STaRRRT: a table of short tandem repeats in regulatory regions of the human genome.

BACKGROUND: Tandem repeats (TRs) are unstable regions commonly found within genomes that have consequences for evolution and disease. In humans, polymorphic TRs are known to cause neurodegenerative and neuromuscular disorders as well as being associated with complex diseases such as diabetes and cancer. If present in upstream regulatory regions, TRs can modify chromatin structure and affect transcription; resulting in altered gene expression and protein abundance. The most common TRs are short tandem repeats (STRs), or microsatellites. Promoter located STRs are considerably more polymorphic than coding region STRs. As such, they may be a common driver of phenotypic variation. To study STRs located in regulatory regions, we have performed genome-wide analysis to identify all STRs present in a region that is 2 kilobases upstream and 1 kilobase downstream of the transcription start sites of genes. RESULTS: The Short Tandem Repeats in Regulatory Regions Table, STaRRRT, contains the results of the genome-wide analysis, outlining the characteristics of 5,264 STRs present in the upstream regulatory region of 4,441 human genes. Gene set enrichment analysis has revealed significant enrichment for STRs in cellular, transcriptional and neurological system gene promoters and genes important in ion and calcium homeostasis. The set of enriched terms has broad similarity to that seen in coding regions, suggesting that regulatory region STRs are subject to similar evolutionary pressures as STRs in coding regions and may, like coding region STRs, have an important role in controlling gene expression. CONCLUSIONS: STaRRRT is a readily-searchable resource for investigating potentially polymorphic STRs that could influence the expression of any gene of interest. The processes and genes enriched for regulatory region STRs provide potential novel targets for diagnosing and treating disease, and support a role for these STRs in the evolution of the human genome.

A genetic variant in telomerase reverse transcriptase (TERT) modifies cancer risk in Lynch syndrome patients harbouring pathogenic MSH2 variants.

Individuals with Lynch syndrome (LS), have an increased risk of developing cancer. Common genetic variants of telomerase reverse transcriptase (TERT) have been associated with a wide range of cancers, including colorectal cancer (CRC) in LS. We combined genotype data from 1881 LS patients, carrying pathogenic variants in MLH1, MSH2 or MSH6, for rs2075786 (G>A, intronic variant), 1207 LS patients for rs2736108 (C>T, upstream variant) and 1201 LS patients for rs7705526 (C>A, intronic variant). The risk of cancer was estimated by heterozygous/homozygous odds ratio (OR) with mixed-effects logistic regression to adjust for gene/gender/country of sample origin considering family identity. The AA genotype of SNP rs2075786 is associated with 85% higher odds at developing cancer compared to GG genotype in MSH2 pathogenic variant carriers (p = 0.0160). Kaplan-Meier analysis also shows an association for rs2075786; the AA allele for MSH2 variant carriers confers risk for earlier diagnosis of LS cancer (log-rank p = 0.0011). We report a polymorphism in TERT to be a possible modifier of disease risk in MSH2 pathogenic variant carriers. The rs2075786 SNP in TERT is associated with a differential risk of developing cancer for MSH2 pathogenic variant carriers. Use of this information has the potential to personalise screening protocols for LS patients.

A polymorphic repeat in the IGF1 promoter influences the risk of endometrial cancer.

Due to the lack of high-throughput genetic assays for tandem repeats, there is a paucity of knowledge about the role they may play in disease. A polymorphic CA repeat in the promoter region of the insulin-like growth factor 1 gene (IGF1 has been studied extensively over the past 10 years for association with the risk of developing breast cancer, among other cancers, with variable results. The aim of this study was to determine if this CA repeat is associated with the risk of developing breast cancer and endometrial cancer. Using a case-control design, we analysed the length of this CA repeat in a series of breast cancer and endometrial cancer cases and compared this with a control population. Our results showed an association when both alleles were considered in breast and endometrial cancers (P=0.029 and 0.011, respectively), but this did not pass our corrected threshold for significance due to multiple testing. When the allele lengths were analysed categorically against the most common allele length of 19 CA repeats, an association was observed with the risk of endometrial cancer due to a reduction in the number of long alleles (P=0.013). This was confirmed in an analysis of the long alleles separately for endometrial cancer risk (P=0.0012). Our study found no association between the length of this polymorphic CA repeat and breast cancer risk. The significant association observed between the CA repeat length and the risk of developing endometrial cancer has not been previously reported.

A novel polymorphic repeat in the upstream regulatory region of the estrogen-induced gene EIG121 is not associated with the risk of developing breast or endometrial cancer.

