Genetic contribution of breast cancer genes in women of black African origin

Breast cancer (BC) is an increasing public health issue worldwide. BC incidence and mortality rates are rising in transitioning countries in Africa, with the most rapid increase occurring in Sub-Saharan Africa (SSA). Female BC represents 25.8% of all cancer diagnosis in SSA. Early age at onset, high grade and triple negative tumors are hallmarks of BC in this region, associated with germline pathogenic variants in susceptibility genes. While several genes have been associated with genetic predisposition (BRCA1, BRCA2, PALB2, TP53, PTEN, CDH1, STK11, ATM, CHEK2, NBN, BARD1, BRIP1, RAD50, RAD51C, RAD51D, … ), most studies have reported contribution of BRCA1 and BRCA2 pathogenic variants. Genetic contribution of BRCA genes has been estimated at 27% in Caucasian women. Available data from population of African origin are scarce and have mainly focused on pathogenic variants of BRCA1 and BRCA2. Reports from main studies on large sample size highlighted that BRCA1 still the major gene associated with BC in SSA. In addition, BRCA2, PALB2, and P53, are also on the top major genes with high penetrance, associated with BC. Mutation spectrum of BC genes in black African women seems to be different from Caucasian with increasing number of founder mutations identified. We hypothesis that the genetic contribution of known BC genes may be different between women of black African origin compared to Caucasians. In this review we explore the genetic contribution of known breast cancer genes in women of African origin, and discuss perspectives for prevention and patients care strategies in the era of precision medicine.

New Insights Into c.815_824dup Pathogenic Variant of BRCA1 in Inherited Breast Cancer: A Founder Mutation of West African Origin

Founder mutations have been reported in BRCA1 and BCRA2 in different ethnic groups with inherited breast cancer. Testing of targeted mutations in specific populations is important for cancer prevention in mutation carriers. In Sub-Saharan Africa, only a few studies have reported specific founder mutations in inherited breast cancer. The pathogenic variant c.815_824dup of BRCA1 has been reported as the most frequent among African American populations with inherited breast cancer and was supposed to have a West African origin. Recent report from Senegal identified this variant in women with inherited breast cancer at the highest frequency ever reported. The variant was linked to a common haplotype confirming its founder effect in West Africa. In this article, we review the mutation history of c.815_824dup and discuss how it spread out of Africa through the transatlantic slave trade.

Genetic variants of RNASE3 (ECP) and susceptibility to severe malaria in Senegalese population

Background

Severe forms of malaria (SM) are an outcome of Plasmodium falciparum infection and can cause death especially in children under 4 years of age. RNASE3 (ECP) has been identified as an inhibitor of Plasmodium parasites growth in vitro, and genetic analysis in hospitalized Ghanaian subjects has revealed the RNASE3 +371G/C (rs2073342) polymorphism as a susceptibility factor for cerebral malaria. The +371 C allele results in an Arg/Thr mutation that abolishes the cytotoxic activity of the ECP protein. The present study aims to investigate RNASE3 gene polymorphisms and their putative link to severe malaria in a malaria cohort from Senegal.

Methods/results

Patients enrolled from hospitals were classified as having either uncomplicated (UM) or severe malaria (SM). The analysis of the RNASE3 gene polymorphisms was performed in 241 subjects: 178 falciparum infected (96 SM, 82 UM) and 63 non-infected subjects as population control group (CTR). Six frequent SNPs (MAF > 3%) were identified, and one SNP was associated with malaria severity by performing a logistic regression analysis SM vs.UM: RNASE3 +499G/C (rs2233860) under age, sex as covariates and HbS/HbC polymorphisms adjustment (p = 0.003, OR 0.43, CI 95% 0.20–0.92). The polymorphisms: +371G/C (rs2073342), +499G/C (rs2233860) and +577A/T (rs8019343) defined a haplotype risk (G-G-T) for malaria severity (Fisher exact test, p = 0.03) (OR 4.1, IC 95% (1.1–14.9).

Conclusion

In addition to the previously described association of +371G/C polymorphism in Ghanaians cohort, the RNASE3 +499G/C polymorphism was associated with susceptibility to SM in a Senegalese population. The haplotype +371G/+499G/+577T defined by RNASE3 polymorphisms was associated with severity. The genetic association identified independently in the Senegalese population provide additional evidence of a role of RNASE3 (ECP) in malaria severity.

