Hepsin Paradox Reveals Unexpected Complexity of Metastatic Process

The existing models of cancer progression assume that a linear sequence of geneticand epigenetic events occurs during this process. In this representation every new event(either loss of a tumor-suppressor, or activation of a proto-oncogene) makes cells even moremalignant. The result is a “super” cell that can form metastases at the distant sites.Metastatic cells are believed to carry all genetic and epigenetic characteristics that arenecessary for metastasis formation. Recently, we have shown that cell-surface proteasehepsin causes disorganization of the basement membrane and promotes prostate cancerprogression and metastasis. In human prostate cancer hepsin is upregulated in theprecancerous lesions and this upregulation is maintained in the primary tumors. Remarkablyand completely unexpected for a metastasis-promoting gene, hepsin is expressed at lowlevels in metastatic lesions and the message is completely absent in metastasis-derivedprostate cancer cell lines. These results demonstrate that genes that play an important role inmetastatic process may exercise their role only at the specific fragments of cancerprogression pathway (for example, during initial invasion and tissue disorganization in theprimary organ) and may have no role in metastatic lesions. Future treatment of cancerpatients may rely heavily on monitoring of tumor progression, as treatment efficient inattenuation of initial tumor progression may be inefficient or even adverse at the advancestages of disease.