E. Yeboah

University of Ghana, Akra, Greater Accra, Ghana

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Publications (14)76.72 Total impact

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    ABSTRACT: Genome-wide association studies (GWAS) have mapped risk alleles for at least ten distinct cancers to a small region of 63,000 bp on chromosome 5p15.33. This region harbors the TERT and CLPTM1L genes; the former encodes the catalytic subunit of telomerase reverse transcriptase and the latter may play a role in apoptosis. To investigate further the genetic architecture of common susceptibility alleles in this region, we conducted an agnostic subset-based meta-analysis (ASSET) across six distinct cancers in 34,248 cases and 45,036 controls. Based on sequential conditional analysis, we identified as many as six independent risk loci marked by common single nucleotide polymorphisms (SNPs): five in the TERT gene (region 1: rs7726159, P=2.10x10-39; region 3: rs2853677, P=3.30x10-36 and PConditional=2.36x10-8; region 4: rs2736098, P=3.87x10-12 and PConditional=5.19x10-6, region 5: rs13172201, P=0.041 and PConditional=2.04x10-6; and region 6: rs10069690, P=7.49x10-15 and PConditional=5.35x10-7) and one in the neighboring CLPTM1L gene (region 2: rs451360; P=1.90x10-18 and PConditional=7.06x10-16). Between three and five cancers mapped to each independent locus with both risk-enhancing and protective effects. Allele specific effects on DNA methylation were seen for a subset of risk loci indicating that methylation and subsequent effects on gene expression may contribute to the biology of risk variants on 5p15.33. Our results provide strong support for extensive pleiotropy across this region of 5p15.33, to an extent not previously observed in other cancer susceptibility loci.
    Human Molecular Genetics 07/2014; · 7.69 Impact Factor
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    ABSTRACT: Genome-wide association studies (GWAS) have identified that a ∼1 M region centromeric to the MYC oncogene on chromosome 8q24.21 harbors at least five independent loci associated with prostate cancer risk and additional loci associated with cancers of breast, colon, bladder, and chronic lymphocytic leukemia (CLL). Because GWAS identify genetic markers that may be indirectly associated with disease, fine-mapping based on sequence analysis provides important insights into patterns of linkage disequilibrium (LD) and is critical in defining the optimal variants to nominate for biological follow-up. To catalog variation in individuals of African ancestry, we resequenced a region (250 kb; chr8:128,050, 768–128, 300,801, hg19) containing several prostate cancer susceptibility loci as well as a locus associated with CLL. Our samples included 78 individuals from Ghana and 47 of African-Americans from Johns Hopkins University. After quality control metrics were applied to next-generation sequence data, 1,838 SNPs were identified. Of these, 285 were novel and not yet reported in any public database. Using genotypes derived from sequencing, we refined the LD and recombination hotspots within the region and determined a set of tag SNPs to be used in future fine-mapping studies. Based on LD, we annotated putative risk loci and their surrogates using ENCODE data, which should help guide laboratory studies. In comparison to the 1000 Genome Project data, we have identified additional variants that could be important in establishing priorities for future functional work designed to explain the biological basis of associations between SNPs and both prostate cancer and CLL.
    The Prostate 05/2014; 74(6):579-89. · 3.84 Impact Factor
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    ABSTRACT: Reasons for the high rates of prostate cancer in African Americans are unknown; both genetic and lifestyle factors have been implicated. A better understanding of prostate cancer rates in West Africans would help clarify why African Americans have such high rates, since African Americans share genetic ancestry with West Africans yet have very different lifestyles and screening practices. To estimate prostate cancer burden in West Africans, we conducted a population-based screening study with biopsy confirmation in Ghana. We randomly selected 1,037 healthy men aged 50-74 from Accra, Ghana for prostate cancer screening with prostate specific antigen (PSA) testing and digital rectal examination (DRE). Men who had a positive screen (DRE+ or PSA>2.5 ng/ml) underwent transrectal ultrasound (TRUS)-guided biopsies. Of the 1,037 men, 154 (14.9%) had a positive DRE and 272 (26.2%) had a PSA>2.5 ng/ml (166 had a PSA>4.0 ng/ml). In total, 352 (33.9%) men had a positive screen by PSA or DRE, and 307 (87%) had a biopsy. Of these, 73 were confirmed to have prostate cancer, yielding a 7.0% screen-detected prevalence of prostate cancer (65 cases, 5.8% with a PSA>4.0 ng/ml). In this relatively unscreened population in Africa, the screen-detected prostate cancer prevalence is high, suggesting a possible role of genetics in both prostate cancer etiology and the disparity in prostate cancer risk between African Americans and Caucasian Americans. Further studies are needed to confirm the high prostate cancer burden in Africans and the role of genetics in prostate cancer etiology.
