumor suppressor p53. Finally, we examine an example of an evolutionarily conserved program for the plasticity of differentiated cells, paligenosis, which helps explain the origins of cancers that arise in adults. Altogether, we highlight new perspectives for understanding the development of cancer and new strategies for preventing carcinogenic cellular transformations from occurring.

Paligenosis: Cellular Remodeling During Tissue Repair.

Complex multicellular organisms have evolved specific mechanisms to replenish cells in homeostasis and during repair. Here, we discuss how emerging technologies (e.g., single-cell RNA sequencing) challenge the concept that tissue renewal is fueled by unidirectional differentiation from a resident stem cell. We now understand that cell plasticity, i.e., cells adaptively changing differentiation state or identity, is a central tissue renewal mechanism. For example, mature cells can access an evolutionarily conserved program (paligenosis) to reenter the cell cycle and regenerate damaged tissue. Most tissues lack dedicated stem cells and rely on plasticity to regenerate lost cells. Plasticity benefits multicellular organisms, yet it also carries risks. For one, when long-lived cells undergo paligenotic, cyclical proliferation and redif-ferentiation, they can accumulate and propagate acquired mutations that activate oncogenes and increase the potential for developing cancer. Lastly, we propose a new framework for classifying patterns of cell proliferation in homeostasis and regeneration, with stem cells representing just one of the diverse methods that adult tissues employ.

Single-Cell Transcriptomics Reveals a Conserved Metaplasia Program in Pancreatic Injury.

BACKGROUND & AIMS: Acinar to ductal metaplasia (ADM) occurs in the pancreas in response to tissue injury and is a potential precursor for adenocarcinoma. The goal of these studies was to define the populations arising from ADM, the associated transcriptional changes, and markers of disease progression. METHODS: Acinar cells were lineage-traced with enhanced yellow fluorescent protein (EYFP) to follow their fate post-injury. Transcripts of more than 13,000 EYFP+ cells were determined using single-cell RNA sequencing (scRNA-seq). Developmental trajectories were generated. Data were compared with gastric metaplasia, KrasG12D-induced neoplasia, and human pancreatitis. Results were confirmed by immunostaining and electron microscopy. KrasG12D was expressed in injury-induced ADM using several inducible Cre drivers. Surgical specimens of chronic pancreatitis from 15 patients were evaluated by immunostaining. RESULTS: scRNA-seq of ADM revealed emergence of a mucin/ductal population resembling gastric pyloric metaplasia. Lineage trajectories suggest that some pyloric metaplasia cells can generate tuft and enteroendocrine cells (EECs). Comparison with KrasG12D-induced ADM identifies populations associated with disease progression. Activation of KrasG12D expression in HNF1B+ or POU2F3+ ADM populations leads to neoplastic transformation and formation of MUC5AC+ gastric-pit-like cells. Human pancreatitis samples also harbor pyloric metaplasia with a similar transcriptional phenotype. CONCLUSIONS: Under conditions of chronic injury, acinar cells undergo a pyloric-type metaplasia to mucinous progenitor-like populations, which seed disparate tuft cell and EEC lineages. ADM-derived EEC subtypes are diverse. KrasG12D expression is sufficient to drive neoplasia when targeted to injury-induced ADM populations and offers an alternative origin for tumorigenesis. This program is conserved in human pancreatitis, providing insight into early events in pancreas diseases.

ATF3 induces RAB7 to govern autodegradation in paligenosis, a conserved cell plasticity program.

