methylnitronitrosoguanidine and Breast-Neoplasms

Breast cancer, cervical cancer, and ovarian cancer are three of the most commonly diagnosed malignancies in women, and more cancer prevention research is urgently needed.. Summary data of a large genome-wide association study of female cancers were derived from the UK biobank. We performed a transcriptome-wide association study and a gene set enrichment analysis to identify correlations between chemical exposure and aberrant expression, repression, or mutation of genes related to cancer using the Comparative Toxicogenomics Database.. We identified five chemicals (NSC668394, glafenine, methylnitronitrosoguanidine, fenofibrate, and methylparaben) that were associated with the incidence of both breast cancer and cervical cancer.. Using a transcriptome-wide association study and gene set enrichment analysis we identified environmental chemicals that are associated with an increased risk of breast cancer, cervical cancer, and ovarian cancer.

Topics: Breast Neoplasms; Environmental Exposure; Female; Fenofibrate; Gene Expression Profiling; Genome-Wide Association Study; Glafenine; Humans; Incidence; Methylnitronitrosoguanidine; Ovarian Neoplasms; Parabens; Phenols; Quinolones; Uterine Cervical Neoplasms

Breast cancer is the most common invasive type of cancer among women. Role of different microRNAs (miRNAs) and poly(ADP-ribose) polymerases (PARPs) in breast cancer has been well established. This study aimed to explore the effects of miR-891b on sensitizing breast cancer cells to alkylating chemotherapeutic drugs through PARPs.. The expression of miR-891b and PARP1 in human breast cancer cells HCC1806 was overexpressed by transfection with their mimics or expressing vector. Then, the transfected cells were exposed to 40 µM N-methyl-N-nitro-N-nitrosoguanidine (MNNG) for 1 h. The correlation between miR-891b and PARP1 was detected by RT-qPCR, western blot, and dual-luciferase reporter assay. Besides, MTT assay and Annexin V assay were done to measure cell proliferation and apoptosis, respectively.. PARP1 was a target of miR-891b, and it was negatively regulated by miR-891b. MiR-891b increased the sensitivity of the HCC1806 cells to the cytotoxic effects of MNNG through suppressing cell proliferation and increasing the percentage of apoptotic cells. Restoration of PARP1 activity in the HCC1806 cells led to loss of miR-891b mediated sensitivity of the HCC1806 cells to MNNG.. MiR-891b increases the sensitivity of the breast cancer cells (HCC1806) to the cytotoxic effects of the chemotherapeutic agent MNNG by suppressing the expression of PARP1.

Topics: Antineoplastic Agents, Alkylating; Breast Neoplasms; Cell Line, Tumor; Down-Regulation; Drug Resistance, Neoplasm; Female; Gene Expression Regulation, Neoplastic; Humans; Methylnitronitrosoguanidine; MicroRNAs; Poly (ADP-Ribose) Polymerase-1

Induction of DNA double strand breaks and alterations in the repair of these breaks is implicated in breast carcinogenesis. Prior studies have demonstrated that peripheral blood mononuclear cells (PBMC) from breast cancer patients exhibit increased numbers of DNA strand breaks after exposure to ionizing radiation, but these studies did not specifically measure DNA double strand breaks and it is not known whether chemical carcinogens produce similar effects.. PBMC from 32 women undergoing breast surgery were genotyped at nine loci of seven DNA repair genes. DNA double strand break repair was measured using the neutral comet assay after exposure to ionizing radiation (0.5 Gy) or bioactivated benzo[a]pyrene (B[a]P, 5 microM.. PBMC from breast cancer patients showed higher levels of residual DNA double strand breaks 30 min after exposure to radiation than PBMC from patients with benign breast disease (1.40 times baseline [95% confidence intervals [CI] 1.29-1.51] versus 1.24 times baseline [95% CI 1.15-1.33], respectively, P = 0.04). The response to B[a]P trended in the same direction, but did not reach statistical significance. The MGMT K178R variant genotype was associated with improved DNA double strand break repair in PBMC exposed to B[a]P.. Reduced repair of radiation-induced DNA double strand breaks in PBMC is a robust biomarker of breast cancer risk. Reduced DNA repair capacity may have a genetic component even in sporadic breast cancer.

