Genetic variants in the H2AFX promoter region are associated with risk of sporadic breast cancer in non-Hispanic white women aged <or=55 years

Identification of prognostic genes signature and construction of ceRNA network in pirarubicin treatment of triple-negative breast cancer

BACKGROUND

The altered long non-coding RNA (lncRNA), circular RNA (circRNA) and mRNA expression in triple-negative breast cancer (TNBC) after pirarubicin (THP) treatment can be a critical factor in the development of tumor. Here, we identify a set of lncRNA, circRNA, and mRNA that can reveal the molecular target and molecular mechanism of THP, and can be used to predict the prognostic characteristics of TNBC.

METHODS

Affymetrix GeneChip sequencing was performed to determine whether lncRNA, circRNA, and mRNA were changed in MDA-MB-231 cells after THP treatment, and qRT-PCR was used to verify the accuracy of GeneChip results. Bioinformatics methods were used to analyze the differentially expressed (DE) lncRNA, circRNA and mRNA, and the co-expression network and ceRNA network were constructed. The STRING database, Kaplan-meier Mapper database, GEPIA database, and Tumor Immunity Estimation Resource were used to screen hub genes with clinical value and important significance.

RESULTS

THP 5 μM could significantly inhibit proliferation, migration and invasion of MDA-MB-231 cells for 24 h. 1547 DE lncRNAs, 4992 DE circRNAs, and 5777 DE mRNAs were identified. The reliability of the GeneChip was verified by qRT-PCR. An mRNA-lncRNA/circRNA co-expression network was constructed based on the Pearson correlation coefficient. Finally, we established a new ceRNA network, including three circRNAs, five miRNAs, and three mRNAs. The mRNAs are associated with immune infiltration. The mRNAs and miRNAs are significantly associated with survival outcomes in TNBC.

CONCLUSION

The results reveal the molecular target and mechanism of THP treatment of TNBC. These ceRNA network can be used as molecular targets for the treatment of TNBC patients and as molecular biomarkers to predict patient prognosis.

Genetic variations in ATM and H2AX loci contribute to risk of hematological abnormalities in individuals exposed to BTEX chemicals

Background

Loci controlling DNA double‐strand breaks (DSBs) repair play an important role in defending against the harmful health effects of benzene, toluene, ethylbenzene, and xylene (BTEX), but their gene variants may alter their repair capacity. The aim of the current study was to determine the relationship of functional polymorphisms ATM‐rs228589 A>T, WRN‐rs1800392 G>T and H2AX‐rs7759 A>G in DBS repair loci with the abnormal hematological indices in workers who exposed to BTEXs.

Methods

We included 141 cases with one or more abnormal hematological parameters, who had been occupationally exposed to BTEX chemicals and 152 controls with a similar exposure condition but without any abnormal hematological parameters. Atmospheric concentrations of BTEXs were measured and whole blood samples were taken from the participants to determine hematologic parameters and SNP genotyping.

Results

Results showed that T allele of ATM‐rs228589 and G allele of H2AX‐rs7759 had a higher frequency in cases than controls (p = 0.012 and p = 0.001, respectively). Also, AT and TT genotypes of ATM‐rs228589 and AG and GG genotypes of H2AX‐rs7759 were higher in cases compared to controls. The AT and TT genotypes of ATM‐rs228589 have significant associations with a risk of hematological abnormalities in the codominant (AT vs. AA, p = 0.018), dominant (AT + TT vs. AA, p = 0.010) and overdominant (AT vs. AA + TT, p = 0.037) models. The GG and AG genotypes of H2AX‐rs7759 were in relation with increased risk of abnormal hematological indices under codominant (GA vs. AA, p = 0.009 & GG vs. AA, p = 0.005), dominant (AG + GG vs. AA, p = 0.001), and recessive (GG vs. AA + AG, p = 0.025) models.

