Promotion by the alpha-adrenoceptor agonist phenylephrine, but not by the beta-adrenoceptor agonist isoproterenol, of gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine in Wistar rats

β-Adrenoceptor Activation in Breast MCF-10A Cells Induces a Pattern of Catecholamine Production Similar to that of Tumorigenic MCF-7 Cells

Adrenaline, which participates in the neuroendocrine response that occurs during stress and perimenopause, may be tumorigenic. This exploratory study aimed at investigating whether non-tumorigenic and tumorigenic human breast epithelial cell lines are able to synthesize adrenaline. The study was carried out in non-tumorigenic (MCF-10A) and tumorigenic (MCF-7) human breast cell lines. Expression of enzymes involved in adrenaline synthesis was characterized by RT-qPCR, immunocytochemistry and western blot. Catecholamines and analogue compounds were quantified by HPLC-ECD. Functional assessment of the impact of drugs on cells’ tumorigenic potential was assessed by determination of cell viability and clonogenic ability. Both MCF-10A and MCF-7 cells produce catecholamines, but the capacity to produce adrenaline is lower in MCF-10A cells. β-adrenoceptor activation increases the capacity of MCF-10A cells to produce adrenaline and favor both cell viability and colony formation. It is concluded that exposure of human breast epithelial cells to β-adrenoceptor agonists increases cell proliferation and the capacity to produce adrenaline, creating an autocrine potential to spread these adrenergic effects in a feed-forward loop. It is conceivable that these effects are related to tumorigenesis, bringing a new perspective to understand the claimed anticancer effects of propranolol and the increase in breast cancer incidence caused by stress or during perimenopause.

The role of propranolol as a radiosensitizer in gastric cancer treatment

Purpose

The National Comprehensive Cancer Network guidelines indicate that radiotherapy in gastric cancer shows limited effectiveness at reducing the growth of gastric cancer. Therefore, enhancing the sensitivity and effect of radiotherapy with propranolol, a β-adrenoceptor antagonist, could reduce tumor growth. The role of propranolol as a radiosensitizer has not been adequately studied; therefore, the purpose of the present study is to evaluate the effect of propranolol as a radiosensitizer against gastric cancer in vivo.

Methods

Sixty-four male nude mice bearing tumor xenografts were randomly divided into four groups. Cell culture was performed using the human gastric adenocarcinoma cell line SGC-7901. Mice with tumor xenografts were treated with propranolol, isoproterenol, and radiation. The data for tumor weight and volume were obtained for statistical analyses. Furthermore, the expression levels of COX-2, NF-κB, VEGF, and EGFR were examined using immunohistochemical techniques and Western blotting.

Results

The growth in the volume and weight of the tumor was lower in mouse models treated with propranolol and radiation therapy compared to the other groups. Decreased expression of NF-κB was also observed in treatment groups where both propranolol and radiation were used, leading to the reduction of COX-2, EGFR, and VEGF expression compared to that in the other groups.

Conclusion

The present study indicated that propranolol potentiates the antitumor effects of radiotherapy in gastric cancer by inhibiting NF-κB expression and its downstream genes: VEGF, EGFR, and COX-2.

Effect of mirtazapine on MNNG-induced gastric adenocarcinoma in rats

OBJECTIVE

In this study, anticancer effects of mirtazapine on rats were investigated in an adenocarcinoma model induced by N-methyl-N-nitro-N-nitrosoguanidine (MNNG) and compared with those of cisplatin.

MATERIALS AND METHODS

For this purpose, 10 mg/kg doses of mirtazapine were administered orally to one group of rats, while 1 mg/kg doses of cisplatin were administered intraperitoneally to another group. At 1 hour after administration, 200 mg/kg doses of MNNG were given orally to both groups. MNNG administration was repeated once every 10 days through 3 months, after which period, gastric tissue was taken and pathologically evaluated.

RESULTS

Mirtazapine prevented adenocarcinoma induction by MNNG in rats to a greater extent than cisplatin. Some of the rats receiving cisplatin demonstrated severe dysplasia in gastric samples and others exhibited mild dysplasia. Rats given mirtazapine were not observed to suffer severe dysplasia, only mild dysplasia being observed.

CONCLUSION

For adenocarcinoma induced by MNNG on rats, mirtazapine was determined more effective than cisplatin. In order to make statement about mechanism of anticancer activity of mirtazapine, wider studies are required.

Occurrence of anticancer activity of prednisolone via adrenalectomy and inhibition of adrenaline in rats

In this study, the anticancer effect of prednisolone was investigated using rats with normal endogen adrenaline levels (intact), reduced adrenaline levels (metyrosine-induced) and adrenaline deficiency (adrenalectomized) via gastric adenocarcinoma model. Gastric adenocarcinoma was induced with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). According to our experimental results, prednisolone could not prevent MNNG-induced adenocarcinoma when used alone in intact rats. There were neither macroscopic nor microscopic signs of cancer in the rat groups that received metyrosine and prednisolone. However, dysplasia occurred in the stomachs of 2 of 10 rats that received metyrosine and prednisolone. There was no adenocarcinoma genesis in the stomachs of adrenalectomized rats that received prednisolone alone. However, yohimbine (a selective blocker of alpha2-adrenoreceptors) pretreatment in adrenalectomized rats negated the anticancer effect of prednisolone. In conclusion, prednisolone was shown not to be an anticancer agent in intact rats when used alone; however, it has anticancer effects in rats whose adrenaline levels were reduced via adrenalectomy or metyrosine, which is a catecholamine synthesis inhibitor.

Alpha1-adrenoceptor stimulation enhances experimental gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine in Wistar rats

The effect of prolonged administration of the norepinephrine-mimicking agent metaraminol, the alpha1-adrenergic agonist phenylephrine and the alpha2-adrenergic agonist clonidine on the incidence of gastric cancers induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), the ornithine decarboxylase activity of the gastric cancer and the labeling index of the gastric mucosa were investigated in Wistar rats. Rats received s.c. injections of metaraminol, phenylephrine or clonidine every other day after 20 weeks of oral treatment with MNNG. At week 52, administration of metaraminol and phenylephrine at the higher dose significantly increased the incidence of gastric cancers, the ornithine decarboxylase activity of the gastric cancers and the labeling index of the antral epithelial cells. Administration of phenylephrine at the lower dose and clonidine at both doses had no significant effect on the incidence of gastric cancers, the ornithine decarboxylase activity of the gastric cancers or the labeling index of the gastric mucosa. Our results suggest that adrenoreceptor stimulation enhances gastric carcinogenesis and that such enhancement is mediated through alpha1-adrenoceptors without alpha2-adrenoceptor involvement.