Genetic Component in Rat Mammary Carcinogenesis

Aryl Hydrocarbon Hydroxylase Activity in Spontaneous Mammary Tumors in Rat

“…In the present study, about two thirds (16/25) of rats aged from 1 to 2 Vi years developed tumors, whereas only a few younger females developed tumors during the observation time. The proportion of malignant tumors in our rats was about one third (10/29), which is the same [13] …”

“…The spontaneous incidence of mammary tumors in female rats varies considerably be tween strains; incidences from 10 to 90% have been reported [ 12], In the Sprague-Dawley strain, the spontaneous mammary tumor rate often approaches 50% of female rats dur ing their life span, with tumors generally oc curring during the second year of life [12,13]. In the present study, about two thirds (16/25) of rats aged from 1 to 2 Vi years developed tumors, whereas only a few younger females developed tumors during the observation time.…”

Gene expression and epigenetic profiles of mammary gland tissue: Insight into the differential predisposition of four rat strains to mammary gland cancer

“…Some studies have shown, for example, that acetylation of histone H3 lysine 9 (acH3K9) or lysine 14 (acH3K14), which is associated with a more relaxed chromatin structure, is able to restrict histone 3 lysine 9 methylation (meH3K9), a repressive modification [40]. The goal of this study was to identify differences in the genetic and epigenetic background of four commonly used laboratory strains, female ACI, Long-Evans, Fischer-344 and Sprague Dawley [7][8][9]18,41,42], that may account for differences in spontaneous mammary tumors.…”

“…For example, the ACI rat, which exhibits high sensitivity to elevated levels of estrogen, with a remarkably reduced latency of tumor development, is used extensively in studies of estrogeninduced mammary cancer [5][6][7]. In comparison, Copenhagen (COP) and Fischer-344 rats are relatively resistant to estrogen-induced mammary carcinogenesis and can be used to provide insight into protective factors [7][8][9]. ACI rats have a very low level of spontaneous and radiation-induced mammary tumors, while the majority of female Fischer-344, Long-Evans and Sprague Dawley rats are more prone to these tumors, suggesting that cancer susceptibility involves a complex array of predetermining factors [5,[9][10][11][12][13][14][15][16][17][18]].…”

“…In comparison, Copenhagen (COP) and Fischer-344 rats are relatively resistant to estrogen-induced mammary carcinogenesis and can be used to provide insight into protective factors [7][8][9]. ACI rats have a very low level of spontaneous and radiation-induced mammary tumors, while the majority of female Fischer-344, Long-Evans and Sprague Dawley rats are more prone to these tumors, suggesting that cancer susceptibility involves a complex array of predetermining factors [5,[9][10][11][12][13][14][15][16][17][18]]. Szpirer and Szpirer described the susceptibility of various strains to carcinogen-and hormone-induced mammary cancer and to spontaneous mammary cancer [19].…”