Chemopreventive Effect Of HCG On Rat Mammary Carcinogenesis

Objective:To explore the chemopreventive effect and mechanism of human Chorionic Gonadochopin(hCG) on mammary carcinogenesis, Sprague-Dawley rats were treated prior to carcinogen N-Nitroso-N-methylurea(MNU) administration, the incidences of mammary adenocarcinomas and the proportions of various kinds of mammary gland structures were evaluated.Materials and method:Sixty female,virgin,Sprague-Dawley rats were divided into five groups randomly. Early hCG intervention group:12 rats received daily intraperitoneal injection(i.p.) of hCG for 21 days from 50 days old,received MNU i.p. when 134, 141, 217, 262 days old. Later hCG intervention group:12 rats received daily hCG i.p. for 21 days from 92 days old, received MNU i.p. when 134, 141, 217, 262 days old. TAM group:12 rats received daily hypodermic injection of TAM for 21 days from 92 days old. Exposure group:12 rats received MNU i.p. when 134, 141, 217, 262 days old. Control group: 12 rats remained undisturbed. All the 60 rats were killed when 276 days old, the mammary tissues were obtained for pathological analysis,the incidences of adenocarcinomas and the proportions of TEB,TD,AB,Lob were evaluated in these groups.ResultsThe incidence of mammary adenocarcinomas in early hCG intervention group, later hCG intervention group,TAM group,exposure group,control group was 8.3%(1/12), 16.7%(2/12), 9.1%(1/11), 60.0%(6/10) and 0(0/12), respectively. The incidence of adenocarcinomas in early hCG intervention group and TAM group was different significantly from exposure group,respectively,while the incidence of adenocarcinomas in later hCG intervention group was not different significantly from exposure group.The incidence of adenocarcinomas in early hCG intervention group and later hCG intervention group was not different significantly from TAM group,respectively,the incidence of adenocarcinomas in early hCG intervention group was not different significantly from later hCG intervention group.The proportions of mammary gland structures in early hCG intervention group and later hCG intervention group were different significantly from TAM group,exposure group and control group.The proportions of Lob in early hCG intervention group and later hCG intervention group (32.6%,30.9%) were higher obviously than TAM group,exposure group and control group (8.5%,8.6%,10.2%), the proportions of TD in early hCG intervention group, later hCG intervention group (8.8%,10.3%) were lower obviously than TAM group,exposure group and control group (35.3%,37.7%,31.0%), the proportions of TEB in early hCG intervention group, later hCG intervention group (1.4%, 1.4%) were lower sligtly than TAM group,exposure group and control group (2.0%,2.6%,1.7%). The proportion of Lob in adenocarcinoma-absent group (29.3%) were higher obviously than adenocarcinoma- present group(17.4%),the proportion of TD in adenocarcinoma-absent group(12.6%) were lower obviously than adeno- carcinoma-present group(25.8%),the proportion of TEB in adenocarcinoma-absent group (1.5%) were lower slightly than adenocarcinoma- present group(2.1%). Conclutions:The administration of hCG could decrease the incidence of mammary adenocarcinomas induced by MNU on SD rats,the protective effect might be equivalent to TAM,and the duration of chemopreventive effect was long.The chemopreventive effect of hCG on the rat mammary carcinogenesis might be derived from the differentiation of mammary structures.