Cancers are generally believed to be derived from single cells that are genetically mutated, resulting in many divisions resulting in an expanding tumor that eventually spreads to local and distant organs. Cancer deaths usually are due to this metastasis affecting the new organs invaded. The initiating cells are often referred to as cancer stem cells. How these turn into heterogeneous populations of cancer cells within the original tumor and even in the metastases is the subject of intense recent research, which has also focused on the tumor's microenvironment and how cancer cells interact with their neighboring supportive cells.In a separate poster presentation at the same AACR Annual Meeting, the Company reported that genes of human cancer jump into adjacent normal cells by fusion of both cells. This study was done in collaboration with researchers from the Garden State Cancer Center, Center for Molecular Medicine and Immunology in Morris Plains, NJ, and the Laboratory of Pathology, Center for Cancer Research, National Cancer Institute, NIH, in Bethesda, MD. This team of scientists discovered a transfer of human genes to normal hamster cells when cells from tissues involved by Hodgkin's lymphoma from two patients were implanted to hamsters. In all, 7 of 24 human genes tested were present in the malignant tumors growing in the hamsters for extended periods of 5 to 6 years, with evidence of metastasis in the hamsters within 21 days of the original grafting of the human tumors. By means of sensitive DNA coloring of the tumor cells, the investigators proved that human and hamster DNA were present in single cancer cells, representing fused cells of both species. "These findings may explain how cancers develop and change with time, spreading by metastasis to other organs by overcoming immunity to the cancer cells and could lead to therapeutic strategies," commented the lead investigator, Dr. David M. Goldenberg, Chief Scientific Officer and Chief Medical Officer of Immunomedics, and President of the Center for Molecular Medicine and Immunology.