Injectable and Oral Contraceptive Use and Cancers of the Breast,Cervix, Ovary,and Endometrium in Black South African Women: Case–Control Study

Background

Oral contraceptives are known to influence the risk of cancers of the female reproductive system. Evidence regarding the relationship between injectable contraceptives and these cancers is limited, especially in black South Africans, among whom injectable contraceptives are used more commonly than oral contraceptives.

Methods and Findings

We analysed data from a South African hospital-based case–control study of black females aged 18–79 y, comparing self-reported contraceptive use in patients with breast (n = 1,664), cervical (n = 2,182), ovarian (n = 182), and endometrial (n = 182) cancer, with self-reported contraceptive use in 1,492 control patients diagnosed with cancers with no known relationship to hormonal contraceptive use. We adjusted for potential confounding factors, including age, calendar year of diagnosis, education, smoking, alcohol, parity/age at first birth, and number of sexual partners. Among controls, 26% had used injectable and 20% had used oral contraceptives. For current and more recent users versus never users of oral or injectable contraceptives, the odds ratios (ORs) for breast cancer were significantly increased in users of oral and/or injectable contraceptives (OR 1.66, 95% CI 1.28–2.16, p<0.001) and separately among those exclusively using oral (1.57, 1.03–2.40, p = 0.04) and exclusively using injectable (OR 1.83, 1.31–2.55, p<0.001) contraceptives; corresponding ORs for cervical cancer were 1.38 (1.08–1.77, p = 0.01), 1.01 (0.66–1.56, p = 0.96), and 1.58 (1.16–2.15, p = 0.004). There was no significant increase in breast or cervical cancer risk among women ceasing hormonal contraceptive use ≥10 y previously (p = 0.3 and p = 0.9, respectively). For durations of use ≥5 y versus never use, the ORs of ovarian cancer were 0.60 (0.36–0.99, p = 0.04) for oral and/or injectable contraceptive use and 0.07 (0.01–0.49, p = 0.008) for injectable use exclusively; corresponding ORs for endometrial cancer were 0.44 (0.22–0.86, p = 0.02) and 0.36 (0.11–1.26, p = 0.1).

Conclusions

In this study, use of oral and of injectable hormonal contraceptives was associated with a transiently increased risk of breast and cervical cancer and, for long durations of use, with a reduced risk of ovarian and endometrial cancer. The observed effects of injectable and of oral contraceptives on cancer risk in this study did not appear to differ substantially. Please see later in the article for the Editors'' Summary     

Genomic hypomethylation in the human germline associates with selective structural mutability in the human genome

The hotspots of structural polymorphisms and structural mutability in the human genome remain to be explained mechanistically. We examine associations of structural mutability with germline DNA methylation and with non-allelic homologous recombination (NAHR) mediated by low-copy repeats (LCRs). Combined evidence from four human sperm methylome maps, human genome evolution, structural polymorphisms in the human population, and previous genomic and disease studies consistently points to a strong association of germline hypomethylation and genomic instability. Specifically, methylation deserts, the ~1% fraction of the human genome with the lowest methylation in the germline, show a tenfold enrichment for structural rearrangements that occurred in the human genome since the branching of chimpanzee and are highly enriched for fast-evolving loci that regulate tissue-specific gene expression. Analysis of copy number variants (CNVs) from 400 human samples identified using a custom-designed array comparative genomic hybridization (aCGH) chip, combined with publicly available structural variation data, indicates that association of structural mutability with germline hypomethylation is comparable in magnitude to the association of structural mutability with LCR-mediated NAHR. Moreover, rare CNVs occurring in the genomes of individuals diagnosed with schizophrenia, bipolar disorder, and developmental delay and de novo CNVs occurring in those diagnosed with autism are significantly more concentrated within hypomethylated regions. These findings suggest a new connection between the epigenome, selective mutability, evolution, and human disease.     

