Clinical significance of sHER2‑ECD and calpain‑10 expression in tumor tissues of patients with breast cancer

Human epidermal growth factor receptor 2 (HER2) is composed of an extracellular domain (ECD), a lipophilic transmembrane region and an intracellular domain (ICD). The most commonly used method to determine the status of HER2 is immunohistochemistry. However, falsenegative results are sometimes given, which causes some patients to lose the opportunity for antiHER2 therapy. We found that calpain10 may prohibit HER2ECD into peripheral blood resulting in a HER2negative result by the immunohistochemical method. We enrolled 289 patients into our experiment to assess the relationship between sHER2ECD and calpain10. The results showed that there was a positive correlation between sHER2ECD and calpain10. Moreover, we also investigated the prognostic values of sHER2ECD and calpain10 in breast cancer patients. According to the followup results, positive sHER2ECD and tissue calpain10 were indicative of a poor prognosis in breast cancer patients. Subsequently, we further validated the relationship between the two molecules in in vitro experiments. In the in vitro experiments, the level of HER2ECD in the culture medium was increased or decreased with a decrease or increase in calpain10 by transfection technology, showing an inverse association. The results indicated that sHER2ECD and tissue calpain10 levels were powerful factors to assess the status of HER2. In combination with tissue HER2 detection, the occurrence of falsenegative HER2 was reduced, providing patients with additional treatment opportunities. In conclusion, sHER2ECD and tissue calpain10 may be used as new prognostic indices for breast cancer.