Wistar Institute researchers have identified a single variant in an important tumor suppressor gene only found in Africans and African-Americans that might explain disparities in the incidence of certain cancers such as colorectal cancer, its resistance to treatment, and overall poor clinical outcomes observed among populations of African descent.
The research paper, “An African-specific polymorphism in theTP53 gene impairs p53 tumor suppressor function in a mouse model,” was published in the journal Genes and Development.
Cancer clinical data shows that African-Americans, among patients with commonly diagnosed cancers, have higher death rates and overall worse survival outcomes. According to the American Cancer Society, being an African-American is a risk factor for colorectal cancer, and African-Americans have the highest colorectal cancer incidence and mortality rates of all racial groups in the United States, for unknown reasons. In an attempt to explain the higher incidence and lower survival of this ethnic group, researchers previously focused on socioeconomic factors, but are now looking into possible genetic factors.
The team focused on a gene variant, the S47 variant of p53, a tumor suppressor gene that is mutated in a large number of cancers. The S47 variant exists only in people of African descent, and was never observed in Caucasian populations, occurring in 2 percent of African-Americans and 8 percent of Africans. To study its impact, researchers created a mouse model of S47, observing that spontaneous cancer occurred in 80 percent of these animals. Among all cancer cases, liver cancer, lymphoma, and colorectal cancer were the more common malignancies.
Researchers believe this data suggests the S47 variant may contribute to an increased cancer risk in those of African descent, highlighting the need to further assess its contribution to cancer risk in these populations.
“Validation of these results in humans will require a large population to determine the significance it has on cancer risk among those of African descent,” senior author Dr. Maureen Murphy said in a news release. “However, we now have some of the strongest evidence ever obtained for a genetic basis for this disparity, and a larger, population-based study is warranted.”