High Level of Radiation-Induced Heat Shock Protein with a Molecular Weight of 27 and 70 kDa is the Hallmark of Radioresistant SP Cells of MCF-7 Breast Cancer Culture.

Abstract

As previously indicated, side population cells (side population, SP) of breast cancer line MCF-7 have greater resistance to the action of low-LET radiation compared to other tumor cells (non SP, NSP). One can assume that one possible reason for the high radioresistance of this fraction of tumor cells is the increased expression of different heat shock proteins (HSP) before and/or after radiation exposure. To verify this hypothesis, we investigated the expression of HSP27 and HSP70 in these populations of cells-before and after irradiation at a dose of 5.0 Gy. The study was performed using scanning microscopy for NSP and SP cells after sorting and immunocytochemical staining. A substantial increase of HSP27 and HSP70 in SP cells was found after irra- diation as'compared with the control. In NSP cells the HSP27 level increased in response to radiation exposure, but to a lesser extent than in SP cells, while the content of HSP70 did not change after irradiation. The results confirm the assumption about HSP27 and HSP70 participation in the formation of SP cell radioresistance by the example of MCF-7 line.