Conclusions

These observations may help to understand the mechanisms of BTEX hematotoxicity and identify useful biomarkers of risk assessment for workers exposed to BTEX.

miR-328-3p promotes migration and invasion by targeting H2AFX in head and neck squamous cell carcinoma

Migration and invasion are the initial step in the metastatic process, while metastasis is responsible for the poor prognosis of head and neck squamous cell carcinoma (HNSCC). Since miRNA has been found as an important regulator of gene expression at the post-transcriptional level in various diseases including carcinoma, exploring the role of miRNA in cancer metastasis will facilitate the target therapy of advanced HNSCC. MiR-328-3p has been reported to be an onco-miRNA or a tumor suppressor in several cancers. However, the role of miR-328-3p in HNSCC migration and invasion remains undefined. In this study, we first demonstrated that miR-328-3p enhanced migration and invasion of HNSCC in vitro, accompanying with a promotion of epithelial-mesenchymal transition (EMT) and mTOR activity. Meanwhile, we confirmed that miR-328-3p directly targeted the 3'UTR of H2A histone family, member X (H2AFX), which served as a tumor suppressor in migration and invasion of HNSCC. Moreover, H2AFX could partially reverse the migration and invasion of HNSCC caused by miR-328-3p. Overall, our results indicated that miR-328-3p enhanced migration and invasion of HNSCC through targeting H2AFX and activated the mTOR pathway.

A gene module identification algorithm and its applications to identify gene modules and key genes of hepatocellular carcinoma

To further improve the effect of gene modules identification, combining the Newman algorithm in community detection and K-means algorithm framework, a new method of gene module identification, GCNA-Kpca algorithm, was proposed. The core idea of the algorithm was to build a gene co-expression network (GCN) based on gene expression data firstly; Then the Newman algorithm was used to initially identify gene modules based on the topology of GCN, and the number of clusters and clustering centers were determined; Finally the number of clusters and clustering centers were input into the K-means algorithm framework, and the secondary clustering was performed based on the gene expression profile to obtain the final gene modules. The algorithm took into account the role of modularity in the clustering process, and could find the optimal membership module for each gene through multiple iterations. Experimental results showed that the algorithm proposed in this paper had the best performance in error rate, biological significance and CNN classification indicators (Precision, Recall and F-score). The gene module obtained by GCNA-Kpca was used for the task of key gene identification, and these key genes had the highest prognostic significance. Moreover, GCNA-Kpca algorithm was used to identify 10 key genes in hepatocellular carcinoma (HCC): CDC20, CCNB1, EIF4A3, H2AFX, NOP56, RFC4, NOP58, AURKA, PCNA, and FEN1. According to the validation, it was reasonable to speculate that these 10 key genes could be biomarkers for HCC. And NOP56 and NOP58 are key genes for HCC that we discovered for the first time.

SAAVpedia: Identification, Functional Annotation, and Retrieval of Single Amino Acid Variants for Proteogenomic Interpretation

Next-generation genome sequencing has enabled the discovery of numerous disease- or drug-response-associated nonsynonymous single nucleotide variants (nsSNVs) that alter the amino acid sequences of a protein. Although several studies have attempted to characterize pathogenic nsSNVs, few have been confirmed as single amino acid variants (SAAVs) at the protein level. Here we developed the SAAVpedia platform to identify, annotate, and retrieve pathogenic SAAV candidates from proteomic and genomic data. The platform consists of four modules: SAAVidentifier, SAAVannotator, SNV/SAAVretriever, and SAAVvisualizer. The SAAVidentifier provides a reference database containing 18 206 090 SAAVs and performs the identification and quality assessment of SAAVs. The SAAVannotator provides functional annotation with biological, clinical, and pharmacological information for the interpretation of condition-specific SAAVs. The SNV/SAAVretriever module enables bidirectional navigation between relevant SAAVs and nsSNVs with diverse genomic and proteomic data. SAAVvisualizer provides various statistical plots based on functional annotations of detected SAAVs. To demonstrate the utility of SAAVpedia, the proteogenomic pipeline with protein-protein interaction network analysis was applied to proteomic data from breast cancer and glioblastoma patients. We identified 1326 and 12 breast-cancer- and glioblastoma-related genes that contained one or more SAAVs, including BRCA2 and FAM49B, respectively. SAAVpedia is a suitable platform for confirming whether a genomic variant is maintained in an amino acid sequence. Furthermore, as a result of the SAAV discovery of these positive controls, the SAAVpedia could play a key role in the protein functional study for the Human Proteome Project (HPP).

