Tacstd2, also known as TROP2, encodes a transmembrane glycoprotein. It is an intracellular calcium signal transducer, signaling cells for self-renewal, proliferation, invasion, and survival. It has stem-cell like qualities and is expressed in many normal tissues, yet overexpressed in numerous cancers [3].

Tacstd2/Trop2 expression is evolutionarily conserved in lungs of various vertebrates. Its level increases in lungs infected with mainly viral pathogens, likely representing a mechanism to maintain/restore epithelial barrier function and contribute to lung regeneration [1]. In solid tumors, Tacstd2 expression is associated with decreased overall survival in some cancers, and is correlated with key driver alterations and a more active immune microenvironment. Pathogenic mutations like TP53 in certain cancers are associated with Tacstd2-high tumors [2]. In urothelial carcinoma, Tacstd2/TROP2 is highly expressed at protein and transcript levels, representing a suitable target for ADC treatment in most cases, and its expression loss is associated with aggressive subtypes [4].

In conclusion, Tacstd2 plays a significant role in both normal physiological processes such as lung response to infection and in disease conditions, particularly cancer. Its overexpression in cancers and associations with key mutations and immune microenvironment make it a potential biomarker and therapeutic target. The understanding from various research, though lacking in KO/CKO mouse model data in these references, provides insights into its functions in different biological and disease contexts.