BCNU-RESISTANT HUMAN GLIOMA-CELLS WITH OVER-REPRESENTATION OF CHROMOSOME-7 AND CHROMOSOME-22 DEMONSTRATE INCREASED COPY NUMBER AND EXPRESSION OF PLATELET-DERIVED GROWTH-FACTOR GENES

We used standard karyotypic analyses of first-division cells to identi fy a subpopulation of cells in primary malignant gliomas with over-rep resentation of chromosomes 7 and 22. These cells are a minor subpopula tion in the primary tumor but become the dominant population after tre atment in vitro of the cells with the chemotherapeutic agent 1,3-bis(2 -chloroethyl)-1-nitrosourea (BCNU). The selection for a cell with this specific karyotypic abnormality suggests that these chromosomes conta in genes important to the growth of BCNU-resistant cells. Southern blo t hybridization analyses demonstrate an increased copy number of the g enes encoding platelet-derived growth factor (PDGF) A-chain and B-chai n, which have been mapped to chromosomes 7 and 22, respectively. Rever se transcription followed by polymerase chain reaction (RT-PCR) analys is demonstrates increased expression of these genes. In addition, thes e cells secrete a mitogenic factor that stimulates H-3-thymidine uptak e in NIH 3T3 cells. This factor is sensitive to anti-PDGF antibodies a nd beta-mercaptoethanol, but not to anti-EGF antibodies. These data su ggest that autocrine and/or paracrine mechanisms occur in human malign ant gliomas, and that over-expression of PDGF may play a role in the g rowth of BCNU-resistant cells in these tumors. (C) 1993 Wiley-Liss, In c.