Genetic variation of acquired structural chromosomal aberrations

Determining the degree of chromosomal instability in breast cancer cells by atomic force microscopy

Chromosomal instability (CIN) is a source of genetic variation and is highly linked to the malignance of cancer. Determining the degree of CIN is necessary for understanding the role that it plays in tumor development. There is currently a lack of research on high-resolution characterization of CIN and the relationship between CIN and cell mechanics. Here, a method to determine CIN of breast cancer cells by high resolution imaging with atomic force microscopy (AFM) is explored. The numerical and structural changes of chromosomes in human breast cells (MCF-10A), moderately malignant breast cells (MCF-7) and highly malignant breast cells (MDA-MB-231) were observed and analyzed by AFM. Meanwhile, the nuclei, cytoskeleton and cell mechanics of the three kinds of cells were also investigated. The results showed the differences in CIN between the benign and cancer cells. Also, the degree of structural CIN increased with enhanced malignancy of cancer cells. This was also demonstrated by calculating the probability of micronucleus formation in these three kinds of cells. Meanwhile, we found that the area of the nucleus was related to the number of chromosomes in the nucleus. In addition, reduced or even aggregated actin fibers led to decreased elasticities in MCF-7 and MDA-MB-231 cells. It was found that the rearrangement of actin fibers would affect the nucleus, and then lead to wrong mitosis and CIN. Using AFM to detect chromosomal changes in cells with different malignancy degrees provides a new detection method for the study of cell carcinogenesis with a perspective for targeted therapy of cancer.

The Emerging Burden of Genetic Instability and Mutation in Melanoma: Role of Molecular Mechanisms

Melanoma is a severe skin cancer affecting thousands of people and a growing public health concern worldwide. The potential hallmarks of melanoma are genetic instability and mutation (GIAM), which are driving mechanisms for phenotypic variation and adaptation in melanoma. In metastatic melanoma, DNA repair-associated genes are frequently expressed at higher levels than in primary cancers, suggesting melanoma cells rely on genetic stability to spread distantly. The tumour microenvironment is affected by genomic instability and melanoma mutation (GIMM), which plays significant roles in developing GIMM and their contributions to the overall disease burden. The GIAM is the crucial vulnerability of cancer cells, determining their sensitivity to harmful treatments, including radiation and many chemotherapeutics. The high incidence of melanoma is typically associated with genetic modifications, and several clinical and genetic interventions have been critical in easing the burden.

The Prognostic Role of Cyclin D1 in Multiple Myeloma: A Systematic Review and Meta-Analysis

Purpose: Cyclin D1 has been identified as a proto-oncogene associated with the uncontrolled proliferation of tumor cells. This systematic review and meta-analysis aims to estimate the prognostic significance of cyclin D1 in multiple myeloma (MM) patients. Method: We searched for qualified data in PubMed, Embase, and Web of Science up to February 2020. Data quality was assessed by the Newcastle-Ottawa scale (NOS). Hazard ratios (HRs) and 95% confidence intervals (95% CIs) were used to evaluate the relationship between cyclin D1 expression and overall survival (OS), progression-free survival (PFS)/event-free survival (EFS) in patients with MM. Result: A total of 13 studies involving 961 patients were included. Overall, pooled analysis revealed significant heterogeneity between cyclin D1 expression and the prognosis of MM (OS, HR = 1.08, 95% CI: 0.71-1.64, I2 = 67.9%; PFS/EFS, HR = 0.97, 95% CI: 0.49-1.93, I2 = 85.8%). Subgroup analysis revealed that the prolongation of OS was relevant to increased expression of cyclin D1 in MM patients in the relapsed and refractory group (OS, HR = 0.46, 95% CI: 0.24-0.90). Another subgroup assessment of OS established that MM patients with CCND1 overexpression in the bortezomib group had longer survival time (HR = 0.30, 95% CI: 0.11-0.82), whereas, those overexpressing CCND1 in the conventional chemotherapy group had poor prognosis (HR = 2.19, 95% CI: 1.18-4.08). We also found that increased cyclin D1 expression correlated favorably with PFS in the autologous stem cell transplantation (ASCT) (HR = 0.45, 95% CI: 0.28-0.73) or reverse transcription-polymerase chain reaction (RT-PCR) group (HR = 0.41, 95% CI: 0.26-0.64). Conclusion: The result of this meta-analysis suggested that CCND1 overexpression might be a predictive biomarker for MM patients when treated with bortezomib, receiving ASCT, or in relapsed and refractory period.