DNA resection at chromosome breaks promotes genome stability by constraining non-allelic homologous recombination

DNA double-strand breaks impact genome stability by triggering many of the large-scale genome rearrangements associated with evolution and cancer. One of the first steps in repairing this damage is 5'→3' resection beginning at the break site. Recently, tools have become available to study the consequences of not extensively resecting double-strand breaks. Here we examine the role of Sgs1- and Exo1-dependent resection on genome stability using a non-selective assay that we previously developed using diploid yeast. We find that Saccharomyces cerevisiae lacking Sgs1 and Exo1 retains a very efficient repair process that is highly mutagenic to genome structure. Specifically, 51% of cells lacking Sgs1 and Exo1 repair a double-strand break using repetitive sequences 12-48 kb distal from the initial break site, thereby generating a genome rearrangement. These Sgs1- and Exo1-independent rearrangements depend partially upon a Rad51-mediated homologous recombination pathway. Furthermore, without resection a robust cell cycle arrest is not activated, allowing a cell with a single double-strand break to divide before repair, potentially yielding multiple progeny each with a different rearrangement. This profusion of rearranged genomes suggests that cells tolerate any dangers associated with extensive resection to inhibit mutagenic pathways such as break-distal recombination. The activation of break-distal recipient repeats and amplification of broken chromosomes when resection is limited raise the possibility that genome regions that are difficult to resect may be hotspots for rearrangements. These results may also explain why mutations in resection machinery are associated with cancer.     

Autonomic dysfunction and plasticity in micturition reflexes in human α-synuclein mice

Although often overshadowed by the motor dysfunction associated with Parkinson's disease (PD), autonomic dysfunction including urinary bladder and bowel dysfunctions are often associated with PD and may precede motoric changes; such autonomic dysfunction may permit early detection and intervention. Lower urinary tract symptoms are common in PD patients and result in significant morbidity. This studies focus on nonmotor symptoms in PD using a transgenic mouse model with overexpression of human α-synuclein (hSNCA), the peptide found in high concentrations in Lewy body neuronal inclusions, the histopathologic hallmark of PD. We examined changes in the physiological, molecular, chemical, and electrical properties of neuronal pathways controlling urinary bladder function in transgenic mice. The results of these studies reveal that autonomic dysfunction (i.e., urinary bladder) can precede motor dysfunction. In addition, mice with hSNCA overexpression in relevant neuronal populations is associated with alterations in expression of neurotransmitter/neuromodulatory molecules (PACAP, VIP, substance P, and neuronal NOS) within neuronal pathways regulating bladder function as well as with increased NGF expression in the urinary bladder. Changes in the electrical and synaptic properties of neurons in the major pelvic ganglia that provide postganglionic innervation to urogenital tissues were not changed as determined with intracellular recording. The urinary bladder dysfunction observed in transgenic mice likely reflects changes in peripheral (i.e., afferent) and/or central micturition pathways or changes in the urinary bladder. SYN-OE mice provide an opportunity to examine early events underlying the molecular and cellular plasticity of autonomic nervous system pathways underlying synucleinopathies.     

On the Interplay of Telomeres,Nevi and the Risk of Melanoma

The relationship between telomeres, nevi and melanoma is complex. Shorter telomeres have been found to be associated with many cancers and with number of nevi, a known risk factor for melanoma. However, shorter telomeres have also been found to decrease melanoma risk. We performed a systematic analysis of telomere-related genes and tagSNPs within these genes, in relation to the risk of melanoma, dysplastic nevi, and nevus count combining data from four studies conducted in Italy. In addition, we examined whether telomere length measured in peripheral blood leukocytes is related to the risk of melanoma, dysplastic nevi, number of nevi, or telomere-related SNPs. A total of 796 cases and 770 controls were genotyped for 517 SNPs in 39 telomere-related genes genotyped with a custom-made array. Replication of the top SNPs was conducted in two American populations consisting of 488 subjects from 53 melanoma-prone families and 1,086 cases and 1,024 controls from a case-control study. We estimated odds ratios for associations with SNPs and combined SNP P-values to compute gene region-specific, functional group-specific, and overall P-value using an adaptive rank-truncated product algorithm. In the Mediterranean population, we found suggestive evidence that RECQL4, a gene involved in genome stability, RTEL1, a gene regulating telomere elongation, and TERF2, a gene implicated in the protection of telomeres, were associated with melanoma, the presence of dysplastic nevi and number of nevi, respectively. However, these associations were not found in the American samples, suggesting variable melanoma susceptibility for these genes across populations or chance findings in our discovery sample. Larger studies across different populations are necessary to clarify these associations.     

