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BackgroundGallbladder cancer (GBC) has a poor prognosis. Although complete surgical resection is the only successful approach for improving survival, additional therapeutic modalities are required for recurrent or surgically unresectable GBCs.Materials and MethodsTo determine the expression status of HER2 and the mismatch repair (MMR) proteins MLH1, MSH2, MSH6, and PMS2, immunohistochemical staining of MMR proteins and HER2 was carried out in 216 surgically resected GBCs. HER2 labeling was scored by adopting a scoring system for gastric carcinomas. Tissues scoring 0 to 2+ were defined as HER2 negative, whereas those scoring 3+ were regarded as HER2-positive. In addition, silver in situ hybridization and microsatellite instability (MSI) analysis were conducted to confirm HER2 amplification and MSI, respectively.ResultsThree of 216 GBCs (1.3%) showed MMR protein deficiency. All three observed MSI cases exhibited dual loss of MSH2 and MSH6 protein expression. However, no cases showed loss of either MLH1 or PMS2 expression. No association was observed between MMR protein deficiency and other clinicopathological factors. HER2 amplification was noted in 30 (13.9%) GBCs and associated with Crohn-like lymphoid reaction (P = 0.023). No survival difference was observed based on HER2 overexpression or HER2 amplification status.ConclusionMMR protein deficiency and HER2 overexpression were observed in a small subset (1.3% and 13.9%, respectively) of GBCs without simultaneous occurrence of deficient MMR protein expression and HER2 overexpression. The presence of Crohn-like lymphoid reaction may help identify cases with HER2 amplification, by using hematoxylin-stained slides. Although the proportion of MMR protein-deficient- and HER2-overexpressing GBCs was small, applying immunotherapy to MMR protein-deficient GBCs and herceptin to HER2-overexpressing GBCs may provide alternative treatment options for patients with GBC.

Objective: Hairy and enhancer of split-1 (HES-1), which is a downstream target of the Notch signaling pathway, has been linked to KRAS mutations. HES-1 has been proposed as harboring oncogenic activity in colorectal cancer but has not been investigated in adenocarcinoma of the small intestine, where the drivers of oncogenesis are not as well understood. Materials and Methods: To investigate the clinicopathologic and prognostic implications of HES-1, HES-1 immunohistochemical expression was analyzed in digital images along with clinicopathological variables, including survival and KRAS genotype, in 185 small intestinal adenocarcinomas. Results: The loss of HES-1 expression (HES-1Loss) was observed in 38.4% (71/185) of the patients, and was associated with higher pT category (P = 0.018), pancreatic invasion (P = 0.005), high grade (P =0.043), and non-tubular histology (P = 0.004). Specifically, in tumors with mutant KRAS (KRASMT), HES-1Loss was related to proximal location (P = 0.024), high T and N categories (P = 0.005 and P = 0.047, respectively), and pancreatic invasion (P = 0.004). Patients with HES-1Loss showed worse overall survival compared to those with intact HES-1 (HES-1Intact) (P = 0.013). Patients with HES-1Loss/KRASMT (median, 17.3 months) had significantly worse outcomes than those with HES-1Intact/KRASWT (39.9 months), HES-1Intact/KRASMT (47.6 month), and HES-1Loss/KRASWT (36.2 months) (P = 0.010). By multivariate analysis, HES-1Loss (hazard ratio = 1.55, 95% confidence interval (CI), 1.07 – 2.26; P = 0.022) remained an independent prognostic factor. Conclusion: HES-1 expression can be used as a potential prognostic marker and may aid in the management of patients with small intestinal adenocarcinomas.