Absence of Association between CCR5 rs333 Polymorphism and Childhood Acute Lymphoblastic Leukemia

CCR5Δ32 in Brazil: Impacts of a European Genetic Variant on a Highly Admixed Population

The genetic background of Brazilians encompasses Amerindian, African, and European components as a result of the colonization of an already Amerindian inhabited region by Europeans, associated to a massive influx of Africans. Other migratory flows introduced into the Brazilian population genetic components from Asia and the Middle East. Currently, Brazil has a highly admixed population and, therefore, the study of genetic factors in the context of health or disease in Brazil is a challenging and remarkably interesting subject. This phenomenon is exemplified by the genetic variant CCR5Δ32, a 32 base-pair deletion in the CCR5 gene. CCR5Δ32 originated in Europe, but the time of origin as well as the selective pressures that allowed the maintenance of this variant and the establishment of its current frequencies in the different human populations is still a field of debates. Due to its origin, the CCR5Δ32 allele frequency is high in European-derived populations (~10%) and low in Asian and African native human populations. In Brazil, the CCR5Δ32 allele frequency is intermediate (4-6%) and varies on the Brazilian States, depending on the migratory history of each region. CCR5 is a protein that regulates the activity of several immune cells, also acting as the main HIV-1 co-receptor. The CCR5 expression is influenced by CCR5Δ32 genotypes. No CCR5 expression is observed in CCR5Δ32 homozygous individuals. Thus, the CCR5Δ32 has particular effects on different diseases. At the population level, the effect that CCR5Δ32 has on European populations may be different than that observed in highly admixed populations. Besides less evident due to its low frequency in admixed groups, the effect of the CCR5Δ32 variant may be affected by other genetic traits. Understanding the effects of CCR5Δ32 on Brazilians is essential to predict the potential use of pharmacological CCR5 modulators in Brazil. Therefore, this study reviews the impacts of the CCR5Δ32 on the Brazilian population, considering infectious diseases, inflammatory conditions, and cancer. Finally, this article provides a general discussion concerning the impacts of a European-derived variant, the CCR5Δ32, on a highly admixed population.

CCR5 and CXCL12 allelic variants: Possible association with childhood neuroblastoma susceptibility?

Neuroblastoma (NB) is a heterogeneous and particularly malignant childhood neoplasm in its higher stages, prone to form metastasis in selected organs and for which there is still no efficient treatment available beyond surgery. Evidence indicates that chemokines and their receptors present involvement as mediators of neuroinflammation and have a neurophysiological role. In the present study, we aimed to verify if CCR5 (rs333) and CXCL12 (rs1801157) allelic variants were associated with NB. For CCR5 (rs333) D32 carriers (OR: 5.96, IC: 2.21-16.06) and for CXCL12 genotype 3'A/3'A (OR:26.18, IC:6.15-111.4) there were statistically significant differences as well to allelic frequency (OR:4.20, IC: 2.19-8.03). Although no correlation was verified regarding prognostic parameters for both CCR5 and CXCL12 polymorphic variants, these polymorphisms may be associated with NB susceptibility which deserve attention for future investigations.

The association between CCR5 Δ32 polymorphism and susceptibility to breast cancer

Background

Chemokine C-C motif receptor 5 (CCR5) gene polymorphisms have been proposed to play important roles in tumors. Δ32 polymorphism of this gene might correlate with breast cancer (BC) susceptibility. Nevertheless, inconsistent conclusions have been achieved as yet. We carried out this meta-analysis to draw a more comprehensive and convincing conclusion on this issue.

Results

No significant correlation of CCR5 Δ32 polymorphism with individual susceptibility to BC was detected in either total analysis (Δ32 vs. WT: OR=1.12, 95% CI=0.76-1.65; WT/Δ32 vs. WT/WT: OR=1.21, 95% CI=0.81-1.80) or subgroup analyses by ethnicity and control source.

Methods

All eligible studies were searched from electronic databases including Chinese National Knowledge Infrastructure (CNKI), PubMed, EMBASE, and Google Scholar Web. Strength of association between CCR5 Δ32 polymorphism and BC susceptibility was evaluated using pooled odds ratios (ORs) with their corresponding 95% confidence intervals (95% CIs). To further detect their correlation in specific populations, subgroup analyses were performed based on ethnicity and control source. Sensitivity analysis was conducted in this meta-analysis to test statistical stability of the final results. Publication bias among included studies was inspected with Begg’s funnel plot and Egger’s test.

Conclusion

CCR5 Δ32 polymorphism may not independently affect the risk of BC.