[Profiles of IgG responses against CSP, GLURP and LSA-3NR2 in urban malaria (Dakar): relations with haemoglobin levels and parasite densities]

Malaria remains a major health problem in sub- Saharan African countries despite substantial decreases in morbidity and mortality due to sustained control programs. Vaccines candidates were mainly tested in rural endemic setting; however increasing proportion of the population is living in urban area. Evaluation of the qualitative or quantitative immune responses to key targets of anti-Plasmodium immunity requires further investigation in urban area. In a cohort of 144 patients with mild malaria living in Dakar, we analyzed IgG responses against target antigens of P. falciparum: CSP, LSA-3NR2 and GLURP by ELISA. A mean age of 15 yrs (4-65 yrs) was found and patients were separated in 59 adults (<15yrs) and 85 children (≤15 yrs). Parasites densities (0,01-15%) did not differ between the two age groups. In contrast, haemoglobin levels appeared lower in children (4.5-16.6 g/dl) (p<0.01). For the immune results, the most recognized antigens were GLURP and CSP compared to LSA-3NR2. Levels of IgG against these antigens were significantly different between the two age groups and they were positively correlated (rho = 0.32; p<0.001). In addition, levels of IgG anti-GLURP were associated with low parasitemia (≤1%) and absence of anemia (≥11g/dl), particularly in adults (p<0.001). In a multiple regression analysis, no significant relationship was found between parasite densities and IgG responses against all the tested antigens. Our study shows the implication of IgG anti-GLURP in humoral immune response against the parasite. The present work contributes to determine IgG levels that can be used as relevant immunologic biomarkers in urban clinical malaria.

Genetic determination and linkage mapping of Plasmodium falciparum malaria related traits in Senegal

Plasmodium falciparum malaria episodes may vary considerably in their severity and clinical manifestations. There is good evidence that host genetic factors contribute to this variability. To date, most genetic studies aiming at the identification of these genes have used a case/control study design for severe malaria, exploring specific candidate genes. Here, we performed a family-based genetic study of falciparum malaria related phenotypes in two independent longitudinal survey cohorts, as a first step towards the identification of genes and mechanisms involved in the outcome of infection. We studied two Senegalese villages, Dielmo and Ndiop that differ in ethnicity, malaria transmission and endemicity. We performed genome-scan linkage analysis of several malaria-related phenotypes both during clinical attacks and asymptomatic infection. We show evidence for a strong genetic contribution to both the number of clinical falciparum malaria attacks and the asymptomatic parasite density. The asymptomatic parasite density showed linkage to chromosome 5q31 (LOD = 2.26, empirical p = 0.0014, Dielmo), confirming previous findings in other studies. Suggestive linkage values were also obtained at three additional chromosome regions: the number of clinical malaria attacks on chromosome 5p15 (LOD = 2.57, empirical p = 0.001, Dielmo) and 13q13 (LOD = 2.37, empirical p = 0.0014 Dielmo), and the maximum parasite density during asymptomatic infection on chromosome 12q21 (LOD = 3.1, empirical p<10⁻⁴, Ndiop). While regions of linkage show little overlap with genes known to be involved in severe malaria, the four regions appear to overlap with regions linked to asthma or atopy related traits, suggesting that common immune related pathways may be involved.

[Evaluation of gingival condition in homozygous children and adolescents with sickle cell anemia in Senegal]

Sickle cell anaemia is an inherited disorder of haemoglobin synthesis leading to haemolytic anaemia. It touches more than 50 million people in the world and 10% of the population in Senegal. Only the homozygous form is symptomatic and appears by painful crises of vaso-occlusive type. There is a lack of works carried out or published in Senegal about potential link between periodontal conditions and sickle-cell anaemia. The main objective of this study is to assess the gingival conditions in Senegalese children and adolescents homozygous sickle cell anaemic. Secondary, the gingival state is correlated with oral hygiene and rate of reticulocytes to determine their relationship. Fifty homozygous attending the Albert Royer Paediatric Hospital of Dakar and unscathed of other systemic pathologies, were examined. The patients are old between 3 and 16 years with an average age 9.4 years +/- 3.8. The gingival state is assessed by measurement of the gingival index (GI) and index of sulculary bleeding (SBI). Partial correlation is performed between the two indexes and average of reticulocytes. The gingival index mean is 1.7 +/- 0.6 and 66% of the patients present a severe inflammation, which is more frequent in the age bracket from 3 to 12 years. The SBI mean is 1 +/- 1.1 and 68% of the patients present gingival bleeding, which is moderate to severe in 18%, with a greater frequency in the age bracket from 13 to 16 years. Strong correlation is found between plaque index, GI and SBI. Damage of gingival state seems not to be linked to the high average of reticulocytes controlling for oral hygiene. Children and adolescent homozygous have an inflammatory periodontium associated to poor oral hygiene, which highlights their needs in periodontal treatments. Early tracking and preventive treatment of periodontal diseases during systematic oral visits must be required.

