Effect of 7,12-dimethylbenz[a]anthracene (DMBA) on gut glutathione metabolism

In Vitro and In Vivo Preventive Effects of Thymoquinone against Breast Cancer: Role of DNMT1

Breast cancer (BC) is one of the most common cancers in women and is a major cause of female cancer-related deaths. BC is a multifactorial disease caused by the dysregulation of many genes, raising the need to find novel drugs that function by targeting several signaling pathways. The antitumoral drug thymoquinone (TQ), found in black seed oil, has multitargeting properties against several signaling pathways. This study evaluated the inhibitory effects of TQ on the MCF7 and T47D human breast cancer cell lines and its antitumor activity against BC induced by a single oral dose (65 mg/kg) of 7,12-dimethylbenzanthracene (DMBA) in female rats. The therapeutic activity was evaluated in DMBA-treated rats who received oral TQ (50 mg/kg) three times weekly. TQ-treated MCF7 and T47D cells showed concentration-dependent inhibition of cell proliferation and induction of apoptosis. TQ also decreased the expression of DNA methyltransferase 1 (DNMT1) in both cancer cell types. In DMBA-treated animals, TQ inhibited the number of liver and kidney metastases. These effects were associated with a reduction in DNMT1 mRNA expression. These results indicate that TQ has protective effects against breast carcinogens through epigenetic mechanisms involving DNMT1 inhibition.

Genotoxic carcinogen 7,12-dimethylbenz[a]anthracene inhibits gap junction intercellular communication through post-transcriptional and post-translational processing involved in connexin 43 stability

Gap junctional intercellular communication (GJIC) is composed of connexin (Cx) and plays an important role in maintaining intracellular homeostasis. Loss of GJIC is involved in the early stages of cancer pathways of non-genotoxic carcinogens; however, the effect of genotoxic carcinogens, including polycyclic aromatic hydrocarbons (PAHs), on GJIC function remains unclear. Therefore, we determined whether and how a representative PAH 7,12-dimethylbenz[a]anthracene (DMBA) suppresses GJIC in WB-F344 cells. First, DMBA significantly inhibited GJIC and dose-dependently reduced Cx43 protein and mRNA expression. In contrast, Cx43 promoter activity was upregulated after DMBA treatment via the induction of specificity protein 1 and hepatocyte nuclear factor 3β, indicating that the promoter-independent loss of Cx43 mRNA can be associated with the inhibition of mRNA stability, which was verified by actinomycin D assay. In addition to a decrease in mRNA stability involved in human antigen R, we also observed DMBA-induced acceleration of Cx43 protein degradation, which was closely related to the loss of GJIC through Cx43 phosphorylation via MAPK activation. In conclusion, the genotoxic carcinogen DMBA suppresses GJIC by inhibiting post-transcriptional and post-translational processing of Cx43. Our findings suggest that the GJIC assay is an efficient short-term screening test for predicting the carcinogenic potential of genotoxic carcinogens.

Antitumor and Antibacterial Efficacy of Gallium Nanoparticles Coated by Ellagic Acid

Cancer is a mortality contributor worldwide, and breast cancer is the most common among women. Despite the numerous breast cancer therapeutic strategies, they either have limitations or sometimes are resisted by cancer, so new approaches are needed to tackle those restrictions. Nanotechnology offers exciting leaps in the diagnosis and treatment of cancer, especially breast cancer. The main objective of this study was to investigate the effect of the newly synthesized gallium nanoparticles coated by Ellagic acid (EA-GaNPs) on the induced mammary gland carcinogenesis in female rats and their antibacterial activities comparison with standard antibiotics (Ketoconazole (100 μg/ml) and Gentamycin (4 μg/ml)) by disc diffusion method using eight different microbial species. The antitumor efficacy of EA-GaNPs was conducted both in vitro and in in vivo. The result of antimicrobial activity of EA-Ga NPs (1 mg/1 mL) revealed moderate toxicity behavior against Gram-positive {Staphylococcus aureus, Bacillus subtilis, Bacillus cereus) and Gram-negative pathogenic bacteria {Escherichia coli, Proteus vulgarfs) also, antifungal activity was detected against {Aspergillus terreus). In vitro study showed that EA-GaNPs inhibited human breast cancer cell line (MCF-7) proliferation with IC50 of 2.86 μg/ml. Although in vivo; the administration of EA-GaNPs to DMBA-treated rats ameliorated the hyperplastic state of mammary gland carcinogenesis induced by DMBA. Additionally, EA-GaNPs administration significantly modulated the activities of ALT and AST, as well as the levels of urea and creatinine in serum. Also, EA-GaNPs administration improved the antioxidant state by increasing Superoxide dismutase activity and GSH content, and decreasing malondialdehyde content in the mammary tissue, besides enhancing the apoptotic activity through elevating the levels of caspase-3 and decreasing the protein intensities of protein kinase B & phosphatidyl inositide 3-kinases. Furthermore, a significant decrease in serum Total iron-binding capacity accompanied by a significant increase in the level of calcium was noted. So, it can be concluded that the newly synthesized nanoparticles EA-GaNPs have an efficient antitumor activity that was manifested by reduction of the viability on the human breast cancer cell line (MCF-7) in vitro. Also, in vivo against the chemically induced mammary gland carcinogenesis in a female rat model. Histopathological findings were in harmony with biochemical and molecular results showing the effectiveness of EA-GaNPs against mammary carcinogenesis. Therefore, EA-GaNPs could be a promising, potent anti-cancer compound.

