Stable radiobiological features in a genetically unstable glioblastoma cell line.

In a human glioblastoma (grade IV) cell line, A7, the change in chromosome number, growth characteristics, radiosensitivity and DNA-repair capacity were determined during continuous culture over approximately 1300 generations. The median chromosome number fell from 101 to 85 while a remarkable variability was retained. The net population doubling time shortened from 21 to 16 h but no alterations were detected either in radiosensitivity or DNA-repair capacity, as measured by colony and plasmid-reconstitution assays respectively. Reviewing radiosensitivity data from the literature, it is considered that the relative radioresistance of glioblastomas might be inherited from the normal tissue from which they are derived.