Differentiated cells across multiple species and organs can re-enter the cell cycle to aid in injury-induced tissue regeneration by a cellular program called paligenosis. Here, we show that activating transcription factor 3 (ATF3) is induced early during paligenosis in multiple cellular contexts, transcriptionally activating the lysosomal trafficking gene Rab7b. ATF3 and RAB7B are upregulated in gastric and pancreatic digestive-enzyme-secreting cells at the onset of paligenosis Stage 1, when cells massively induce autophagic and lysosomal machinery to dismantle differentiated cell morphological features. Their expression later ebbs before cells enter mitosis during Stage 3. Atf3-/- mice fail to induce RAB7-positive autophagic and lysosomal vesicles, eventually causing increased death of cells en route to Stage 3. Finally, we observe that ATF3 is expressed in human gastric metaplasia and during paligenotic injury across multiple other organs and species. Thus, our findings indicate ATF3 is an evolutionarily conserved gene orchestrating the early paligenotic autodegradative events that must occur before cells are poised to proliferate and contribute to tissue repair.

ELAPOR1 is a secretory granule maturation-promoting factor that is lost during paligenosis.

A single transcription factor, MIST1 (BHLHA15), maximizes secretory function in diverse secretory cells (like pancreatic acinar cells) by transcriptionally upregulating genes that elaborate secretory architecture. Here, we show that the scantly studied MIST1 target, ELAPOR1 (endosome/lysosome-associated apoptosis and autophagy regulator 1), is an evolutionarily conserved, novel mannose-6-phosphate receptor (M6PR) domain-containing protein. ELAPOR1 expression was specific to zymogenic cells (ZCs, the MIST1-expressing population in the stomach). ELAPOR1 expression was lost as tissue injury caused ZCs to undergo paligenosis (i.e., to become metaplastic and reenter the cell cycle). In cultured cells, ELAPOR1 trafficked with cis-Golgi resident proteins and with the trans-Golgi and late endosome protein: cation-independent M6PR. Secretory vesicle trafficking was disrupted by expression of ELAPOR1 truncation mutants. Mass spectrometric analysis of co-immunoprecipitated proteins showed ELAPOR1 and CI-M6PR shared many binding partners. However, CI-M6PR and ELAPOR1 must function differently, as CI-M6PR co-immunoprecipitated more lysosomal proteins and was not decreased during paligenosis in vivo. We generated Elapor1-/- mice to determine ELAPOR1 function in vivo. Consistent with in vitro findings, secretory granule maturation was defective in Elapor1-/- ZCs. Our results identify a role for ELAPOR1 in secretory granule maturation and help clarify how a single transcription factor maintains mature exocrine cell architecture in homeostasis and helps dismantle it during paligenosis.NEW & NOTEWORTHY Here, we find the MIST1 (BHLHA15) transcriptional target ELAPOR1 is an evolutionarily conserved, trans-Golgi/late endosome M6PR domain-containing protein that is specific to gastric zymogenic cells and required for normal secretory granule maturation in human cell lines and in mouse stomach.

Close Observation versus Additional Surgery after Noncurative Endoscopic Resection of Esophageal Squamous Cell Carcinoma.

INTRODUCTION: After noncurative endoscopic submucosal dissection (ESD) of superficial esophageal squamous cell carcinoma (SESCC), additional esophagectomy is generally recommended. However, considering its high mortality and morbidity, it is uncertain if additional surgery improves the clinical outcomes. This study aimed to compare the clinical outcomes between patients who were observed without additional treatment and those who underwent radical esophagectomy. METHODS: A total of 52 patients with SESCC who underwent complete but noncurative ESD from January 2008 to December 2016 at the Samsung Medical Center and Asan Medical Center in Korea were retrospectively analyzed. Clinicopathologic characteristics and oncologic outcomes were compared between the observation group (n = 23) and the additional surgery group (n = 29). RESULTS: During a mean follow-up of 34.4 and 41.7 months, respectively, the rates of death (observation vs. surgery, 17.4 vs. 10.3%; p = 0.686), recurrence (observation vs. surgery, 13 vs. 17.2%; p = 1.000), and disease-specific death (observation vs. surgery, 4.3 vs. 6.9%; p = 1.000) did not significantly differ between the 2 groups. The 3-year overall survival was 86.3 and 96.4%, respectively (p = 0.776). The 3-year recurrence-free survival (observation vs. surgery, 85.0 vs. 88.7%; p = 0.960) and disease-specific survival (observation vs. surgery, 95.2 vs. 96.4%; p = 0.564) also did not significantly differ. CONCLUSIONS: The clinical outcomes of close observation of noncuratively resected SESCC are comparable to those of additional surgery, at least in the midterm. The wait-and-see strategy could be a feasible management option after noncurative ESD of SESCC in selected patients.

