Effect of zinc supplementation on the expression of metallothionein and p53 in mus musculus with induced metastatic breast cancer
|Background: Zinc is considered an important regulator of apoptosis, cell cycle and oxidative stress and thus is interesting from the perspective of tumour development. The aim of this study was to evaluate the effect of zinc supplementation on metallothionein 1 and 2, metal-regulatory transcription factor 1 (MTF-1) and p53 gene expression on animal model with induced advanced breast cancer. Material and methods: 40 Balb/c female mice were equally distributed to 2x2 groups according to tumor presence (tumour/control) and zinc supplementation (supplemented/not supplemented). 4T1 metastatic breast cancer cell line was used to induce neoplatic process and total 0.15 mg/g zinc sulphate divided in 4 doses was applied to mice. After 1 month, animals were inducted to anaesthesia, the weight and size of tumor was measured and following organs were isolated: primary tumour, brain, liver, lung, spleen, kidney, blood. RNA was isolated and qRT-PCR was performed with b-actin as housekeeping gene. Following TaqMan probes were used: Mm 00485274_m1 Mtf1; Mm 01731290_g1 Trp53; Mm 00496660_g1 Mt1; Mm 04207591_g1 Mt2. Factorial ANOVA with Bonferroni post-hoc test were used for statistical analysis. Animal experiments were approved by Ethic commission Faculty of Medicine, Masaryk University, Brno, CZ. Results: The tumour size of zinc-treated animals was 40% smaller (p = 0.04) in the end of experiment. Significant differences in the gene expression were observed between organs; while significantly highest levels were observed in liver and kidney, significantly lowest levels were determined in primary tumor, lung and spleen. Brain showed significantly elevated expression of MTF-1 and MT2 only. In mice with tumours, hepatic MT-2 and -1 expression increased 22-fold and 3-fold when exposed to Zn treatment (p < 0.05). Animals without Zn supplementation did not show similar trend. In kidney, level of MT1 and 2 was significantly lower in cancer mice. When zinc-treated, MT level increased up to the level as in healthy controls. In other tissues there are no such characteristics changes in MT expression. Conclusions: Zinc supplementation significantly reduces the progression of breast cancer, most likely through metallothionein-mediated pathways. Liver and kidney are tissues with highest zinc turnover, with MT level being decreased in cancer cases and restored up to control level, when treated with zinc.