Genetic study of ICAM1 in clinical malaria in Senegal

Many genes have been implicated in the risk of severe malaria, generally based on candidate gene studies in case/control populations. Among these genes, there has been conflicting reports for the implication of a variant of the intercellular adhesion molecule 1 (ICAM1), ICAM1(Kilifi), in the risk of severe malaria, while in vitro studies provided independent support for a functional role of this variant. In order to explore the possible implication of ICAM1 in the susceptibility/resistance to malaria and to try to understand its clinical relevance in the disease process, we have conducted linkage and association studies of ICAM1 in two Senegalese villages located in regions of endemic malaria. We explored the full genetic variability of ICAM1, and tested it on several clinical malarial traits which are under genetic control, focusing principally on variables related to the parasite density and the number of malarial attacks. Our study provides no evidence for a role of ICAM1 variability on the malarial phenotypes studied.

[Hypertrophic obstructive cardiomyopathy in child. About two cases]

The authors report two cases of hypertrophic obstructive cardiomyopathy in young girls, age 3 months and 8 years old. The disease manifested itself as a cardiac heart failure in the infant's case and a syncop in the other case. Cardiac echocardiography showed in he first case asymetric hypertrophic cardiomyopathy with ventricular outflow tract obstruction gradient of 100 mmhg, and concentric hypertrophic with 120 mmhg in the second case. Its evolution was fatal in both cases and led to sudden death at home. This disease is severe as no therapeutic treatment can modify its course.

Serological HLA class I alleles in Senegalese blood donors detected HBs Ag positive

We analysed the HLA class I alleles in 96 blood donors HBs Ag positive compared with 93 healthy control individuals (HBs negative). The most frequent HLA-A, -B, -C alleles found were, A23 (33.6%); A2 (25%); A30 (25%); B8 (31.5%); B7 (16.3%); B58 (11.9%); B35 (11.9%); B49 (11.9%); B53 (10.8%); Cw7 (39.1%); Cw3 (36.9%); Cw4 (36.9%). Significant differences (P<0.001) were found between the blood donors and the controls for the following HLA alleles, A1; A23; B8 and Cw3. The detection of HBe antigen was positive in 26/84 blood donors. It was observed a significant difference (P<0.01; odds ratios (OR)=6.25) between positive and negative HBe antigens blood donors for HLA-A1 allele.

[Prognostic value of cytokines and HLA markers in patients with cerebral malaria in Senegal]

41 patients senegalese patients suffering from clinically defined severe malaria were studied in the intensive medical care unit of the Hôpital Principal in Dakar, Senegal. All of these individuals lived in Dakar, an area of low and seasonal Plasmodium falciparum transmission. In this study, we aim to determine in one hand, the cytokine levels of TNF-alpha, TNF-alpha sRI, TNF-alpha sRII, IL-2 sR, IL-6, IL-6 sR, and IL-10 to evaluate their prognostic value in the course of the disease; in the other hand, the influence of the HLA-DR alleles in the susceptibility to get severe malaria. At the day of admission (day 0) and 3 days later, one or two blood samples were collected for each patient to assess different biological parameters. Plasma samples were tested for cytokines cited above by ELISA (Medegenix EASIA kits) and DNA samples for HLA-DR by PCR-SSP genotyping. The concentrations of all the cytokines and/or their receptors were significantly increased at day 0 in the patients who died (TNF-alpha = 455 +/- 480 pg/ml, IL6 = 511 +/- 396 pg/ml) and decreased rapidly in the patients who survived from the disease (TNF-alpha = 354 +/- 629 pg/ml, IL6 = 453 +/- 706 pg/ml). A fatal issue seems likely related to the age of patients (20 +/- 12 years for surviving patients and 31 +/- 16 years for patients who died) and the kinetic of the cytokines. Significant differences were observed (pc < 0.001) between patients with severe malaria and a control group for the following HLA alleles: DR3, DR10 and DR13. The HLA-DR13 allele was found positively and highly associated with severe malaria.