ADAR1 Suppresses Interferon Signaling in Gastric Cancer Cells by MicroRNA-302a-Mediated IRF9/STAT1 Regulation.

ADAR (adenosine deaminase acting on RNA) catalyzes the deamination of adenosine to generate inosine, through its binding to double-stranded RNA (dsRNA), a phenomenon known as RNA editing. One of the functions of ADAR1 is suppressing the type I interferon (IFN) response, but its mechanism in gastric cancer is not clearly understood. We analyzed changes in RNA editing and IFN signaling in ADAR1-depleted gastric cancer cells, to clarify how ADAR1 regulates IFN signaling. Interestingly, we observed a dramatic increase in the protein level of signal transducer and activator of transcription 1 (STAT1) and interferon regulatory factor 9 (IRF9) upon ADAR1 knockdown, in the absence of type I or type II IFN treatment. However, there were no changes in protein expression or localization of the mitochondrial antiviral signaling protein (MAVS) and interferon alpha and beta-receptor subunit 2 (IFNAR2), the two known mediators of IFN production. Instead, we found that miR-302a-3p binds to the untranslated region (UTR) of IRF9 and regulate its expression. The treatment of ADAR1-depleted AGS cells with an miR-302a mimic successfully restored IRF9 as well as STAT1 protein level. Hence, our results suggest that ADAR1 regulates IFN signaling in gastric cancer through the suppression of STAT1 and IRF9 via miR-302a, which is independent from the RNA editing of known IFN production pathway.

Prostaglandin E2 Activates YAP and a Positive-Signaling Loop to Promote Colon Regeneration After Colitis but Also Carcinogenesis in Mice.

BACKGROUND & AIMS: Prostaglandin E2 (PGE2) is mediator of inflammation that regulates tissue regeneration, but its continual activation has been associated with carcinogenesis. Little is known about factors in the PGE2 signaling pathway that contribute to tumor formation. We investigated whether yes-associated protein 1 (YAP1), a transcriptional co-activator in the Hippo signaling pathway, mediates PGE2 function. METHODS: DLD-1 and SW480 colon cancer cell lines were transfected with vectors expressing transgenes or small hairpin RNAs and incubated with recombinant PGE2, with or without pharmacologic inhibitors of signaling proteins, and analyzed by immunoblot, immunofluorescence, quantitative reverse-transcription polymerase chain reaction, transcriptional reporter, and proliferation assays. Dextran sodium sulfate (DSS) was given to induce colitis in C57/BL6 (control) mice, as well as in mice with disruption of the hydroxyprostaglandin dehydrogenase 15 gene (15-PGDH-knockout mice), Yap1 gene (YAP-knockout mice), and double-knockout mice. Some mice also were given indomethacin to block PGE2 synthesis. 15-PGDH knockout mice were crossed with mice with intestine-specific disruption of the salvador family WW domain containing 1 gene (Sav1), which encodes an activator of Hippo signaling. We performed immunohistochemical analyses of colon biopsy samples from 26 patients with colitis-associated cancer and 51 age-and sex-matched patients with colorectal cancer (without colitis). RESULTS: Incubation of colon cancer cell lines with PGE2 led to phosphorylation of cyclic adenosine monophosphate-responsive element binding protein 1 and increased levels of YAP1 messenger RNA, protein, and YAP1 transcriptional activity. This led to increased transcription of the prostaglandin-endoperoxide synthase 2 gene (PTGS2 or cyclooxygenase 2) and prostaglandin E-receptor 4 gene (PTGER4 or EP4). Incubation with PGE2 promoted proliferation of colon cancer cell lines, but not cells with knockdown of YAP1. Control mice developed colitis after administration of DSS, but injection of PGE2 led to colon regeneration in these mice. However, YAP-knockout mice did not regenerate colon tissues and died soon after administration of DSS. 15-PGDH-knockout mice regenerated colon tissues more rapidly than control mice after withdrawal of DSS, and had faster recovery of body weight, colon length, and colitis histology scores. These effects were reversed by injection of indomethacin. SAV1-knockout or 15-PGDH-knockout mice did not develop spontaneous tumors after colitis induction, but SAV1/15-PGDH double-knockout mice developed polyps that eventually progressed to carcinoma in situ. Administration of indomethacin to these mice prevented spontaneous tumor formation. Levels of PGE2 correlated with those of YAP levels in human sporadic colorectal tumors and colitis-associated tumors. CONCLUSIONS: PGE2 signaling increases the expression and transcriptional activities of YAP1, leading to increased expression of cyclooxygenase 2 and EP4 to activate a positive signaling loop. This pathway promotes proliferation of colon cancer cell lines and colon tissue regeneration in mice with colitis. Constitutive activation of this pathway led to formation of polyps and colon tumors in mice.