BACKGROUND: The estrogen-induced gene 121 (EIG121) has been associated with breast and endometrial cancers, but its mechanism of action remains unknown. In a genome-wide search for tandem repeats, we found that EIG121 contains a short tandem repeat (STR) in its upstream regulatory region which has the potential to alter gene expression. The presence of this STR has not previously been analysed in relation to breast or endometrial cancer risk. RESULTS: In this study, the lengths of this STR were determined by PCR, fragment analysis and sequencing using DNA from 223 breast cancer patients, 204 endometrial cancer patients and 220 healthy controls to determine if they were associated with the risk of developing breast or endometrial cancer. We found this repeat to be highly variable with the number of copies of the AG motif ranging from 27 to 72 and having a bimodal distribution. No statistically significant association was identified between the length of this STR and the risk of developing breast or endometrial cancer or age at diagnosis. CONCLUSIONS: The STR in the upstream regulatory region of EIG121 is highly polymorphic, but is not associated with the risk of developing breast or endometrial cancer in the cohorts analysed here. While this polymorphic STR in the regulatory region of EIG121 appears to have no impact on the risk of developing breast or endometrial cancer, its association with disease recurrence or overall survival remains to be determined.

Polyamine aza-cyclic compounds demonstrate anti-proliferative activity in vitro but fail to control tumour growth in vivo.

Cationic polyamines such as the poly(propylenimine) dendrimers (DAB16) are anti-tumour agents (Dufes et al., 2005, Cancer Res 65:8079-8084). Their mechanism of action is poorly understood, but the lack of in vivo toxicity suggests cancer specificity. To explore this polyamine pharmacophore we cross-linked the aza-cyclic compound, hexacyclen, with 1,4-dibromobutane or 1,8-dibromooctane to yield the polyamines [poly(butylhexacyclen)--CL4] or [poly(octylhexacyclen)--CL8] respectively, both free of primary amines. We characterised the compounds and their respective nanoparticles and examined their interaction with the putative targets of the cationic polyamines: the cell membrane and DNA. Like DAB 16, CL4 and CL8 bind plasmid DNA and all three compounds interrupted the cell cycle of A431 epidermoid carcinoma cells in the S-phase. Additionally all three compounds disrupted erythrocyte membranes, with CL8 and DAB 16 being more active, in this respect, than CL4. CL4 (IC(50) =775.1 µg mL(-1)) and CL8 (IC(50) =8.4 µg mL(-1)), in a similar manner to DAB 16, were anti-proliferative against A431 cells; although unlike DAB 16, CL4 and CL8 were not tumouricidal against A431 xenografts in mice, indicating that primary amines may play an important role in the in vivo activity of DAB 16.

Cancer-specific transgene expression mediated by systemic injection of nanoparticles.

The lack of safe and efficient systemic gene delivery vectors has largely reduced the potential of gene therapy in the clinic. Previously, we have reported that polypropylenimine dendrimer PPIG3/DNA nanoparticles are capable of tumor transfection upon systemic administration in tumor-bearing mice. To be safely applicable in the clinic, it is crucial to investigate the colloidal stability of nanoparticles and to monitor the exact biodistribution of gene transfer in the whole body of the live subject. Our biophysical characterization shows that dendrimers, when complexed with DNA, are capable of forming spontaneously in solution a supramolecular assembly that possesses all the features required to diffuse in experimental tumors through the enhanced permeability and retention effect. We show that these nanoparticles are of sizes ranging from 33 to 286 nm depending on the DNA concentration, with a colloidal stable and well-organized fingerprint-like structure in which DNA molecules are condensed with an even periodicity of 2.8 nm. Whole-body nuclear imaging using small-animal nano-single-photon emission computed tomography/computer tomography scanner and the human Na/I symporter (NIS) as reporter gene shows unique and highly specific tumor targeting with no detection of gene transfer in any of the other tissues of tumor-bearing mice. Tumor-selective transgene expression was confirmed by quantitative reverse transcription-PCR at autopsy of scanned animals, whereas genomic PCR showed that the tumor sites are the predominant sites of nanoparticle accumulation. Considering that NIS imaging of transgene expression has been recently validated in humans, our data highlight the potential of these nanoparticles as a new formulation for cancer gene therapy.

Polymeric amphiphile branching leads to rare nanodisc shaped planar self-assemblies.

Self-assembly is fundamental to the biological function of cells and the fabrication of nanomaterials. However, the origin of the shape of various self-assemblies, such as the shape of cells, is not altogether clear. Polymeric, oligomeric, or low molecular weight amphiphiles are a rich source of nanomaterials, and controlling their self-assembly is the route to tailored nanosystems with specific functionalities. Here, we provide direct evidence that a particular molecular architecture, polymeric branching, leads to a rare form of self-assembly, the planar nanodisc. Cholesterol containing self-assemblies formed from amphiphilic linear or branched cetyl poly(ethylenimine) (Mn approximately 1000 Da) or amphiphilic cetyl poly(propylenimine) dendrimer derivatives (Mn approximately 2000 Da) show that branching, by reducing the hydrophilic headgroup area, alters the shape of the self-assemblies transforming closed 60 nm spherical bilayer vesicles to rare 50 nm x 10 nm planar bilayer discs. Increasing the hydrophilic headgroup area, by the inclusion of methoxy poly(ethylene glycol) moieties into the amphiphilic headgroup, transforms the planar discs to 100 nm spherical bilayer vesicles. This study provides insight into the key role played by molecular shape on molecular self-organization into rare nanodiscs.