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Background & Aims WAP 4-disulfide core domain protein 2 (WFDC2), also known as human epididymis protein 4, is a small secretory protein that is highly expressed in fibrosis and human cancers, particularly in the ovaries, lungs, and stomach. However, the role of WFDC2 in carcinogenesis is not fully understood. The present study aimed to investigate the role of WFDC2 in gastric carcinogenesis with the use of preneoplastic metaplasia models. Methods Three spasmolytic polypeptide–expressing metaplasia (SPEM) models were established in both wild-type and Wfdc2-knockout mice with DMP-777, L635, and high-dose tamoxifen, respectively. To reveal the functional role of WFDC2, we performed transcriptomic analysis with DMP-777–treated gastric corpus specimens. Results Wfdc2-knockout mice exhibited remarkable resistance against oxyntic atrophy, SPEM emergence, and accumulation of M2-type macrophages in all 3 SPEM models. Transcriptomic analysis revealed that Wfdc2-knockout prevented the up-regulation of interleukin-33 (IL33) expression in the injured mucosal region of SPEM models. Notably, supplementation of recombinant WFDC2 induced IL33 production and M2 macrophage polarization, and ultimately promoted SPEM development. Moreover, long-term treatment with recombinant WFDC2 was able to induce SPEM development. Conclusions WFDC2 expressed in response to gastric injury promotes SPEM through the up-regulation of IL33 expression. These findings provide novel insights into the role of WFDC2 in gastric carcinogenesis.

Background & Aims: The loss of parietal cells from the gastric mucosa (oxyntic atrophy) is a critical step in the pathogenesis of chronic gastritis and gastric adenocarcinoma. Parietal cells are known to secrete epidermal growth factor receptor (EGFR) ligands, which are critical regulators of differentiation in the gastric mucosa. Although all of the actions of EGFR ligands are mediated through a common EGFR protein, individual ligands may produce different physiologic responses. Previous investigations have suggested that a deficit in EGFR signaling in waved-2 mice accelerates the emergence of metaplasia after induction of acute oxyntic atrophy. We sought to determine whether specific EGFR ligands regulate the metaplastic response to oxyntic atrophy. Methods: To induce spasmolytic polypeptide-expressing metaplasia (SPEM), amphiregulin (AR) and transforming growth factor-α–deficient mice and their wild-type littermates were treated with DMP-777 for 0–14 days and for 14 days followed by 14 days of recovery off drug. We evaluated the gastric mucosal response to oxyntic atrophy using cell lineage–specific markers. Results: Although loss of transforming growth factor-α did not influence the induction of SPEM, loss of AR caused an acceleration and amplification in the induction of SPEM after acute oxyntic atrophy. Trefoil factor family 2/spasmolytic polypeptide and intrinsic factor dual-immunostaining cells significantly increased in the SPEM of AR-deficient mice. At the bases of glands, intrinsic factor immunoreactive cells also were costained for 5-bromo-2'-deoxyuridine, suggesting their re-entry into the cell cycle. Conclusions: The absence of AR promoted the rapid emergence of SPEM in response to oxyntic atrophy.

Background & Aims Loss of parietal cells causes the development of spasmolytic polypeptide-expressing metaplasia (SPEM) through transdifferentiation of chief cells. In the presence of inflammation, SPEM can advance into a more proliferative metaplasia with increased expression of intestine-specific transcripts. We used L635 to induce acute SPEM with inflammation in mice and investigated the roles of inflammatory cells in the development of SPEM. Methods To study the adaptive immune system, Rag1 knockout, interferon-γ–deficient, and wild-type (control) mice received L635 for 3 days. To study the innate immune system, macrophages were depleted by intraperitoneal injection of clodronate liposomes 2 days before and throughout L635 administration. Neutrophils were depleted by intraperitoneal injection of an antibody against Ly6G 2 days before and throughout L635 administration. Pathology and immunohistochemical analyses were used to determine depletion efficiency, metaplasia, and proliferation. To characterize SPEM in each model, gastric tissues were collected and levels of Cftr , Dmbt1 , and Gpx2 mRNAs were measured. Markers of macrophage polarization were used to identify subpopulations of macrophages recruited to the gastric mucosa. Results Administration of L635 to Rag1 knockout, interferon-γ–deficient, and neutrophil-depleted mice led to development of proliferative SPEM and up-regulation of intestine-specific transcripts in SPEM cells, similar to controls. However, macrophage-depleted mice given L635 showed significant reductions in numbers of SPEM cells, SPEM cell proliferation, and expression of intestine-specific transcripts, compared with control mice given L635. In mice given L635, as well as patients with intestinal metaplasia, M2 macrophages were the primary inflammatory component. Conclusions Results from studies of mouse models and human metaplastic tissues indicate that M2 macrophages promote the advancement of SPEM in the presence of inflammation.

