E2F1 and breast cancer: First, a number of human cancers, including hepatocellular carcinoma, lung cancer, esophageal cancer, colorectal cancer, bladder cancer, prostate carcinoma, Ewings' sarcoma, and germ cell carcinoma, exhibited increased expression of H19 [22]; secondly, the ectopic expression of H19 enhances the tumorigenicity of breast cancer cells [26]; thirdly, silencing H19 by siRNA attenuated the clonogenicity and anchorage-independent growth of the lung cancer cells and breast cancer cells [27]; lastly, the expression of H19 is up-regulated by both c-Myc and E2F1 oncogenes [23, 27].