Irradiated homozygous TGF-beta1 knockout fibroblasts show enhanced clonogenic survival as compared with TGF-beta1 wild-type fibroblasts.
OBJECTIVE
To study the role of transforming growth factor beta1 (TGF-beta1) on cellular radiation sensitivity by analysing mouse lung fibroblasts of different TGF-beta1 genotypes.


METHODS
Heterozygous TGF-beta1 knock-out mice were mated to produce offspring of different TGF-beta1 genotypes as confirmed by PCR-genotyping. Primary lung fibroblast populations were established from new-born animals of specific genotypes (TGF-beta1(+/+), TGF-beta1(+/-), TGF-beta1(-/-)). Production of TGF-beta1 was tested by ELISA. TGF-beta1 receptor-II mRNA expression was analysed by RT-PCR. Colony formation of untreated, TGF-beta1-treated and/or irradiated primary lung fibroblasts was determined under different medium conditions.


RESULTS
Plating efficiencies under different medium conditions were independent of TGF-beta1 genotype. Production of TGF-beta1 correlated with the genotype: heterozygous TGF-beta1 knock-out fibroblasts (TGF-beta1(+/-)) produced 60-65% of wild-type (TGF-beta1(+/+) cells). As expected, homozygous TGF-beta1 knock-out fibroblasts (TGF-beta1(-/-)) did not produce TGF-beta1. Radiation exposure significantly enhanced TGF-beta1 production in TGF-beta1(+/+) cells by a factor of 2. No such stimulation was observed in TGF-beta1(+/-) cells. TGF-beta1(+/-) and especially TGF-beta1(-/-) cells were significantly more radioresistant than TGF-beta1(+/+) cells. TGF-beta1 treatment significantly reduced clonogenic survival for both TGF-beta1(+/+) and TGF-beta1(-/-) cells. TGF-beta1 treatment of TGF-beta1(-/-) cells resulted in an enhancement of radiation sensitivity.


CONCLUSIONS
The data are the first direct evidence that TGF-beta1 is a major autocrine regulator of intrinsic radiation sensitivity of mouse lung fibroblasts.
Von Pfeil
A
A
Section of Radiobiology & Molecular Environmental Research, Department of Radiation Oncology, University of Tübingen, Rüntgenweg 11, 72076 Tübingen, Germany.
Hakenjos
L
L
Herskind
C
C
Dittmann
K
K
Weller
M
M
Rodemann
H P
HP
D030201:Activin Receptors, Type I / Q000235:genetics; D000818:Animals; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D002478:Cells, Cultured; D003114:Colony-Forming Units Assay; D004307:Dose-Response Relationship, Radiation; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects; D005838:Genotype; D006720:Homozygote; D051379:Mice; D018345:Mice, Knockout; D017346:Protein Serine-Threonine Kinases; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011836:Radiation Tolerance / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D000077293:Receptor, Transforming Growth Factor-beta Type I; D018125:Receptors, Transforming Growth Factor beta / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016212:Transforming Growth Factor beta / Q000172:deficiency* / Q000235:genetics* / Q000494:pharmacology / Q000502:physiology; D053773:Transforming Growth Factor beta1
D012333:RNA, Messenger; D018125:Receptors, Transforming Growth Factor beta; C508961:Tgfb1 protein, mouse; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D017346:Protein Serine-Threonine Kinases; D030201:Activin Receptors, Type I; D000077293:Receptor, Transforming Growth Factor-beta Type I