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Expression of retrovirus-related functions in the methylcholanthrene-induced rat myelogenous leukemia
Abstract:
The rat MR-leukemia (MR-Le) induced in Wistar rats by methylcholanthrene and whole-body irradiation, has been shown to be transmitted by means of cell-free filtrates of spleen and liver extracts. These earlier results lead us to determine the expression of retroviral functions by MR-Le myeloblasts in vivo and in vitro. DNA polymerase activity associated with particulate material purified from plasma of rats carrying MR-Le and from MR-Le tissue culture fluid, increased with the number of MR-Le myeloblasts. Interspecies-specific antigenic determinants, common to some mammalian retroviruses, are expressed on the surface of MR-Le cells. Electrophoretic pattern of the MR-Le viral material purified from leukemic plasma and tissue culture fluid revealed the presence of polypeptides with molecular weights related to proteins of mammalian retroviruses which were not identical with main structural proteins of the endogenous rat C-type helper virus (RaLV). The results strongly support the proposition that RaLV-unrelated rat retrovirus is involved in the onset of MR-Le.
Insights
A novel rat retrovirus, unrelated to the endogenous rat leukemia virus (RaLV), is implicated in methylcholanthrene-induced leukemia (MR-Le). This discovery offers new insights into retroviral involvement in rat leukemia development.
Area of Science:
- Oncology
- Virology
- Molecular Biology
Background:
- Methylcholanthrene-induced leukemia (MR-Le) in Wistar rats can be transmitted via cell-free filtrates.
- Previous studies suggested a potential infectious agent in MR-Le pathogenesis.
Purpose of the Study:
- To investigate the expression of retroviral functions in MR-Le myeloblasts.
- To identify the specific retroviral agent involved in MR-Le.
Main Methods:
- Assessed DNA polymerase activity in leukemic plasma and tissue culture fluid.
- Analyzed cell surface antigens on MR-Le cells for retroviral markers.
- Examined viral material using electrophoresis to determine protein composition.
Main Results:
- Increased DNA polymerase activity correlated with MR-Le myeloblast count.
- MR-Le cells expressed interspecies-specific retroviral antigenic determinants.
- Purified viral material contained proteins distinct from endogenous rat C-type helper virus (RaLV).
Conclusions:
- The findings strongly suggest the involvement of a RaLV-unrelated rat retrovirus in the initiation of MR-Le.
- This unidentified retrovirus represents a novel factor in rat leukemia development.