Relationship Between Immunophenotypes, Genetic Profiles, and Clinicopathologic Characteristics in Small Bowel Adenocarcinoma.

Small bowel adenocarcinoma (SBA) is rare, and scant data exist regarding its molecular and clinicopathologic characteristics. This study aimed to clarify the correlation between immunophenotypes, DNA mismatch repair status, genomic profiling, and clinicopathologic characteristics in patients with SBA. We examined 68 surgical resections from patients with primary SBA for immunohistochemical analyses of CK7, CK20, CD10, CDX2, MUC1, MUC2, MUC4, MUC5AC, and MUC6 expression as well as mismatch repair status. Genomic profiling was performed on 30 cases using targeted next-generation sequencing. Tumor mucin phenotypes were classified as gastric, intestinal, gastrointestinal, or null based on MUC2, MUC5AC, MUC6, and CD10 immunostaining. The expression of these proteins was categorized into 3 classifications according to their relationship to: (1) tumor location: CK7/CK20, MUC4, and MUC6; (2) histologic type: mucinous adenocarcinoma was positive for MUC2 and negative for MUC6; and (3) TNM stage: CD10 was downregulated, whereas MUC1 was upregulated in advanced TNM stages. CDX2 was a specific marker for SBA generally expressed in the small intestine. MUC1 and MUC4 expression was significantly associated with worse prognosis. MUC2 expression correlated with better prognosis, except for mucinous adenocarcinoma. Although the difference was not statistically significant, gastric-type tumors were more frequently located in the duodenum and were absent in the ileum. APC and CTNNB1 mutations were not found in the gastric-type tumors. The SBA immunophenotype correlated with tumor location, biological behavior, and genomic alterations. Our results suggest that the molecular pathway involved in carcinogenesis of gastric-type SBA differs from that of intestinal-type SBA.

Clinical significance of programmed cell death-ligand expression in small bowel adenocarcinoma is determined by the tumor microenvironment.

BACKGROUND: Comprehensive genomic analysis has shown that small bowel adenocarcinoma (SBA) has different genomic profiles from gastric and colorectal cancers. Hence, it is essential to establish chemotherapeutic regimens based on SBA characteristics. The expression of programmed cell death-ligand 1 (PD-L1) and programmed cell death-ligand 2 (PD-L2) in SBA is not fully understood. Anti-PD-L1/PD-1 therapy uses tumor-infiltrating lymphocytes (TILs); therefore, the status of TILs in the tumor microenvironment (TME) may influence their efficacy. The ratio of FoxP3+ to CD8+ T cells has been reported to be useful in predicting the prognosis of digestive system cancers. AIM: To investigate the clinicopathological significance of PD-L1/2 expression according to the status of TILs in SBA tissues. METHODS: We performed immunohistochemical analysis for PD-L1, PD-L2, CD8, FoxP3, and DNA mismatch repair (MMR) proteins using formalin-fixed, paraffin-embedded tissues from 50 patients diagnosed with primary SBA. The immunoreactivities of PD-L1 and PD-L2 were determined separately in tumor cells and tumor-infiltrating immune cells throughout the tumor center and invasive margins, and finally evaluated using the combined positive score (CPS). We assessed CD8+ and FoxP3+ T cells in the intratumoral and tumor-surrounding stroma. Subsequently, we calculated and summed the ratio of FoxP3 to CD8+ T cell counts. Immune-related cell densities were graded as low or high. Immunohistochemical results were compared with clinicopathological factors and patient prognosis. The distribution of cancer-specific survival (CSS) was estimated using the Kaplan-Meier method, and the log-rank test was used to test for significant differences in CSS. A Cox proportional hazard model was also used to assess the effect of tumor variables on CSS. RESULTS: PD-L1 expression was positive in 34% in tumor cells (T-PD-L1) and 54% in tumor-infiltrating immune cells (I-PD-L1) of the cases examined. T-PD-L2 was positive in 34% and I-PD-L2 was positive in 42% of the cases. PD-L1 CPS ≥ 10 and PD-L2 CPS ≥ 10 were observed in 50% and 56% of the cases, respectively. Deficient MMR (dMMR) was 14% of the cases. T-PD-L1, I-PD-L1 and PD-L1 CPS ≥ 10 were all significantly associated with dMMR (P = 0.037, P = 0.009, and P = 0.005, respectively). T-PD-L1, I-PD-L1, and PD-L1 CPS ≥ 10 were all associated with deeper depth of invasion (P = 0.001, P = 0.024, and P = 0.002, respectively). I-PD-L2 expression and PD-L2 CPS ≥ 10 were significantly higher in the differentiated histological type (P = 0.015 and P = 0.030, respectively). The I-PD-L1 and I-PD-L2 levels were significantly associated with better CSS (P = 0.037 and P = 0.015, respectively). CD8-high was significantly associated with less lymph node metastasis (P = 0.047), less distant metastasis (P = 0.024), less peritoneal dissemination (P = 0.034), and earlier TNM stage (P = 0.047). The CD8-high group had better prognosis than the CD8-low group (P = 0.018). FoxP3 expression was not associated with any clinicopathological factors or prognosis. We found that patients with PD-L2 CPS ≥ 10 tended to have worse prognosis in the FoxP3/CD8-low group (P = 0.088). CONCLUSION: The clinicopathological significance of PD-L1/2 expression may differ depending on the TME status. Immune checkpoint inhibitors may improve the prognosis of SBA patients with low FoxP3/CD8 ratio and PD-L2 expression.

