Effect Of Melatonin On Mammary Cancer Induced By DMBA In Rat

ObjectiveTo study the effection and mechanism of melatonin on mammary cancer induced by DMBA in rat.MethodFifty-seven 6-week-old female Wistar rats, weighted around 110-130g were used. They were housed (ten animals per cage) under the conditions of controlled temperature(21±2)℃. The animals had free access to commercial pelleted rat food and water, they were randomly assigned to three experimental groups of 19 animals each.: group A received a daily administrationof melatonin10 mg/kg dailyfor 14 days from6 to8weeks of age..group B received a dailyadministration of melatoninl 0 mg/kg dailyfor 14 daysfrom 8 to 10 weeks of age. They were given a single intragastricadministration of DMBA 200mg/kg given at noon at 8 weeks of age . Experiment last 26 weeks, Observe rats twice a week, record occurrence time and diameter of tumor, the number of tumor, Rats were feeding for 24 weeks after DMBA-induced and sacrificed . cut tumor tissues do conventional HE staining, using a light microscope pathomorphological study on tumor cells, immunohistochemical stainingResults1. Tumor incidence: Group A is 4.4%, group B is 50%, group C is 82.35%, in group A, group B, the tumor incidence rate was lower than that in group C (P <0.05). 2. Tumor latency: tumors in the animals, the average incubation period for 139.6 days in group A, group B 131.4 days, and 115.2days for group C, the incubation period significantly prolong in group A and B (P <0.01).3. The average tumor volume: tumor size formula (V = 1/2 ab~2), group A426.8, group B733.3, group C2127.1, statistically significant (P <0.05).4. Optical microscope: Group A 11 breast cancer of eight rats are all invasive ductal cancer, group B 14 breast tumors of nine rats are 13 invasive ductal carcinoma, cell differentiation better infiltration degree lower than the control group, and in group C 22 breast tumors of 14 rat are breast cancer, 20 are invasive ductal carcinoma, two pilary carcinomaand ,groupC significant difference under Light microscope structure.5. Immunohistochemistry: Ki67 positive rate in group A is 41.7%, Group B is 42.8% in group C is 77.3%, group C and group A, group B are significant difference (P <0.05).ER positive rate in group A is 75%, Group B is 71.4% in group C is 36.4%, group C is significant difference to group A and group B (P <0.05).ConclusionWe can get stable model of breast cancer.by DMBA intragastric administration melatonin significantly inhibited the occurrence and development of breast cancer induced by DMBA in rats, inhibitory effect of melatonin on breast cancer may be through the role of estrogen receptor pathway, the specific mechanism of molecular biology pending further study.