Gastric cancer (GC) is the third leading cause of cancer-related deaths worldwide. Recent high-throughput analyses of genomic alterations revealed several driver genes and altered pathways in GC. However, therapeutic applications from genomic data are limited, largely as a result of the lack of druggable molecular targets and preclinical models for drug selection. To identify new therapeutic targets for GC, we performed array comparative genomic hybridization (aCGH) of DNA from 103 patients with GC for copy number alteration (CNA) analysis, and whole-exome sequencing from 55 GCs from the same patients for mutation profiling. Pathway analysis showed recurrent alterations in the Wnt signaling [APC, CTNNB1, and DLC1 (deleted in liver cancer 1)], ErbB signaling (ERBB2, PIK3CA, and KRAS), and p53 signaling/apoptosis [TP53 and BCL2L1 (BCL2-like 1)] pathways. In 18.4% of GC cases (19/103), amplification of the antiapoptotic gene BCL2L1 was observed, and subsequently a BCL2L1 inhibitor was shown to markedly decrease cell viability in BCL2L1-amplified cell lines and in similarly altered patient-derived GC xenografts, especially when combined with other chemotherapeutic agents. In 10.9% of cases (6/55), mutations in DLC1 were found and were also shown to confer a growth advantage for these cells via activation of Rho-ROCK signaling, rendering these cells more susceptible to a ROCK inhibitor. Taken together, our study implicates BCL2L1 and DLC1 as potential druggable targets for specific subsets of GC cases.gastric cancer | copy number alteration | whole-exome sequencing | patient-derived xenograft | druggable target G astric cancer (GC) is a highly prevalent malignancy and is the third leading cause of cancer-related deaths in the world (1). In unresectable and metastatic cases, the clinical outcome for this disease remains poor (median survival is 10-14 mo) (2), and other treatment options are often limited because of the lack of effective therapeutic approaches and molecular prognostic markers (2, 3). To date, with the exception of the application of trastuzumab [ERBB2 (ErbB2 receptor tyrosine kinase 2) antagonist] or ramucirumab [VEGFR2 (Vascular endothelial growth factor receptor 2) antagonist] for advanced GC cases (4, 5), drugs that target GC on a molecular level are limited.Recent genomic studies have demonstrated the heterogeneous genomic characteristics of GC (6-10). In addition, previous studies of patients with GC by whole-genome and whole-exome sequencing (WES) have identified frequent somatic mutations in tumor suppressors such as TP53, ARID1A, APC, and FAT4, and oncogenes including PI3KCA, KRAS, and RHOA (6-10). However, these findings, although academically meaningful, are far from ready for clinical applications, largely because of the lack of identified druggable molecular targets and the availability of reliable preclinical models for validation of potential target inhibitors.To identify novel therapeutic targets for GC, we explored genomic alterations in GC through an integrated genomic data set from WE...

Dysplasia is considered a key transition state between pre-cancer and cancer in gastric carcinogenesis. However, the cellular or phenotypic heterogeneity and mechanisms of dysplasia progression have not been elucidated. We have established metaplastic and dysplastic organoid lines, derived from Mist1-Kras(G12D) mouse stomach corpus and studied distinct cellular behaviors and characteristics of metaplastic and dysplastic organoids. We also examined functional roles for Kras activation in dysplasia progression using Selumetinib, a MEK inhibitor, which is a downstream mediator of Kras signaling. Here, we report that dysplastic organoids die or show altered cellular behaviors and diminished aggressive behavior in response to MEK inhibition. However, the organoids surviving after MEK inhibition maintain cellular heterogeneity. Two dysplastic stem cell (DSC) populations are also identified in dysplastic cells, which exhibited different clonogenic potentials. Therefore, Kras activation controls cellular dynamics and progression to dysplasia, and DSCs might contribute to cellular heterogeneity in dysplastic cell lineages.

