Dr Chantal Babb
Dr Chantel Babb
Dept MRC/NHLS Cancer Epidemiology Research Group, National Health Laboratory Services (NHLS) and National Cancer Registry and Research.
Email: chantal.babb@nhls.ac.za
Project title
Prostate cancer in black South African men, extending replication of genome wide association study findings.
Project description
Prostate cancer is the most common cancer in black South African men and the second most common cancer in white men (National Cancer Registry data 2004) with more than 4300 men were newly diagnosed and 2000 men dying from this disease each year. It is estimated that 1 in every 23 South African men who reach the age of 74 will develop this disease. However, this is believed to be an underestimate because of incomplete statistics and to some degree under diagnosis due to poor access to health care facilities that offer screening and diagnostics. The number of prostate cancer cases is steadily increasing because of longer lifespan and a more westernised lifestyle. Worldwide prostate cancer varies greatly between different ethnic groups, with African American men having some of the highest rates and Japanese men the lowest. International variations in prostate cancer frequency suggest that both environmental and genetic factors play a role. Older age, African ancestry in the USA and a family history of prostate cancer has long been recognized as known risk factors. Numerous genome wide studies have identified certain genetic variations that may be associated with risk of developing this disease. The majority of these studies have been done in western countries and only a few of these associations have been replicated or novel associations reported in men of African descent living in Europe and North America. Very few of these genetic variations have been studied in African men residing in Africa, and the large genetic differences within the African populations have not been properly investigated.
The on-going Johannesburg Cancer Case Control Study (JCCCS) at the NHLS/MRC Cancer Epidemiology Research Group (CERG) began in Johannesburg’s tertiary hospitals in 1995 and have recruited and interviewed over 20000 newly diagnosed black adult cancer patients attending public hospitals for cancer treatment. There are 250 prostate cancer cases at present, with ongoing collection. This has created a unique resource of data and samples for research on all types of cancer. Lifestyle and behavious information from the questionnaire with blood samples have been collected and detailed hospital reports are available for the majority of the patients. This collection allowes researchers to compare the genetic variations in cases and appropriate people not affected with prostate cancer (controls), together with environmental factors. The aim of the present study is to determine how common genetic variations previously associated with risk of developing prostate cancer are in the SA black patients and how these genetic factors along with various environmental factors, for example smoking and alcohol use, increase the risk of prostate cancer.
Having both genetic and environmental information on patients makes this a unique opportunity to evaluate the role that both play on rish of developing prostate cancer. Ultimately the results from this study will be combined with data from other African based studies to map the genetic variations responsible for causing prostate cancer in Africa.
Non-scientific report
At the time of the grant application 250 people with prostate cancer had been recruited throughthe JCCCS and because of continued recruitment more people may be added. DNA extractions are being done by a National Research Foundation – Department of Science and Technology (NRF-DST) intern (Ms B Ndlovu) and even though some blood samples have been frozen for over 10 years are providing good quality DNA. These DNA samples will be used later in the study when we look at the genetic variations previously found to influence rish for this disease in other populations.
To date a full list of all variants that have been previously found to increase or decrease risk for prostate cancer has been completed. The majority of these have been found in European and American populations and very few have been looked at in men residing in Africa. Africans are known to have greater genetic variety and for this reason we want to investigate as many of these variations as possible. Genes that have been repeatedly found to be connected to risk of prostate cancer, over various populations will be looked at in more details, namely sequencing (each DNA base in the gene will be looked at, or “read”) to determine if previously not described variations are in the gene.