Adenocarcinoma in the human stomach evolves in the setting of Helicobacter pylori-induced oxyntic atrophy and chronic mucous cell metaplasia. Two types of metaplasia associated with development of intestinal-type cancers are observed in the human stomach: intestinal metaplasia (IM; intestinal type goblet cells in the stomach) and Spasmolytic Polypeptide (TFF2) Expressing Metaplasia (SPEM; with the presence of antral type TFF2-expressing mucous cells in the oxyntic region). Our previous study showed that SPEM developed from transdifferentiation of mature chief cells, rather than originating from aberrant differentiation of resident progenitor cells. Recent investigations have noted evidence for increased Ras activity in up to a third of gastric cancers. Thus, we have hypothesized that activated Ras, specifically induced in mature chief cells, elicits transdifferentiation of chief cells into SPEM and progression of SPEM to more intestinalized metaplasia. To test this hypothesis, we have examined a novel mouse model of metaplasia in the stomach in Mist1-CreERT2Tg/+;LSLK-Ras(G12D)Tg/+;mT/mGTg/+ mice. Tamoxifen (TAM) treatment induces the expression of activated K-Ras specifically in mature chief cells and marks the K-Ras-induced chief cells with GFP as a lineage tracer. This mouse model rapidly develops SPEM and IM within 3 months, following TAM induction of activated K-Ras expression in mature chief cells. At 1 week post TAM treatment, we found several groups of metaplastic glands between normal oxyntic glands that were positive for SPEM markers. At 3 months post TAM treatment, oxyntic glands were replaced withmetaplastic glands that showed highly proliferative mucous cell populations at the bases and the cells in the metaplastic glands were strongly positive for clusterin and TFF3 with distinct goblet cell morphologies, and also positive for Pdx1. Some glands were positive for IM markers such as villin and Cdx1. The mice at 4 months post TAM treatment developed severe inflammation, metaplasia, dysplasia and the invasive adenocarcinoma. Consistent with active K-Ras expression, cells with nuclear expression of phospho-ERK1/2 were also observed at the bases of metaplastic glands. Interestingly, we observed that the metaplastic glands were positive for GFP, indicating that they were derived from transdifferentiation of Cre-induced chief cells. Therefore, the induction of activated Ras specifically in mature chief cells initially leads to transdifferentiation of chief cells into SPEM followed by evolution of goblet cell IM and eventual neoplastic lesions. These studies demonstrate that expression of activated Ras in Chief cells can lead to the development of the entire spectrum of metaplastic and neoplastic lineages leading to gastric cancer.

