ERBB2 and neoplasm: Moreover, trastuzumab inhibits the proteolytic cleavage of HER2, preventing shedding of the extracellular domain (ECD) and the generation of phosphorylated truncated p95-HER2, which has been implicated in tumor growth and progression [11]; this activity is reflected by the significant decrease of HER2 ECD in serum of patients in clinical trials after treatment [12, 13].