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Reversion of Kirsten sarcoma virus transformed human cells: elimination of the sarcoma virus nucleotide sequences
Abstract:
The virus-specific nucleotide sequences in the RNA and DNA of a Kirsten mouse sarcoma virus (Ki-MSV)-transformed non-producer human osteosarcoma cell clone and two subclones of these cells that reverted to a normal phenotype have been analysed by hybridization of sarcoma virus-specific complementary DNA (cDNA) to cellular RNA or DNA. Whereas the transformed clone had acquired de novo Ki-MSV sequences in the RNA and DNA of the cells, both the revertant cell lines seemed to have lost most or all of this information from the cellular nucleic acids. The DNA from the revertant cells lacked the sequences represented either in the Ki-MSV-specific cDNA or in the total cDNA of the leukaemia-sarcoma virus complex. Thus, the reversion of the virus-transformed human cells to normal morphology is associated with the loss of most or all of the proviral sequences from the cellular DNA.
Insights
Revertant human osteosarcoma cells lost Kirsten mouse sarcoma virus (Ki-MSV) sequences, indicating proviral DNA loss is key to normal cell phenotype reversion. This study analyzes viral nucleic acid integration and loss in cancer cell transformation.
Area of Science:
- Molecular Biology
- Virology
- Cancer Research
Background:
- Kirsten mouse sarcoma virus (Ki-MSV) transformation of human osteosarcoma cells leads to altered cellular phenotype.
- Reversion to a normal phenotype in virus-transformed cells suggests underlying genetic or epigenetic changes.
- Understanding viral sequence integration and loss is crucial for cancer biology.
Purpose of the Study:
- To investigate the presence and loss of virus-specific nucleotide sequences in transformed and reverted human osteosarcoma cells.
- To determine the association between proviral sequence loss and the reversion of normal cell morphology.
- To analyze the integration and de novo acquisition of Ki-MSV sequences in cellular nucleic acids.
Main Methods:
- Hybridization analysis of complementary DNA (cDNA) derived from Ki-MSV.
- Comparing viral sequences in RNA and DNA of transformed cells versus reverted subclones.
- Assessing the presence of Ki-MSV and leukaemia-sarcoma virus complex sequences in cellular DNA.
Main Results:
- Transformed human osteosarcoma cells acquired de novo Ki-MSV sequences in both RNA and DNA.
- Revertant cell lines showed a significant loss of most or all Ki-MSV-specific information from cellular nucleic acids.
- Proviral sequences, represented in Ki-MSV cDNA and leukaemia-sarcoma virus complex cDNA, were absent in revertant cell DNA.
Conclusions:
- Reversion of virus-transformed human cells to a normal phenotype is strongly associated with the loss of proviral sequences.
- The loss of integrated viral DNA appears to be a critical factor in the phenotypic reversion of these cancer cells.
- This suggests a mechanism where viral genome excision or silencing contributes to tumor suppression.