DNA polymerase beta promoter mutations affect gene transcription, translation and the sensitivity of esophageal cancer cells to cisplatin treatment

Collaboration of Hprt/K-RAS/c-Myc mutation in the oncogenesis of T-lymphocytic leukemia: a comparative study

Aim: Leukemia is a malignant clonal illness stem from the mutations of hematopoietic cells. Acute lymphoblastic leukemia is one of the utmost prevalent kinds of leukemia, is brought on by atypical lymphoid progenitor cell division in the bone marrow. Materials & methods: A comparative study between, titanium Nanoparticle-loaded doxorubicin or cisplatin and lactoferrin-loaded doxorubicin or cisplatin, on 7,12-dimethylbenz[a]-anthracene (DMBA)-induced leukemia was investigated and confirming the hypothesis that messenger RNA of Hprt/K-RAS/c-Myc/SAT-2/P53/JAK-2 is a forthcoming signaling pathways in leukemia. Results: A significant alteration in Hprt, K-RAS, C-Myc, P53, JAK-2 and SAT-2 genes was observed post DMBA intoxication the aforementioned Nanodrugs modulated these signaling pathways. Conclusion: The carrier-loaded drugs triggered cytotoxicity of cancer cells via enhancing drug efficacy and bio-availability.

Polymorphic mutations in the polb gene promoter and their impact on transcriptional activity

Background

DNA polymerase β is one of the key enzymes involved in DNA damage repair and its proper expression is strictly controlled within different cells. We previously reported that three genetic mutations in the promoter region of the polb gene are prevalent in the Chinese Han population and two types of mutation are associated with thymic hyperplasia. The purpose of this study was to explore whether other mutated sites exist within the promoter region of the polb gene.

Methods

Genomic DNAs of 421 healthy Chinese Han individuals were extracted from whole blood samples and used for gene amplification of the promoter region of the polb gene. After gel purification, PCR amplicons were sequenced by the Sanger sequencing method and used for sequence alignment with the Lasergene program. PCR products with novel mutations were then subcloned into luciferase reporter plasmid pGL4.10 and transfected into 293T cells for dual‐luciferase activity analysis.

Results

In total, 11 mutated sites were detected in the Chinese Han population and eight of these were reported for the first time. Using a dual luciferase reporter system, it was found that one novel mutation −142 C > G could decrease the transcription activity of the polb gene, whereas two novel mutations, −152_−151insC and −218 C > G, could significantly increase the transcription activity of the polb gene.

Conclusions

High polymorphic sites could be found in the promoter region of polb gene and approximately half of them could influence its transcription activity.

Two polymorphic mutations in promoter region of DNA polymerase β in relatively higher percentage of thymic hyperplasia patients

Background

DNA polymerase β is one of the key enzymes involved in the repair of DNA damage, and its high or low expression is closely related to tumorigenesis. In a previous study on lung cancer, we found three genetic mutations in the promoter region of the Polb gene could be detected in the Han Chinese population. The purpose of this study was to explore the relationship between these mutations and thymic hyperplasia.

Methods

Genomic DNA was extracted from 59 thymic hyperplasia patients by the salting out method and used for amplification of the promoter region of the Polb gene. The Polb gene mutation and its frequency were analyzed systematically by comparing them with the deposited wild‐type gene sequence in the NCBI database. The three typical mutated sequences in the promoter region of Polb gene, ‐196G > T, ‐168C > A and ‐188_‐187insCGCCC, were then amplified and ligated to pGL4.10 vector, so as to get the vectors used for the infection of 293T cells to explore their transcription activities by dual‐luciferase reporter system.

Results

Two types of mutations, ‐168C>A and‐188_‐187insCGCCC, were found in a significantly higher percentage in patients with thymic hyperplasia than in normal healthy people after sequencing analysis of 59 patients and 60 healthy controls. These results suggest that the two mutations may be closely related to thymic hyperplasia. in vitro functional experiments showed that‐168C>A could significantly increase promoter activity, whereas ‐188_‐187insCGCCC could significantly reduce promoter activity, suggesting that these two mutations may affect the expression level of the Polb gene in cells.

Conclusions

Two types of mutations in the promoter region of the Polb gene, ‐168C>A and‐188_‐187insCGCCC, are associated with thymic hyperplasia and may become a new risk factor for this disease.

Key points

Significant findings of the study

Genetic mutations in the Polb gene are reported to be associated with different kinds of cancers. However, their relationship with thymic hyperplasia is still unclear.

What this study adds

For the first time, we report that two nucleotide mutations in the promoter region of the Polb gene are closely related with thymic hyperplasia after sequencing 59 patients and 60 healthy controls in the Han Chinese population.

[Genetic Mutation Screening of DNA Polymerase in Human Lung Cancer]

BACKGROUND

DNA polymerase β is one of the key enzymes for DNA repair and it was reported that about 30 percent of different types of cancers carried mutations in its coding gene Polb. However, it is still controversial whether it is true or false because of the small sample size in these studies. In current study, we performed genetic screening of promoter and coding regions of Polb gene in 69 Chinese lung cancer patients using Sanger sequencing method, so as to elucidate real mutation frequency of Polb mutations in Chinese Han population.

METHODS

Salting out extraction method was used to get the genome DNAs from tumor and normal matched tissues of 69 lung cancer patients. The promoter and 14 coding regions of Polb gene were then amplified using these DNAs as the template. After purification, amplicons were sequenced and aligned to the wild type Polb gene in NCBI database, in order to find out the mutated sites of Polb gene in Chinese lung cancer patients.