Genetic variants in ATM, H2AFX and MRE11 genes and susceptibility to breast cancer in the polish population

Background

DNA damage repair is a complex process, which can trigger the development of cancer if disturbed. In this study, we hypothesize a role of variants in the ATM, H2AFX and MRE11 genes in determining breast cancer (BC) susceptibility.

Methods

We examined the whole sequence of the ATM kinase domain and estimated the frequency of founder mutations in the ATM gene (c.5932G > T, c.6095G > A, and c.7630-2A > C) and single nucleotide polymorphisms (SNPs) in H2AFX (rs643788, rs8551, rs7759, and rs2509049) and MRE11 (rs1061956 and rs2155209) among 315 breast cancer patients and 515 controls. The analysis was performed using high-resolution melting for new variants and the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method for recurrent ATM mutations. H2AFX and MRE11 polymorphisms were analyzed using TaqMan assays. The cumulative genetic risk scores (CGRS) were calculated using unweighted and weighted approaches.

Results

We identified four mutations (c.6067G > A, c.8314G > A, c.8187A > T, and c.6095G > A) in the ATM gene in three BC cases and two control subjects. We observed a statistically significant association of H2AFX variants with BC. Risk alleles (the G of rs7759 and the T of rs8551 and rs2509049) were observed more frequently in BC cases compared to the control group, with P values, odds ratios (OR) and 95% confidence intervals (CIs) of 0.0018, 1.47 (1.19 to 1.82); 0.018, 1.33 (1.09 to 1.64); and 0.024, 1.3 (1.06 to 1.59), respectively. Haplotype-based tests identified a significant association of the H2AFX CACT haplotype with BC (P <  0.0001, OR = 27.29, 95% CI 3.56 to 209.5). The risk of BC increased with the growing number of risk alleles. The OR (95% CI) for carriers of ≥ four risk alleles was 1.71 (1.11 to 2.62) for the CGRS.

Conclusions

This study confirms that H2AFX variants are associated with an increased risk of BC. The above-reported sequence variants of MRE11 genes may not constitute a risk factor of breast cancer in the Polish population. The contribution of mutations detected in the ATM gene to the development of breast cancer needs further detailed study.

A comparison of estimates of doses to radiotherapy patients obtained with the dicentric chromosome analysis and the γ-H2AX assay: Relevance to radiation triage

The γ-H2AX assay was investigated as an alternative to the time-consuming dicentric chromosome assay (DCA). Radiation doses to 25 radiotherapy patients were estimated in parallel by DCA and the γ-H2AX assay. The γ-H2AX assay yielded doses in line with the calculated equivalent whole body doses in 92% of the patients, whereas the success rate of DCA was only 76%. The result shows that the γ-H2AX assay can be effectively used as a rapid and more precise alternative to DCA.

Breast cancer genetics in young women: What do we know?

Breast cancer (BC) in young women, generally defined in oncology as women who are 40 years of age or younger, represents 2 out of 10 BC cases in developing countries. Several research studies, including genetic cancer panel tests, genome-wide association studies, expression analyses and polymorphisms reports, have found that young women with BC exhibit a higher genetic susceptibility and specific genomic signature compared to postmenopausal women with BC. Thus, international guidelines recommend genetic counseling for this age population. This review presents the current state of the art of genetics and genomics with regards to young women with BC.