Poor prognosis in Epstein-Barr virus-negative gastric cancer with lymphoid stroma is associated with immune phenotype.

BACKGROUND: Gastric cancer with lymphoid stroma (GCLS) is pathologically characterized by poorly developed tubular structures with a prominent lymphocytic infiltration. Its clinical and prognostic features differ in patients positive and negative for Epstein-Barr virus (EBV) infection. This study analyzed the expression of programmed cell death-1 (PD-1), programmed cell death ligand-1 (PD-L1), and the density of tumor-infiltrating lymphocytes (TILs) including CD3+ and CD8+ T cells, as well as their prognostic significance in patients with GCLS. METHODS: The study included 58 patients with GCLS (29 EBV+ and 29 EBV-) who underwent curative resection. Expression of CD3, CD8, PD-1, and PD-L1 in tumor cells and TILs was analyzed using a quantitative multispectral imaging system (Opal™), with these results validated by immuno-histochemical assays for PD-L1 on whole slide sections. RESULTS: The proportion of tumors overexpressing PD-L1 (31.0 vs. 0%, P = 0.002), TIL density (4548 vs. 2631/mm2, P < 0.001), and intra-tumoral CD8+ T-cell density (2650 vs. 1060/mm2, P < 0.001) were significantly higher in EBV+ than in EBV- GCLS. In addition, CD8+/CD3+ T-cell ratio was higher in EBV+ than in EBV- GCLS (55.3 vs. 35.8%, P < 0.001). Lower TIL density, defined as < 1350/mm2, was a significant negative factor of survival. CONCLUSIONS: Despite histopathological similarity, quantitative multispectral imaging revealed differences in the tumor immune micro-environment between EBV+ and EBV- GCLS, indicating that the underlying pathogenesis differs in these two disease entities. TIL density may be a prognostic marker in patients with GCLS.

Novel endoscopic categorization for prediction of chemoradiotherapy response in locally advanced esophageal cancer.

