Genetic research has led to a change in the perception of cancer through the discovery of genes that may

predispose people to develop certain forms of cancer.

Genes and Cancer

The study of genetics has piloted the exploration of cancer on a cellular level. Two types of genes have been

implicated in the transformation of normal cells into malignant ones, the first of which is called an oncogene. Cancer

occurs when the growth and differentiation of cells within tissue become uncontrolled. An oncogene develops when

a gene that stimulates cell growth is altered to become hyperactive. Cancers result from only one mutant allele in a

gene, examples of which include growth factors or receptors for growth factors, cytoplasmic relays in stimulatory

signaling pathways, and transcription factors that activate growth-promoting genes. Unlike the oncogene, tumor

suppressor genes play a protective role that normally limits the growth of cancer. Mutations in a tumor suppressor

gene require both alleles to be altered if they are going to permit cancerous growth. Examples include BRCA1

 and BRCA2, two genes known to be associated with increased risk of breast cancer.

A number of genes have been discovered that, when subject to mutation, increase a person’s risk or getting certain

cancers. Research involving all twenty-three chromosomes lead to the identification of roughly thirty recessive

oncogenes and more than a hundred dominant oncogenes.

Most cancers arise from a complex interplay between many genetic changes that occur over time or from repeated

exposure to certain environmental factors. Nevertheless, approximately 5–10% of cancers are believed to be

 hereditary insofar as they are caused by an inherited gene mutation. Although only a small percentage of all

cancers are hereditary, their identification and study will have important implications for the prevention, screening,

and treatment of this disease.

Inherited Genetic Alterations

Genetic testing is available for a few of the known gene mutations. As technology improves, testing for more

such genes will be possible. Individuals whose test results are positive have a specific gene mutation that puts

them at increased risk for developing certain cancers, but it does not ensure that they will get the disease. This

finding can warn families to take preventative measures and thus reduce the risk of getting cancer. A negative test

result (no mutation found) does not mean that a person will remain cancer-free particularly in connection with the

development of cancers that are independent of inherited mutation. Genetic tests cannot detect all mutations,

and they fail to measure the impact of environmental and lifestyle factors.

By Elizabeth Godshall and Vanessa Oddo MACGN Summer Interns through the Washington Internship Program