tumor associated calcium signal transducer 2

Overview

Tumor-associated calcium signal transducer 2 (TROP2), encoded by the TACSTD2 gene and also known as trophoblast cell-surface antigen 2 (Trop-2), is a type I transmembrane glycoprotein that was originally identified on trophoblast cells of the placenta. It functions as a calcium signal transducer and is implicated in the regulation of cell proliferation, survival, and adhesion. Under normal physiological conditions, TROP2 expression is restricted to a limited set of epithelial tissues; however, it is broadly and frequently overexpressed across a wide range of solid tumors, including non-small cell lung cancer (NSCLC), small cell lung cancer (SCLC), pancreatic cancer, and breast, gastric, and urothelial carcinomas. This tumor-enriched expression pattern, combined with its extracellular accessibility as a membrane-bound antigen, makes TROP2 a highly attractive therapeutic target.

The protein's association with cancer invasiveness and poorer patient outcomes has driven extensive efforts to exploit it as an antibody-drug conjugate (ADC) target. Several TROP2-directed ADCs have advanced through clinical development, with at least one receiving regulatory approval from both the Food and Drug Administration (FDA) and China's National Medical Products Administration (NMPA) for use in patients with acquired resistance to third-generation EGFR tyrosine kinase inhibitors (TKIs). Beyond ADCs, TROP2 is now being explored in radioimmunotherapy, bispecific antibody formats, and proteolysis-targeting chimera (PROTAC)-based platforms, reflecting its versatility as an oncological target.

Focus of Latest Publications

Recent publications have continued to evaluate tumor associated calcium signal transducer 2 (TROP2/TACSTD2) as a clinically relevant surface target across several cancers, especially in the context of antibody-drug conjugates (ADCs) and biomarker selection. In ovarian cancer, TROP2 expression was assessed alongside HER2 and nectin-4 across histotypes to determine whether target abundance varies by disease subtype and could inform patient selection for ADC-based therapy. In metastatic breast cancer, serial circulating tumor cell (CTC) imaging was used to monitor TROP2 and HER2 during treatment with TROP2- or HER2-directed ADCs, showing marked heterogeneity of target expression at the single-cell level and indicating that baseline TROP2 levels on CTCs did not predict depth of response.

Several studies linked TROP2 to treatment response or resistance biology. In pancreatic ductal adenocarcinoma, prolonged Kras-MAPK inhibition induced an interferon/NF-κB-driven cell-state transition with EMT features, accompanied by marked upregulation of TROP2; the authors reported that combining the TROP2-directed ADC sacituzumab govitecan with Kras or ERK inhibitors significantly suppressed tumor growth in xenograft models. In metastatic prostate cancer treated with 177Lu-PSMA-617, plasma extracellular vesicle proteomics identified Trop-2 among several cell-surface proteins associated with worse overall survival and correlated with tumor burden measures, supporting its potential as part of a liquid-biopsy biomarker panel. In small cell lung carcinoma, TROP2 was included among therapeutic targets examined in paired biopsy samples to compare target protein expression in de novo and transformed disease, reflecting ongoing interest in its role in patient stratification.

TROP2 has also been incorporated into emerging therapeutic strategies beyond ADC monotherapy. A phase 3 trial in PD-L1-positive advanced non-small-cell lung cancer evaluated sacituzumab tirumotecan, a TROP2-targeting ADC, in combination with pembrolizumab as first-line treatment. In another preclinical study, TROP2 was used as a tumor-specific receptor to build a bispecific antibody designed to target Frizzled and inhibit Wnt signaling selectively in tumor cells while sparing normal intestinal tissue. Across these reports, TROP2 is consistently presented as a surface marker with therapeutic and biomarker potential, but with expression heterogeneity and context dependence that may limit simple expression-based prediction of benefit.