Serum PTN as an Early Indicator for Diagnosis and Prognosis of Non-Small Cell Lung Cancer

Pleotrophin (PTN), a secretory growth factor, is also known as heparin affinity regulatory peptide (Laaroubi et al., 1995), heparin binding growth associated molecule (Hampton et al., 1992), heparin binding growth factor-8 (Milner et al., 1989), and heprin binding neutrophic factor (Kovesdi et al., 1990), due to its high affinity to heparin. PTN shares 50% homogeneous amino acid sequenc with midkine (MK), and these two consist the family of heparin binding growth factors (Kovesdi et al., 1990). PTN is highly consistent among different species, which was reported to present in insects, chicken, mouse, cows, fishes, frogs and human (Tsutsui et al., 1991; Englund et al., 2006). The overexpression of PTN through either autocrine or pericrine is associated with various metastatic human cancers, including breast, prostatic, ovarian, pancreatic and lung cancer, as well as melanoma, choriocarcinoma, and gliobastoma (Schulte et al., 1996; Jager et al., 1997; Lu et al., 2005). It was reported that PTN promoted cell mitosis, migration and chemotaxis (Kadomatsu et al., 2004). Usually, serum PTN in patients with metastatic tumors were easily detected (Kadomatsu et al., 2004), and were highly consistent with the expression of PTN in tumor tissues (Souttou et al., 1998).