Cancer is perhaps one of the most irksome diseases whose causes are often elusive and unrecognizable. The etiological agents of cancer are difficult to estimate and it is not attributed to purely genetic or purely environmental factors, and therefore, cancer research has been largely focused on the interaction between genes and the environment (Mucci et al., 2001). A large number of studies have investigated the possible causes of various types of cancers, implicating diet, heredity and environment as its major determinants. Most diseases are a result of complex interactions between a person’s genetic make-up and the environmental agents he/she is exposed to (NIEHS, 2011). Therefore, the possibility of the involvement of gene-environment interactions in the occurrence of cancers is being investigated worldwide.
A disease occurs when there is an interaction between “genetic susceptibility factors” and “modifiable environmental factors”, and variations in the genetic make-up of an individual influence his/her susceptibility to environmental factors that are responsible for a disease (CDC, 2000). Therefore, owing to genetic variation, some individuals are more susceptible to a particular disease than others are, and these variations govern the extent of effect a particular environmental condition has on the risk of a disease in an individual.
Can Gene-Environment Interactions be Measured?
Gene-environment interaction can be defined as that which occurs when a “genetic and environmental exposure work together to cause a disease outcome in some or all cases” (Brennan, 2002). Since the genetic make-up of an individual determines the susceptibility to environmental carcinogens, researchers are toiling to find out the combinations of environmental factors and susceptible gene polymorphisms that make one individual more prone to cancer than others. This raises the need to measure gene-environment interactions. Although a direct measurement is not possible, several models such as the additive model and the multiplicative model have been explored (Brennan, 2002).
Studies on the Association of Gene-Environment Interactions with Cancer
A few genes are involved in the metabolism and excretion of potentially toxic compounds, and in the repair of mistakes that occur during DNA replication and other cellular activities. These genes are the body’s major defenses against cancer. These genes may contain polymorphisms, which are responsible for causing variation in the response and susceptibility to environmental agents that are possible carcinogens. Because of the effect of various environmental factors on these specific genes, researchers have been seeking whether there is any link between gene-environment interactions and cancer (Brennan, 2002). Environmental factors that have the ability to induce cancers include pollution, diet, ionizing UV light, exposure to pathogens such as bacteria and viruses, tobacco use and type of...