THE NON-VARIATION IN RADIOSENSITIVITY OF DIFFERENT PROLIFERATIVE STATES OF HUMAN GLIOMA-CELLS

The radiosensitivity of the human glioma cell line U-343MGa, while gro wing as spheroids and as conventional monolayers, was studied. The sph eroids were first irradiated with Co-60 photons, and the radiosensitiv ity was then analysed in different cell layers with varying proliferat ive activity. The different cell layers were isolated by automated seq uential trypsinization. A relatively high radioresistance was found in all analysed cell layers, and the inner, mainly quiescent cells, were as resistant as the outer proliferating cells. It was, in parallel ex periments on monolayers, shown that serum starved quiescent cells were as resistant as proliferating cells, and that direct cellular cloning did not give lower cell survival values than delayed cloning, as has been shown for other cell types. Thus, the studied glioma cells were e qually radioresistant under all tested proliferative conditions when c onventional low-LET radiation was applied. The spheroids were then irr adiated with cyclotron accelerated helium ions with an intermediate io nization density, LET approximate to 55 KeV/mu M, and this gave a clea r decrease in survival in all cell layers.