The effectiveness of green tea in protection against cancer is attributed to its catechins or polyphenolic antioxidants. The aim of the present investigation is to study the effect of green tea extract on mammary tumor in Swiss mice using histopathological, ultrastrustural, and immunohistochemical techniques. Mice were divided into 3 groups, two treated groups, and one control group. All groups were injected with mammary tumor cells. Group II received 5mg green tea extract in 0.2 ml distilled water/mice for 14 days before injection, while Group III received 5 mg green tea daily 14 days after the tumor injection. In comparison with the control group, H & E stained sections from cultured tumors of group II revealed that the malignant tumor cells invade the surrounding adipose tissue and skeletal muscle in addition to appearance of wide areas of necrosis and apoptotic figures. Furthermore, ultrastructural studies showed regular nuclear envelope, patches of heterochromatin, and early sign of apoptosis. While sections of cultured tumors in group III showed presence of increased number of apoptotic bodies with reduced tumor thickness, and lack of invasion of the surrounding muscles. EM examination showed aggregation of heterochromatin, damaged mitochondria, in addition to dilated profiles of endoplasmic reticulum studded with ribosomes. Examination of vascular endothelial growth factor (VEGF) immunostained sections, group. II showed high expression of proliferating newly formed blood vessels at the periphery of the tumor. On the other hand, sections of group III revealed low count of proliferating blood vessels. Animals received green tea after tumor injection showed heterogeneous moderate staining of p53 marking the apoptotic cells near the areas of necrosis and strong expression of p53 in tumor of animals received green tea before injection. In conclusion, green tea inhibited the tumor growth through the induction of apoptosis, and prevention of blood vessels formation which are important for introducing nutrients and oxygen to the growing tumor.
Key words: EM, VEGF, p53, Mammary Tumor Cells, and Green Tea.