In vivo effects of olive oil and trans-fatty acids on miR-134, miR-132, miR-124-1, miR-9-3 and mTORC1 gene expression in a DMBA-treated mouse model

Both the intake of beneficial olive oil and of harmful trans-fatty acids (TFAs) in consumed foods are of great significance in tumor biology. In our present study we examined the effects they exert on the expression patterns of miR-134, miR-132, miR-124-1, miR-9-3 and mTOR in the liver, spleen and kidney of mice treated with 7,12-dimethylbenz [a] anthracene (DMBA). Feeding of TFA-containing diet significantly increased the expression of all studied miRs and mTORC1 in all organs examined, except the expression of mTORC1 in the spleen and kidney. Diet containing olive oil significantly reduced the expression of miR-124-1, miR-9-3 and mTORC1 in the liver and spleen. In the kidney, apart from the mTORC1 gene, the expression of all miRs examined significantly decreased compared to the DMBA control. According to our results, the cell membrane protective, antioxidant, and anti-inflammatory effects of olive oil and the cell membrane damaging, inflammatory, and carcinogenic properties of TFA suggest negative feedback regulatory mechanisms. In contrast to our expectations, mTORC1 gene expression in the kidney has not been shown to be an appropriate biomarker-presumably, because the many complex effects that regulate mTOR expression may quench each other.

Crystal structure and chemotherapeutic efficacy of the novel compound, gallium tetrachloride betaine, against breast cancer using nanotechnology

The objective of this study was to investigate the antitumor efficacy of a novel synthesized compound, betaine gallium-tetrachloride (BTG), alone or combined with ZnO-nanoparticles (BTG + ZnO-NPs) on the incidence of 7, 12-dimethylbenz-anthrathene-induced mammary tumor in female rats. Crystal and molecular structure of the prepared BTG were identified using X-ray crystallography. In vitro study revealed BTG more cytotoxic than BTG + ZnO-NPs on human breast cancer (MCF-7) cell line. In vivo study demonstrated that the blood antioxidant status of tumor-bearing rats (DMBA group) was significantly lower than normal noticeable by a significant decrease in GSH content, GPx, SOD, and CAT activities associated with a significantly high MDA content. Both treatments have significantly elevated SOD and CAT activities with a concomitant decrease of MDA level compared to DMBA group. However, BTG + ZnO-NPs accentuated the decrease of GSH regarding DMBA group. The results showed also that both treatments significantly activate caspase-3 enzyme and apoptosis in mammary glands. Their administration to tumor-bearing rats was found to significantly reduce plasma iron and iron-binding capacity (TIBC) compared to DMBA group. Regarding liver function, both treatments significantly reduced the increase of ALT and AST activities compared to DMBA group. However, BTG + ZnO-NPs decreased albumin below normal level. Histopathological studies showed that normalization of tissue structures was higher in BTG than BTG + ZnO-NPs treatment. According to the results obtained, it is observed that the antitumor effect of BTG alone was as strong as BTG + ZnO-NPs and even more efficient in some aspects accordingly, a combination is not needed. Thus, the novel synthetic gallium derivatives may potentially present a new hope for the development of breast cancer therapeutics, which should attract further scientific and pharmaceutical interest.