Gastric cancer is one of the most common neoplasms, ranking as the second leading cause of cancer-related deaths worldwide. The predominant factor associated to gastric cancer is Helicobacter pylori infection, which leads to a chronic inflammatory response and subsequent oxyntic atrophy. Parietal cell loss result in two types of metaplasia, the intestinal metaplasia (IM) characterized by the presence of cells with goblet cell morphology and spasmolytic polypeptide-expressing metaplasia (SPEM) that shows morphological characteristics of the deep antral glands and express trefoil factor 2 (spasmolytic polypeptide). Although metaplastic lesions are considered neoplastic precursors, their direct association to cancer is still in debate. Similar to other cancers, gastric cancers are marked by global gene expression alterations. MicroRNAs (miRNAs) are small noncoding RNAs involved in the post-transcriptional regulation of gene expression and an increasing number of studies has been showing their aberrant expression in cancer. In order to identify miRNAs involved in the early stages of gastric cancer we performed a miRNA profiling on laser capture micro-dissected IM and SPEM cells from patient lesions. Using a qRT-PCR approach for quantitation of 754 human miRNAs, we identified 77 miRNAs differentially expressed in the metaplastic samples (greater than two-fold) in comparison to normal chief cells. The highest number of dysregulated miRNAs was observed in IM,which showed 45 up-regulated and 25 down-regulatedmiRNAs. In SPEM, 28 miRNAs were found up-regulated (21 of them also up-regulated in IM), whereas no down-regulation was detected. Some of the up-regulated miRNAs have already been associated to cancer in general (miR-26-a, miR-191, miR-155), as well as specifically to gastric cancer (miR-18b, miR-196b and miR-106a). However, the regulation of some of the top up-regulated miRNAs revealed here including miR-802, miR-922 and miR-622 are still poorly characterized in cancer. In a comparison with a previous mRNA profiling study performed on a similar group of samples, we observed that 108 out of the 568 mRNAs found up-regulated in IM are predicted targets of the 26 microRNAs down-regulated in IM, revealing a potential mechanism for the regulation of those genes in gastric metaplasia. Particularly interesting are 4 members of the miR-30 family, with 31 predicted mRNA targets amongst those up-regulated in IM. Although miR-30 family members have been described as down-regulated in gastric cancer, no data on their targets in this neoplasia is currently available. An extended characterization of the microRNAs identified here will provide a better understanding of their function in gastric metaplasia and progression to neoplasia, as well as might reveal useful early stage biomarkers or therapeutic targets.

Background & Aims Gastric cancer evolves in the setting of a pathologic mucosal milieu characterized by both loss of acid-secreting parietal cells and mucous cell metaplasias. Indeed, mucous cell metaplasia is considered the critical preneoplastic lesion for gastric cancer. Previous investigations have shown that infection of mice with Helicobacter felis or induction of acute parietal cell loss with the drug DMP-777 leads to the emergence of a type of metaplasia designated spasmolytic polypeptide-expressing metaplasia (SPEM). We have hypothesized that SPEM arises from proliferating cells in gland bases, either from a cryptic progenitor cell or by transdifferentiation of mature chief cells. Methods Taking advantage of the chief cell-restricted expression of Mist1-Cre-ER T2 , we used lineage mapping to examine whether SPEM lineages were derived from chief cells in 3 independent models of induction by DMP-777 treatment, L-635 treatment, or H felis infection. Results Treatment of mice with L-635 for 3 days led to rapid parietal cell loss, induction of a prominent inflammatory infiltrate, and emergence of SPEM. In all 3 models, SPEM developed, at least in part, from transdifferentiation of chief cells. We further found that acute parietal cell loss in the setting of inflammation (L-635 treatment) led to more rapid induction and expansion of SPEM derived from transdifferentiation of chief cells. Conclusions These studies provide direct evidence by lineage tracing that SPEM evolves from differentiated chief cells. Thus, mature gastric chief cells have the ability to act as cryptic progenitors and reacquire proliferative capacity within the context of mucosal injury and inflammation.

Background & Aims Intestinal metaplasia (IM) and spasmolytic polypeptide-expressing metaplasia (SPEM) are precursors to gastric carcinogenesis. We sought to identify molecular biomarkers of gastric metaplasias and gastric cancer by gene expression profiling of metaplastic lesions from patients. Methods Complementary DNA microarray analysis was performed on IM and SPEM cells isolated from patient samples using laser capture microdissection. Up-regulated transcripts in metaplastic lesions were confirmed by immunostaining analysis in IM, SPEM, and gastric cancer tissues. Proteins that were highly expressed specifically in gastric cancer tissues were analyzed for their association with survival in a test set (n = 450) and a validation set (n = 502) of samples from gastric cancer patients. Results Compared with normal chief cells, 858 genes were differentially expressed in IM or SPEM samples. Immunostaining was detected for 12 proteins, including 3 new markers of IM ( ACE2 , LGALS4 , AKR1B10 ) and 3 of SPEM ( OLFM4 , LYZ , DPCR1 ). Of 13 proteins expressed in IM or SPEM, 8 were expressed by 17%–50% of human gastric cancer tissues ( MUC13 , OLFM4 , CDH17 , KRT20 , MUC5AC , LGALS4 , AKR1B10 , REG4 ). Expression of CDH17 or MUC13 correlated with patient survival in the test and validation sets. Multivariate analysis showed that CDH17 was an independent prognostic factor in patients with stage I or node-negative disease. Conclusions We identified several novel biomarkers for IM, SPEM, and gastric cancer using gene expression profiling of human metaplastic lesions. Expression of CDH17 and MUC13 was up-regulated in gastric cancer tissues. CDH17 is a promising prognostic marker for early stage gastric cancer.

