The role of thrombomodulin in modulating ITGB3 expression and its implications for triple-negative breast cancer progression.

Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer (BC) compared to other BC subtypes in clinical settings. Currently, there are no effective therapeutic strategies for TNBC treatment. Therefore, there is an urgent need to identify suitable biomarkers or therapeutic targets for TNBC patients. Thrombomodulin (TM) plays a role in cancer progression and metastasis in many different cancers. However, the role of TM in TNBC is not yet fully understood. First, silenced-TM in MDA-MB-231 cells caused an increase in proliferative and metastatic activity. In contrast, overexpression of TM in Hs578T cells caused a reduction in proliferation, invasion, and migration rate. Using RNA-seq analysis, we found that Integrin beta 3 (ITGB3) expression may be a downstream target of TM. Furthermore, we found an increase in ITGB3 levels in TM-KD cells by QPCR and western blot analysis but a decrease in ITGB3 levels in TM-overexpressing cells. We found phospho-smad2/3 levels were increased in TM-KD cells but decreased in TM-overexpressing cells. This implies that TM negatively regulates ITGB3 levels through the activation of the smad2/3 pathway. Silencing ITGB3 in TM-KD cells caused a decrease in proliferation and migration. Finally, we found that higher ITGB3 levels were correlated with poor overall survival and relapse-free survival in patients with TNBC. Our results indicated a novel regulatory relationship between TM and ITGB3 in TNBC.