Comparison of Linked Color Imaging and White Light Imaging Colonoscopy for Detection of Colorectal Adenoma Requiring Endoscopic Treatment: A Single-Center Randomized Controlled Trial.

BACKGROUND: Linked color imaging (LCI) improves detection of colorectal neoplastic lesions during colonoscopy. However, polyps <5 mm in diameter often do not require resection, and the benefits of LCI are unclear for detection of colorectal polyps ≥5 mm that are indicated for endoscopic resection in clinical practice. This randomized controlled trial compared rates of detection of adenoma polyps, stratified by size, for LCI and white light imaging (WLI). METHODS: We compared ADR (5 mm-) and PDR (5 mm-), which were defined as the proportion of patients with at least one adenoma or polyp with a diameter of 5 mm or larger in the LCI and WLI groups. Moreover, we estimated ADR and PDR for diameters between 5 and 10 mm (ADR (5-9 mm), PDR (5-9 mm) ) and for diameters larger than 10 mm (ADR (10 mm-), PDR (10 mm-) ). RESULTS: Data from 594 patients (LCI, n=305; WLI, n=289) were analyzed. ADR (5 mm-) and PDR (5 mm-) were significantly higher in the LCI group than in the WLI group (ADR (5 mm-): P=0.016, PDR (5 mm-): P=0.020). In the assessment of adenoma and polyp size, ADR (5-9 mm) and PDR (5-9 mm) were significantly higher in the LCI group than in the WLI group, although no significant differences were seen in ADR (10 mm-) and PDR (10 mm-) between these groups. CONCLUSIONS: Polyps ≥5 mm, which are indicated for endoscopic treatment, were more easily visualized with LCI mode than with WLI mode. The improvement in detection rate was obvious for polyps <10 mm, which are easier to miss.

Risk factors for small intestinal adenocarcinomas that are common in the proximal small intestine.

The frequency of primary small intestinal adenocarcinoma is increasing but is still low. Its frequency is approximately 3% of that of colorectal adenocarcinoma. Considering that the small intestine occupies 90% of the surface area of the gastrointestinal tract, small intestinal adenocarcinoma is very rare. The main site of small intestinal adenocarcinoma is the proximal small intestine. Based on this characteristic, dietary animal proteins/lipids and bile concentrations are implicated and reported to be involved in carcinogenesis. Since most nutrients are absorbed in the proximal small intestine, the effect of absorbable intestinal content is a suitable explanation for why small intestinal adenocarcinoma is more common in the proximal small intestine. The proportion of aerobic bacteria is high in the proximal small intestine, but the absolute number of bacteria is low. In addition, the length and density of villi are greater in the proximal small intestine. However, the involvement of villi is considered to be low because the number of small intestinal adenocarcinomas is much smaller than that of colorectal adenocarcinomas. On the other hand, the reason for the low incidence of small intestinal adenocarcinoma in the distal small intestine may be that immune organs reside there. Genetic and disease factors increase the likelihood of small intestinal adenocarcinoma. In carcinogenesis experiments in which the positions of the small and large intestines were exchanged, tumors still occurred in the large intestinal mucosa more often. In other words, the influence of the intestinal contents is small, and there is a large difference in epithelial properties between the small intestine and the large intestine. In conclusion, small intestinal adenocarcinoma is rare compared to large intestinal adenocarcinoma due to the nature of the epithelium. It is reasonable to assume that diet is a trigger for small intestinal adenocarcinoma.