Copper and resveratrol attenuates serum catalase, glutathione peroxidase, and element values in rats with DMBA-induced mammary carcinogenesis

In this paper, a hypothesis was assessed whether or not the intoxication with copper and supplementation with copper plus resveratrol would result in changes in the activities of catalase and glutathione peroxidase and moreover if the characteristic changes would appear in concentrations of copper, iron, calcium, magnesium, and zinc in the serum of rats with chemically induced carcinogenesis. Female Sprague-Dawley rats were divided into study groups which, apart from the standard diet, were treated with copper (42.6 mg Cu/kg food as CuSO4·5H2O) or copper plus resveratrol (0.2 mg/kg body) via gavage for a period from 40 days until 20 weeks of age. In cancer groups, the rats were treated with a dose of 80 mg/body weight of 7,12-dimethyl-1,2-benz[a]anthracene (DMBA) given in rapeseed oil at 50 and 80 days of age to induce mammary carcinogenesis. The control groups included the rats kept in the same conditions and fed with the same diet as the animals from the study groups, but not DMBA-treated. The activity of catalase significantly decreased in groups of rats with mammary carcinogenesis that were supplemented with copper (p < 0.05) or copper plus resveratrol (p < 0.001) in comparison with the control groups that received the same diets. In cancer groups of nonsupplemented rats, the increase of glutathione peroxidase activity was observed. The process of carcinogenesis and the applied supplementation significantly altered the concentrations of trace elements in serum, in particular as concerns iron and copper. The mean serum iron levels in rats with breast cancer were significantly lower than those in the control groups (p < 0.001). The mean serum copper levels significantly decreased in the groups of rats with mammary carcinogenesis that were supplemented with copper or copper plus resveratrol in comparison with the control groups that received the same diets (p < 0.001). The characteristic changes in iron content and the zinc/copper and zinc/iron ratios in blood may be used as one of the prognostic factors in breast cancer research.

Chemopreventive and antioxidant efficacy of (6)-paradol in 7,12-dimethylbenz(a)anthracene induced hamster buccal pouch carcinogenesis

The present study evaluated the chemopreventive potential of (6)-paradol, a pungent phenolic constituent of ginger, on 7,12-dimethylbenz(a)anthracene (DMBA)-induced hamster buccal pouch carcinogenesis. The mechanistic pathway for the chemopreventive potential of (6)-paradol was evaluated by measuring the status of tumor incidence, volume and burden as well as by analyzing the status of phase II detoxification agents, lipid peroxidation and antioxidants. Oral squamous cell carcinoma was induced in hamster buccal pouches by painting them with 0.5% DMBA in liquid paraffin three times a week for 14 weeks. We observed 100% tumor formation with marked biochemical abnormalities in tumor-bearing animals compared to control animals. Oral administration of 30 mg/kg b.w. (6)-paradol to DMBA-treated hamsters on alternate days from DMBA painting for 14 weeks, significantly reduced the formation of tumors and improved the status of detoxification agents, lipid peroxidation and antioxidants. Therefore, the present study suggests that (6)-paradol has potent chemopreventive, anti-lipid peroxidative and antioxidant potentials as well as a modulating effect on phase II detoxification enzyme and reduced glutathione (GSH) in DMBA-induced hamster buccal pouch carcinogenesis.

The effect of melatonin on 7,12-dimethyl-benz[a]anthracene injury in comparison with vitamin E + selenium in mouse kidneys

The aims of this study were to observe the changes in antioxidative defense enzymes and renal morphology after 7,12-dimethyl-benz[a]anthracene (7,12-DMBA) administration in mice and to investigate the possible protective effects of melatonin against 7,12-DMBA-induced renal damage in comparison with vitamin E + selenium (vit E + Se). Forty female mice were divided into four groups: control, DMBA, DMBA + vit E + Se and DMBA + melatonin. In the DMBA group, mice were given injections of 7,12-DMBA (20 mg/kg). DMBA + vit E + Se group mice received injections of 7,12-DMBA + vit E + Se (20 mg/kg + 90 mg/kg + 1.8 microg/kg). In the melatonin group, mice were given injections of 7,12-DMBA + melatonin (20 mg/kg + 4.2 mg/kg). The experiment lasted for 21 days. Mice were killed and the kidneys were taken for enzyme analyses and histologic examination. Catalase (CAT) and glutathione peroxidase (GSH-Px) activities were found significantly decreased in the DMBA group and in the DMBA + vit E + Se group when compared with the control group (P < 0.05), whereas CAT and GSH-Px activities were found significantly elevated in the DMBA + melatonin group when compared with the control (P < 0.05) and the DMBA group (P < 0.01). Exposure to DMBA resulted in tubular alterations in renal cortex. Morphometric analysis revealed proximal and distal tubular damage (P < 0.05). These alterations were found to be prevented by melatonin but not with vit E + Se administration. These results reveal that melatonin stimulates CAT and GSH-Px activities and prevents renal injury better than vit E + Se combination in mice kidneys.

