Cyclic nucleotide levels in human breast cancer and in rat mammary tissues during tumor development

The levels of cyclic adenosine 3:5-monophosphate (cAMP) and cyclic guanosine 3:5-monophosphate (cGMP) were studied in dimethylbenz(a)anthracene (DMBA)-induced mammary tumors of Sprague-Dawley rats and in human breast cancer. In the rat carcinomas, these levels were significantly lower than in non-malignant tissues when calculated on the basis of DNA content, but higher (cAMP) or equal (cGMP) when calculated on the basis of weight. In human breast cancer the cyclic nucleotide levels were higher than in non-malignant tissues according to both methods of calculation. No correlation was found in human carcinomas between the cyclic nucleotide levels and mitotic index, nuclear grade, tumor size, or lymph node involvement. The rat tumors were subclassified according to state of differentiation, mitotic index, and state of development. Not all the sub-groups had cAMP levels different from normal values. Differences in cAMP levels between the sub-groups could not be correlated with tumor growth rates and/or mitotic index. Thus, cyclic nucleotides may not be useful in prognosis of breast cancer.     

Endogenous estrogen status, but not genistein supplementation, modulates 7,12-dimethylbenz[a]anthracene-induced mutation in the liver cII gene of transgenic big blue rats

A growing number of studies suggest that isoflavones found in soybeans have estrogenic activity and may safely alleviate the symptoms of menopause. One of these isoflavones, genistein, is commonly used by postmenopausal women as an alternative to hormone replacement therapy. Although sex hormones have been implicated as an important risk factor for the development of hepatocellular carcinoma, there are limited data on the potential effects of the estrogens, including phytoestrogens, on chemical mutagenesis in liver. Because of the association between mutation induction and the carcinogenesis process, we investigated whether endogenous estrogen and supplemental genistein affect 7,12-dimethylbenz[a]anthracene (DMBA)-induced mutagenesis in rat liver. Intact and ovariectomized female Big Blue rats were treated with 80 mg DMBA/kg body weight. Some of the rats also received a supplement of 1,000 ppm genistein. Sixteen weeks after the carcinogen treatment, the rats were sacrificed, their livers were removed, and mutant frequencies (MFs) and types of mutations were determined in the liver cII gene. DMBA significantly increased the MFs in liver for both the intact and ovariectomized rats. While there was no significant difference in MF between the ovariectomized and intact control animals, the mutation induction by DMBA in the ovariectomized groups was significantly higher than that in the intact groups. Dietary genistein did not alter these responses. Molecular analysis of the mutants showed that DMBA induced chemical-specific types of mutations in the liver cII gene. These results suggest that endogenous ovarian hormones have an inhibitory effect on liver mutagenesis by DMBA, whereas dietary genistein does not modulate spontaneous or DMBA-induced mutagenesis in either intact or ovariectomized rats.     

三苯氧胺对二甲基苯蒽诱发的大鼠乳腺癌的影响

应用 Ｄ Ｍ Ｂ Ａ 诱发的雌性 Ｓ Ｄ 大鼠乳腺癌模型,初步探讨了大鼠乳腺受致癌剂作用后,三苯氧胺对乳腺癌发生的影响。结果显示：三苯氧胺使恶性肿瘤出现的平均潜伏期明显延长,恶性肿瘤的发生率明显降低。     

7,12-Dimethylbenz[a]anthracene-induced bone marrow toxicity is p53-dependent.

Polycyclic aromatic hydrocarbons (PAHs) are known immunotoxins and carcinogens. Our laboratory and others have demonstrated that metabolism of these compounds by CYP1B1 is required for carcinogenicity and immunotoxicity to occur. Previously, our laboratory reported significantly decreased bone marrow cellularity in mice following 7,12-dimethlybenz[a]anthracene (DMBA) administration. In addition, we have observed that DMBA causes apoptosis via activation of both caspase-8 and -9 in pre-B cells co-cultured with bone marrow stromal cells in vitro. In this study, we investigated the importance of the p53 protein in the bone marrow response to DMBA. Through the use of p53 gene knockout mice, we demonstrated that the effect of DMBA on bone marrow cellularity is p53-dependent. In addition, apoptosis of primary cultures of progenitor B cells cultured with bone marrow stromal cells and DMBA is also p53-dependent. The results of this study provide evidence for the importance of p53 in the signaling pathways by which PAHs cause immunotoxicity.     

Weight cycling did not increase tumor incidence in high fat–fed rats treated with a low-dose 7,12-dimethylbenzyl(1)anthracene

The present study tested the hypothesis that weight cycling (WC, repeated weight gain and loss) increases the tumorigenesis in rats exposed to carcinogen. Female Wistar rats consumed a high-fat diet (35% weight per weight) and were divided: (1) ad lib–fed rats that were treated with 7,12-dimethylbenzyl(1)anthracene (DMBA, 2 mg) at 55 days of age (AL-DMBA); (2) WC rats that were treated with DMBA (WC-DMBA); and (3) vehicle-treated WC rats (WC-VEH). In this study, WC did not alter blood parameter concentrations and did not influence insulin sensitivity. Mammary tissue F₂-isoprostane concentrations were lowest in WC-VEH and highest in AL-DMBA groups. Tumor incidence and burden were similar among all groups. The data obtained from this study do not support our hypothesis. This may be due to low dose of DMBA used, strain and age of the rats, number of WC cycles, and the amount of trans–fatty acids in the diets.     

