Computerized Assessment of Occlusion and Muscle Activity during Use of a Multilayer Clear Retainer: A Preliminary Study.

The aim of this preliminary study was to evaluate the short-term changes of occlusal contacts and muscle activity after orthodontic treatment during the use of a multi-layer clear retainer. Evaluation was done with the T-scan and BioEMG systems. A total of 18 subjects were included, who were evaluated at three time intervals-T0 at debonding, T1 at one month after retainer delivery, and T2 at four months after retainer delivery. The T-scan and electromyography (EMG) data were recorded simultaneously. The T-scan system recorded the occlusion time, disclusion time and force distribution. The EMG waves were quantified by calculating the asymmetry index and activity index. The time variables changed but not significantly. Occlusal force decreased in the anterior dentition and increased in the posterior dentition during T0-T2. There was no clear evidence of a relationship between unbalanced occlusal forces and muscle activity. In most subjects, the temporalis anterior muscle was more dominant than the masseter muscle. From this preliminary computerized study, there were no significant changes in the state of the occlusion or muscle activity during the short-term retention period.

Analysis of the serial circulating tumor cell count during neoadjuvant chemotherapy in breast cancer patients.

We evaluated the prognostic implications of the circulating tumor cell (CTC) count in non-metastatic, HER2-negative breast cancer patients who failed to achieve pathologic complete response (pCR) after neoadjuvant chemotherapy (NCT). A total of 173, non-metastatic breast cancer patients treated with NCT were prospectively enrolled. CTCs were obtained from blood drawn pre-NCT and post-NCT using a SMART BIOPSY SYSTEM isolation kit (Cytogen Inc., Seoul, Korea) with immunofluorescence staining. Excluding 26 HER2-positive patients, Relapse-free survival (RFS) and overall survival (OS) related to the CTC count and the association of the CTC count with the treatment response to given therapy were analyzed in 147 HER2-negative patients. Among 147 HER2-negative patients, 28 relapses (19.0%) and 13 deaths (8.8%, all breast cancer-specific) were observed during a median follow-up of 37.3 months. One hundred and seven patients (72.8%) were hormone receptor-positive, and 40 patients (27.2%) had triple-negative breast cancer (TNBC). One or more CTCs were identified in 88 of the 147 patients (59.9%) before NCT and 77 of the 134 patients (52.4%) after NCT. In the entire HER2-negative patient cohort, the initial nodal status was the most significant factor influencing RFS and OS. In TNBC, 11 patients (27.5%) achieved pCR and patients that failed to achieve pCR with ≥ 5 CTCs after NCT, showed worse RFS (HR, 10.66; 95% CI, 1.80-63.07; p = 0.009) and OS (HR, 14.00; 95% CI, 1.26-155.53; p = 0.032). The patients with residual tumor and a high number of the CTCs after NCT displayed the worse outcome. These findings could provide justification to launch a future, well designed trial with longer follow-up data to obtain regulatory approval for clinical use of the assay, especially for the ER-positive, HER2-negative breast cancer subset.

High polymerase ε expression associated with increased CD8+T cells improves survival in patients with non-small cell lung cancer.

DNA replicase polymerase ε (POLE) is critical in proofreading and correcting errors of DNA replication. Low POLE expression plays a pivotal role in accumulation of mutations and onset of cancer, contributing to development and growth of tumor cells. The aim of this study is to reveal the survival, alternative genes and antitumoral immune activities in non-small cell lung cancer (NSCLC) patients with low POLE expression and provide treatment strategies that can increase their survival rates. This study investigated the clinicopathologic parameters, various tumor-infiltrating lymphocytes (TILs), endogenous retrovirus, molecular interactions and in vitro drug screen according to POLE mutation/expression in 168 and 1,019 NSCLC patients from the Konkuk University Medical Center (KUMC) and the Cancer Genome Atlas, respectively. We identified mutations of 75 genes in the sequencing panels, with POLE frame shift p.V1446fs being the most frequent (56.8%) in KUMC based on 170 targeted sequencing panels. Mutant and high expression of POLE correlated with favorable prognosis with increased TILs and tumor mutation burden, compared with wild type and low expression of POLE. We found specific molecular interactions associated with cell cycle and antigen presentation. An in vitro drug screen identified dasatinib that inhibited growth of the NSCLC cell line with low POLE expression. POLE could contribute to the future development of anticancer drugs for patients with NSCLC.

High prevalence of the MLH1 V384D germline mutation in patients with HER2-positive luminal B breast cancer.

