KLK4 and small cell lung carcinoma: Cell culture supernatants of two CTC lines, namely BHGc7 and 10, were analyzed for secreted proteases, including matrix metalloproteinases (MMPs), ADAM/TS, cathepsins, kallikreins, and others, and compared to proteases expressed by SCLC cell lines (GLC14, GLC16, NCI-H526 and SCLC26A).