    The Journal of urology 04/2014; · 3.75 Impact Factor
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    ABSTRACT: Age-adjusted mortality rates for prostate cancer are higher for African-American men compared with those of European ancestry. Recent data suggest that West African men also have elevated risk for prostate cancer relative to European men. Genetic susceptibility to prostate cancer could account for part of this difference. We conducted a genome-wide association study (GWAS) of prostate cancer in West African men in the Ghana Prostate Study. Association testing was performed using multivariable logistic regression adjusted for age and genetic ancestry for 474 prostate cancer cases and 458 population-based controls on the Illumina HumanOmni-5 Quad BeadChip. The most promising association was at 10p14 within an intron of a long non-coding RNA (lncRNA RP11-543F8.2) 360 kb centromeric of GATA3 (p = 1.29E-7). In sub-analyses, SNPs at 5q31.3 were associated with high Gleason score (≥7) cancers, the strongest of which was a missense SNP in PCDHA1 (rs34575154, p = 3.66E-8), and SNPs at Xq28 (rs985081, p = 8.66E-9) and 6q21 (rs2185710, p = 5.95E-8) were associated with low Gleason score (<7) cancers. We sought to validate our findings in silico in the African Ancestry Prostate Cancer GWAS Consortium, but only one SNP, at 10p14, replicated at p < 0.05. Of the 90 prostate cancer loci reported from studies of men of European, Asian or African-American ancestry, we were able to test 81 in the Ghana Prostate Study, and 10 of these replicated at p < 0.05. Further genetic studies of prostate cancer in West African men are needed to confirm our promising susceptibility loci.
    Human Genetics 11/2013; · 4.63 Impact Factor
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    ABSTRACT: Prostate cancer (CaP) is the leading cancer among men of African descent in the USA, Caribbean, and Sub-Saharan Africa (SSA). The estimated number of CaP deaths in SSA during 2008 was more than five times that among African Americans and is expected to double in Africa by 2030. We summarize publicly available CaP data and collected data from the men of African descent and Carcinoma of the Prostate (MADCaP) Consortium and the African Caribbean Cancer Consortium (AC3) to evaluate CaP incidence and mortality in men of African descent worldwide. CaP incidence and mortality are highest in men of African descent in the USA and the Caribbean. Tumor stage and grade were highest in SSA. We report a higher proportion of T1 stage prostate tumors in countries with greater percent gross domestic product spent on health care and physicians per 100,000 persons. We also observed that regions with a higher proportion of advanced tumors reported lower mortality rates. This finding suggests that CaP is underdiagnosed and/or underreported in SSA men. Nonetheless, CaP incidence and mortality represent a significant public health problem in men of African descent around the world.
    Prostate cancer. 01/2013; 2013:560857.
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    ABSTRACT: BPH and lower urinary tract symptoms (LUTS) are very common among older men in Western countries. However, the prevalence of these two conditions in the developing countries is less clear. We assessed the age-standardized prevalence of BPH and/or LUTS among West Africans in a probability sample of 950 men aged 50-74 in Accra, Ghana, with no evidence of biopsy-confirmed prostate cancer after screening with PSA and digital rectal examination (DRE). Information on LUTS was based on self-reports of the International Prostate Symptom Score (IPSS). BPH was estimated using DRE, PSA levels and imputed prostate volume. The prevalence of DRE-detected enlarged prostate was 62.3%, while that of PSA≥1.5 ng ml(-1) (an estimate of prostate volume ≥ 30 cm(3)) was 35.3%. The prevalence of moderate-to-severe LUTS (IPSS≥8) was 19.9%. The prevalence of IPSS≥8 and an enlarged prostate on DRE was 13.3%. Although there is no universally agreed-upon definition of BPH/LUTS, making comparisons across populations difficult, BPH and/or LUTS appear to be quite common among older Ghanaian men. We found that after age standardization, the prevalence of DRE-detected enlarged prostate in Ghanaian men is higher than previously reported for American men, but the prevalence of LUTS was lower than previously reported for African Americans. Further studies are needed to confirm these findings and identify the risk factors for BPH in both Africans and African Americans.
    Prostate cancer and prostatic diseases 09/2011; 15(2):170-6. · 2.10 Impact Factor
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    ABSTRACT: Chronic antigenic stimulation is associated with hypergamma-globulinemia. Higher rates of hypergamma-globulinemia in tropical populations are maintained even with migration to temperate regions. We conducted a population-based screening study to assess the prevalence and risk factors for hypergamma-globulinemia in Ghana, Africa. 917 Ghanaian males (50-74 years) underwent in-person interviews and health examinations. Serum from all persons was analyzed by electrophoresis performed on agarose gel; serum with a discrete/localized band was subjected to immunofixation. 54 persons with monoclonal proteins were excluded and 17 samples were insufficient for analysis. Using logistic regression and Chi-square statistics we analyzed patterns of hypergamma-globulinemia. Among 846 study subjects, the median γ-globulin level was 1.86 g/dL. On the basis of a U.S. reference, 616 (73%) had hypergamma-globulinemia (>1.6 g/dL) and 178 (21%) had γ-globulin levels >2.17 gm/dl. On multivariate analyses, lower education status (P = 0.0013) and never smoking (P = 0.038) were associated with increased γ-globulin levels. Self-reported history of syphilis was associated with hypergamma-globulinemia. We conclude that three quarters of this population-based adult Ghanaian male sample had hypergamma-globulinemia with γ-globulin levels >1.6 g/dL. Future studies are needed to uncover genetic and environmental underpinnings of our finding, and to define the relationship between hypergamma-globulinemia, monoclonal gammopathy of undetermined significance (MGUS), and multiple myeloma.