Genetic analysis of Japanese patients with small bowel adenocarcinoma using next-generation sequencing.

BACKGROUND: Small bowel adenocarcinomas (SBAs) are rare and there is little comprehensive data on SBA genomic alterations for Asian patients. This study aimed to profile genomic alterations of SBA in Japanese patients using targeted next-generation sequencing (NGS). METHODS: We examined 22 surgical resections from patients with primary SBA. SBA genomic alterations were analyzed by NGS. Mismatch repair (MMR) status was determined by immunohistochemical analysis. Mucin phenotypes were classified as gastric (G), intestinal (I), gastrointestinal (GI), and null (N) types on MUC2, MUC5AC, MUC6, and CD10 immunostaining. RESULTS: The most common genomic alterations found in SBA tumors were TP53 (n = 16), followed by KRAS (n = 6), APC (n = 5), PIK3CA (n = 4), CTNNB1 (n = 3), KIT (n = 2), BRAF (n = 2), CDKN2A (n = 2), and PTEN (n = 2). Deficient MMR tumors were observed in 6 out of 22 patients. Tumor mucin phenotypes included 2 in G-type, 12 in I-type, 3 in GI-type, and 5 in N-type. APC and CTNNB1 mutations were not found in G-type and GI-type tumors. KRAS mutations were found in all tumor types except for G-type tumors. TP53 mutations were found in all tumor types. Although no single gene mutation was associated with overall survival (OS), we found that KRAS mutations were associated with significant worse OS in patients with proficient MMR tumors. CONCLUSIONS: SBA genomic alterations in Japanese patients do not differ significantly from those reports in Western countries. Tumor localization, mucin phenotype, and MMR status all appear to impact SBA gene mutations.

Pilot Study Indicates Helicobacter pylori Infection May Induce Small Intestinal Mucosal Injury.

BACKGROUND AND AIM: Helicobacter pylori infection is a primary cause of gastroduodenal ulcers. To investigate whether there is an association between H. pylori infection and small intestinal mucosal injury. METHODS: Patients were selected from a general pool of subjects who underwent capsule endoscopy for current or past obscure gastrointestinal bleeding. Characteristics including age, gender, history, treatment with nonsteroidal anti-inflammatory drugs (NSAIDs) and/or acid suppressant, diagnosis, and H. pylori infection were investigated. Patients infected with H. pylori had positive test result, ranging 30 days before to 30 days after capsule endoscopy. Patients diagnosed with inflammatory diseases, malignant tumors, etc. were excluded. All video images were re-evaluated to count small intestinal mucosal breaks. Eligible patient variables were compared. RESULTS: A total of 92 patients (30 infected with H. pylori/62 uninfected) were eligible. By univariate analysis of the number of mucosal breaks, patients treated with NSAIDs were found to have more mucosal breaks than patients untreated (38%: 8/21 vs. 18%: 13/71; p = 0.004), and the possible association was detected between patients infected with H. pylori and those who were not (67%: 14/21 vs. 37%: 26/71; p = 0.081). When comparing the H. pylori infected and uninfected patients, the rate of patients with mucosal breaks was greater in infected patients (47%: 14/30 vs. 11%: 7/62; p = 0.001). After excluding patients treated with NSAIDs, the number of mucosal breaks was also greater in patients infected with H. pylori (1.2 ± 1.5 vs. 0.38 ± 0.62; p = 0.001). CONCLUSION: There is a possibility that H. pylori infection induces small intestinal mucosal injury.