[70]. Numerous physiological processes involving cellular invasion, blastocyst implantation, and placental development occur under reduced oxygen environments [71]. We have shown that these physiological processes manifested high levels of H19 RNA [23]. Thus, it seemed logical to test whether H19 RNA levels are modulated under hypoxic stress. In one specific tumor such as human hepatocellular carcinoma (HCC), H19 RNA levels are much higher in both the primary and the metastatic tumor than in normal liver (Fig. S1). Here, H19 is linked to metastatic neoplasm.