    American Journal of Hematology 07/2011; 86(7):554-8. · 4.00 Impact Factor
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    ABSTRACT: In search of common risk alleles for prostate cancer that could contribute to high rates of the disease in men of African ancestry, we conducted a genome-wide association study, with 1,047,986 SNP markers examined in 3,425 African-Americans with prostate cancer (cases) and 3,290 African-American male controls. We followed up the most significant 17 new associations from stage 1 in 1,844 cases and 3,269 controls of African ancestry. We identified a new risk variant on chromosome 17q21 (rs7210100, odds ratio per allele = 1.51, P = 3.4 × 10(-13)). The frequency of the risk allele is ∼5% in men of African descent, whereas it is rare in other populations (<1%). Further studies are needed to investigate the biological contribution of this allele to prostate cancer risk. These findings emphasize the importance of conducting genome-wide association studies in diverse populations.
    Nature Genetics 06/2011; 43(6):570-3. · 35.21 Impact Factor
  • Urology 01/2011; 78(3). · 2.42 Impact Factor
  • Urology 01/2009; 74(4). · 2.42 Impact Factor
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    ABSTRACT: To determine the prevalence of monoclonal gammopathy of undetermined significance (MGUS), a precursor of multiple myeloma (MM), in Ghanaian men vs white men and to test for evidence to support an underlying race-related predisposition of the 2-fold higher prevalence of MGUS in African Americans vs whites. Between September 1, 2004, and September 30, 2006, 917 men (50-74 years) underwent in-person interviews and physical examinations. Serum samples from all participants were analyzed by electrophoresis performed on agarose gel; any serum sample with a discrete or localized band was subjected to immunofixation. Age-adjusted and standardized (to the 2000 world population) prevalence estimates of MGUS and 95% confidence intervals (CIs) were computed in the Ghanaian men and compared with MGUS prevalence in 7996 white men from Minnesota. Associations between selected characteristics and MGUS prevalence were assessed by the Fisher exact test and logistic regression models. Of the 917 study participants, 54 were found to have MGUS, yielding an age-adjusted prevalence of 5.84 (95% CI, 4.27-7.40) per 100 persons. No significant variation was found by age group, ethnicity, education status, or prior infectious diseases. The concentration of monoclonal immunoglobulin was undetectable in 41 (76%) of the 54 MGUS cases, less than 1 g/dL in 10 patients (19%), and 1 g/dL or more in only 3 patients (6%). Compared with white men, the age-adjusted prevalence of MGUS was 1.97-fold (95% CI, 1.94-2.00) higher in Ghanaian men. The prevalence of MGUS in Ghanaian men was twice that in white men, supporting the hypothesis that race-related genetic susceptibility could explain the higher rates of MGUS in black populations. An improved understanding of MGUS and MM pathophysiology would facilitate the development of strategies to prevent progression of MGUS to MM.
    Mayo Clinic Proceedings 01/2008; 82(12):1468-73. · 5.79 Impact Factor
  • Article: MP09.01
    M. Kyei, E. Yeboah, Y. Tettey, R. Kumoji
    Urology 01/2006; 68:105-105. · 2.42 Impact Factor
  • Article: MP10.02
    E. Yeboah, M. Kyei, Y. Tettey, R. Kumoji
    Urology 01/2006; 68:114-115. · 2.42 Impact Factor
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    ABSTRACT: Purpose Prostate cancer (CaP) is the leading cancer diagnosed in Sub-Saharan Africa (SSA). However, relatively little is known about the clinical detection of CaP in SSA. In order to evaluate CaP detection in SSA, we evaluated the outcomes of prostate biopsies under conditions of usual clinical care. Methods Retrospective data were collected from 4,672 Black African men, who underwent prostate biopsy in Gaborone, Botswana; Accra, Ghana; Dakar, Senegal Cape Town, South Africa; Wadmedani, Sudan; and Kampala, Uganda. Clinical and pathological characteristics were collected using medical records information for prostate biopsies that were undertaken during the period 2005–2011. Comparison groups of White South Africans (N = 398) who underwent prostate biopsy, and African American (AA; N = 117) and European American (EA; N = 975) men with prostate cancer were also obtained. Results Usual biopsy practices varied across SSA centers. The mean age at biopsy was 68.1 years (range: 25–100). The percentage of CaP identified was 11%, 36%, 43%, 48%, 87%, and 94% in Sudan, Senegal, South Africa, Ghana, Botswana, and Uganda, respectively. The Gleason scores 6 and 7 were predominant in Botswana, Senegal, and South Africa while the Gleason scores ≥ 8 were predominant in Sudan and Uganda. Compared to AA and EA, SSA and White South African men had substantially higher Gleason grade disease, and initial PSA at diagnosis was strongly associated with disease aggressiveness. Conclusions The knowledge gained from studies of prostate cancer in Africa may in turn improve our understanding of aggressive prostate cancer diagnosed anywhere in the world.
    Journal africain du cancer / African Journal of Cancer 5(3).