Genetic variants of H2AX gene were associated with PM2.5-modulated DNA damage levels in Chinese Han populations

Exposure to particulate matter 2.5 (PM2.5) may result in DNA damage. Histone variant H2AX phosphorylation plays a central role in the response to damaged chromatin. In the current study, we investigated whether H2AX gene polymorphisms account for PM2.5-modulated DNA damage levels. A total of 307 healthy urban residents were collected from three cities in southern, central, and northern China, Zhuhai, Wuhan, and Tianjin, respectively. The dust mass concentrations of PM2.5 were detected by Gilian 5000 pumps, and the DNA damage levels were measured using comet assay. Seven potentially functional single nucleotide polymorphisms (SNPs) of H2AX gene were selected and genotyped by Illumina Infinium(®) BeadChip. We found that three SNPs (rs10790283 G > A, rs604714 C > A and rs7759 A > G) were significantly associated with DNA damage levels (adjusted P = 0.002, 0.018 and 0.027, respectively). Significant interactions (P < 0.05) were observed between certain genetic polymorphisms and PM2.5-modulated DNA damage levels. These results suggested that genetic variations of H2AX might be associated with the DNA damage levels in urban residents with different exposure to PM2.5. Further studies with large sample size in independent populations merit validating these findings.

Histone H2A.Z deregulation in prostate cancer. Cause or effect?

Genetic and epigenetic changes are at the root of all cancers. The epigenetic component involves alterations of the post-synthetic modifications of DNA (methylation) and histones (histone posttranslational modifications, PTMs) as well as of those of their molecular "writers," "readers," and "erasers." Noncoding RNAs (ncRNA) can also play a role. Here, we focus on the involvement of histone alterations in cancer, in particular that of the histone variant H2A.Z in the etiology of prostate cancer. The structural mechanisms putatively responsible for the contribution of H2A.Z to oncogenic gene expression programs are first described, followed by what is currently known about the involvement of this histone variant in the regulation of androgen receptor regulated gene expression. The implications of this and their relevance to oncogene deregulation in different stages of prostate cancer, including the progression toward androgen independence, are discussed. This review underscores the increasing awareness of the epigenetic contribution of histone variants to oncogenic progression.

Genetic risk score and acute skin toxicity after breast radiation therapy

Genetic predisposition has been shown to affect the severity of skin complications in breast cancer patients after radiotherapy. Limited data exist regarding the use of a genetic risk score (GRS) for predicting risk of tissue radiosensitivity. We evaluated the impact of different single-nucleotide polymorphisms (SNPs) in genes related to DNA repair mechanisms and oxidative stress response combined in a GRS on acute adverse effects induced by breast radiation therapy (RT). Skin toxicity was scored according to the Radiation Therapy Oncology Group (RTOG) criteria in 59 breast cancer patients who received RT. After genotyping, a multilocus GRS was constructed by summing the number of risk alleles. The hazard ratio (HR) for GSTM1 was 2.4 (95% confidence intervals [CI]=1.1-5.3, p=0.04). The other polymorphisms were associated to an increased adverse radiosensitivity, although they did not reach statistical significance. GRS predicted roughly 40% risk for acute skin toxicity per risk allele (HR 1.37, 95% CI=1.1-1.76, p<0.01). Patients in the top tertile had a fivefold higher risk of skin reaction (HR 5.1, 95% CI=1.2-22.8, p=0.03). Our findings demonstrate that the joint effect of SNPs from oxidative stress and DNA damage repair genes may be a promising approach to identify patients with a high risk of skin reaction after breast RT.

Functional characterization of genetic polymorphisms in the H2AFX distal promoter

Due to the critical role of the H2AX histone variant in double-strand break repair, genetic variants in the H2AX gene, H2AFX, may influence cancer susceptibility. Genetic association studies have correlated H2AFX upstream variants with cancer risk; however it is unclear if any are causal. H2AFX has at least two alternate transcripts that encode the same reading frame; a short 0.6kb transcript that lacks an intron or poly-A tail and is predicted to be highly expressed during the replication stage of the cell cycle, and a long 1.6kb poly-A tailed transcript that is expressed in a replication-independent manner. To examine the functional impact of the rs643788, rs8551, rs7759, and rs2509049 upstream variants, we characterized their influence on gene expression, cell survival after DNA assault, and transcription factor binding. Analysis of allelic imbalance using quantitative sequencing of cDNA from lymphoblast cell lines did not reveal any difference in expression of the 1.6kb polyadenylated transcript between the common H2AFX upstream haplotypes. We did, however, identify a previously unreported 197 base pair intron in the H2AFX 3'untranslated region that appears to be present regardless of haplotype. Assessment of cell survival after irradiation treatment did not show any difference in survival between cell lines of different haplotypes. Gel shift assays revealed that the rs643788 C allele disrupts YY1 transcription factor binding and the rs2509049 C allele binds more strongly to a protein complex than does the rs2509049 T allele. Though we did not identify any differences in expression or survival between haplotypes, differential protein binding at two of the polymorphisms suggests further functional analyses may reveal a role for these variants in influencing gene expression at specific points of the cell cycle or in specific tissues.