BACKGROUND AND AIM: Preoperative chemoradiotherapy (CRT) followed by esophagectomy is a well-known treatment modality for patients with locally advanced esophageal cancer (EC). This study developed an algorithm to predict pathological complete response (CR) in these patients using post-CRT endoscopic category with biopsy and validated the proposed algorithm. METHODS: A retrospective review of 141 consecutive patients who completed preoperative CRT and underwent surgical resection for locally advanced EC was performed. The post-CRT endoscopic findings of each patient were stratified into five categories. RESULTS: The distribution of post-CRT endoscopic categories was significantly different between the pathological CR and non-pathological CR groups (P < 0.001). About 76.8% (73/95) of patients in category 0, 1, or 2 achieved pathological CR. In contrast, 91.3% (42/46) of endoscopic categories 3 and 4 patients did not achieve pathological CR. Sensitivity of post-CRT biopsy was 11.1%. Therefore, an algorithm combining biopsy results and dichotomized post-CRT endoscopic category (category 0, 1, or 2 vs category 3 or 4) was developed. The sensitivity, specificity, and accuracy in predicting pathological CR by the proposed algorithm were 64.8%, 95.9%, and 82.8%, respectively. In the multivariate analysis, the proposed algorithm remained a significant negative factor of survival (P < 0.001). CONCLUSIONS: Algorithm using post-CRT endoscopic category with biopsy may help identify locally advanced EC patients who achieved pathological CR after preoperative CRT. Modalities to accurately detect subepithelial remnant EC may further aid in predicting pathological CR.

Combinatory RNA-Sequencing Analyses Reveal a Dual Mode of Gene Regulation by ADAR1 in Gastric Cancer.

BACKGROUND: Adenosine deaminase acting on RNA 1 (ADAR1) is known to mediate deamination of adenosine-to-inosine through binding to double-stranded RNA, the phenomenon known as RNA editing. Currently, the function of ADAR1 in gastric cancer is unclear. AIMS: This study was aimed at investigating RNA editing-dependent and editing-independent functions of ADAR1 in gastric cancer, especially focusing on its influence on editing of 3' untranslated regions (UTRs) and subsequent changes in expression of messenger RNAs (mRNAs) as well as microRNAs (miRNAs). METHODS: RNA-sequencing and small RNA-sequencing were performed on AGS and MKN-45 cells with a stable ADAR1 knockdown. Changed frequencies of editing and mRNA and miRNA expression were then identified by bioinformatic analyses. Targets of RNA editing were further validated in patients' samples. RESULTS: In the Alu region of both gastric cell lines, editing was most commonly of the A-to-I type in 3'-UTR or intron. mRNA and protein levels of PHACTR4 increased in ADAR1 knockdown cells, because of the loss of seed sequences in 3'-UTR of PHACTR4 mRNA that are required for miRNA-196a-3p binding. Immunohistochemical analyses of tumor and paired normal samples from 16 gastric cancer patients showed that ADAR1 expression was higher in tumors than in normal tissues and inversely correlated with PHACTR4 staining. On the other hand, decreased miRNA-148a-3p expression in ADAR1 knockdown cells led to increased mRNA and protein expression of NFYA, demonstrating ADAR1's editing-independent function. CONCLUSIONS: ADAR1 regulates post-transcriptional gene expression in gastric cancer through both RNA editing-dependent and editing-independent mechanisms.

The incidence and locational predilection of metachronous tumors after endoscopic resection of high-grade dysplasia and early gastric cancer.

BACKGROUND: The incidence of metachronous lesions after endoscopic resection (ER) of high-grade dysplasia (HGD) has not been evaluated, and optimal surveillance strategy remains vague. This study aimed to evaluate the incidence and characteristics of metachronous tumors including HGD and early gastric cancer (EGC) arising after ER. PATIENTS: The medical records of 2779 patients with 2981 lesions (445 patients with HGD and 2334 patients with EGC) who underwent ER and surveillance endoscopy at Asan Medical Center between April 1999 and December 2011 were retrospectively reviewed, and clinicopathological features of metachronous tumors were analyzed. RESULTS: Ninety-six metachronous lesions (17 HGD and 79 EGC) occurred in 92 patients during median 42 months of follow-up period (range 26-58 months). The 5-year and 10-year overall cumulative incidences of metachronous tumors were 4.6 and 10.5 %, respectively, and were on steady rise up to 10 years. The 5- and 10-year cumulative incidences of metachronous lesions were 4.1 and 8.4 % in HGD group and 4.7 and 11.3 % in EGC group (P = 0.578), respectively. The size of metachronous tumors was significantly smaller than initial lesion (2.3 vs. 1.9 cm, P = 0.039). Lower third of the stomach was most frequent site for both initial and metachronous lesions (77.1 and 70.8 %, respectively) and age was the significant predicting factor for metachronous tumors. CONCLUSIONS: Cumulative incidence of metachronous tumors after ER of HGD was comparable to the incidence after ER of EGC. Surveillance endoscopy can be considered at least for 10 years, with special attention on the lower third of the stomach.

