PHILADELPHIA (August 23, 2019) – The fact that people of African ancestry tend to have higher incidence and mortality for many cancers is already well-established, but new data from researchers at Fox Chase Cancer Center shows there may be important genetic differences among different black ethnic subgroups relevant to cancer.
“Research has helped to address some of the disparities that exist in cancer, but inequities remain,” said Camille Ragin, PhD, MPH, associate professor in the Cancer Prevention and Control Program at Fox Chase. “I believe if we want to be successful in addressing inequities that impact blacks as it relates to cancer, we need to look a little bit deeper than looking at blacks versus other races.”
To look at these differences in the genetic makeup of self-identified blacks, Ragin and her team established the Cancer Prevention Project of Philadelphia (CAP3) to serve as a resource for research addressing racial disparities in cancer. CAP3 recruits participants from the Philadelphia and New York metropolitan areas, New Jersey, and Delaware.
To date, almost 1,000 participants have been recruited but data have been published for 752 persons of African descent.
Participants in CAP3 completed a questionnaire detailing health and demographic information, and urine and saliva were collected. Ragin and colleagues looked at two forms of a molecule called NNAL that is excreted in the urine of smokers. The ratio of these two forms helps to determine how effective an individual is at metabolizing tobacco smoke by detoxifying and removing it from the body. Participants were classified as poor, intermediate, or extensive metabolizers.
“When we categorized all of the smokers, we found that the majority of these individuals were poor metabolizers of tobacco and they were all blacks,” Ragin said. “This tells us one important message: that, at least based on the data we were able to generate here, black individuals tend to be more likely to be poor metabolizers of tobacco, so they may be more susceptible to the damage of tobacco.”
Samples were also used to look at ancestry informative markers in the DNA repair pathway and identified three distinct ethnic subgroups: U.S.-born, Caribbean-born, and Africa-born blacks. Of the 752 blacks recruited to CAP3, 51.3 percent were U.S.-born, 27.8 percent were Caribbean-born, and 19.6 percent were Africa-born.
Ragin and colleagues found that U.S.-born blacks were more likely to be current smokers, with 27.6 percent reporting current smoker status compared with 3.4 percent for Caribbean-born blacks and 0.0 percent for Africa-born blacks.
“This tells us that U.S.-born blacks should be targeted for intervention because they are the ones smoking more,” Ragin said. “If we want to reduce the effects of tobacco in cancer development, targeted interventions towards African Americans rather than all blacks or immigrant blacks may be an effective strategy.”
Research could also explore why immigrant blacks tend not to be smokers. If researchers could understand that phenomenon it could inform the design of interventions to prevent smoking in other groups, Ragin said.
Moving forward, Ragin and her team plan to validate these findings in a larger sample. Participants continue to be recruited to CAP3 from health fairs, community centers, places of worship, and senior centers. Establishment of strong community partnerships has aided in recruitment.
Ragin and colleagues have also started working on trials to address smoking in blacks.
“If we want to address cancer disparities in blacks, that is a low-hanging fruit that we will need to tackle,” Ragin said. “The fact that we are suggesting that black individuals are poor metabolizers means perhaps studies might incorporate education of blacks about this very thing. It is possible that if individuals knew they are susceptible they would be more likely not to smoke or may become more motivated to try to quit or at least consider lung cancer screening if eligible.”
The paper, “The Cancer Prevention Project of Philadelphia: Preliminary Findings Examining Diversity Among the African Diaspora,” was published in Ethnicity & Health.
This research was supported in part by grants RSG-14-033-01-CPPB from the American Cancer Society and CA006927 from the National Cancer Institute, an appropriation from the Commonwealth of Pennsylvania, and institutional support from the Cancer Prevention Program at Fox Chase Cancer Center.