ABSTRACT
Cancers of the digestive system are the second-most-common cause of deaths (next to that of respiratory system) from malignant neoplasms in the United States (1). The number of estimated new cancer cases for the major gastrointestinal organs (esophagus, stomach, colon, and rectum) will be larger than that of lung cancer in 1993 (1). Since the best means of reducing mortality from the disease and improv ing the posttherapeutic life quality at present consists of detection of a patholog ically early stage and prevention, a clear understanding of the mechanism of carci nogenesis and its susceptibility factors is vital.