ADAR1 and MicroRNA; A Hidden Crosstalk in Cancer.

The evolution of cancer cells is believed to be dependent on genetic or epigenetic alterations. However, this concept has recently been challenged by another mode of nucleotide alteration, RNA editing, which is frequently up-regulated in cancer. RNA editing is a biochemical process in which either Adenosine or Cytosine is deaminated by a group of RNA editing enzymes including ADAR (Adenosine deaminase; RNA specific) or APOBEC3B (Apolipoprotein B mRNA Editing Enzyme Catalytic Subunit 3B). The result of RNA editing is usually adenosine to inosine (A-to-I) or cytidine to uridine (C-to-U) transition, which can affect protein coding, RNA stability, splicing and microRNA-target interactions. The functional impact of these alterations is largely unclear and is a subject of extensive research. In the present review, we will specifically focus on the influence of ADARs on carcinogenesis via the regulation of microRNA processing and functioning. This follows a brief review of the current knowledge of properties of ADAR enzyme, RNA editing, and microRNA processing.

Bone marrow involvement is not associated with the clinical outcomes of gastric mucosa-associated lymphoid tissue lymphoma.

Objective Bone marrow (BM) examination is recommended as part of the initial staging work-up in patients with gastric mucosa-associated lymphoid tissue (MALT) lymphoma. However, the clinical significance of BM involvement in gastric MALT lymphoma patients has not been evaluated. Materials and methods From November 1995 to September 2014, 496 subjects who were diagnosed with gastric MALT lymphoma and underwent BM examination were eligible to be included in this study. BM involvement was found in 33 patients (6.7%) by retrospective review, and after exclusions, the clinical outcomes of 28 patients with BM involvement and 412 patients without BM involvement were evaluated. Results When comparing the characteristics of patients, age (median 60 vs. 53 years, p = 0.007) and Helicobacter pylori infection rate (71.0% vs. 85.5%, p = 0.040) were different between patients with and without BM involvement, while the location, macroscopic findings, and depth of invasion were similar. The overall complete remission (CR) rate was 85.2% during a median follow-up period of 42 months (interquartile range, 23-66 months) and did not differ between the two groups (78.6 and 85.7%, p = 0.280). Eradication therapy was performed as the first-line treatment in 18 of the 28 patients (64.3%) with BM involvement, and CR was achieved in 13 patients (72.2%). Logistic regression analysis showed that age and location in the upper part of the stomach were factors related to remission failure. Conclusion Gastric MALT lymphoma has a favorable outcome, and eradication therapy can be justified in selected cases even with BM involvement, when these patients are closely monitored.

EUS-guided 22-gauge fine needle biopsy for the diagnosis of gastric subepithelial tumors larger than 2 cm.

