RESUMO
Cell kinetic and histologic parameters of six xenografted tumours with volume doubling times ranging from 6 to 43 d were investigated in order to obtain kinetic information on a panel of tumours to be used in radiobiological studies. The six tumours covered a range of histologies and their DNA indices varied from 2.7 to 1.4. The length of the cell cycle (Tc), potential doubling time (Tpot) and labelling index (LI) were determined by continuous labelling with [3H]TdR and autoradiography in three tumours, Tc varied from 30 to 40 h. Determinations of the length of the S phase (Ts) were found to be less reliable by this method. Data on Ts and LI were also determined in all six tumours using bromodeoxyuridine (Brd) labelling and the single sample method: values of Tpot were slightly longer than those obtained via the autoradiographic method. In addition, multiple samples were taken after BrdU labelling. Tc was determined by fitting the data obtained from mid-S, mid-G2 and mid-G1 windows to curves described by a damped oscillator. Data obtained via the mid-S window were found to be most reliable. Generally, cell cycle times obtained by the BrdU method were longer than those observed with the autoradiographic method. Differences between the two methods could be explained by inaccuracies in the determination of Ts, LI and Tc and differences in the experimental approach. We consider the BrdU labelling method to be a suitable alternative for the time-consuming autoradiography, if data on Ts or Tpot are sufficient. Due to difficulties in the reproducibility of the immunofluorescence staining and asynchronization of cells approximately 10 h after labelling, the method of windows analysis was affected by similar problems to those observed in interpretation of percentage labelled mitosis (PLM) curves. However, the method may serve as an alternative to determine cell cycle times in vitro and, if improved technically, in vivo. Careful comparison of the data obtained from mid-S, mid-G1 and mid-G2 windows may increase the reliability of the determination of cell kinetic parameters.