HER2-positive luminal B breast cancer (BC), a subset of the luminal B subtype, is ER-positive and HER2-positive BC which is approximately 10% of all BC. However, HER2-positive luminal B BC has received less attention and is less represented in previous molecular analyses than other subtypes. Hence, it is important to elucidate the molecular biology of HER2-positive luminal B BC to stratify patients in a way that allows them to receive their respective optimal treatment. We performed molecular profiling using targeted next-generation sequencing on 94 HER2-positive luminal B BC to identify its molecular characteristics. A total of 134 somatic nonsynonymous mutations, including 131 nonsynonymous single nucleotide variants and three coding insertions/deletions were identified in 30 genes of 75 samples. PIK3CA was most frequently mutated (38/94, 40.4%), followed by TP53 (31/94, 33.0%), and others were detected at lower frequencies. Recurrent germline mutations of MLH1 V384D were found in 13.8% (13/94), with a significantly high TP53 mutations rate. The frequency of MLH1 V384D germline mutation in individuals with HER2-positive luminal B BC was significantly higher than that observed in the controls. All 13 cases were classified as microsatellite stable tumors. Tumor mutation burdens (TMB) were not significantly different between MLH1 V384D carrier and wild type. The concordant results of microsatellite instability (MSI) and TMB suggest that the haploinsufficiency of MLH1 plays a role as a tumor predisposition factor rather than a direct oncogenic driver. Our study identified, for the first time, that MLH1 V384D germline variant is frequently detected in HER2-positive luminal B BC. MLH1 V384D germline variant may not only contribute to gastrointestinal cancer predisposition but may also contribute to BC in East Asians.

Yeast-based assays for characterization of the functional effects of single nucleotide polymorphisms in human DNA repair genes.

DNA repair mechanisms maintain genomic integrity upon exposure to various types of DNA damage, which cause either single- or double-strand breaks in the DNA. Here, we propose a strategy for the functional study of single nucleotide polymorphisms (SNPs) in the human DNA repair genes XPD/ERCC2, RAD18, and KU70/XRCC6 and the checkpoint activation gene ATR that are essentially involved in the cell cycle and DNA damage repair. We analyzed the mutational effects of the DNA repair genes under DNA-damaging conditions, including ultraviolet irradiation and treatment with genotoxic reagents, using a Saccharomyces cerevisiae system to overcome the limitations of the human cell-based assay. We identified causal variants from selected SNPs in the present analyses. (i) R594C SNP in RAD3 (human XPD/ERCC2) caused severe reductions in the growth rate of mutant cells upon short-wavelength UV irradiation or chemical reagent treatment. (ii) The growth rates of the selected variants in RAD18, YKU70, and MEC1 were similar to those of wild-type cells on methyl methanesulfonate and hydroxyurea treated media. (iii) We also assessed the structural impact of the SNPs by analyzing differences in the structural conformation and calculating the root mean square deviation, which is a measure of the discordance of the Cα atoms between protein structures. Based on the above results, we propose that these analytical approaches serve as efficient methods for the identification of causal variants of human disease-causing genes and elucidation of yeast-cell based molecular mechanisms.

Effects of a new type of clear overlay retainer on occlusal contacts.

The popularity of clear overlay retainers (CORs) has increased recently because of their advantages such as better esthetics, cost effectiveness, easy fabrication, and good compliance. However, a deficiency in posterior occlusal settling is a reported limitation of CORs. The aim of this study was to evaluate the posterior occlusal contact changes in a new type of clear orthodontic retainer called Oral-treaper (OTP), which consists of three layers and has stronger mechanical characteristics than do conventional retainers. Three patients who completed fixed orthodontic treatment received OTP as a removable retainer. Cast models were fabricated after the removal of fixed appliances (T1) and after 4 to 11 months of using the retainers (T2). We evaluated all the cast models to compare the post-orthodontic settling pattern during the use of the OTPs. The depth of occlusal contacts was evaluated using color maps. The OTP did not prevent vertical settling in all patients but resulted in an improvement in posterior occlusal contact points.

The impact of intermittent versus continuous exposure to EGFR tyrosine kinase inhibitor on selection of EGFR T790M-mutant drug-resistant clones in a lung cancer cell line carrying activating EGFR mutation.

