Because the mammary gland tissues used for immunohistochemical staining and real-time PCR were independent samples, we could not correlate the expression of nuclear EGFR and the expression levels of cyclin D1 mRNA. However, a trend (tendency) of positive correlation was established between the expression Fosbretabulin mouse level of nuclear EGFR and the expression level of cyclin D1 mRNA for tumor tissue samples that did not reach significance (r s = 0.883, P = 0.059). These findings also suggest that nuclear EGFR might partly regulate the expression of cyclin D1. Figure 3 Expression of cyclin D1 in mammary glands and LGX818 in vitro spontaneous breast cancer tissues from TA2

mice. 3A, Cyclin D1 staining could be observed occasionally in epithelial cells from five month-old TA2 mice (IHC, 200×). 3B, Cyclin D1 staining was present in the nuclei of epithelial cells in mammary gland tissues of spontaneous breast cancer-bearing TA2 mice (IHC, 200×). 3C, Cyclin D1 staining was present in the nuclei of CCI-779 supplier hyperplastic epithelial cells of spontaneous breast cancer-bearing TA2 mice (IHC, 200×). 3D, Cyclin D1 staining was also present in spontaneous breast cancer tissues of TA2 mice (IHC, 200×). The Labeling Index of cyclin D1 increased apparently from Group A to Group

C. Figure 4 Expression of PCNA in mammary glands and spontaneous breast cancer tissues from TA2 mice. PCNA staining could be observed in the

nuclei of epithelial cells from five month-old TA2 mice (4A) and spontaneous breast cancer-bearing TA2 mice (4B) (IHC, 400×). PCNA staining was present in the nuclei of spontaneous breast cancer cells from TA2 mice (4C) (IHC, 400×). Table 4 Cyclin D1 and PCNA labeling index of normal mammary glands and cancer tissues from spontaneous breast cancer -bearing TA2 mice (%)   n Cyclin D1 PCNA Group B    Nucleus EGFR (+) 15 15.15 ± 5.16* 37.81 ± 12.77    Nucleus EGFR (-) 13 8.77 ± 7.95 33.71 ± 15.78 Group C    Nucleus EGFR (+) 11 31.17 ± 12.50* 44.9212.01    Nucleus EGFR (-) 17 18.54 ± 17.98 33.9413.92 *:compared to samples without nuclear EGFR expression, P < 0.05 Group B: normal mammary glands from spontaneous breast cancer-bearing TA2 Methocarbamol mice; Group C: spontaneous breast cancer tissue from TA2 mice. Discussion Breast cancer is one of the most common malignant tumors in adult females and develops as a result of altered expression of multiple genes and abnormal cellular pathways. In recent years, accumulating data has shown that alterations of the stromal compartment can also influence tumor cell behavior through paracrine growth factor pathways[9]. Proteoglycans are the main constituents of the ECM, and their synthesis and degradation are regulated by many effectors that control the development and function of the mammary gland.