Reduced tumorigenicity of rat glioma cells in the brain when mediated by hygromycin phosphotransferase.
OBJECTIVE
A variant of C6 glioma cells, C6R-G/H cells express hygromycin phosphotransferase (HPT) and appear to have reduced tumorigenicity in the embryonic brain. The goal of this study was to investigate their reduced capacity to generate tumors in the adult rat brain.


METHODS
Cell lines were implanted into rat brains and tumorigenesis was evaluated. After 3 weeks, all rats with C6 cells showed signs of neurological disease, whereas rats with C6R-G/H cells did not and were either killed then or allowed to survive until later. Histological studies were performed to analyze tumor size, malignancy, angiogenesis, and cell proliferation. Cells isolated from rat brain tumors were analyzed for mutation to HPT by testing their sensitivity to hygromycin.


CONCLUSIONS
The results indicate that HPT suppresses tumor formation. Three weeks after implantation, only 44% of animals implanted with C6R-G/H cells developed tumors, whereas all animals that received C6 glioma cells developed high-grade gliomas. The C6R-G/H cells filled a 20-fold smaller maximal cross-sectional area than the C6 cells, and exhibited less malignant characteristics, including reduced angiogenesis, mitosis, and cell proliferation. Similar results were obtained in the brain of nude rats, indicating that the immune system did not play a significant role in suppressing tumor growth. The combination of green fluorescent protein (GFP) and HPT was more effective in suppressing tumorigenesis than either plasmid by itself, indicating that the GFP may protect against inactivation of the HPT. Interestingly. hygromycin resistance was lost in tumor cells that were recovered from a group of animals in which C6R-G/H cells formed tumors, confirming the correlation of HPT with reduced tumorigenicity.
Hormigo
A
A
Department of Pharmacology, and Kaplan Comprehensive Cancer Center, New York University Medical Center, New York, USA.
Friedlander
D R
DR
Brittis
P A
PA
Zagzag
D
D
Grumet
M
M
D000818:Animals; D001932:Brain Neoplasms / Q000473:pathology / Q000503:physiopathology / Q000517:prevention & control*; D002455:Cell Division / Q000187:drug effects; D002934:Cinnamates; D004351:Drug Resistance; D005260:Female; D016147:Genes, Tumor Suppressor; D005910:Glioma / Q000473:pathology / Q000503:physiopathology / Q000517:prevention & control*; D006084:Graft Rejection; D049452:Green Fluorescent Proteins; D006921:Hygromycin B / Q000031:analogs & derivatives / Q000494:pharmacology; D008164:Luminescent Proteins / Q000235:genetics / Q000494:pharmacology; D008938:Mitosis / Q000187:drug effects; D009154:Mutation / Q000502:physiology; D009368:Neoplasm Transplantation; D009389:Neovascularization, Pathologic; D010641:Phenotype; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics / Q000494:pharmacology*; D051381:Rats; D011921:Rats, Inbred WKY; D011923:Rats, Nude; D011993:Recombinant Fusion Proteins / Q000494:pharmacology; D014162:Transfection; D014407:Tumor Cells, Cultured
D002934:Cinnamates; D008164:Luminescent Proteins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D006921:Hygromycin B; C026273:hygromycin A; D017853:Phosphotransferases (Alcohol Group Acceptor); C063242:hygromycin-B kinase