Topics: Benzo(a)pyrene; Bleomycin; BRCA2 Protein; Breast Neoplasms; Carcinogens; Comet Assay; DNA; DNA Damage; DNA Repair; Female; Genotype; Humans; Leukocytes, Mononuclear; Methylnitronitrosoguanidine; Middle Aged; Polymorphism, Single Nucleotide; Radiation, Ionizing; Ubiquitin-Protein Ligases

In an effort to improve the efficacy of cancer chemotherapy by intervening into the cellular responses to chemotherapeutic change, we have used adenoviral overexpression of N-methylpurine DNA glycosylase (MPG or ANPG/AAG) in breast cancer cells to study its ability to imbalance base excision repair (BER) and sensitize cancer cells to alkylating agents. Our results show that MPG-overexpressing cells are significantly more sensitive to the alkylating agents methyl methanesulfonate, N-methyl-N'-nitro-N-nitrosoguanidine, methylnitrosourea, dimethyl sulfate, and the clinical chemotherapeutic temozolomide. Sensitivity is further increased through coadministration of the BER inhibitor methoxyamine, which covalently binds abasic or apurinic/apyrimidinic (AP) sites and makes them refractory to subsequent repair. Methoxyamine reduction of cell survival is significantly greater in cells overexpressing MPG than in control cells, suggesting a heightened production of AP sites that, if made persistent, results in increased cellular toxicity. We further explored the mechanism of MPG-induced sensitivity and found that sensitivity was associated with a significant increase in the number of AP sites and/or single-strand breaks in overexpressing cells, confirming a MPG-driven accumulation of toxic BER intermediates. These data establish transient MPG overexpression as a potential therapeutic approach for increasing cellular sensitivity to alkylating agent chemotherapy.

Topics: Adenoviridae; Alkylating Agents; Antineoplastic Agents, Alkylating; Apoptosis; Blotting, Western; Breast Neoplasms; Cell Line, Tumor; Cell Proliferation; Cell Survival; Comet Assay; Dacarbazine; DNA Glycosylases; DNA Repair; Dose-Response Relationship, Drug; Genetic Therapy; Genetic Vectors; Humans; Hydroxylamines; Immunohistochemistry; Methyl Methanesulfonate; Methylnitronitrosoguanidine; Methylnitrosourea; Oligonucleotides; Sensitivity and Specificity; Sulfuric Acid Esters; Temozolomide; Time Factors

The 39-kDa DNA polymerase beta (pol beta) is an essential enzyme in short-patch base excision repair pathway. A wild-type and a truncated forms of pol beta proteins are expressed in primary colorectal and breast adenocarcinomas and in a primary culture of renal cell carcinoma. To test whether pol beta has a contributory role in tumorigenicity of human tumor cell lines, we have undertaken a study to determine expression of pol beta in colon, breast, and prostate tumor cell lines. Unlike primary colon tumor cells, three types of pol beta mRNA have been identified in HCT116, LoVo, and DLD1, colon tumor cell lines. A 111-bp-deleted pol beta transcript was expressed in MCF7, a breast tumor cell line, but not in primary breast tumor cells. An expression of a smaller pol beta transcript has been revealed in DU145, a prostate tumor cell line, whereas, a single base (T) deletion in mRNA at codon 191 was found in prostate cancer tissue. Interestingly, a wild-type pol beta transcript was also expressed in all tumor cell lines similar to primary tumor cells. Furthermore, the cell extract of LoVo exhibited highest gap-filling synthesis function of pol beta when the extract of DU145 showed lowest activity. MNNG, a DNA alkylating agent, enhanced the gap-filling synthesis activity in extracts of LoVo cell line. Furthermore, the cellular viability of LoVo and HCT116 cells is sensitive to MNNG when DU145 cells are resistant. These results demonstrate heterogeneity in pol beta mRNA expression, which may be a risk factor related to tumorigenic activities of tumor cell lines.

Topics: Breast Neoplasms; Cell Survival; Colonic Neoplasms; DNA Polymerase beta; DNA Repair; DNA, Neoplasm; Female; Gene Expression; Humans; Male; Methylnitronitrosoguanidine; Neoplasms; Prostatic Neoplasms; RNA, Messenger; RNA, Neoplasm; Tumor Cells, Cultured; Tumor Stem Cell Assay

The effect of three reactive potent chemical carcinogens on the passage of MCF-7 cells through the cell cycle was investigated. While these cells, which express wild-type p53, were arrested in G(1) after treatment with actinomycin D (a positive control), treatment with anti-benzo[a]pyrene dihydrodiol epoxide, N-acetoxy-N-2-fluorenylacetamide or N-methyl-N'-nitro-N-nitrosoguanidine, at doses consistent with survival of significant numbers of cells, caused the cells to accumulate in S phase, with little increase in those in G(1). This property of these three reactive potent carcinogens, of diverse chemical types, to induce evasion of G(1) arrest (the stealth property) presumably increases the likelihood of malignant change, because DNA replication continues on a damaged template. This stealth characteristic may be a major contributor to the tumorigenicity of DNA-adducting chemical carcinogens in general.

