[Study of codon 72 of p53 gene as a risk-factor in cervical cancer in Senegal]

A Review of Cancer Genetics and Genomics Studies in Africa

Cancer is the second leading cause of death globally and is projected to overtake infectious disease as the leading cause of mortality in Africa within the next two decades. Cancer is a group of genomic diseases that presents with intra- and inter-population unique phenotypes, with Black populations having the burden of morbidity and mortality for most types. At large, the prevention and treatment of cancers have been propelled by the understanding of the genetic make-up of the disease of mostly non-African populations. By the same token, there is a wide knowledge gap in understanding the underlying genetic causes of, and genomic alterations associated with, cancer among black Africans. Accordingly, we performed a review of the literature to survey existing studies on cancer genetics/genomics and curated findings pertaining to publications across multiple cancer types conducted on African populations. We used PubMed MeSH terms to retrieve the relevant publications from 1990 to December 2019. The metadata of these publications were extracted using R text mining packages: RISmed and Pubmed.mineR. The data showed that only 0.329% of cancer publications globally were on Africa, and only 0.016% were on cancer genetics/genomics from Africa. Although the most prevalent cancers in Africa are cancers of the breast, cervix, uterus, and prostate, publications representing breast, colorectal, liver, and blood cancers were the most frequent in our review. The most frequently reported cancer genes were BRCA1, BRCA2, and TP53. Next, the genes reported in the reviewed publications’ abstracts were extracted and annotated into three gene ontology classes. Genes in the cellular component class were mostly associated with cell part and organelle part, while those in biological process and molecular function classes were mainly associated with cell process, biological regulation, and binding, and catalytic activity, respectively. Overall, this review highlights the paucity of research on cancer genomics on African populations, identified gaps, and discussed the need for concerted efforts to encourage more research on cancer genomics in Africa.

Association of TP53 rs1042522 with cervical cancer in the sub-Saharan African population: a meta-analysis

OBJECTIVE

TP53 plays a crucial role in preventing cancer development. Previous studies in sub-Saharan Africa (SSA) reported inconclusive findings for the association of the TP53 rs1042522 C > G variant with cervical cancer. We therefore performed a meta-analysis to summarise this association in the SSA population.

METHODS

Online databases were searched to identify suitable articles according to the PRISMA guidelines. We included studies published in English or French that provided the sample sizes and genotype counts for both cases and controls and evaluated the association between TP53 rs1042522 and cervical cancer in the SSA population. A fixed-effect model was used to calculate the pooled odds ratio (OR) and 95% confidence intervals (95% CIs).

RESULTS

A total of 699 cervical cancer cases and 1008 controls from eight studies in SSA were included in this meta-analysis. Women harbouring the variant G allele of the TP53 rs1042522 were at increased risk of cervical cancer in allelic (G vs. C; OR = 1.30, 95% Cl = 1.12-1.50), homozygous (GG vs. CC; OR = 1.62, 95% CI = 1.20-2.19) and recessive (GG vs. CG + GG; OR = 1.74, 95% CI = 1.34-2.25) genetic models. However, the dominant genetic model (CG + GG vs. CC; OR = 1.20, 95% CI = 0.96-1.48) was not significantly associated with cervical cancer.

CONCLUSIONS

Our meta-analysis revealed that harbouring variant G allele of TP53 rs1042522 is associated with cervical cancer risk in the SSA population.

Genetic Susceptibility for Cervical Cancer in African Populations: What Are the Host Genetic Drivers?

Human papillomavirus (HPV) is an essential but not a sufficient cervical cancer etiological factor. Cancer promoters, such as host genetic mutations, significantly modulate therapeutic responses and susceptibility. In cervical cancer, of interest have been viral clearing genes and HPV oncoprotein targets, for which conflicting data have been reported among different populations. This expert analysis evaluates cervical cancer genetic susceptibility biomarkers studied in African populations. Notably, the past decade has seen Africa as a hotbed of biomarker and precision medicine innovations, thus potentially informing worldwide biomarker development strategies. We conducted a critical literature search in PubMed/MEDLINE, Google Scholar, and Scopus databases for case-control studies reporting on cervical cancer genetic polymorphisms among Africans. We found that seven African countries conducted cervical cancer molecular epidemiology studies in one of Casp8, p53, CCR2, FASL, HLA, IL10, TGF-beta, and TNF-alpha genes. This analysis reveals a remarkable gap in cervical cancer molecular epidemiology among Africans, whereas cervical cancer continues to disproportionately have an impact on African populations. Genome-wide association, whole exome- and whole-genome sequencing studies confirmed the contribution of candidate genes in cervical cancer. With such advances and omics technologies, the role of genetic susceptibility biomarkers can be exploited to develop novel interventions to improve current screening, diagnostic and prognostic methods worldwide. Exploring these genetic variations is crucial because African populations are genetically diverse and some variants or their combined effects are yet to be discovered and translated into tangible clinical applications. Thus, translational medicine and flourishing system sciences in Africa warrant further emphasis in the coming decade.

Genetic susceptibility to cervical cancer: role of common polymorphisms in apoptosis-related genes

Cervical cancer is a common malignancy which poses a significant health burden among women, especially those living in the developing countries. Although human papillomavirus (HPV) infection has been unequivocally implicated in the etiopathogenesis of the cancer, it alone is not adequate to contribute to the malignant transformation of cervical cells. Most HPV infections regress spontaneously, and only a small proportion of women have persistent infections which eventually lead to malignancy. This suggests that interplays between HPV infection and other cofactors certainly exist during the process of cervical carcinogenesis, which synergistically contribute to the differential susceptibility of an individual to the malignancy. Undoubtedly, host genetic factors represent a major element involved in such a synergistic interaction, and accumulating evidence suggests that polymorphisms in apoptosis-related genes play an important role in the genetic susceptibility to cervical cancer. This review consolidates the recent literatures on the role of common polymorphisms in apoptosis-related genes in genetic susceptibility to cervical cancer.