Current diagnostic assays for many
cancers are
antigen-based and rely on the detection of circulating
proteins that are associated with a particular
cancer. These assays depend on the expression, synthesis, and release of specific
proteins by cells (e.g.,
tumor cells) through either active secretion or shedding, or as a consequence of cell death (either
necrosis or apoptosis). As such, these antigenic
proteins must "escape" the primary site of disease, saturate the antigen-processing capacity of the individual's immune components, gain access to the circulation, and reach a sufficient steady-state concentration to be detected by
enzyme- or radiolabel-based immunoassays. These events usually occur after the initial establishment of disease. Thus, and despite the fact that certain specific antigenic
epitopes exhibit common recognition among patients with the same
tumor types, the use of these
antigen-based
cancer assays has not been widely accepted in clinical practice, and many individual countries differ in the use of these potential diagnostic factors. Lately, an increasing number of studies demonstrated that
procathepsin D secreted from
cancer cells, acts as a
mitogen on
cancer cells and stimulates their pro-invasive and pro-metastatic properties. In this report, we focused on the possibility to use anti-
procathepsin D autoantibodies as a diagnostic and/or predictive marker for
cancers.