Gastric adenocarcinoma of the intestinal type is believed to develop through a series of histopathologic stages, originally described by Correa, that include chronic gastritis, gastric atrophy, intestinal metaplasia, dysplasia and finally cancer (1). Intestinal metaplasia has been the focus of great fascination by many pathologists, since it was unexpected to find intestinal type mucosa containing goblet cells in the body or antrum of the stomach. Numerous studies have implicated intestinal metaplasia as a useful biomarker for gastric cancer risk, and even possibly a precursor to gastric malignancy. However, this evidence has been largely correlative. In patients with gastric cancer, intestinal metaplasia is frequently found in the stomach, even with early gastric cancer. Intestinal metaplasia is much more prevalent in high-risk areas for gastric cancer compared to low risk areas. Finally, in several studies where serial endoscopies and biopsies were performed, patients with intestinal metaplasia, particularly type III, frequently developed gastric cancer (2). Intestinal metaplasia has been used as the key biomarker in studies of H. pylori eradication or gastric cancer prevention, defining the preneoplastic lesion often considered the “point-of-no-return” (3). Indeed, since the gastric cancers that developed in this setting also showed intestinal differentiation, it seemed logical to conclude that the cancers arose directly from these intestinal metaplastic cells. Neverthless, in contrast with other neoplasms, little genetic mutational evidence exists to implicate intestinal metaplastic lineages as true direct precursors of gastric neoplasia. Recent investigations have also highlighted the existence of a second metaplastic lineage, Spasmolytic Polypeptide-Expressing Metaplasia (SPEM) (4). SPEM is a metaplastic mucous cell lineage with phenotypic characteristics of deep antral gland cells including strong expression of Trefoil Factor 2 (TFF2, previously designated as spasmolytic polypeptide). In the past, this underappreciated mucous lineage was described with various names including pseudopyloric metaplasia or mucous metaplasia or antralization of the corpus, but mostly the lineage was ignored. Indeed, it is now appreciated that atrophy of the corpus and body of the stomach is always associated with the development of SPEM. In addition, SPEM is at least as strongly associated with the development of gastric cancer as intestinal metaplasia (4). Moreover, while intestinal metaplasia tends to be spotty or multifocal, SPEM typically appears diffusely throughout the body and corpus of the stomach in patients that progress to gastric cancer (5). SPEM is not simply an expansion of antral type mucosa, since gastrin cells are not present and SPEM cells express a number of proteins, such as HE-4, that are not expressed in the antrum (6). However, both the precise connection between intestinal metaplasia and SPEM and the relationship between SPEM and gastric cancer remain unclear. Recent studies have examined the cellular origin of SPEM in mice. These investigations have demonstrated that SPEM develops in the fundus in the setting of parietal cell loss following chronic Helicobacter infection (7, 8). acute parietal cell loss due to treatment with DMP-777 (9), or chronic genetic parietal cell ablation by transgenically expressed toxin (10). These studies have led to accumulating evidence that SPEM may originate from transdifferentiation of mature chief cells into SPEM (6). In the case of H. felis infection, gastritis cystica profunda and dysplasia evolve from preexisting regions of SPEM (11). Still these studies have not been able to address intestinal metaplasia because Helicobacter-infected mice do not typically develop intestinal metaplasia. Intestinal goblet cells do develop in the fundus of transgenic mice where cdx2, a transcription factor, which is a master developmental regulator of intestinal differentiation, is targeted to the stomach using elements of the H+/K+-ATPase β subunit promoter (12, 13). Interestingly, amphiregulin-deficient mice developed SPEM after 6 months of age, and a subset of mice did go on to develop goblet cell intestinal metaplasia (14). In that case, compound glands containing both SPEM and intestinal metaplasia were clearly present. While murine studies have not been able to clarify the relationship between intestinal metaplasia and SPEM, studies in Mongolian gerbils have provided additional insights. Mongolian gerbils develop both SPEM and intestinal metaplasia in the fundus following infection with Helicobacter pylori (15). In