Protein analysis of urachal carcinoma tissue based on different antibody-drug conjugate therapeutic targets.

852 Background: Urachal carcinoma (UrC) is an extremely rare cancer, and there is still a lack of standard drug treatment models for advanced UrC. Antibody-drug conjugate (ADC) therapy represents a promising cancer treatment method. However, the efficacy of ADC on UrC remains unclear due to the scarcity of knowledge about the immunohistochemical features of relevant targets. This study focused on the immunohistochemical features of UrC based on ADC therapeutic targets and its relationship with overall survival (OS), providing a basis for UrC treatment. Methods: A total of 45 postoperative pathological specimens confirmed to be UrC were collected. Using immunohistochemistry, protein expression levels of ADC targets HER2, Nectin-4, Claudin18.2, Trop2, Mesothelin, and the immunotherapy target PD-L1 were assessed, with the proportion of high expression (2+ or 3+) of target proteins evaluated. 38 cases with complete clinical information were screened to evaluate the relationship between the expression of target proteins and OS. Results: Among the ADC therapeutic targets, Trop2 had the highest high expression rate (55.6%) in UrC tissues, followed by Mesothelin (46.7%), Claudin18.2 (31.1%), Nectin-4 (22.2%), and HER2 (15.6%). The high expression rate of PD-L1 was 15.6%. The median age of UrC patients was 53.5 years. Sheldon stage I, III and IV patients accounted for 2.6%, 89.5% and 7.9%, respectively. Survival analysis revealed that the five-year survival rate was 85.7% in the low Trop2 expression group and 49.2% in the high expression group. High expression of Trop2 was associated with poor OS (P=0.031). Conclusions: The target proteins of ADC are expressed in UrC tissue. Trop2 exhibits a significant high expression rate, and UrC patients with high Trop2 expression have a worse prognosis. Trop2 could be a pivotal target for future ADC treatment of UrC.