Mutational analysis of TP53 gene in Tunisian familial hematological malignancies and sporadic acute leukemia cases

Association of TP53 gene polymorphisms with the risk of acute lymphoblastic leukemia in Moroccan children

BACKGROUND

TP53 gene plays a pivotal role in maintaining genetic stability and prevention of malignancies. Alterations of this gene are implicated in more than half of human cancers. To the best of our knowledge, this study is the first to explore TP53 polymorphisms in Moroccan childhood acute lymphoblastic leukemia (ALL).

METHODS AND RESULTS

DNA samples of 45 ALL children were obtained from peripheral blood. A total of 333 healthy Moroccans were used as controls. Polymerase chain reaction and Sanger sequencing were performed to analyze TP53 hotspot exons in cases. We identified a significant protective effect of the TP53-Arg variant at rs1042522 [OR 0.4593 (0.249-0.8472), p = 0.0127] and the Pro/Arg genotype [OR 0.0350 (0.0047-0.2583), p = 0.0010]. Additionally, we found a novel association between the C-allele of Arg213Arg 1800372 [OR 2.7736 (1.3821-5.5664), p = 0.0041] and the risk of childhood ALL. Importantly, TC/CC genotypes of this polymorphism were revealed to enhance the risk of ALL among females [OR 9.0 (3.1555-25.6693), p < 0.0001]. Arg213Arg was also noticed to be associated with the hemoglobin count of patients at diagnosis by linear regression (p = 0.0318). The analysis of penetrance showed a significant association of the CG/GG genotypes at rs1042522 and TC/CC genotypes at rs1800372 to childhood ALL via dominant model [OR 0.2090 (0.09074-0.4814), p = 0.0002 and OR 3.4205 (1.6084-7.2742), p = 0.0014 for rs1042522 and rs1800372 respectively]. No association was found between TP53 polymorphisms and patients survival.

CONCLUSION

Altogether, our findings indicated that TP53 polymorphisms are significantly involved in the genetic susceptibility to childhood ALL in Morocco.

Importance of p53 gene polymorphisms in myelodysplastic syndrome disease

Aim: Myelodysplastic syndrome (MDS) is a clonal disease with a high risk of conversion to acute myeloid leukemia, characterized by increased apoptosis and decreased hematopoiesis. The pathogenesis of MDS has not been fully explained. ~50% of cases have abnormal karyotype and this rate is around 80% in secondary MDS. The p53 protein is an important regulator of stem cell homeostasis and is involved in a range of cellular events such as cell cycle regulation, apoptotic and inflammatory response. The TP53 gene, which has important roles in maintaining genomic integrity, is frequently mutated in cancers; however, some gene polymorphisms are known to be associated with cancer, as well as mutations. Our aim in the study is to determine the prevalence of four common p53 single nucleotide polymorphisms in MDS and their effects on disease development. For this reason, 100 cases followed up with the diagnosis of MDS or newly diagnosed in Ege University Faculty of Medicine, Department of Internal Medicine, Department of Hematology were included in the study. Materials and Methods: DNAs isolated from peripheral blood leukocytes of MDS cases were studied by real-time PCR method, p53 polymorphisms (rs35163653, rs35993958, rs1800371, rs1042522) were determined by using appropriate probes and melting curve analysis. Results: Among the four common p53 polymorphisms examined, especially the non-ancestral G allele in the rs1042522 polymorphism was observed to be increased in MDS cases (C: 30.3%; G: 69.7%). In this polymorphism, which is known to be functional, that is, affecting the function of the synthesized protein, the transition of the C nucleotide at position 417 to G (C>G) causes the coding of the amino acid proline at position 72 of the protein to arginine (P72R). Conclusion: Our study is the first to investigate the p53 polymorphisms of rs35163653, rs35993958, rs1800371 and rs1042522 in the MDS disease group. Of these, rs1042522 polymorphism has been shown to be associated with cancer susceptibility and susceptibility, and it is thought that it may pose a high risk for MDS disease as well. In conclusion, rs1042522 polymorphism may be used as a marker in the diagnosis of MDS in the future by repeating this study for MDS disease with a larger case group.

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.