Detection of Genetic Alterations by MASA Method and its Clinical Application

Naoko Hayashi, Hiroshi Egami, Sadamu Takano, Michio Ogawa, Shoji Nakamori¹⁾, Shingi Imaoka¹⁾, Yusuke Namamura²⁾

Department of Surgery II, Kumamoto University Medical School
Department of Surgical Oncology, Center for Adult Diseases¹⁾
Laboratory of Molecular Medicine, Institute of Medical Scinece, University of Tokyo²⁾

The mutant-allele-specific amplification (MASA) method is capable of detecting one tumor cell containing genetic changes in a sample containing 10,000 normal cells. We screened 120 colorectal cancers from patients who had no histologically detectable lymph-node metastasis at the time of operation for K-ras and p53 mutations, and examined corresponding regional lymph nodes at the genetic level by the MASA method. Somatic mutations were identified in 71 tumors; 27 of 37 patients with genetically positive lymph nodes had a tumor recurrence within 5 years of surgery; none of 34 patients without genetically confirmed lymph node metastasis had a recurrence. Thus, we found that tumor cells in lymph nodes identified by this genetic method had prognostic significance. We also analyzed, DNA samples from pancreatic juice for the K-ras mutation, to diagnose pancreatic cancer in the early stage. K-ras mutations in pancreatic juice were detected in 4 of 5 (80%) with pancreatic cancer. Hence, clinical application of the MASA method may be useful for determining the prognosis of cancer patients and for detecting cancer in the early stage.

Key words
mutant-allele-amplification (MASA) method, lymph node metastasis of colorectal cancer, K-ras gene mutations in pancreatic juice

Reprint requests
Michio Ogawa Department of Surgery II, Kumamoto University Medical School
1-1-1 Honjo, Kumamoto, 860 JAPAN

Accepted
December 11, 1996

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