Are Molecular Alterations Linked to Genetic Instability Worth to Be Included as Biomarkers for Directing or Excluding Melanoma Patients to Immunotherapy?

The improvement of the immunotherapeutic potential in most human cancers, including melanoma, requires the identification of increasingly detailed molecular features underlying the tumor immune responsiveness and acting as disease-associated biomarkers. In recent past years, the complexity of the immune landscape in cancer tissues is being steadily unveiled with a progressive better understanding of the plethora of actors playing in such a scenario, resulting in histopathology diversification, distinct molecular subtypes, and biological heterogeneity. Actually, it is widely recognized that the intracellular patterns of alterations in driver genes and loci may also concur to interfere with the homeostasis of the tumor microenvironment components, deeply affecting the immune response against the tumor. Among others, the different events linked to genetic instability—aneuploidy/somatic copy number alteration (SCNA) or microsatellite instability (MSI)—may exhibit opposite behaviors in terms of immune exclusion or responsiveness. In this review, we focused on both prevalence and impact of such different types of genetic instability in melanoma in order to evaluate whether their use as biomarkers in an integrated analysis of the molecular profile of such a malignancy may allow defining any potential predictive value for response/resistance to immunotherapy.

DNA repair gene polymorphisms and chromosomal aberrations in healthy, nonsmoking population

Nonspecific structural chromosomal aberrations (CAs) can be found at around 1% of circulating lymphocytes from healthy individuals but the frequency may be higher after exposure to carcinogenic chemicals or radiation. The frequency of CAs has been measured in occupational monitoring and an increased frequency of CAs has also been associated with cancer risk. Alterations in DNA damage repair and telomere maintenance are thought to contribute to the formation of CAs, which include chromosome type of aberrations and chromatid type of aberrations. In the present study, we used the result of our published genome-wide association studies to extract data on 153 DNA repair genes from 866 nonsmoking persons who had no known occupational exposure to genotoxic substances. Considering an arbitrary cut-off level of P< 5 × 10^-3, single nucleotide polymorphisms (SNPs) tagging 22 DNA repair genes were significantly associated with CAs and they remained significant at P < 0.05 when adjustment for multiple comparisons was done by the Binomial Sequential Goodness of Fit test. Nucleotide excision repair pathway genes showed most associations with 6 genes. Among the associated genes were several in which mutations manifest CA phenotype, including Fanconi anemia, WRN, BLM and genes that are important in maintaining genome stability, as well as PARP2 and mismatch repair genes. RPA2 and RPA3 may participate in telomere maintenance through the synthesis of the C strand of telomeres. Errors in NHEJ1 function may lead to translocations. The present results show associations with some genes with known CA phenotype and suggest other pathways with mechanistic rationale for the formation of CAs in healthy nonsmoking population.

The Interactions of DNA Repair, Telomere Homeostasis, and p53 Mutational Status in Solid Cancers: Risk, Prognosis, and Prediction

The disruption of genomic integrity due to the accumulation of various kinds of DNA damage, deficient DNA repair capacity, and telomere shortening constitute the hallmarks of malignant diseases. DNA damage response (DDR) is a signaling network to process DNA damage with importance for both cancer development and chemotherapy outcome. DDR represents the complex events that detect DNA lesions and activate signaling networks (cell cycle checkpoint induction, DNA repair, and induction of cell death). TP53, the guardian of the genome, governs the cell response, resulting in cell cycle arrest, DNA damage repair, apoptosis, and senescence. The mutational status of TP53 has an impact on DDR, and somatic mutations in this gene represent one of the critical events in human carcinogenesis. Telomere dysfunction in cells that lack p53-mediated surveillance of genomic integrity along with the involvement of DNA repair in telomeric DNA regions leads to genomic instability. While the role of individual players (DDR, telomere homeostasis, and TP53) in human cancers has attracted attention for some time, there is insufficient understanding of the interactions between these pathways. Since solid cancer is a complex and multifactorial disease with considerable inter- and intra-tumor heterogeneity, we mainly dedicated this review to the interactions of DNA repair, telomere homeostasis, and TP53 mutational status, in relation to (a) cancer risk, (b) cancer progression, and (c) cancer therapy.

