Simple methods to detect and follow metastatic tumors
Breast Cancer: HER2 is a cell membrane-spanning protein with functional extracellular and intracellular domains. Although HER2 is only one of several proteins capable of stimulating tumor cell growth, it is one of the few where targeted therapeutics have been developed that specifically interfere with extracellular protein interactions and intracellular cell growth signaling. Some of these drugs (Herceptin, for example) block interaction of the extracellular domain of HER2, thereby preventing HER2-driven cell division. Others, such as Tykerb, enter the cell and directly inhibit the tyrosine kinase signaling pathway that triggers cell growth.
The external portion of HER2 found in serum is referred to as the extracellular domain (ECD). Enzymes in the blood cleave the ECD at the cell surface, and small amounts of ECD are present in all sera. When HER2 is overproduced, higher amounts of ECD are present. This is the rationale for HERTEST. Many HER2 breast tumors result in serum levels above the normal range. A 20% rise from one test to the next is considered evidence of HER2 tumor growth, while effective drug therapy results in a 20% decrease in as little as three weeks.
Lung and Kidney Cancer: We are introducing a second blood test, CHECKMARK, to measure another marker, soluble PD-L1. High blood levels indicate a poorer pr collaboraognosis in patients with lung, kidney and several other cancers. But we are collaborating with clinical researchers to evaluate additional utility--can CHECKMARK measure the effectiveness of the immunotherapy drugs called checkpoint inhibitors?