PTN and lung cancer: The results showed that PTN mRNA was expressed in nine SCLC and three NSCLC cells.17 In a subsequent small sample study, 87% of SCLC patients and 63% of NSCLC patients had elevated serum levels of PTN, suggesting the potential role of serum PTN levels in the diagnosis of lung cancer.18 Recent studies suggest that serum PTN may be a useful marker for the diagnosis and prognosis of lung cancer.19 Pleiotrophin is overexpressed in SCLC tissues and the levels of PTN expression are associated with the diagnosis and prognosis.20