Intestinal‐type gastric adenocarcinoma arises in a field of pre‐existing metaplasia. While biomarkers of cancer and metaplasia have been identified, the definition of dysplastic transition as a critical point in the evolution of cancer has remained obscure. We have evaluated Trop2 as a putative marker of the transition from metaplasia to dysplasia in the stomach in multiple mouse models of metaplasia induction and progression. In addition, TROP2 expression was evaluated in human samples by immunostaining tissue microarrays for metaplasia, dysplasia, and gastric cancer. Dysplastic mouse organoids were evaluated in vitro following shRNA knockdown of Trop2 expression. In mouse models, no Trop2 was observed in the normal corpus and Trop2 was not induced in acute models of metaplasia induction with either L635 or DMP‐777. In Mist1‐Kras mice, Trop2 expression was not observed in metaplasia at 1 month after Kras induction, but was observed in dysplastic glands at 3–4 months after Kras induction. In human tissues, no Trop2 was observed in normal corpus mucosa or SPEM, but Trop2 expression was observed in incomplete intestinal metaplasia, with significantly less expression in complete intestinal metaplasia. Trop2 expression was observed in all dysplastic and 84% of gastric cancer lesions, although expression levels were variable. Dysplastic mouse organoids from Mist1‐Kras mice expressed Trop2 strongly. Knockdown of Trop2 with shRNA markedly reduced organoid growth and budding behavior, and induced the upregulation of apical villin expression. We conclude that Trop2 is upregulated in the transition to dysplasia in the stomach and promotes dysplastic cell behaviors. © 2020 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Objective: To investigate the molecular characteristics of AGEJ compared with EAC and gastric adenocarcinoma. Summary of Background Data: Classification of AGEJ based on differential molecular characteristics between EAC and gastric adenocarcinoma has been long-standing controversy but rarely conducted due to anatomical ambiguity and epidemiologic difference. Methods: The molecular classification model with Bayesian compound covariate predictor was developed based on differential mRNA expression of EAC (N ¼ 78) and GCFB (N ¼ 102) from the Cancer Genome Atlas (TCGA) cohort. AGEJ/cardia (N ¼ 48) in TCGA cohort and AGEJ/upper third GC (N ¼ 46 pairs) in Seoul National University cohort were classified into the EAC-like or GCFB-like groups whose genomic, transcriptomic, and proteomic characteristics were compared. Results: AGEJ in both cohorts was similarly classified as EAC-like (31.2%) or GCFB-like (68.8%) based on the 400-gene classifier. The GCFB-like group showed significantly activated phosphoinositide 3-kinase-AKT signaling with decreased expression of ERBB2. The EAC-like group presented significantly different alternative splicing including the skipped exon of RPS24, a significantly higher copy number amplification including ERBB2 amplification, and increased protein expression of ERBB2 and EGFR compared with GCFB-like group. High-throughput 3D drug test using independent cell lines revealed that the EAC-like group showed a significantly better response to lapatinib than the GCFB-like group (P ¼ 0.015). Conclusions: AGEJ was the combined entity of the EAC-like and GCFB-like groups with consistently different molecular characteristics in both Seoul National University and TCGA cohorts. The EAC-like group with a high Bayesian compound covariate predictor score could be effectively targeted by dual inhibition of ERBB2 and EGFR.

We have identified aquaporin 5 (AQP5) as a specific marker of SPEM in both mouse and human gastric corpus. In human stomach, AQP5-expressing SPEM cells are present at the bases of glands with incomplete, but not complete, intestinal metaplasia.

These loci may serve as novel methylation markers for patients with GC.

Background Spasmolytic polypeptide-expressing metaplasia (SPEM) is considered a precursor lesion of intestinal metaplasia and intestinal-type gastric cancer (GC), but little is known about microRNA alterations during metaplasia and GC developments. Here, we investigate miR-30a expression in gastric lesions and identify its novel target gene which is associated with the intestinal-type GC. Methods We conducted in situ hybridization and qRT-PCR to determine miR-30a expression in gastric tissues. miR-30a functions were determined through induction or inhibition of miR-30a in GC cell lines. A gene microarray was utilized to confirm miR-30a target genes in GC, and siRNA-mediated target gene suppression and immunostaining were performed. The Cancer Genome Atlas data were utilized to validate gene expressions. Results We found down-regulation of miR-30a during chief cell transdifferentiation into SPEM. MiR-30a level was also reduced in the early stage of GC, and its level was maintained in advanced GC. We identified a novel target gene of miR-30a and ITGA2, and our results showed that either ectopic expression of miR-30a or ITGA2 knockdown suppressed GC cell proliferation, migration, and tumorigenesis. Levels of ITGA2 inversely correlated with levels of miR-30a in human intestinal-type GC. Conclusion We found down-regulation of miR-30a in preneoplastic lesions and its tumor-suppressive functions by targeting ITGA2 in GC. The level of ITGA2, which functions as an oncogene, was up-regulated in human GC. The results of this study suggest that coordination of the miR-30a-ITGA2 axis may serve as an important mechanism in the development of gastric precancerous lesions and intestinal-type GC.

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