Caucasian men accounted for about 106 new cases of prostate cancer per 100,000 men for the years 2011-2015. For African American men, that number jumped to nearly 179 per 100,000. University of Illinois Cancer Center member Alan Diamond has received a U.S. Department of Defense grant to study the accuracy of his hypothesis that the gene SELENOF is a contributing factor in the disparity.
The combination of genetics and environmental factors likely play a role in why African American men experience a higher incidence of prostate cancer, as well as having a worse clinical outcome, said Diamond, PhD, pathology professor at the University of Illinois at Chicago College of Medicine. In prior studies, Diamond has compared the amount of SELENOF in prostate cancer to normal tissue, and the gene is expressed at significantly lower levels in African American men compared to Caucasian men.
“We believe that reduced levels of SELENOF contribute to the risk of experiencing and dying from prostate cancer and that the differences in the SELENOF gene between African American and Caucasian men contributes to the increased risk in that population,” Diamond said.
About 165,000 new prostate cancer cases are anticipated in 2018, according to the National Cancer Institute. Nearly 30,000 will die from the disease, accounting for about 5 percent of all cancer deaths. A little more than 11 percent of men will be diagnosed with prostate cancer at some point during their lifetime, based on 2013-2015 data. In 2015, there were an estimated 3.1 million men living with prostate cancer in the U.S., the NCI said.
Along with determining the differences in levels of SELENOF between African American and Caucasian men, Diamond will also ascertain whether the absence of the gene in the prostate reduces the time when prostate cancer appears, the frequency of the tumors and their severity. The experiments will be conducted in mouse models. A third goal in the new grant is to determine the mechanism by which reduced SELENOF levels contribute to a higher prostate cancer risk and poorer clinical outcomes.
Diamond’s interest in prostate cancer began about 20 years ago after he read a high-profile study indicating that men taking a supplemental amount of selenium – a mineral naturally found in the soil that also appears in water and some foods – could prevent some of the most common cancer types, including prostate cancer. The study, Diamond said, was undertaken after a large number of published animal studies concluded that adding low levels of selenium to diets could prevent prostate cancer in mice; human epidemiological data also indicated an inverse association between selenium intake and prostate cancer.
The largest prostate cancer trial involving 35,000 men followed the initial study to determine the validity of taking either selenium, vitamin E or both to prevent the disease. After the results showed there was no benefit to taking selenium, Diamond shifted his focus to concentrate on selenium-containing proteins in naturally occurring polymorphisms in corresponding genes with the risk of contracting or dying from cancer. One of the genes was SELENOF.
With the assistance of several researchers in UIC’s urology department, Diamond reviewed human clinical samples that revealed SELENOF levels were lower in cancer tissue, compared to benign tissue, in the prostate cancers of African American men as opposed to Caucasian men. This, Diamond said, was the basis for his first U.S. Department of Defense grant.
“We anticipate that our results will identify factors contributing to the disparity in prostate cancer between African Americans and Caucasians and may lead to new biomarkers to identify those men at elevated risk,” Diamond said. “Developing new interventions will reduce the high risk of contracting and dying from prostate cancer in men in the United States, particularly African American men.”