The irradiation effects on the cytoskeletons of C3H/He mouse mammary tumor cells and vascular basement membrane in relation to vascular invasion: a model of intraoperative radiotherapy.

We investigated the short-term effects of a single high-dose radiation upon transplanted MM46 tumor cells in mice by means of immunohistochemistry and electron microscopy. The irradiation induced: 1) giant cell formation from the 3rd day, 2) arrest of tumor cell mitosis in prophase and metaphase due to the disorganization of the mitotic spindles, 3) changes in immunoreactivity of laminin and cytoskeletons, and 4) multilayering of the vascular basal lamina and perivascular fibrosis. The above findings suggest a decrease in tumor cell compliance, growth and invasiveness and the potentiation of defensive host responses against vascular invasion after irradiation. The analysis of the temporal sequences of the events indicates that the time lapse between the optimal host response, tumor growth and invasion constitutes a critical period.