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Some effects of chlorambucil on nuclear protein phosphorylation in the Yoshida ascites sarcoma
Abstract:
The ability of nuclei, isolated from Yoshida ascites sarcoma cells, to phosphorylate nuclear proteins in the presence of [gamma-32P]ATP has been investigated. Comparisons were made between a strain sensitive to the effects of the alkylating agent, chlorambucil, with a corresponding resistant strain both before and after drug-treatment of tumour-bearing animals. There was no gross quantitative differences between the drug-sensitive and-resistant untreated cells but treatment resulted in increased levels in the sensitive strain. Qualitative differences were seen before treatment in the phosphorylation pattern of the tris-saline-soluble nuclear sap fraction. The high molecular weight species in the fraction from sensitive cells showed phosphorylations which were absent, or present at very low levels, in the corresponding fraction from drug-resistant cells. Changes were observed in the tris-saline-soluble and non-histone protein fractions from drug-sensitive cells following treatment of tumour-bearing animals. Only minor alterations in patterns of phosphorylation were seen in fractions from drug-resistant cells.
Insights
Nuclear protein phosphorylation differs between drug-sensitive and drug-resistant Yoshida ascites sarcoma cells. Chlorambucil treatment alters phosphorylation patterns in sensitive cells, suggesting a mechanism for drug resistance in cancer.
Area of Science:
- Biochemistry
- Molecular Biology
- Cancer Research
Background:
- Nuclear protein phosphorylation is crucial for cellular regulation.
- Drug resistance in cancer impacts treatment efficacy.
- Yoshida ascites sarcoma is a model for studying cancer drug resistance.
Purpose of the Study:
- To investigate nuclear protein phosphorylation in drug-sensitive and drug-resistant Yoshida ascites sarcoma cells.
- To compare phosphorylation patterns before and after chlorambucil treatment.
- To identify potential molecular differences associated with chlorambucil resistance.
Main Methods:
- Isolation of nuclei from Yoshida ascites sarcoma cells.
- In vitro phosphorylation assays using [gamma-32P]ATP.
- Fractionation of nuclear proteins (tris-saline-soluble and non-histone).
- Analysis of phosphorylation patterns using gel electrophoresis.
Main Results:
- No significant quantitative differences in nuclear protein phosphorylation between untreated sensitive and resistant cells.
- Chlorambucil treatment increased phosphorylation levels in the sensitive strain.
- Qualitative differences in phosphorylation patterns of high molecular weight nuclear sap proteins were observed between sensitive and resistant cells prior to treatment.
- Drug treatment induced changes in tris-saline-soluble and non-histone protein fractions of sensitive cells, with minimal changes in resistant cells.
Conclusions:
- Differential phosphorylation of nuclear proteins may contribute to chlorambucil sensitivity or resistance in Yoshida ascites sarcoma.
- Specific phosphorylation patterns in nuclear sap fractions could serve as biomarkers for drug response.
- Further research into these phosphorylation differences may reveal novel therapeutic targets for overcoming drug resistance.