[HLA-DQ allele typing in a Senegalese population: comparative study of serology and PCR-SSP]

In this study, we compared the serological standard typing method and the DNA genotyping PCR-SSP for the characterization of HLA-DQ alleles in a senegalese population. For this purpose, 120 individuals leaving in Dielmo were typed using the microlymphocytotoxicity assay and the PCR-SSP DQ low Resolution method. A discordance of 42.5% (51/120) was found between these two methods. Thirty % (36/120) of serological typed persons failed to be typed by PCR-SSP method whereas 1% (1/120) assigned by PCR-SSP failed to be characterized by serology. Advantages and limits of these two typing methods and also the genetic background of our study population were valid arguments to comment our findings. The PCR-SSP, as suggested by several authors, is reliable, accurate and fast for HLA class II alleles characterization. Nevertheless, it needs, to become an alternative HLA typing method, available primers adapted to genetic background of study population.

[Association between Class I HLA alleles and HBs antigen carrier status among blood donors in Senegal]

The course of hepatitis B virus (HBV) infection may be influenced by the host immune response. A prospective study was carried out in ninety-eight subjects (mean age = 23 years) HBs antigens carriers of hepatitis B and living in Dakar, Senegal. We analysed the HLA-A, -B, and C antigens distribution compared to that one of a control (HBs negative) healthy senegalese population (n = 96) living in Dielmo village where a longitudinal study was set-up since 1990. The HLA class I typing was performed by microlymphocytotoxicity assays. The most frequent HLA-A, -B, -C antigens found were: locus A: A23 (33.6%), A2 (25%), A30 (25%), locus B: B8 (31%), B7 (16.3%), B58 (11.9%), B35 (11%), B49 (11%), B53 (10.8%) and locus C: Cw7 (39.1%), Cw17 (39.1%), Cw3 (36.9%), Cw4 (36.6%). Significant differences (P < 0.001) were found between the donors and the control group for the following HLA antigens: A1, A23, B8 and Cw3. The detection of HBe antigen was positive in 26/84 blood donors. It was observed a significant difference (p < 0.01) between positive and negative HBe donors for HLA-A1 allele with an odds ratio of 6.25. All the donors carrying the HLA haplotype: A1-B8-Cw7 (11.5%) were positive in HBe antigen. HLA: B8-Cw7 haplotype (detected in 8.5% of positive donors) seems to be likely associated with a liver cancer according to many reports. An adequate follow-up should be set-up for positive HBe subjects carrying a susceptible HLA type.

[Identification of HLA-DR alleles for susceptibility to rheumatoid polyarthritis in Senegal]

Rheumatoid arthritis is the most frequent inflammatory rheumatism disease. Several studies were aimed to understand its physiopathogenesis in particular the association between some HLA-DR alleles and rheumatoid arthritis. A prospective study was carried out in 34 patients suffering from RA (30 Women and 4 men). The diagnosis was clinically and radiologically made. The control group included 220 persons of which the HLA-DR distribution was known. The HLA-DRB1 alleles were typed by PCR-SSP (Sequence Specific Primers). The most frequent HLA-DR alleles found in patients group were: DR10 (85.3%), DR52 (53%), DR14 (38.2%), DR11 (26.5%), and DR13 (20.3%). A significant difference was observed between RA patients and control group for the following alleles: DR3, DR10, DR18, and DR52 (p < 0.001; Chi square with Yates' correction). HLA-DR3 and DR10 were positively associated with RA. The relative risk was up 30 for DR10.

[Susceptibility to neuro-malaria and HLA-DR alleles in Senegal]

A prospective study was carried out in 46 patients suffering from severe malaria. The control group included 220 persons of which the HLA-DR distribution was known. The HLA-DRB1 alleles were typed by PCR-SSP (Sequence Specific Primers). The most frequent HLA-DR alleles found in patients group were: DR52 (82.8%), DR13 (57.1%), DR10 (28.6%), DR53 (25.7%), DR3 (20%), DR18 (20%). A significant difference was observed between patients with severe malaria and control group for the following alleles: DR3, DR10, DR13 (p < 0.001; Chi square with Yates' correction) and their relative risk were respectively 14.67; 6.29; 2.84. HLA-DR3 was considered as the major marker associated to severe malaria.

[Radiological aspects of giant cementoma of the jaws (Pindborg)]

In reference to 7 cases of Pindborg's giant cementoma in Senegalese women, the authors describe their radiological aspects. The different aspects of these tumors are emphasized according to their location on the maxilla or the mandible and whether they are anterior or posterior.