Fig. 1.

Primary tumor induced PMN change. This figure shows the process of how primary organ responses directed PMN formation. STEP 1: Some molecules at primary site induce response like inflammation and hypoxia at primary site. These responses assist the proliferation of primary tumor and up-regulates expression of certain molecules. STEP 2: Those molecules are transported from primary site to secondary site through blood vessel. STEP 3: Those molecules induce PMN formation at secondary site through various approaches. Also, some of the molecules that induce response at primary site functioned similarly at secondary site, inducing similar responses that affect PMN formation. The change of PMN built a unique environment which favored metastatic tumor cells for colonization. This figure shows that many molecules and pathways are similar at both sites during primary tumor proliferation and PMN formation, suggesting that PMN formation could be a byproduct of primary tumor growth, and the organ specificity of metastasis might lie within the similarity between organs