Topics: 7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide; Acetoxyacetylaminofluorene; Alkylating Agents; Breast Neoplasms; Carcinogens; Cell Cycle; Cell Survival; Dactinomycin; Dose-Response Relationship, Drug; G1 Phase; Humans; Methylnitronitrosoguanidine; Nocodazole; Stereoisomerism; Tumor Cells, Cultured

We have developed a "comparative growth assay" that complements current assays of drug effects based on cytotoxicity. A co-culture of two cell lines, one of which is fluorescently labeled, is exposed to a cytotoxic agent and the proportion of fluorescent cells is compared with that of a baseline unexposed co-culture. For demonstration purposes, two HCT116 cell lines (an hMLH1 homozygous and an hMLH1 heterozygous mutant), altered by insertion of vector alone or the same vector carrying an insert for the expression of enhanced green fluorescent protein (EGFP), were exposed to numerous "anti-cancer" agents. The assay was further validated in a system of two cell lines differing only in the expression of the breast cancer resistance protein (BRCP). The assay allowed the estimation of the duration of action of a particular agent. Assessment of the agent's differential activity over a given time in culture could be expressed as a selection rate, which we chose to describe on an "average selection per day" basis. We conclude that this assay: 1) provides insight into the differential dynamic effects of chemotherapeutic agents or radiation; and 2) allows, through the use of matched cell lines, the investigation of critical physiologic features that govern cell sensitivity.

Topics: Anti-Bacterial Agents; Antineoplastic Agents; ATP Binding Cassette Transporter, Subfamily G, Member 2; ATP-Binding Cassette Transporters; Breast Neoplasms; Cell Culture Techniques; Cell Division; Coculture Techniques; Colonic Neoplasms; Dose-Response Relationship, Drug; Dose-Response Relationship, Radiation; Drug Resistance, Neoplasm; Flow Cytometry; Fluorescent Dyes; Genetic Vectors; Gentamicins; Green Fluorescent Proteins; Humans; Luminescent Proteins; Methylnitronitrosoguanidine; Mitoxantrone; Mutation; Neoplasm Proteins; Time Factors; Transfection; Tumor Cells, Cultured

Humans show heterogeneous susceptibility to cancer development, suggesting the involvement of various genetic backgrounds in control of the production of endogenous carcinogens, the metabolism of carcinogens, the repair of DNA damage, cell proliferation and defence mechanisms including immune reactions. Gastric cancer is the major cancer in Japan. However, little is known about the genes linked with its development. In 1967, we found that N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) induced gastric cancers in Wistar rats. Subsequently the Buffalo strain of rats was reported to be resistant to MNNG stomach carcinogenesis, while ACI rats were very sensitive. In a carcinogenesis study using F1 and F2 rats, we suggested that this trait of MNNG stomach carcinogenesis-resistance was regulated by a single autosomal dominant allele. The O6-methylguanine adduct levels in gastric mucosa induced by MNNG were the same in Buffalo and ACI rats, but cell proliferation induced by MNNG was much higher in ACI than Buffalo animals. Chromosome mapping of the gene responsible for susceptibility to MNNG-induced carcinogenesis is now in progress and its identification will hopefully give us clues to the involvement of genetic traits in susceptibility to gastric cancer in humans. In addition, the genetic background of susceptibility to breast cancer is also being studied. In Japan, about 5% of all cases of breast cancer are familial. We have studied BRCA1, the breast cancer susceptibility gene, as a determinant of susceptibility to breast cancer by linkage analyses in 11 families, but our results indicate that BRCA1 may not be important for development of familial breast cancer in Japanese.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; BRCA1 Protein; Breast Neoplasms; Female; Gastric Mucosa; Genetic Predisposition to Disease; Humans; Japan; Lod Score; Methylnitronitrosoguanidine; Middle Aged; Neoplasm Proteins; Neoplasms; Ovarian Neoplasms; Polymorphism, Genetic; Rats; Rats, Inbred ACI; Rats, Inbred BUF; Rats, Wistar; Species Specificity; Stomach Neoplasms; Transcription Factors