Cancer ecogenetics: studying genetic and environment interactions through epidemiology.

CANCER ECOGENETICS Are cancer epidemiologists ready for molecular geneticists? This could have been the subtitle of a workshop, 'Genetic and Environmental Factors in Etiologic Studies of Cancer,' a European regional scientific meeting of the International Epidemiology Association, held in Reykjavik, Iceland, 13-15 June 1986. Under scrutiny was the intersection of two apparently contradictory trends in research on the origins of human cancer. On the one hand, cancer, at least at the level of the cell, is a genetic disease. Most tumours have chromosomal abnormalities and, if the cancer cell did not pass on to its progeny new rules for bad cellular behaviour, cancer would not be a lethal disease. A score of oncogenes, discovered by laboratory scientists pursuing the hypothesis that cancer is an infectious disease, gave further insight that DNA sequences, long part of the human genome, could become activated and result in clinical cancer. Studies of cancer genetics proceeded mostly in laboratories, apart from any epidemiological assessment of potential environmental influences. On the other hand, it is often said that 80 to 90% of human cancers are due to environmental factors, ncluding behavioural ones such as personal diet. GeojTaphical and temporal differences of cancer rates, jccupational cancers, and, most compellingly, epilemiological studies of cancer in migrant populations eft little apparent role for the action of genes that night predispose to cancer. Hence, two decades of ase-control studies have tried to identify specific invironmental factors in cancer aetiology. Nearly all of hese studies failed to collect data or specimens that xjuld be used to address genetic hypotheses of cancer letiology.