The urothelium: a battleground for oncogenesis.

A discussion of the term urothelium and reasons for its general adoption are presented. The unique asymmetric unit membrane of the superficial cells is described and its function as a significant barrier against water, some electrolytes and so forth is reviewed. The urothelium bears the brunt of the attack by pollutants and various oncogens. The ongoing battle may be of long duration or recurrent. Many factors enter into the development of a tumor. In addition to actual carcinogens there are irritants, promoters, initiators, weak carcinogens and co-carcinogens. The attack is on the asymmetric unit membrane and the Golgi complex or other coding units. The specialized membrane is destroyed and, instead, a thinner, smooth, flexible membrane develops and overlying it a filamentous glycocalix. The mechanism for specialization by the urothelial cell has been destroyed by the oncogen. Cancer does not occur in unicellular organisms. The cells of all multicellular organisms specialize. The first step toward neoplasia in multicellular organisms is the destruction of specialized mechanisms or coding units of a group of specialized cells, the second step is stimulation by governors and the third is inadequate blood supply. The ultimate in the cancer cell of a multicellular organism, anaplasia, is the return to the unicellular stage.