Drug-resistant cell lines are essential tools for investigating the mechanisms of resistance to molecular-targeted anti-cancer drugs. However, little is known about how to establish clinically relevant drug-resistant cell lines. Our study examined the impact of a drug-free period on the establishment of a cell line with clinically relevant resistance to molecular-targeted drugs. We used PC9 cells, a lung cancer cell line carrying EGFR mutation, because this is a validated target for EGFR tyrosine kinase inhibitors (TKI). PC9 cells were intermittently or continuously exposed to increasing concentrations of gefitinib (0.01 µM to 1.0 µM) and the emergence of the most common acquired resistance mutation in EGFR, T790M, was determined. T790M was detected at a 25-fold lower drug concentration in cells continuously exposed to gefitinib (PC9/GRc) than in cells intermittently exposed to gefitinib (PC9/GRi) (0.04 µM vs 1.0 µM, respectively). The mutation frequencies at those drug concentrations were 19.8% and 8.0% in PC9/GRc and PC9/GRi cells, respectively. After drug-free culture for 8 weeks, resistance to gefitinib decreased in the PC9/GRi cells but not in the PC9/GRc cells. In the PC9/GRc cells, the frequency of the T790M mutation was consistently about 20% from 0.04 µM to 1.0 µM of gefitinib. In the PC9/GRc cells, the T790M mutation was detected in all single-cell clones, at frequencies ranging from 7.0% to 37.0%, with a median of 19.5% (95% confidence interval, 17.3%-20.9%). In conclusion, compared with intermittent drug exposure, continuous exposure might select better minor drug-resistant clones when creating cell lines resistant to molecular-targeted drugs.

Functional Validation of Rare Human Genetic Variants Involved in Homologous Recombination Using Saccharomyces cerevisiae.

Systems for the repair of DNA double-strand breaks (DSBs) are necessary to maintain genome integrity and normal functionality of cells in all organisms. Homologous recombination (HR) plays an important role in repairing accidental and programmed DSBs in mitotic and meiotic cells, respectively. Failure to repair these DSBs causes genome instability and can induce tumorigenesis. Rad51 and Rad52 are two key proteins in homologous pairing and strand exchange during DSB-induced HR; both are highly conserved in eukaryotes. In this study, we analyzed pathogenic single nucleotide polymorphisms (SNPs) in human RAD51 and RAD52 using the Polymorphism Phenotyping (PolyPhen) and Sorting Intolerant from Tolerant (SIFT) algorithms and observed the effect of mutations in highly conserved domains of RAD51 and RAD52 on DNA damage repair in a Saccharomyces cerevisiae-based system. We identified a number of rad51 and rad52 alleles that exhibited severe DNA repair defects. The functionally inactive SNPs were located near ATPase active site of Rad51 and the DNA binding domain of Rad52. The rad51-F317I, rad52-R52W, and rad52-G107C mutations conferred hypersensitivity to methyl methane sulfonate (MMS)-induced DNA damage and were defective in HR-mediated DSB repair. Our study provides a new approach for detecting functional and loss-of-function genetic polymorphisms and for identifying causal variants in human DNA repair genes that contribute to the initiation or progression of cancer.

Impact of genetic polymorphisms in base excision repair genes on the risk of breast cancer in a Korean population.

The contribution of single nucleotide polymorphisms (SNPs) in base excision repair (BER) genes to the risk of breast cancer (BC) was evaluated by focusing on two key genes: apurinic/apyrimidinic endonuclease 1 (APEX1) and 8-oxoguanine DNA glycosylase (OGG1). Genetic variations in the genes encoding these DNA repair enzymes may alter their functions and increase susceptibility to carcinogenesis. The aim of this study was to analyze polymorphisms in two BER genes, exploring their associations and particularly the combined effects of these variants on BC risk in a Korean population. Three SNPs of two BER genes were genotyped using the Illumina GoldenGate™ method. In total, 346 BC patients and 361 cancer-free controls were genotyped for these BER gene polymorphisms and analyzed for their correlation with BC risk in multiple logistic regression models. Multiple logistic regression models adjusted for age, family history of BC, and body mass index were used. The APEX1 Asp148Glu polymorphism was weakly associated with BC risk. The combined analysis among the BER genes, however, showed significant effects on BC risk. The APEX1 Asp148Glu carrier, in combination with OGG1 rs2072668 and OGG1 Ser326Cys, was strongly associated with an increased risk of BC. Moreover, the combination of the C-C haplotype of OGG1 with the APEX1 Asp148Glu genotype was also associated with an additive risk effect of BC [ORs=2.44, 2.87, and 3.50, respectively]. The combined effect of APEX1 Asp148Glu was found to be associated with an increased risk of BC. These results suggest that the combined effect of different SNPs within BER genes may be useful in predicting BC risk.

Association between Interferon-Inducible Protein 6 (IFI6) Polymorphisms and Hepatitis B Virus Clearance.