DNA Repair Gene Polymorphisms and Chromosomal Aberrations in Exposed Populations

DNA damage and unrepaired or insufficiently repaired DNA double-strand breaks as well as telomere shortening contribute to the formation of structural chromosomal aberrations (CAs). Non-specific CAs have been used in the monitoring of individuals exposed to potential carcinogenic chemicals and radiation. The frequency of CAs in peripheral blood lymphocytes (PBLs) has been associated with cancer risk and the association has also been found in incident cancer patients. CAs include chromosome-type aberrations (CSAs) and chromatid-type aberrations (CTAs) and their sum CAtot. In the present study, we used data from our published genome-wide association studies (GWASs) and extracted the results for 153 DNA repair genes for 607 persons who had occupational exposure to diverse harmful substances/radiation and/or personal exposure to tobacco smoking. The analyses were conducted using linear and logistic regression models to study the association of DNA repair gene polymorphisms with CAs. Considering an arbitrary cutoff level of 5 × 10^-3, 14 loci passed the threshold, and included 7 repair pathways for CTA, 4 for CSA, and 3 for CAtot; 10 SNPs were eQTLs influencing the expression of the target repair gene. For the base excision repair pathway, the implicated genes PARP1 and PARP2 encode poly(ADP-ribosyl) transferases with multiple regulatory functions. PARP1 and PARP2 have an important role in maintaining genome stability through diverse mechanisms. Other candidate genes with known roles for CSAs included GTF2H (general transcription factor IIH subunits 4 and 5), Fanconi anemia pathway genes, and PMS2, a mismatch repair gene. The present results suggest pathways with mechanistic rationale for the formation of CAs and emphasize the need to further develop techniques for measuring individual sensitivity to genotoxic exposure.

Uniparental disomy of chromosome 21: A statistical approach and application in paternity tests

Considering the overall frequency of paternity investigation cases including mutational events, there is a real possibility that at least a fraction of all inconsistencies reported in paternity cases are caused not by polymerase slippage mutations, but to chromosomic abnormalities, as Uniparental Disomy (UPD). We report here the investigation of a trio paternity case (mother, child and alleged father), with observed inconsistencies that can alternatively be explained by occurrence of maternal uniparental isodisomy of chromosome 21 (miUPD21). A total of 350 short tandem repeat (STR) and single nucleotide polymorphism (SNP) markers were tested, statistically suggesting true biological linkage within the trio. Additionally, we propose miUPD21 explains, with significantly greater probability, the occurrence of detected inconsistencies, when compared to alternative hypothesis of multiple and simultaneous slippage mutations. Similar cases could have their statistical conclusions improved or even altered by including unusual chromosomal segregation patterns in the hypothesis formulation, as well as in mathematical calculations. Such reports of allelic inconsistencies being explained by chromosomal alterations are common in clinical genetics, and such situations might have impact on forensic investigation.

Distinct pathways associated with chromosomal aberration frequency in a cohort exposed to genotoxic compounds compared to general population

Non-specific structural chromosomal aberrations (CAs) observed in peripheral blood lymphocytes of healthy individuals can be either chromosome-type aberrations (CSAs) or chromatid-type aberrations (CTAs) depending on the stage of cell division they are induced in and mechanism of formation. It is important to study the genetic basis of chromosomal instability as it is a marker of genotoxic exposure and a predictor of cancer risk. For that purpose, we conducted two genome-wide association studies (GWASs) on healthy individuals in the presence and absence of apparent genotoxic exposure from the Czech Republic and Slovakia. The pre-GWAS cytogenetic analysis reported the frequencies of CSA, CTA and total CA (CAtot). We performed both linear and binary logistic regression analysis with an arbitrary cut-off point of 2% for CAtot and 1% for CSA and CTA. Using the statistical threshold of 1.0 × 10-5, we identified five loci with in silico predicted functionality in the reference group and four loci in the exposed group, with no overlap between the associated regions. A meta-analysis on the two GWASs identified further four loci with moderate associations in each of the studies. From the reference group mainly loci within genes related to DNA damage response/repair were identified. Other loci identified from both the reference and exposed groups were found to be involved in the segregation of chromosomes and chromatin modification. Some of the discovered regions in each group were implicated in tumourigenesis and autism.

CCDN1 rs603965 polymorphism may serve as a genetic biomarker of brain tumor: A meta-analysis of 5,769 subjects

Introduction

Some studies already tried to assess the associations between cyclin D1 (CCND1) polymorphisms and brain tumor. However, the results of these studies were not consistent. Thus, we performed the present meta‐analysis to explore the relationship between CCND1 polymorphisms and brain tumor in a larger pooled population.

