PTN, also named heparin affinity regulatory peptide (HARP) in some studies, is a potent angiogenic factor, which stimulates proliferation and migration of endothelial cells during normal development and in cancer (Zhang and Deuel, 1999; Perez-Pinera et al., 2007; Perez-Pinera et al., 2008; Papadimitriou et al., 2022; Papadimitriou et al., 2009; Mikelis and Papadimitriou, 2008; Mikelis et al., 2007). The gene discussed is PTN; the disease is cancer.