CD8+ T cells are key factors mediating hepatitis B virus (HBV) clearance. However, these cells are killed through HBV-induced apoptosis during the antigen-presenting period in HBV-induced chronic liver disease (CLD) patients. Interferon-inducible protein 6 (IFI6) delays type I interferon-induced apoptosis in cells. We hypothesized that single nucleotide polymorphisms (SNPs) in the IFI6 could affect the chronicity of CLD. The present study included a discovery stage, in which 195 CLD patients, including chronic hepatitis B (HEP) and cirrhosis patients and 107 spontaneous recovery (SR) controls, were analyzed. The genotype distributions of rs2808426 (C > T) and rs10902662 (C > T) were significantly different between the SR and HEP groups (odds ratio [OR], 6.60; 95% confidence interval [CI], 1.64 to 26.52, p = 0.008 for both SNPs) and between the SR and CLD groups (OR, 4.38; 95% CI, 1.25 to 15.26; p = 0.021 and OR, 4.12; 95% CI, 1.18 to 14.44; p = 0.027, respectively). The distribution of diplotypes that contained these SNPs was significantly different between the SR and HEP groups (OR, 6.58; 95% CI, 1.63 to 25.59; p = 0.008 and OR, 0.15; 95% CI, 0.04 to 0.61; p = 0.008, respectively) and between the SR and CLD groups (OR, 4.38; 95% CI, 1.25 to 15.26; p = 0.021 and OR, 4.12; 95% CI, 1.18 to 14.44; p = 0.027, respectively). We were unable to replicate the association shown by secondary enrolled samples. A large-scale validation study should be performed to confirm the association between IFI6 and HBV clearance.

Association of GNLY genetic polymorphisms with chronic liver disease in a Korean population.

Granulysin (GNLY) is found in cytotoxic granules of cytolytic T lymphocytes and natural killer (NK) cells, which are critical for hepatitis B virus (HBV) clearance. GNLY cytotoxicity plays an important role in the defense against viruses or intracellular bacteria. We hypothesized that genetic variation in the GNLY gene could affect the resistance of hosts against HBV infection. We compared the distribution frequencies of GNLY polymorphisms between an HBV-induced chronic liver disease (CLD) group and a spontaneous recovery (SR) control group to determine whether GNLY polymorphisms play a role in HBV clearance. A total of 117 patients in the SR group and 230 patients in the CLD group were enrolled. Samples derived from complex infections, including hepatitis C and human immunodeficiency virus, and those associated with insufficient clinical information (10 samples in SR and 24 samples in CLD) were excluded from the study. The final analysis included 107 SR and 206 CLD samples. DNA was extracted from peripheral blood, and GNLY genotypes were determined by the GoldenGate(®) method. The genotype distribution of the single-nucleotide polymorphisms (SNPs) rs2886767 (C>T), rs1561285 (G>C), and rs11127 (T>C) were significantly different between the SR and CLD groups in a recessive model (p<0.015). These three SNPs were in a complete linkage disequilibrium (LD) block. Diplotype distributions of haplotype (HT) 1 (C-G-T) and HT2 (T-C-C) were significantly different between the SR and CLD groups in a recessive model (p=0.025) and a dominant model (p=0.008). All p-values remained significant after multiple comparisons. GNLY polymorphism genotypes and diplotypes were associated with the chronicity of HBV. These data suggested that genetic variation of GNLY may be an important factor in HBV clearance through the CD8+ T or NK cell-mediated removal of HBV-infected cells from the host.

SNP-SNP interactions between DNA repair genes were associated with breast cancer risk in a Korean population.

BACKGROUND: Single nucleotide polymorphisms (SNPs) in nucleotide excision repair (NER) pathway genes may modulate DNA repair capacity and increase susceptibility to breast cancer (BC). A case-control study was conducted by evaluating genes involved in DNA repair to identify polymorphisms associated with BC. METHODS: The 384 SNPs of 38 candidate genes were genotyped using the Illumina GoldenGate method. Genotypes were determined in a case-control study that consisted of 346 BC patients and 361 controls. Odds ratios and 95% confidence intervals were computed using logistic regression models. Multiple logistic regression models adjusted for age, family history of BC, and body mass index were used. RESULTS: Gene-gene interaction analysis among the DNA repair pathway genes showed significant effects on BC risk. ERCC2 rs50872 (TC genotype) in combination with XPA rs2808668 (TC genotype) and rs1800975 (AG genotype) was strongly associated with an increased risk of BC (P = .0004 and .0002, P(Bonferroni) = .023 and .014, respectively). Moreover, the T-G (including rs2808668 and rs1800975) haplotype in XPA combined with the ERCC2 T allele in rs50872 carriers was also associated with additive risk effect of BC (odds ratios: 2.58, 2.62, and 3.49, respectively). CONCLUSION: Genetic variation in DNA repair genes involved in NER mechanisms increased the risk of BC development. These results suggested that a stronger combined effect of SNPs via gene-gene interaction may help to predict BC risk.