OBJECTIVE: EUS-guided fine needle biopsy (EUS-FNB) was introduced to obtain tissue cores. However, data on the efficacy of EUS-FNB for the diagnosis of gastric subepithelial tumors (SET) are limited. This study was aimed to determine the tissue acquisition and diagnostic yield of EUS-FNB using a novel 22-gauge FNB needle. MATERIAL AND METHODS: Between May 2012 and February 2014, we retrieved data on 78 consecutive patients who underwent 22-gauge EUS-FNB for tissue sampling of gastric SET larger than 2 cm. Relevant tumor and EUS-related parameters were reviewed retrospectively. RESULTS: The median tumor diameter was 2.8 cm and tumors were punctured successfully in 77 SET (98.7%). EUS-FNB was diagnostic in 81.8% of SET (63/77), by obtaining core biopsy tissue in 96.8% (61/63) and aspirates in 27.0% (17/63). FNB specimens permitted immunostaining for the diagnosis of gastrointestinal stromal tumors (GIST) in 30 SET (47.6%), 20 leiomyomas (31.7%), and 3 schwannomas (4.8%). Diagnoses could be made without immunostaining in 10 SET (15.9%). Tissue adequacy was optimal in 85.7% of FNB specimens by endosonographers' on-site visual evaluation. Endosonographers' evaluation of tissue adequacy was the only factor significantly associated with a higher diagnostic yield in univariate analysis. No adequate high-power fields for GIST risk stratification were available in FNB specimens. There was a single case of post-procedural bleeding (1.3%). CONCLUSION: EUS-FNB using 22-gauge needle obtains a high yield for the diagnosis of gastric SET ≥2 cm, mostly via core tissue acquisition. Endosonographers should pay careful attention to the adequacy of FNB specimens.

Outcomes of endoscopically inserted self-expandable metal stents in malignancy according to the type of stent and the site of obstruction.

BACKGROUND/AIMS: Self-expandable metal stents (SEMSs) can be used for the palliation of malignant obstruction in the upper gastrointestinal tract. This study assessed the feasibility and efficacy of endoscopically inserted SEMSs for the palliation of malignant obstruction in the stomach and duodenum. METHODS: Between January 2011 and April 2014, 220 patients with gastric or duodenal obstruction due to malignancy underwent endoscopic SEMS insertion at Asan Medical Center. The associations of technical/clinical outcomes and complications with the type of stent and site of obstruction were analyzed. RESULTS: The 220 patients included 125 men (56.8 %) and 95 women (43.2 %); median patient age was 63 years. Fully covered, partially covered, and uncovered SEMSs were inserted into 16, 77, and 120 patients, respectively. Obstructions were located in the gastric outlet, including the duodenal bulb, in 106 patients, and in the duodenal second and third portions in 114 patients. Technical success was achieved in 213 of 220 patients (96.8 %) and clinical success in 184 of 213 (86.4 %). Clinical success rates were similar to the type of stent, but were significantly greater for gastric outlet (95/104, 91.3 %) than for duodenal (89/109, 81.7 %) obstructions (p = 0.039). Stent migration was observed in 20 patients (9.1 %) and stent obstruction in 51 (23.2 %). Rates of stent migration were significantly higher for fully covered (6/16, 37.5 %) than for partially covered (7/77, 9.1 %) and uncovered (7/120, 5.8 %) SEMSs (p < 0.001) and were significantly higher for gastric outlet (16/104, 15.4 %) than for duodenal (4/109, 1.2 %) obstructions (p = 0.003). Rates of stent obstruction were similar for fully covered (2/16, 12.5 %), partially covered (17/77, 22.1 %), and uncovered (32/120, 26.7 %) SEMSs (p = 0.409) and in patients with gastric outlet (26/104, 25.0 %) and duodenal (25/109, 22.9 %) obstruction (p = 0.724). CONCLUSIONS: SEMS selection for malignant obstruction of the upper gastrointestinal tract depends on the site of obstruction.

A new role for IFRD1 in regulation of ER stress in bladder epithelial homeostasis.

