Association of genomic variants at the human leukocyte antigen locus with cervical cancer risk, HPV status and gene expression levels

The human leukocyte antigen (HLA) locus on chromosome 6 has been reported to be associated with cervical cancer. We investigated two independent single-nucleotide polymorphisms in a large case-control series of cervical dysplasia and carcinoma that has been newly established by the German Cervigen Consortium, comprising a total of 2481 cases and 1556 healthy females. We find significant associations for both variants, rs9272117 at HLA-DQA1 and rs2844511 at MICA and HCP5, with cervical disease. Both variants showed evidence of association with invasive cervical cancer (rs9272117: OR 0.89, 95% CI 0.79-0.99, P = .036; rs2844511: OR 1.17, 95% CI 1.04-1.31, P = .008) and with high-grade dysplasia (rs9272117: OR 0.78, 95% CI 0.70-0.87, P = 7.1 × 10^-6 ; rs2844511: OR 1.13, 95% CI 1.01-1.26, P = .035), as well as in a combined analysis of both groups (rs9272117: OR 0.83, 95% CI 0.75-0.91, P = 6.9 × 10^-5 ; rs2844511: OR 1.14, 95% CI 1.04-1.26, P = .005). Variant rs2844511, but not rs9272117, also showed modest evidence of association with low-grade dysplasia (OR 1.26, 95% CI 1.04-1.54, P = .019). In case-only analyses, rs2844511 tended to predict HPV status (P = .044) and rs9272117 tended to associate with HPV16 (P = .022). RNA studies in cervical samples showed a significant correlation in the transcript levels of MICA, HCP5 and HLA-DQA1, suggesting extensive co-regulation. All three genes were upregulated in HPV16-positive samples. In stratified analyses, rs9272117 was associated with HLA-DQA1 levels, specifically in HPV-positive samples, while rs2844511 was associated with MICA and HCP5 levels. The risk allele of rs2844511 was required for correlations between MICA or HCP5 with HLA-DQA1. Altogether, our results support 6p21.32-33 as the first consistent cervical cancer susceptibility locus and provide evidence for a link between genetic risk variants, HPV16 status and transcript levels of HLA-DQA1, HCP5 and MICA, which may contribute to tumor immune evasion.

Clinical and Biological Manifestation of RNF168 Deficiency in Two Polish Siblings

Germline mutations in the RING finger protein gene RNF168 have been identified in a combined immunodeficiency disorder called RIDDLE syndrome. Since only two patients have been described with somewhat different phenotypes, there is need to identify further patients. Here, we report on two Polish siblings with RNF168 deficiency due to homozygosity for a novel frameshift mutation, c.295delG, that was identified through exome sequencing. Both patients presented with immunoglobulin deficiency, telangiectasia, cellular radiosensitivity, and increased alpha-fetoprotein (AFP) levels. The younger sibling had a more pronounced neurological and morphological phenotype, and she also carried an ATM gene mutation in the heterozygous state. Immunoblot analyses showed absence of RNF168 protein, whereas ATM levels and function were proficient in lymphoblastoid cells from both patients. Consistent with the absence of RNF168 protein, 53BP1 recruitment to DNA double-strand breaks (DSBs) after irradiation was undetectable in lymphoblasts or primary fibroblasts from either of the two patients. γH2AX foci accumulated normally but they disappeared with significant delay, indicating a severe defect in DSB repair. A comparison with the two previously identified patients indicates immunoglobulin deficiency, cellular radiosensitivity, and increased AFP levels as hallmarks of RNF168 deficiency. The variability in its clinical expression despite similar cellular phenotypes suggests that some manifestations of RNF168 deficiency may be modified by additional genetic or epidemiological factors.

Assessment of an APOBEC3B truncating mutation, c.783delG, in patients with breast cancer

PURPOSE

APOBEC3B belongs to the family of DNA-editing enzymes. A copy number variant targeting the genomic APOBEC3A-APOBEC3B locus has a significant impact on breast cancer risk, but the relative contribution of APOBEC3B is uncertain. In this study, we investigate a loss-of-function mutation that selectively targets APOBEC3B, for its association with breast cancer risk.

METHODS

We performed exome sequencing on genomic DNA samples of 6 Byelorussian patients with familial breast cancer. We then studied through mutation-specific genotyping four hospital-based breast cancer case-control series from Belarus, Russia, Germany, and Iran, respectively, comprising a total of 3070 breast cancer patients and 2878 healthy females. Results were evaluated using fixed-effects meta-analyses.

RESULTS

Exome sequencing uncovered a frameshift mutation, APOBEC3B*c.783delG, that was recurrent in the study populations. Subsequent genotyping identified this mutation in 23 additional breast cancer cases and 9 healthy female controls, with an adjusted Odds Ratio 2.29 (95% CI 1.04; 5.03, P = 0.04) in the combined analysis. There was an enrichment of the c.783delG mutation in patients with breast cancer diagnosed below 50 years of age (OR 3.22, 95% CI 1.37; 7.56, P = 0.007).

CONCLUSIONS

APOBEC3B*c.783delG showed evidence of modest association with breast cancer and seemed to contribute to earlier onset of the disease. These results may need to be reconciled with proposals to consider APOBEC3B as a possible therapeutic target in breast cancer.