Genetic variant rs16430 6bp > 0bp at the microRNA-binding site in TYMS and risk of sporadic breast cancer risk in non-Hispanic white women aged ≤ 55 years

Thymidylate synthase (TYMS) is involved in the folate metabolism and provision of nucleotides needed for DNA synthesis and repair. Thus, functional genetic variants in TYMS may alter cancer risk. In the study, we evaluated associations of three germline variants (rs2790 A > G, rs16430 6 bp > 0 bp, and rs1059394 C > T) in the predicted miRNA-binding sites of TYMS with risk of sporadic breast cancer in non-Hispanic white women aged ≤ 55. We found that carriers of the rs16430 0 bp variant allele had an increased risk of breast cancer [adjusted odd ratio (OR) = 1.37, 95% confidence interval (CI): 1.08-1.73; P = 0.010], compared with carriers of the 6 bp/6 bp genotype. This increased risk was more evident in older subjects (OR = 1.47, 95% CI = 1.06-2.03, P = 0.022), never smokers (OR = 1.67, 95% CI = 1.23-2.25, P < 0.001), never drinkers (OR = 1.44, 95% CI = 1.01-2.05, P = 0.043), and estrogen receptor-positive patients (OR = 1.46, 95% CI = 1.11-1.92, P = 0.006), regardless of tumor stages. The results are consistent with the functional analyses of rs16430 as previously reported, which showed that the 0 bp allele had a decrease in both luciferase activity by ∼ 70% and mRNA levels by ∼ 50% compared with the 6bp allele. Additionally, the rs16430 variant was predicted to influence the binding activity of miR-561. Taken together, these findings indicate that the TYMS rs16430 may contribute to the etiology of sporadic breast cancer in non-Hispanic white women aged ≤ 55 yr. Further validation in large population-based or cohort studies is needed.

Sex- and subtype-specific analysis of H2AFX polymorphisms in non-Hodgkin lymphoma

H2AFX encodes a histone variant involved in signaling sites of DNA damage and recruiting repair factors. Genetic variants in H2AFX may influence risk of non-Hodgkin lymphoma (NHL), a heterogeneous group of lymphoid tumors that are characterized by chromosomal translocations. We previously reported that rs2509049, a common variant in the promoter of H2AFX, was associated with risk for NHL in the British Columbia population. Here we report results for 13 single nucleotide polymorphisms (SNPs) in 100 Kb surrounding H2AFX in an expanded collection of 568 NHL cases and 547 controls. After correction for multiple testing, significant associations were present for mantle cell lymphoma (p=0.007 for rs604714) and all B-cell lymphomas (p=0.046 for rs2509049). Strong linkage disequilibrium in the 5 Kb upstream of H2AFX limited the ability to determine which specific SNP (rs2509049, rs7759, rs8551, rs643788, rs604714, or rs603826), if any, was responsible. There was a significant interaction between sex and rs2509049 in the all B-cell lymphomas group (p=0.002); a sex-stratified analysis revealed that the association was confined to females (p=0.001). Neither the overall nor the female-specific association with rs2509049 was replicated in any of four independent NHL sample sets. Meta-analysis of all five study populations (3,882 B-cell NHL cases and 3,718 controls) supported a weak association with B-cell lymphoma (OR=0.92, 95% CI=0.86-0.99, p=0.034), although this association was not significant after exclusion of the British Columbia data. Further research into the potential sex-specificity of the H2AFX-NHL association may identify a subset of NHL cases that are influenced by genotype at this locus.