A healthy bladder requires the homeostatic maintenance of and rapid regeneration of urothelium upon stress/injury/infection. Several factors have been identified to play important roles in urothelial development, injury and disease response, however, little is known about urothelial regulation at homeostasis. Here, we identify a new role for IFRD1, a stress-induced gene that has recently been demonstrated to play a critical role in adult tissue proliferation and regeneration, in maintenance of urothelial function/ homeostasis in a mouse model. We show that the mouse bladder expresses IFRD1 at homeostasis and its loss alters the global transcriptome of the bladder with significant accumulation of cellular organelles including multivesicular bodies with undigested cargo, lysosomes and mitochondria. We demonstrate that IFRD1 interacts with several mRNA-translation-regulating factors in human urothelial cells and that the urothelium of Ifrd1-/- mice reveal decreased global translation and enhanced endoplasmic reticulum (ER) stress response. Ifrd1-/- bladders have activation of the unfolded protein response (UPR) pathway, specifically the PERK arm, with a concomitant increase in oxidative stress and spontaneous exfoliation of urothelial cells. Further, we show that such increase in cell shedding is associated with a compensatory proliferation of the basal cells but impaired regeneration of superficial cells. Finally, we show that upon loss of IFRD1, mice display aberrant voiding behavior. Thus, we propose that IFRD1 is at the center of many crucial cellular pathways that work together to maintain urothelial homeostasis, highlighting its importance as a target for diagnosis and/or therapy in bladder conditions.

The coordinated management of ribosome and translation during injury and regeneration.

Diverse acute and chronic injuries induce damage responses in the gastrointestinal (GI) system, and numerous cell types in the gastrointestinal tract demonstrate remarkable resilience, adaptability, and regenerative capacity in response to stress. Metaplasias, such as columnar and secretory cell metaplasia, are well-known adaptations that these cells make, the majority of which are epidemiologically associated with an elevated cancer risk. On a number of fronts, it is now being investigated how cells respond to injury at the tissue level, where diverse cell types that differ in proliferation capacity and differentiation state cooperate and compete with one another to participate in regeneration. In addition, the cascades or series of molecular responses that cells show are just beginning to be understood. Notably, the ribosome, a ribonucleoprotein complex that is essential for translation on the endoplasmic reticulum (ER) and in the cytoplasm, is recognized as the central organelle during this process. The highly regulated management of ribosomes as key translational machinery, and their platform, rough endoplasmic reticulum, are not only essential for maintaining differentiated cell identity, but also for achieving successful cell regeneration after injury. This review will cover in depth how ribosomes, the endoplasmic reticulum, and translation are regulated and managed in response to injury (e.g., paligenosis), as well as why this is essential for the proper adaptation of a cell to stress. For this, we will first discuss how multiple gastrointestinal organs respond to stress through metaplasia. Next, we will cover how ribosomes are generated, maintained, and degraded, in addition to the factors that govern translation. Finally, we will investigate how ribosomes and translation machinery are dynamically regulated in response to injury. Our increased understanding of this overlooked cell fate decision mechanism will facilitate the discovery of novel therapeutic targets for gastrointestinal tract tumors, focusing on ribosomes and translation machinery.

Regulation of the double-stranded RNA response through ADAR1 licenses metaplastic reprogramming in gastric epithelium.

Cells recognize both foreign and host-derived double-stranded RNA (dsRNA) via a signaling pathway that is usually studied in the context of viral infection. It has become increasingly clear that the sensing and handling of endogenous dsRNA is also critical for cellular differentiation and development. The adenosine RNA deaminase, ADAR1, has been implicated as a central regulator of the dsRNA response, but how regulation of the dsRNA response might mediate cell fate during injury and whether such signaling is cell intrinsic remain unclear. Here, we show that the ADAR1-mediated response to dsRNA was dramatically induced in 2 distinct injury models of gastric metaplasia. Mouse organoid and in vivo genetic models showed that ADAR1 coordinated a cell-intrinsic, epithelium-autonomous, and interferon signaling-independent dsRNA response. In addition, dsRNA accumulated within a differentiated epithelial population (chief cells) in mouse and human stomachs as these cells reprogrammed to a proliferative, reparative (metaplastic) state. Finally, chief cells required ADAR1 to reenter the cell cycle during metaplasia. Thus, cell-intrinsic ADAR1 signaling is critical for the induction of metaplasia. Because metaplasia increases cancer risk, these findings support roles for ADAR1 and the response to dsRNA in oncogenesis.