Toxicity induced by the chemical carcinogen 7,12-dimethylbenz[a]anthracene and the protective effects of selenium in Wistar rats

7,12-Dimethylbenz[a]anthracene (DMBA), a polycyclic aromatic hydrocarbon (PAH), has been used extensively as a tool to initiate mammary carcinogenesis and subsequent chemoprevention. On the other hand, selenium (Se) is potentially useful in oncology because this element possesses anticarcinogenic and chemopreventive properties. Se-containing enzymes such as glutathione peroxidase (GPx) play an important role in PAH metabolism and detoxification. In this study, rats were administered a single, oral dose of DMBA (12 mg). In the Se group, rats received 20 microg Se daily via gavage, starting 2 wk before the DMBA administration and continued for 1 wk. One hundred twenty days after DMBA administration the rats were sacrificed and toxicity was evaluated using histopathological and biochemical criteria. Five rats (30%) died in the DMBA group within the study period, whereas no death occurred in the DMBA-Se-treated group. Malignant tumor frequency was 33% in the DMBA group, while no malignant tumors occurred in the DMBA-Se-treated group. Some inflammatory changes rather than epithelial changes were found upon histopathological examination. GPx activity and blood urea nitrogen levels were higher and kidney GST activity was lower in the DMBA-Se-treated group compared to DMBA alone. In conclusion, Se appears to be effective in preventing some of the adverse effects associated with DMBA.

Molecular regulation of angiogenesis and tumorigenesis by signal transduction pathways: evidence of predictable and reproducible patterns of synergy in diverse neoplasms

A large number of oncogenes, tumor suppressor genes, and signal transduction pathways have been described. Currently, a framework that allows prediction of tumor behavior based upon oncogenes, tumor suppressors, and signal transduction pathways is lacking. In 1869, Mendeleev published a periodic table of elements which allowed prediction of properties of elements based upon atomic weights that allowed prediction of chemical and physical properties of elements yet to be discovered. In this paper, I will discuss recurrent patterns of synergy found in the literature and our laboratory between tumor suppressor genes, oncogenes, and signaling pathways that allows one to predict the signaling pathway in a given tumor based upon the inactivation of a tumor suppressor gene. These patterns can be found in multiple different human neoplasms. Conversely, one can predict the inactivation of a tumor suppressor based upon the activation status of a signaling pathway. This knowledge can be used by a clinician or pathologist with access to immunohistochemistry to make predictions based upon simple technologies and determine the signaling pathways involved in a patient's tumor. These strategies may be useful in the design of prevention and treatment strategies for cancer.

Gut glutathione metabolism and changes with 7,12-DMBA and glutamine

INTRODUCTION

The mechanism by which oral glutamine (GLN) prevents 7,12-dimethylbenz(a)anthracene (DMBA)-induced breast cancer is unknown. While GLN triples the negative extraction of gut glutathione (GSH) in rats, DMBA significantly disrupts it. Actual gut GSH flux has not been reported. We hypothesized that the gut is a producer of GSH; DMBA blocks gut GSH production and supplemental oral GLN antagonizes this effect.

MATERIALS AND METHODS

Eighty Sprague-Dawley rats were randomized to four groups (n = 20/group): DMBA + GLN, DMBA + FA, OIL + GLN, OIL + FA. Rats (age 50 days) were gavaged with a one-time dose of 100 mg/kg DMBA or oil. Rats were gavaged with AES-14 as GLN (1 gm/kg/day) or an isonitrogenous amount of Freamine (FA) from 1 week before till sacrifice at 1 week after DMBA (greatest effect on gut GSH extraction). Arterial and portal blood was taken for GLN and GSH levels, and blood flow was measured using (14)C-PAH. Gut GLN and GSH fluxes (uptake or production) were calculated.

