CISPLATIN INDUCES RADIOPROTECTION IN HUMAN T98G GLIOMA-CELLS

Malignant gliomas are often treated with cisplatin (cis-diamminedichlo roplatinum(II), CDDP) and radiation but results remain unsatisfactory. To investigate whether CDDP induces radioresistance in glioma, T98G h uman glioblastoma cells were pretreated 5 times with 10(-6) M CDDP for 24 hours and then the sensitivity of wild type (wt) and pretreated ce lls towards radiation (9Gy Co-60) and CDDP was tested in a colorimetri c assay (MTT). The growth rates of wt and pretreated cells were 1.8 +/ - 0.2 and 3.1 +/- 0.2 respectively (p=0.000155) 216 hours post radiati on. Pretreated cells also developed resistance to CDDP (resistance fac tor 2.35). Glutathione (GSH) which potentially mediates resistance to both treatments was measured. Incubation for 6 hours with 10(-5) M CDD P increased GSH levels by a factor of 2.28 (p<0.0001). However, neithe r basal nor increased levels differed between wt and pretreated cells. These data show that CDDP pretreatment can induce resistance against radiation and CDDP independently of GSH.