Effect of EME1 exon variant Ile350Thr on risk and early onset of breast cancer in southern Chinese women

Essential meiotic endonuclease 1 homolog 1 (EME1) is a key DNA repair protein that participates in the recognition and repair of DNA double-strand breaks. Deficiency of the EME1 gene can lead to spontaneous genomic instability and thus contribute to tumorgenesis. We hypothesized that the exon variants of EME1 confer genetic susceptibility to breast cancer. In a case-control study of 748 breast cancer patients and 778 normal controls, we analyzed the association between two exon variants of EME1 (i.e.,Ile350Thr: rs12450550T > C and Glu69Asp: rs3760413T > G) and breast cancer risk. We found that compared to the common Ile/Ile genotype, the Thr variant genotypes (Thr/Ile + Thr/Thr) conferred a 1.47-fold increased risk of breast cancer (OR=1.47, 95% CI=1.13-1.92). The variant Ile350Thr was also associated with early onset of breast cancer (r = -0.116, P = 0.002). The mean age of onset was 44.4 years for Thr/Thr genotype carriers and 46.5 years for Thr/Ile genotype carriers, which was significantly lower than that (49.4 years) for Ile/Ile genotype carriers (P = 0.006). Moreover, no significant association was observed between the Glu69Asp variant and breast cancer risk. Our findings suggest that the EME1 variant Ile350Thr contributes to an increased risk and early onset of breast cancer.

Biological effects of low-dose radiation from computed tomography scanning

PURPOSE

With the widespread use of computed tomography (CT), the risks of low-dose radiation from CT have been increasingly highlighted. This study aims to illustrate the CT-induced biological effects and analyze the potential beneficial or harmful outcomes so as to provide radiologists with reasonable advice on CT usage.

MATERIALS AND METHODS

The related literature was analyzed according to the topics of stochastic effect, hereditary effect, deterministic effect, accumulative injuries, hormesis and adaptive response; population epidemiology data were also analyzed.

RESULTS

CT accounts for 9% of X-ray examinations and approximately 40-67% of medical-related radiation, the dose is within the range of low-dose radiation (LDR). Two opposite viewpoints exist nowadays regarding the biological effects of CT scanning: They are either harmful or harmless. Approximately 0.6% and 1.5% of the cumulative cancer risk could be attributed to diagnostic X-rays in the UK and Germany, respectively. The probability of CT scans induced-cancer is about 0.7% and CT angiography's risk is around 0.13%. It is estimated that approximately 29,000 cancers could be related to CT scans in the USA every year. Meanwhile, another investigation of 25,104 patients who underwent 45,632 CT scans in 4 years showed that the majority of CT-induced cancers were accidents rather than certainties of frequent CT scans.

CONCLUSION

Although the LDR effects of CT are still controversial, the current problems include the high frequency-use and abuse of CT scans, the increase of radiation dose and accumulative dose in high-accuracy CT, and the poor understanding of carcinogenic risks. The underlying biological basis needs further exploring and the ratio of risks and benefits should be considered.

H2AFX polymorphisms are associated with decreased risk of diffuse large B cell lymphoma in Koreans

Polymorphisms of the H2A histone family member X (H2AFX) gene have been associated with decreased non-Hodgkin lymphoma (NHL, -417AA) risk and increased breast cancer (1654AG/GG, and -1420GA/AA) risk. We investigated whether H2AFX polymorphisms are associated with the risk of NHL and its subtypes in 573 NHL Korean patients and 721 cancer-free control subjects, using high resolution melting polymerase chain reaction and an automatic sequencer. There was no association between polymorphisms and the risk of overall NHL, all B cell lymphoma, or all T cell lymphoma. However, the -1420 AA genotype was associated with decreased diffuse large B cell lymphoma (DLBCL) risk (OR, 0.65; 95% CI, 0.43-0.97), and there was a trend for allele dose-effect (p-trend=0.03). The -1187 CC genotype was associated with decreased DLBCL risk with borderline significance (OR, 0.70; 95% CI, 0.48-1.02). There was a trend for an allele dose-effect with borderline significance (p-trend=0.06). These results suggest that the -1420 AA genotype of H2AFX may be associated with reduced DLBCL risks in the Korean population.