RESULTS

DMBA abrogated the normal GSH production (negative flux) in OIL + FA while not affecting GLN metabolism. GLN maintained GSH production in DMBA + GLN.

CONCLUSIONS

Oral GLN restores to normal GSH production in DMBA-treated animals suggesting one of the mechanism(s) by which GLN prevents breast cancer in this model. Unchanged uptake of GLN in the DMBA-treated animals may indicate a block in GSH transport rather than actual intracellular production.

Effect of glutamine on glutathione, IGF-I, and TGF-beta 1

BACKGROUND

Our previous results have showed that oral glutamine (GLN) supplementation decreased carcinogenesis in 7,12-dimethylbenz[a]antracene (DMBA) breast cancer model. We also have found that GLN raises blood glutathione (GSH) levels in an implantable breast cancer model. The process of tumor growth was accompanied by depressed GSH production and increased levels of insulin-like growth factor-I (IGF-I) and transforming growth factor beta1 (TGF-beta 1). GSH is counter-regulatory to IGF-I. We therefore hypothesized that in DMBA model of breast cancer, the increased GSH levels seen with oral GLN would be associated with lowered levels of IGF-I &TGF-beta(1).

METHODS

Time-dated pubertal Sprague-Dawley rats were gavaged at time 0 with 1 g/kg/day glutamine (GLN) (n = 18), isonitrogenous Freamine (FA) (n = 18), or water (H(2)O) (n = 18). Rats were further randomized on day 7 to 100 mg/kg DMBA or oil. After 14 days, the animals were sacrificed and blood GSH, IGF-1, TGF-beta 1, breast tissue, and gut mucosa GSH levels were measured.

RESULTS

Oral GLN increased significantly blood, breast tissue, and gut mucosa levels of GSH in both DMBA and control groups in comparison with the control groups not treated with GLN. At the same time, the levels of blood IGF-I and TGF-beta 1 decreased significantly in both DMBA-treated and control groups. DMBA did not significantly affect any of these levels. CONCLUSIONS ;Oral GLN increased GSH levels and lowered IGF-I and TGF-beta 1 in a range that is considered clinically significant. However, the effect of GLN in maintaining normal gut GSH production in the presence of DMBA was much more significant. Inconsistent with our hypothesis, reduction in IGF and TGF-beta 1 levels did not correlate with DMBA's effect on gut GSH production.

Timing of oral glutamine on DMBA-induced tumorigenesis

INTRODUCTION

A single dose of oral 7,12-dimethylbenz(a)anthracene (DMBA) in pubertal rats causes breast tumors by 11 weeks and is associated with ablation of the normal gut glutathione (GSH) production for up to 4 weeks. We hypothesized that glutamine (GLN), known to restore the gut GSH production inhibited by DMBA, given only during this 4-week period, would prevent breast cancer initiation.

METHODS

160 Female Sprague-Dawley rats were divided to 10 groups (n = 16/group): Long Term (LT): DMBA + GLN, DMBA + FA, DMBA + H2O, OIL + GLN, OIL + FA, OIL + H2O; Short Term (ST): DMBA + GLN, DMBA + FA, OIL + GLN, OIL + FA At age 50 days old, rats received a one-time dose of 100 mg/kg DMBA or sesame oil. LT rats were gavaged daily with isonitrogenous GLN, (FA), or water (H2O) the entire study. ST rats were gavaged with GLN, freamine, or H2O the first 4 weeks and then H2O the remaining 7 weeks. All rats were pair-fed defined chow. Rats were sacrificed at 11 weeks, observed for tumors, blood assayed for GLN, GSH, gut GLN and GSH and uptake or production calculated using labeled C-14-PAH.

RESULTS

ST and LT GLN were equally effective in preventing tumor formation. GLN doubled gut GSH production in LT animals as compared to all other groups (P < 0.05). Control rats developed no tumors and had superior gut GSH production as compared with tumor-bearing rats.

CONCLUSIONS

Oral GLN when given only during the 4 weeks of known gut GSH ablation had the same tumor prevention efficacy as prolonged GLN administration. Not previously reported, GLN appears to affect the initiation of tumor formation in this model.