Program Coordinators: Dr. I. Bernard Weinstein, United States
Dr. Takashi Sugimura, Japan


The year April 1, 1983, to March 31, 1984, is the final year of the second 5-year program of the U.S.-Japan Cooperative Cancer Research Program. The aim of the Etiology Program Area is to clarify the causes of human cancers and to determine the mechanisms of carcinogenesis. It has been envisaged that cancer prevention may be eventually achieved through progress in the science of cancer etiology.
Two seminars were held during this period in the United States. One seminar concerned carcinogenicity, mutagenicity and metabolism of heterocyclic amines. Identification of mutagenic and carcinogenic heterocyclic amines from cooked beef was demonstrated. The importance of the metabolic processing and mechanism of formation of these heterocyclic amines in cooked beef and commercial beef extracts was stressed. The presence of other mutagens in food such as coffee was also introduced. The identification of these heterocyclic amines in usual foods, their quantitation, studies on activation mechanisms of those heterocyclic amines in the target organs and also actual risk estimation of those compounds were discussed as future problems. The second seminar was focused on eukaryotic DNA replication and repair. Initiation mechanism of DNA replication through DNA polymeraseprimase complex was extensively discussed. The recent information on replication of tumor viruses was of considerable help in understanding the initiation of replication. The molecular cloning of DNA synthesizing enzymes, the replication fidelity and the mechanism of DNA repair relevant to the mutator genes were presented.
The study on mutagenic heterocyclic amines was initiated in Japan, and pioneering work in the field of viral and cellular DNA replication was conducted in the United States However, recent rapid progress in both fields in both countries made these two seminars quite timely and beneficial to the scientists of the United States and Japan.
Seven scientists came to the United States from Japan as exchange scientists four conducting collaborative research in the area of viral oncology and three in the area of chemical carcinogenesis. Two scientists came to Japan from the United States as exchange scientists and carried out collaborative research in the area of viral oncology. Although the exchange visits were relatively short, this program was effective in supporting research of mutual interest and helped to initiate new collaborative research which will further promote future exchanges under this program.