Levels of expression of pleiotrophin and protein tyrosine phosphataseζ are decreased in human colorectal cancers

Pleiotrophin (PTN) and midkine (MK) form a distinct family of heparin binding growth factors. In a variety of human cancers, MK mRNA levels have been found to be increased as compared to adjacent non-cancerous tissues. We examined the expression of PTN, its putative receptor, namely protein tyrosine phosphataseζ (PTPζ, also known as RPTPβ), and a related protein, receptor-type protein tyrosine phosphataseγ (RPTPγ), in human colorectal cancers and the adjacent normal mucosae. PTN and PTPζ mRNA levels were generally decreased in colorectal cancers as compared to those in adjacent normal mucosae, while the RPTPγ level was not significantly different between them.