Supplementary Material for: KRT18 as a Novel Biomarker of Urothelial Papilloma While Evaluating Low-Grade Papillary Urothelial Neoplasms: Bi-Center Analysis

Introduction: Although urothelial papilloma (UP) is an indolent papillary neoplasm that can mimic the morphology of low-grade papillary urothelial carcinoma (PUC), there is no immunomarker to differentiate reliably these two entities. In addition, the molecular characteristics of UP are not fully understood.
Methods: We conducted an in-depth proteomic analysis of papillary urothelial lesions (n=31), including UP and PUC along with normal urothelium. Protein markers distinguishing UP and PUC were selected with machine learning analysis, followed by internal and external validation using immunohistochemistry.
Results: In the proteomic analysis, UP and PUC showed overlapping proteomic profiles. We identified EHD4 and KRT18 as candidate diagnostic biomarkers of UP. Through immunohistochemical validation in two independent cohorts (n=120), KRT18 was suggested as a novel UP diagnostic marker, able to differentiate UP from low-grade PUC. We also found that 3.5% of patients with UP developed urothelial carcinoma in subsequent resections, supporting the malignant potential of UP. KRT18 downregulation was significantly associated with UPs subsequently progressing to urothelial carcinoma, following their initial diagnosis.
Conclusion: This is the first study that successfully revealed UP’s comprehensive proteomic landscape, while it also identified KRT18 as a potential diagnostic biomarker of UP.

引言：尽管尿路上皮乳头状瘤（urothelial papilloma, UP）是一种惰性乳头状肿瘤，其形态可模拟低级别乳头状尿路上皮癌（low-grade papillary urothelial carcinoma, PUC），但目前尚无可靠的免疫标志物可对这两种病变实体进行鉴别。此外，尿路上皮乳头状瘤的分子特征尚未完全阐明。
方法：本研究对31例乳头状尿路上皮病变标本进行了深度蛋白质组学分析，涵盖尿路上皮乳头状瘤、低级别乳头状尿路上皮癌及正常尿路上皮组织。通过机器学习分析筛选出可鉴别尿路上皮乳头状瘤与低级别乳头状尿路上皮癌的蛋白标志物，随后采用免疫组织化学方法进行内部与外部验证。
结果：蛋白质组学分析显示，尿路上皮乳头状瘤与低级别乳头状尿路上皮癌的蛋白质组谱存在重叠。本研究鉴定出EHD4与KRT18作为尿路上皮乳头状瘤的潜在诊断生物标志物。通过对120例独立队列样本的免疫组织化学验证，KRT18被证实为一种新型尿路上皮乳头状瘤诊断标志物，可有效区分尿路上皮乳头状瘤与低级别乳头状尿路上皮癌。本研究同时发现，3.5%的尿路上皮乳头状瘤患者在后续切除手术中被检出尿路上皮癌，证实了尿路上皮乳头状瘤具有恶性潜能。初始诊断后进展为尿路上皮癌的尿路上皮乳头状瘤样本中，KRT18的表达下调与疾病进展显著相关。
结论：本研究首次完整揭示了尿路上皮乳头状瘤的全蛋白质组图谱，并同时鉴定出KRT18作为尿路上皮乳头状瘤的潜在诊断生物标志物。