Historical assumptions

John Beard wrote in 1902 that cancer cells resemble embryonic cells trophoblastic. At the beginning of pregnancy, these cells made sure that the embryo can implant in the uterus. The growth is aggressive and chaotic. The cells divided quickly and would gain their energy from sugar fermentation. They suppressed the immune system of the mother and produced human chorionic gonadotropin (hCG), which is now recognized as a tumor marker. The growth stops when the embryo from the seventh week, the pancreas produces enzymes. Without these enzymes would give the most malignant tumor, a choriocarcinoma. The assumption that cancer tumors would gain energy from the fermentation of sugar (ie, the tumor would live anaerobic) was the basis for many outdated treatment methods.
In 1908, Ellermann and Bang discovered a virus that caused leukemia in chickens.
Peyton Rous was then filtered of 1911 from a muscle tumor with the high filter rating of 120 nanometers, an extract, with which he could again cause cancer. He suspected a virus in this extract. 1966 Rous was awarded for the discovery of the Rous sarcoma virus (RSV), the Nobel Prize.