Introduction
The molecular and clinicopathological features of primary small bowel adenocarcinoma (SBA) are less well understood than those of colorectal and gastric cancers, primarily due to its rarity. Cancer stem cells, a small subpopulation of tumor cells, are capable of initiating tumors and contributing to relapse. However, the clinicopathological significance of cancer stem cell marker expression in SBA remains unclear.
Aims & Methods
To investigate the localization and clinicopathological relevance of stem cell markers in SBA, we conducted immunohistochemical analysis of CD44, CD44v, CD44v9, CD133, Lgr5, β-catenin and E-cadherin using formalin-fixed paraffin-embedded tissue samples from 57 SBA cases. DNA mismatch repair (MMR) status was assessed through immunostaining for MLH1, MSH2, MLH6, and PMS2. We then compared the expression patterns with clinicopathological data, including sex, age, localization, histological type, depth of invasion, lymph node metastasis, distant metastasis, clinical stage, disease-free survival and cancer-specific survival. Correlations between protein expression and prognosis were evaluated using the Kaplan-Meier method and Cox proportional hazards regression analysis.
Results
The mean follow-up period was 52 months (median: 46; range: 4–110 months), during which 19 patients died. Tumor localization was as follows: duodenum (n=24), jejunum (n=28), and ileum (n=5). Histologically, 47 tumors were well differentiated, 6 poorly differentiated, and 4 were mucinous adenocarcinoma. According to the TNM classification, 15 cases were stage I, 18 stage II, 10 stage III, and 14 stage IV. Positive expression rates for each protein were CD44, 54%; CD44v6, 46%; CD44v9, 49%; CD133, 39%; and Lgr5, 37%. Lgr5 expression was significantly correlated with lymph node metastasis, distant metastasis, and advanced TNM stage. It was also associated with reduced membranous β-catenin staining, indicative of Wnt/β-catenin pathway activation. CD44 and its variants were significantly associated with both lymph node metastasis and distant metastasis, as well as abnormal reduced membranous β-catenin staining and E-cadherin staining. CD133 was expressed in 39% of cases but did not correlate with any clinicopathological factors. Notably, its expression was higher in MMR-proficient tumors compared to MMR-deficiency ones. Univariate analysis identified histological type, depth of invasion, lymph node metastasis, CD44, CD44v6, CD44v9, CD133 and Lgr5 expression as significantly associated with cancer-specific survival. In multivariate analysis, both lymph node status (hazard ratio: 16.4) and Lgr5 expression (hazard ratio: 3.7) retained independent prognostic significance. For disease-free survival, univariate analysis using the Cox proportional hazards model revealed that lymph node metastasis, CD44v6 and Lgr5 had significant prognostic value. Multivariate analysis confirmed lymph node metastasis (hazard ratio: 31.2) and Lgr5 expression (hazard ratio: 28.7) as independent predictors of poorer disease-free survival.
Conclusion
Our findings suggest that all analyzed cancer stem cell markers had prognostic relevance in SBA. CD44 and its variant isoforms expression are associated with epithelial-mesenchymal transition. Lgr5 expression is linked to Wnt/β-catenin pathway and is an independent predictor of poor cancer-specific survival and disease-free survival, regardless of lymph node metastasis.