Extracellular gelsolin binds lipoteichoic acid and modulates cellular response to proinflammatory bacterial wall components

The various functions of gelsolin in extracellular compartments are not yet clearly defined but include actin scavenging and antiinflammatory effects. Gelsolin was recently reported to bind endotoxin (LPS) from various Gram-negative bacteria with high affinity. In this study we investigate whether gelsolin also interacts with bacterial wall molecules of Gram-positive bacteria such as lipoteichoic acid (LTA) and whether gelsolin's interaction with bacterial lipids from Gram-negative or Gram-positive bacteria affects their cellular inflammatory responses. A peptide based on the PPI binding site of gelsolin (160-169) binds purified LTA at the same molecular ratio that it binds phosphatidylinositol 4,5-bisphosphate. The OD of recombinant human plasma gelsolin was found to decrease following the addition of purified LTA, and the binding of gelsolin to LTA inhibits F-actin depolymerization by gelsolin. Simultaneously, the ability of LTA to activate translocation of NF-kappaB, E-selectin expression, and adhesion of neutrophils to LTA-treated human aortic endothelial cells was compromised by gelsolin. Gelsolin was able to partially inhibit LPS- or LTA-induced release of IL-8 from human neutrophils but was unable to prevent Gram-positive Bacillus subtilis or Gram-negative Pseudomonas aeruginosa growth and had no effect on the antibacterial activity of the cathelicidin-derived antibacterial peptide LL37. These data suggest that extracellular gelsolin is involved in the host immune recognition of LTA or LPS following release of these molecules from the bacterial outer membrane during cell division or attack by drugs and immune components.     

ABCG1 influences the brain cholesterol biosynthetic pathway but does not affect amyloid precursor protein or apolipoprotein E metabolism in vivo

Cholesterol homeostasis is of emerging therapeutic importance for Alzheimer's disease (AD). Agonists of liver-X-receptors (LXRs) stimulate several genes that regulate cholesterol homeostasis, and synthetic LXR agonists decrease neuropathological and cognitive phenotypes in AD mouse models. The cholesterol transporter ABCG1 is LXR-responsive and highly expressed in brain. In vitro, conflicting reports exist as to whether ABCG1 promotes or impedes Abeta production. To clarify the in vivo roles of ABCG1 in Abeta metabolism and brain cholesterol homeostasis, we assessed neuropathological and cognitive outcome measures in PDAPP mice expressing excess transgenic ABCG1. A 6-fold increase in ABCG1 levels did not alter Abeta, amyloid, apolipoprotein E levels, cholesterol efflux, or cognitive performance in PDAPP mice. Furthermore, endogenous murine Abeta levels were unchanged in both ABCG1-overexpressing or ABCG1-deficient mice. These data argue against a direct role for ABCG1 in AD. However, excess ABCG1 is associated with decreased levels of sterol precursors and increased levels of SREBP-2 and HMG-CoA-reductase mRNA, whereas deficiency of ABCG1 leads to the opposite effects. Although functions for ABCG1 in cholesterol efflux and Abeta metabolism have been proposed based on results with cellular model systems, the in vivo role of this enigmatic transporter may be largely one of regulating the sterol biosynthetic pathway.     

The Orf18 gene product from conjugative transposon Tn916 is an ArdA antirestriction protein that inhibits type I DNA restriction-modification systems

Gene orf18, which is situated within the intercellular transposition region of the conjugative transposon Tn916 from the bacterial pathogen Enterococcus faecalis, encodes a putative ArdA (alleviation of restriction of DNA A) protein. Conjugative transposons are generally resistant to DNA restriction upon transfer to a new host. ArdA from Tn916 may be responsible for the apparent immunity of the transposon to DNA restriction and modification (R/M) systems and for ensuring that the transposon has a broad host range. The orf18 gene was engineered for overexpression in Escherichia coli, and the recombinant ArdA protein was purified to homogeneity. The protein appears to exist as a dimer at nanomolar concentrations but can form larger assemblies at micromolar concentrations. R/M assays revealed that ArdA can efficiently inhibit R/M by all four major classes of Type I R/M enzymes both in vivo and in vitro. These R/M systems are present in over 50% of sequenced prokaryotic genomes. Our results suggest that ArdA can overcome the restriction barrier following conjugation and so helps increase the spread of antibiotic resistance genes by horizontal gene transfer.