Molecular analysis of DNA isolated from the different stages of X-ray-lnduced transformation in vitro
✍ Scribed by Bozena Krolewski; John B. Little
- Publisher
- John Wiley and Sons
- Year
- 1989
- Tongue
- English
- Weight
- 683 KB
- Volume
- 2
- Category
- Article
- ISSN
- 0899-1987
No coin nor oath required. For personal study only.
✦ Synopsis
A major challenge in radiation carcinogenesis is to identify the cellular gene or genes involved in initiating the process. We examined the transforming activities of DNAs obtained from C3H1 OT1/2 cells during x-ray-induced morphological transformation. DNAs extracted from mass cultures of 10T1/2 cells at different times after irradiation with 600 rad and from type Ill-transformed foci were transfected into NIH 3T3 cells. The results indicate that certain oncogenes are activated beginning 3 wk after irradiation, well before the appearance o f macroscopically visible transformed foci. For DNA isolated from x-ray-transformed 10T1/2 cells (type Ill foci), the frequencies o f transfection were 0.003-0.1 1 foci/pg o f genomic DNA with NIH 3T3 cells and 0.004-0.04 foci/p,g genomic DNA using 10T1/2 cells as recipients. Southern blot analysis o f DNAs obtained from 23 primary transfectants and from 23 x-ray-transformed cell lines indicated no gross rearrangements or amplification of any of the 14 oncogenes screened (v-Ha-ras, v-Ki-ras, N-ras, v-myc, v-raf, v-src, v-fes, v-abl, v-mos, v-erbA, v-erbB, v-myb, v-fos, v-sis). This suggests that x-irradiation may activate as yet unidentified oncogenes. The occurrence of positive transfection 3 wk after irradiation is discussed in terms of the hypothesis that transformation may not occur as a direct consequence o f the exposure t o x-rays but develops as a rare event in the progeny o f the irradiated cells at some latertime, as a consequence of the delayed activation of certain genes.