THE ROLE OF RAS MUTATION IN PANCREATIC-CANCER, PRECANCEROUS LESIONS, AND CHRONIC-PANCREATITIS

Point mutations in K-ras codon 12 were detected in 7 of 10 specimens (70%) of frozen tissues. To determine when point mutations appear in the oncogenic stage, paraffin-embedded tissues of pancreatic cancer, hyperplastic ductal lesions in pancreatic cancer and in chronic pancreatitis were used. DNA extracted from the paraffin-embedded tissues classified as cancer, atypical and nonatypical hyperplasia of the pancreatic duct epithelium, and normal tissue from pancreatic cancer patients and those classified as atypical hyperplasia of the pancreatic duct epithelium and normal tissue from chronic pancreatitis patients were amplified by the polymerase chain reaction (PCR) method. Point mutations were detected in 8 of 17 cancer cases (47.0%). In 5 of 8 point mutation positive cases, atypical hyperplasias were found in the surrounding tissues. In all 5 of these atypical hyperplasia, point mutations, that is, GGT-GTT (Gly-Val) and GGT-GAT (Gly-Asp), were detected. The same transitions were observed in the cancer of these 5 cases. These results suggest a strong relationship between cancer and atypical hyperplasia surrounding cancer. Although atypical hyperplasia around cancer was histologically very similar to that found in chronic pancreatitis, all 5 atypical and 5 nonatypical hyperplasias in chronic pancreatitis were negative for ras point mutation. Thus, the result argues against an association between chronic pancreatitis and pancreatic cancer.