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Objectives: Subepithelial lesions (SELs) are associated with various endoscopic resection (ER) outcomes and diagnostic challenges. We aimed to establish a tool for predicting ER‐related outcomes and diagnosing SELs and to investigate the predictive value of endoscopic ultrasound (EUS). Methods: Phase 1 (system development) was performed in a retrospective cohort (n = 837) who underwent EUS before ER for SELs at eight hospitals. Prediction models for five key outcomes were developed using logistic regression. Models with satisfactory internal validation performance were included in a mobile application system, SEL endoscopic resection predictor (SELERP). In Phase 2, the models were externally validated in a prospective cohort of 200 patients. Results: An SELERP was developed using EUS characteristics, which included 10 models for five key outcomes: post‐ER ulcer management, short procedure time, long hospital stay, high medication costs, and diagnosis of SELs. In Phase 1, 10 models were derived and validated (C‐statistics, 0.67–0.99; calibration‐in‐the‐large, −0.14–0.10; calibration slopes, 0.92–1.08). In Phase 2, the derived risk prediction models showed convincing discrimination (C‐statistics, 0.64–0.73) and calibration (calibration‐in‐the‐large, −0.02–0.05; calibration slopes, 1.01–1.09) in the prospective cohort. The sensitivities and specificities of the five diagnostic models were 68.3–95.7% and 64.1–83.3%, respectively. Conclusion: We developed and prospectively validated an application system for the prediction of ER outcomes and diagnosis of SELs, which could aid clinical decision‐making and facilitate patient–physician consultation. EUS features significantly contributed to the prediction. Trial registration: Chinese Clinical Trial Registry, http://www.chictr.org.cn (ChiCTR2000040118). [ABSTRACT FROM AUTHOR]

Colorectal cancer is a major health problem with a significant impact on the patients' quality of life. 5‐Fluorouracil is the most common chemotherapy drug used for this type of cancer. While its molecular mechanism is the inhibition of DNA synthesis via the inhibition of thymine nucleotide synthetase, its complete anticancer mechanism is not clear. Membrane‐associated RING‐CH‐1 (MARCH1) is an E3 ubiquitin ligase that plays an important role in antigen presentation. However, MARCH1 has not been studied in the context of colorectal cancer. In this study, we demonstrated that MARCH1 is highly expressed in colorectal cancer tissues and cell lines. Furthermore, migration and invasion of colorectal tumor cells were inhibited via transfection with small interfering RNAs to suppress the expression of MARCH1. The western blot analysis showed that MARCH1 regulates epithelial–mesenchymal transition and the PI3K/AKT pathway. Moreover, 5‐fluorouracil inhibited the proliferation, migration, and invasion of tumor cells, via the targeting of MARCH1 and the consequent downregulation of the PI3K/AKT pathway, impacting the progression of epithelial–mesenchymal transition. In conclusion, our study shows that MARCH1 may play a role as an oncogene in colorectal cancer and may represent a new target molecule of 5‐fluorouracil. [ABSTRACT FROM AUTHOR]