H2AX Phosphorylation: Its Role in DNA Damage Response and Cancer Therapy

Double-strand breaks (DSBs) are the most deleterious DNA lesions, which, if left unrepaired, may have severe consequences for cell survival, as they lead to chromosome aberrations, genomic instability, or cell death. Various physical, chemical, and biological factors are involved in DSB induction. Cells respond to DNA damage by activating the so-called DNA damage response (DDR), a complex molecular mechanism developed to detect and repair DNA damage. The formation of DSBs triggers activation of many factors, including phosphorylation of the histone variant H2AX, producing gammaH2AX. Phosphorylation of H2AX plays a key role in DDR and is required for the assembly of DNA repair proteins at the sites containing damaged chromatin as well as for activation of checkpoints proteins which arrest the cell cycle progression. In general, analysis of gammaH2AX expression can be used to detect the genotoxic effect of different toxic substances. When applied to clinical samples from cancer patients, evaluation of gammaH2AX levels may allow not only to monitor the efficiency of anticancer treatment but also to predict of tumor cell sensitivity to DNA damaging anticancer agents and toxicity of anticancer treatment toward normal cells.

The functional promoter polymorphism (-842G>C) in the PIN1 gene is associated with decreased risk of breast cancer in non-Hispanic white women 55 years and younger

PIN1, an isomerase that causes conformational changes in proteins, plays an important role in mammary epithelial cell growth both physiologically and pathologically. Thus, genetic variants in the PIN1 gene may alter protein function and cancer risk. We have previously demonstrated an association between a PIN1 promoter variant (-842G>C; rs2233678) and risk of squamous cell carcinoma of the head and neck, a finding supported by additional functional data. In the present study, we genotyped two promoter single nucleotide polymorphisms (SNPs) (-842G>C, rs2233678 and -667T>C, rs2233679) and one synonymous SNP (Gln33Gln; G>A, rs2233682) in exon 2 to evaluate their associations with risk of sporadic breast cancer in non-Hispanic white women 55 years and younger. We found that the carriers of -842C variant alleles had decreased risk of breast cancer with an adjusted odd ratio (OR) of 0.67 and 95% confidence interval (CI) of 0.50-0.90. This reduced risk was more evident in women after reproductive age of 45 (OR = 0.63, 95% CI = 0.42-0.93), ever-smokers (OR = 0.56, 95% CI = 0.36-0.88), and ever-drinkers (OR = 0.67, 95% CI = 0.45-0.99). No such associations were observed for PIN1 -667T>C and PIN1 Gln33Gln. However, the haplotypes of these three SNPs were also associated with reduced risk of breast cancer. In conclusion, the PIN1 polymorphisms may contribute to the etiology of sporadic breast cancer in non-Hispanic white women 55 years and younger. Further validation in large population-based studies is needed.

Role of H2AX in DNA damage response and human cancers

H2AX, the evolutionarily conserved variant of histone H2A, has been identified as one of the key histones to undergo various post-translational modifications in response to DNA double-strand breaks (DSBs). By virtue of these modifications, that include acetylation, phosphorylation and ubiquitination, H2AX marks the damaged DNA double helix, facilitating local recruitment and retention of DNA repair and chromatin remodeling factors to restore genomic integrity. These modifications are essential for effective DSB repair, so is their removal for cell, to recover from checkpoint arrest. Because of these vital roles during DSB signaling and also its activation during early cancer stages, H2AX is emerging as an intriguing gene in tumor biology, supported further by frequent deletion of the region harboring this gene. This review focuses on the insights gained from recent studies on dynamic regulation of H2AX in DSB repair. Also, posing future challenges in the area of chromatin reorganization and retention of epigenetic signature post-DSB-repair with implication of its haploinsufficiency in human cancers.