Daphnetin ameliorates 7,12-dimethylbenz[a]anthracene-induced mammary carcinogenesis through Nrf-2-Keap1 and NF-κB pathways

Cancer is a faction of disorders that conjugated primarily with oxidative imbalance. In mammary carcinoma, oxidative stress secondarily changes various gene expressions and signalling pathways that bring genomic instability and mutagenic alterations that fascinating carcinogenesis. Several coumarin compounds are active against various malignancies. Among them, daphnetin (DAP) exhibits valuable safety and bioactivity profile that contributes towards its efficacy against cancer. In this study, the antioxidative and chemotherapeutic potential of DAP against 7,12-dimethylbenz(a)anthracene (DMBA)- induced mammary carcinogenesis was evaluated in female Sprague-Dawley rats. Besides this, we have determined the effect of DAP on Keap1-Nrf-2, associated HO-1 and NF-κB expressions behind the antioxidative and anti-proliferating activity. In our findings, a protective effect of DAP was established against lipid peroxidation, enzymic (Total SOD, MnSOD, CuZnSOD, CAT, GPx) and non-enzymic (GSH) antioxidative markers in serum, liver, kidney and breast tissue of both control and experimental groups. An up-regulation of protective Nrf-2 & HO-1 with a synchronized suppression in Keap1 & NF-κB mRNA and protein expressions were observed. DAP revealed the inhibition of p-AKT which accountable for decrease in NF-κB expressions but shown to be ineffective on p-ERK1/2. This study revealed that DAP inhibits mammary carcinogenesis through multiple mechanisms. Dual efficacy of DAP on Nrf-2-Keap1 pathway and NF-κB expressions propose it as a potential chemotherapeutic agent in mammary cancer management.     

Improving discrimination in the grading of rat mammary tumors using two-dimensional mapping of histopathological observations

This work aims at characterizing rat mammary tumors induced by 7,12-dimethylbenz(a)anthracene (DMBA) and the respective malignancy potential, commonly graded with histopathology features grouped by intensity levels. Tumors were described over fourteen multiple ranged microscopic parameters and a comprehensive characterization of the histological patterns and their relation with tumor grade was carried out by principal component analysis (PCA). The number of histological patterns present on a tumor tends to correlate with malignant features. High grade tumors are characterized by the presence of several structural patterns, with cribriform prevalence and necrosis. The cribriform pattern correlates with grading, i.e., tumors having a higher predominance of the cribriform pattern are likely to be more malignant. The findings may represent a benchmark for similar characterization studies in other models.     

Tangeretin ameliorates oxidative stress in the renal tissues of rats with experimental breast cancer induced by 7,12-dimethylbenz[a]anthracene

Tangeretin, a citrus polymethoxyflavone, is an antioxidant modulator which has been shown to exhibit a surfeit of pharmacological properties. The present study was hypothesized to explore the therapeutic activity of tangeretin against 7,12-dimethylbenz[a]anthracene (DMBA) induced kidney injury in mammary tumor bearing rats. Recently, we have reported the chemotherapeutic effect of tangeretin in the breast tissue of DMBA induced rats. Breast cancer was induced by “air pouch technique” with a single dose of 25 mg/kg of DMBA. Tangeretin (50 mg/kg/day) was administered orally for four weeks. The renoprotective nature of tangeretin was assessed by analyzing the markers of oxidative stress, proinflammatory cytokines and antioxidant competence in DMBA induced rats. Tangeretin treatment revealed a significant decline in the levels of lipid peroxides, inflammatory cytokines and markers of DNA damage, and a significant improvement in the levels of enzymatic and non-enzymatic antioxidants in the kidney tissue. Similarly, mRNA, protein and immunohistochemical analysis substantiated that tangeretin treatment notably normalizes the renal expression of Nrf2/Keap1, its downstream regulatory proteins and the inflammatory cytokines in the DMBA induced rats. Histological and ultrastructural observations also evidenced that the treatment with tangeretin effectively protects the kidney from DMBA-mediated oxidative damage, hence, proving its nephroprotective nature.     

Origin of a malignant adenocarcinoma cell line induced by retrovirus-like particles from DMBA rat mammary tumors

Summary Intraperitoneal inoculation of neonate Sprague Dawley rats with cell-free extracts containing retrovirus-like particles from DMBA-induced rat mammary tumors resulted in a fivefold increase of benign mammary neoplasias in the survivor animals, in comparison to the spontaneous tumor incidence rate. In addition, four animals developed metastasizing abdominal adenocarcinomas. The ascitic cells of one of the abdominal tumors were established as a permanent tissue culture line (HH-1). After subsequent animal passage, cells of the permanent line HH-9 clone 14 showed increased malignancy manifested by the number of takes per animals injected, and by the number of remote metastases observed.Supported by the Deutsche Forschungsgemeinschaft, SFB 34     

Estrogen Activation of G-Protein–Coupled Estrogen Receptor 1 Regulates Phosphoinositide 3-Kinase and mTOR Signaling to Promote Liver Growth in Zebrafish and Proliferation of Human Hepatocytes

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