Mongolian gerbils, intestinal metaplasia developed in pre-existing SPEM glands and mixed glands expressing both SPEM and intestinal metaplasia were clearly present (15). All of these studies have supported the notion that intestinal metaplasia may develop from pre-existing SPEM. No published studies in humans have addressed directly the question of the relationship of SPEM to intestinal metaplasia in humans. We have therefore examined the morphological characteristics of SPEM and intestinal metaplasia in gastric resections specimens exclusively from the fundus. These studies have uncovered several critical observations about the induction of metaplasias in the stomach. First, SPEM can develop as a very localized phenomenon. Figure 1 demonstrates that SPEM can develop in single or groups of glands surrounded by regions with normal appearing mucous neck cells in the fundic mucosa. At times these SPEM gland groups are associated with adjacent areas with the appearance of mucous neck cell hyperplasia. These regions do not appear to interact with regions of intestinal metaplasia. The focal phenotype of SPEM glands suggests that they may act as part of a normal local reparative mechanism for the gastric mucosa. Figure 1 Focal early lesions for SPEM induction We have also sought to determine if there is a relationship between SPEM glands and intestinal metaplasia in gastric resections. Examination of resection sections containing regions of both SPEM and intestinal metaplasia led to identification of regions with compound glands where SPEM cells were observed in the deep portions of the glands with intestinal metaplastic lineages in the luminal portions of the glands (Figure 2). Thus, goblet cells staining with either Alcian Blue or Muc2 were observed on the luminal aspects of glands that contain PAS-positive and TFF2-staining SPEM at their bases (Figure 2). It is important to emphasise that these were not residual pyloric type glands, since these sections were taken from areas surrounded by corpus mucosa. While we did observe scattered proliferative Ki67-positive cells within SPEM, in regions with intestinal metaplasia immediately adjacent to or overlying SPEM, we observed strong staining for Ki67 in cells within the region demarcating the zone between SPEM and intestinal metaplasia (Figure 2). Many of the Ki67-positive cells were also stained for MUC2. Thus, we observed clear evidence for the existence of intestinal metaplasia emanating from SPEM. The elevated proliferation in intestinal metaplasia adjacent to SPEM may indicate a transition or secondary differentiation of SPEM into intestinal metaplasia. Figure 2 Compound glands containing SPEM and Intestinal Metaplasia These data indicate that the standard concept proposed by Professor Correa now merits further expansion or modification (Figure 3). Work in mouse models and human tissue suggests that loss of parietal cells leads initially to the induction of SPEM. With chronic inflammation in the setting of parietal cell loss, SPEM may give rise to a further differentiation into intestinal metaplasia. This evolution of mucous cell metaplastic lineages has been noted previously for the Ulcer Associated Lineages (UACL) identified in patients with inflammatory bowel disease (16). While these findings create a strategy for the induction and progression of metaplastic lineages in humans, they do not address the actual origin of gastric adenocarcinoma. It is particularly exciting to consider that if SPEM is derived from chief cell transdifferentiation, then chief cells themselves, or a subset of chief cells, represent an unrecognized progenitor population that can be induced in the pathological stomach. Given the more differentiated nature of intestinal metaplasia, it now seems somewhat less likely that gastric cancer arises from a goblet cell-containing epithelium. Still, we must acknowledge that at present it remains uncertain whether either SPEM or intestinal metaplasia is a true precursor for cancer. Nevertheless, it seems likely that evolution of intestinal metaplasia from SPEM may lead to a hyperproliferative state in which the infected and inflamed mucosa may be more susceptible to establishment of deleterious mutations in stem or progenitor populations. Thus, SPEM and intestinal metaplasia may be commensals for the neoplastic process rather than true direct precursors. Taken together, this work suggests that a broader view of metaplastic initiation and pre-neoplastic progression is merited in evaluating gastric carcinogenesis. Figure 3 A revised model for the evolution of metaplasia in the stomach