RESULTS

In this study, we totally found only 5 mutated sites in Polb gene. In detail, 3 mutations (-196G>T, -188_-187insCGCCC, -168C>A) were located in the promoter region; 2 mutations (587C>G, 612A>T) were found in coding regions. Specially, mutations of -188_-187insCGCCC and 587C>G (resulting to the amino acid substitution of Thr to Ser at position 196) had never been reported by other groups before. However, all these 5 mutated sites could be detected in both tumor and matched normal tissues, which inferred that they are not lung tumor specific mutations.

CONCLUSIONS

No lung tumor specific mutations of Polb gene could be found in Chinese lung cancer patients and Polb gene mutation might not be a molecular marker for Chinese lung cancer patients.

APE1 and NPM1 protect cancer cells from platinum compounds cytotoxicity and their expression pattern has a prognostic value in TNBC

Background

Triple negative breast cancer (TNBC) is a breast cancer subgroup characterized by a lack of hormone receptors’ expression and no HER2 overexpression. These molecular features both drastically reduce treatment options and confer poor prognosis. Platinum (Pt)-salts are being investigated as a new therapeutic strategy. The base excision repair (BER) pathway is important for resistance to Pt-based therapies. Overexpression of APE1, a pivotal enzyme of the BER pathway, as well as the expression of NPM1, a functional regulator of APE1, are associated with poor outcome and resistance to Pt-based therapies.

Methods

We evaluated the role of NPM1, APE1 and altered NPM1/APE1 interaction in the response to Pt-salts treatment in different cell lines: APE1 knockout (KO) cells, NPM1 KO cells, cell line models having an altered APE1/NPM1 interaction and HCC70 and HCC1937 TNBC cell lines, having different levels of APE1/NPM1. We evaluated the TNBC cells response to new chemotherapeutic small molecules targeting the endonuclease activity of APE1 or the APE1/NPM1 interaction, in combination with Pt-salts treatments. Expression levels’ correlation between APE1 and NPM1 and their impact on prognosis was analyzed in a cohort of TNBC patients through immunohistochemistry. Bioinformatics analysis, using TCGA datasets, was performed to predict a molecular signature of cancers based on APE1 and NPM1 expression.

Results

APE1 and NPM1, and their interaction as well, protect from the cytotoxicity induced by Pt-salts treatment. HCC1937 cells, having higher levels of APE1/NPM1 proteins, are more resistant to Pt-salts treatment compared to the HCC70 cells. A sensitization effect by APE1 inhibitors to Pt-compounds was observed. The association of NPM1/APE1 with cancer gene signatures highlighted alterations concerning cell-cycle dependent proteins.

Conclusions

APE1 and NPM1 protect cancer cells from Pt-compounds cytotoxicity, suggesting a possible improvement of the activity of Pt-based therapy for TNBC, using the NPM1 and APE1 proteins as secondary therapeutic targets. Based on positive or negative correlation with APE1 and NPM1 gene expression levels, we finally propose several TNBC gene signatures that should deserve further attention for their potential impact on TNBC precision medicine approaches.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1294-9) contains supplementary material, which is available to authorized users.

Exploring novel candidate genes from the Mouse Genome Informatics database: Potential implications for avian migration research

To search for genes associated with migratory phenotypes in songbirds, we selected candidate genes through annotations from the Mouse Genome Informatics database and assembled an extensive candidate-gene library. Then, we implemented a next-generation sequencing approach to obtain DNA sequences from the Painted Bunting genome. We focused on those sequences that were conserved across avian species and that aligned with candidate genes in our mouse library. We genotyped short sequence repeats from the following candidate genes: ADRA1d, ANKRD17, CISH and MYH7. We studied the possible correlations between allelic variations occurring in these novel candidate migration genes and avian migratory phenotypes available from the published literature. We found that allele variation at MYH7 correlated with a calculated index of speed of migration (km/day) across 11 species of songbirds. We highlight the potential of the Mouse Genome Informatics database in providing new candidate genes that might play a crucial role in regulating migration in birds and possibly in other taxa. Our research effort shows the benefits and limitations of working with extensive genomic datasets and offers a snapshot of the challenges related to cross-species validation in behavioral and molecular ecology studies.

Base excision repair-mediated resistance to cisplatin in KRAS(G12C) mutant NSCLC cells

KRAS mutations in NSCLC are supposed to indicate a poor prognosis and poor response to anticancer treatments but this feature lacks a mechanistic basis so far. In tumors, KRAS was found to be mutated mostly at codons 12 and 13 and a pool of mutations differing in the base alteration and the amino acid substitution have been described. The different KRAS mutations may differently impact on cancerogenesis and drug sensitivity. On this basis, we hypothesized that a different KRAS mutational status in NSCLC patients determines a different profile in the tumor response to treatments. In this paper, isogenic NSCLC cell clones expressing mutated forms of KRAS were used to determine the response to cisplatin, the main drug used in the clinic against NSCLC. Cells expressing the KRAS(G12C) mutation were found to be less sensitive to treatment both in vitro and in vivo. Systematic analysis of drug uptake, DNA adduct formation and DNA damage responses implicated in cisplatin adducts removal revealed that the KRAS(G12C) mutation might be particular because it stimulates Base Excision Repair to rapidly remove platinum from DNA even before the formation of cross-links. The presented results suggest a different pattern of sensitivity/resistance to cisplatin depending on the KRAS mutational status and these data might provide proof of principle for further investigations on the role of the KRAS status as a predictor of NSCLC response.