Cancer Drugs: From Nitrogen Mustards to Gleevec

Whereas infectious diseases are the scourge of developing countries, cancer is the most significant affliction in developed countries. At the beginning of 2005, the American Cancer Society announced that, for the first time, cancer had surpassed heart disease as the number one killer of Americans. Cancer, which is the uncontrollable multiplication of cells, has been in existence as long as animals have; evidence of cancers has been found in dinosaur bones. Cancers have also been found on mummies dating back 2,500 years. An operation to remove cancer was documented in the Ebers papyrus found in Egypt. In ancient times cancer was a relatively rare disease, because infectious diseases often made the life span so short that cancer had little chance to proliferate. Hippocrates (460–370 B.C.) coined the word cancer, which means “crab” in Greek. There are over 110 types of cancer, which can be divided into four categories depending on the tissue involved: carcinoma, lymphoma, leukemia, and sarcoma. Carcinomas are the most common, with 85–90% of all cancers falling into this category. Carcinomas are tumors that originate in epithelial tissue such as skin, breast, lung, prostate, stomach, colon, ovary, and so forth. Lymphomas are cancers of the lymphatic system. Leukemia is the cancer of the blood, bone marrow, and liver. Sarcomas, the rarest of all four types, are tumors arising from cells in connective tissue, bone, or muscle. It seems inconceivable that we had almost no clue about the origin of cancers up until the mid-1970s, despite the existence of cancer that predates human life. The debate raged on as to what caused cancer, with one camp believing that carcinogens (cancer-causing agents such as chemicals, X-ray, and ultraviolet light) were to blame, whereas the other thought that viruses were the culprits. The carcinogen theory took root first. As early as 1775, British doctor Percival Pott made the astute epidemiological observation that young English boys employed as chimney sweeps were more prone to develop scrotal skin cancers than their French counterparts. Further scrutiny revealed that the continental sweeps bathed more frequently after work, which prompted Pott to speculate that long exposure to coal tar caused skin cancer. In 1915, 140 years later, Katsusaburo Yamagiwa and Koichi Ichikawa confirmed Pott’s theory in an animal model.