BCNU-resistant human glioma cells with over-representation of chromosomes 7 and 22 demonstrate increased copy number and expression of platelet-derived growth factor genes.
We used standard karyotypic analyses of first-division cells to identify a subpopulation of cells in primary malignant gliomas with over-representation of chromosomes 7 and 22. These cells are a minor subpopulation in the primary tumor but become the dominant population after treatment 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 contain genes important to the growth of BCNU-resistant cells. Southern blot hybridization analyses demonstrate an increased copy number of the genes encoding platelet-derived growth factor (PDGF) A-chain and B-chain, which have been mapped to chromosomes 7 and 22, respectively. Reverse transcription followed by polymerase chain reaction (RT-PCR) analysis demonstrates increased expression of these genes. In addition, these cells secrete a mitogenic factor that stimulates 3H-thymidine uptake in NIH 3T3 cells. This factor is sensitive to anti-PDGF antibodies and beta-mercaptoethanol, but not to anti-EGF antibodies. These data suggest that autocrine and/or paracrine mechanisms occur in human malignant gliomas, and that over-expression of PDGF may play a role in the growth of BCNU-resistant cells in these tumors.
Scheck
A C
AC
Neuro-Oncology Research, Barrow Neurological Institute of St. Joseph's Hospital, Phoenix, AZ 85013.
Mehta
B M
BM
Beikman
M K
MK
Shapiro
J R
JR
D001483:Base Sequence; D014408:Biomarkers, Tumor; D015139:Blotting, Southern; D002330:Carmustine / Q000494:pharmacology*; D002869:Chromosome Aberrations; D002892:Chromosomes, Human, Pair 22; D002897:Chromosomes, Human, Pair 7; D004273:DNA, Neoplasm / Q000032:analysis; D004351:Drug Resistance / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000235:genetics*; D005909:Glioblastoma / Q000235:genetics*; D006133:Growth Substances / Q000032:analysis / Q000378:metabolism; D006801:Humans; D007621:Karyotyping; D008969:Molecular Sequence Data; D010982:Platelet-Derived Growth Factor / Q000235:genetics*; D011003:Ploidies; D016133:Polymerase Chain Reaction; D012334:RNA, Neoplasm / Q000032:analysis; D017479:Receptors, Platelet-Derived Growth Factor / Q000235:genetics; D014407:Tumor Cells, Cultured
D014408:Biomarkers, Tumor; D004273:DNA, Neoplasm; D006133:Growth Substances; D010982:Platelet-Derived Growth Factor; D012334:RNA, Neoplasm; D017479:Receptors, Platelet-Derived Growth Factor; D002330:Carmustine