Methods

PubMed, Web of Science, Embase, and CNKI were searched for related articles. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to assess the potential associations.

Results

Totally nine studies with 5,769 subjects were analyzed. A significant association with brain tumor susceptibility was observed for the rs603965 polymorphism in GG versus GA + AA (dominant comparison, p = 0.003, OR = 0.72, 95% CI 0.57–0.89, I² = 64%), AA versus GG + GA (recessive comparison, p = 0.004, OR = 1.46, 95% CI 1.13–1.88, I² = 67%), and G versus A (allele comparison, p = 0.0004, OR = 0.77, 95% CI 0.66–0.89, I² = 66%) in overall population. Further subgroup analyses by ethnicity yielded similar positive results in both Asians and Caucasians. Moreover, in stratified analyses by type of disease, we noticed that the rs603965 polymorphism was significantly associated with the susceptibility to glioma, but such positive results were not detected in pituitary adenoma or meningioma. Additionally, a significant association with tumor grade was also observed for the rs603965 polymorphism in G versus A (allele comparison, p = 0.02, OR = 0.74, 95% CI 0.59–0.95, I² = 26%).

Conclusions

Our findings suggested that CCND1 rs603965 polymorphism may serve as a potential genetic biomarker of brain tumor, especially for glioma.

MiR-193a-3p inhibits pancreatic ductal adenocarcinoma cell proliferation by targeting CCND1

Background: MicroRNAs (miRNAs) could modulate gene expression at the posttranscriptional level by promoting mRNA degradation or blocking mRNA translation, thus affecting the occurrence and development of cancer. Methods: In this work, qRT-PCR was conducted to detect the expression of miR-193a-3p and CCND1. The ability of cell proliferation was evaluated via CCK-8 assay. Cell apoptosis and cell cycle distribution were detected by flow cytometry. Bioinformatic techniques were employed to research the regulatory relationship between miR-193a-3p and target genes. The relationship between miR-193a-3p and CCND1 was verified via dual-luciferase reporter assays. Results: MiR-193a-3p expression in pancreatic ductal adenocarcinoma (PDAC) tissue was significantly lower than in non-cancerous tissue. After overexpressing miR-193a-3p in PDAC cells, their multiplication ability was significantly inhibited, apoptosis was accelerated, and the cell cycle was blocked in the G1 and G2/M phases. CCND1 was confirmed to have a targeted relationship with miR-193a-3p. Moreover, CCND1 expression was significantly lower in PDAC cells with an overexpression of miR-193a-3p. Conclusions: MiR-193a-3p targeted CCND1 to suppress tumor growth in PDAC cells. MiR-193a-3p may function as a tumor inhibitor in PDAC development, which could offer a promising therapeutic and prognostic strategy for PDAC treatment.

Genetic variation associated with chromosomal aberration frequency: A genome-wide association study

Chromosomal aberrations (CAs) in human peripheral blood lymphocytes (PBL) measured with the conventional cytogenetic assay have been used for human biomonitoring of genotoxic exposure for decades. CA frequency in peripheral blood is a marker of cancer susceptibility. Previous studies have shown associations between genetic variants in metabolic pathway, DNA repair and major mitotic checkpoint genes and CAs. We conducted a genome-wide association study on 576 individuals from the Czech Republic and Slovakia followed by a replication in two different sample sets of 482 (replication 1) and 1288 (replication 2) samples. To have a broad look at the genetic susceptibility associated with CA frequency, the sample sets composed of individuals either differentially exposed to smoking, occupational/environmental hazards, or they were untreated cancer patients. Phenotypes were divided into chromosome- and chromatid-type aberrations (CSAs and CTAs, respectively) and total chromosomal aberrations (CAtot). The arbitrary cutoff point between individuals with high and low CA frequency was 2% for CAtot and 1% for CSA and CTA. The data were analyzed using age, sex, occupation/cancer and smoking history as covariates. Altogether 11 loci reached the P-value of 10^-5 in the GWAS. Replication 1 supported the association of rs1383997 (8q13.3) and rs2824215 (21q21.1) in CAtot and rs983889 (5p15.1) in CTA analysis. These loci were found to be associated with genes involved in mitosis, response to environmental and chemical factors and genes involved in syndromes linked to chromosomal abnormalities. Identification of new genetic variants for the frequency of CAs offers prediction tools for cancer risk in future. Environ. Mol. Mutagen. 60:17-28, 2019. © 2018 Wiley Periodicals, Inc.