Procathepsin D and cancer: From molecular biology to clinical applications.

Procathepsin D (pCD) is overexpressed and secreted by cells of various tumor types including breast and lung carcinomas. pCD affects multiple features of tumor cells including proliferation, invasion, metastases and apoptosis. Several laboratories have previously shown that the mitogenic effect of pCD on cancer cells is mediated via its propeptide part (APpCD). However, the exact mechanism of how pCD affects cancer cells has not been identified. Recent observations have also revealed the possible use of pCD/APpcD as a marker of cancer progression. The purpose of this review is to summarize the three major potentials of pCD-tumor marker, potential drug, and screening agent.