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Antagonistic action between cyclic AMP and estrogen in phosphorylation of mammary tumor nuclear proteins
Abstract:
A new protein kinase-dependent phosphorylation occurs in the nuclei of hormone-dependent, 7,12-dimethylbenz[alpha]anthracene (DMBA)-induced mammary carcinoma following preincubation of tumor slices with cyclic adenosine 3',5'-monophosphate (cAMP). The presence of 17beta-estradiol in the medium inhibits this effect. Both events have been observed in vivo in the nuclei of DMBA-induced tumors. The phosphorylation pattern of nuclei in hormone-independent mammary tumor, DMBA No. 1, however, is not affected by preincubation with either cAMP or estrogen. These findings suggest that the antagonistic effect of cAMP and estrogen in the growth control of mammary tumors is exerted through a specific action on nuclear protein phosphorylation and that these events correlate with the hormone-dependency of the tumors.
Insights
Cyclic adenosine 3
Area of Science:
- Oncology
- Molecular Biology
- Biochemistry
Background:
- Hormone-dependent mammary tumors, like those induced by 7,12-dimethylbenz[alpha]anthracene (DMBA), are a significant area of cancer research.
- Understanding the molecular mechanisms underlying hormone dependency is crucial for developing targeted therapies.
Purpose of the Study:
- To investigate the role of nuclear protein phosphorylation in the growth control of hormone-dependent mammary tumors.
- To explore the interplay between cyclic adenosine 3',5'-monophosphate (cAMP) and estrogen in regulating these phosphorylation events.
Main Methods:
- Utilized in vitro studies with preincubated tumor slices from DMBA-induced mammary carcinoma.
- Examined nuclear protein phosphorylation patterns in response to cyclic adenosine 3',5'-monophosphate (cAMP) and 17beta-estradiol.
- Correlated findings with in vivo observations in DMBA-induced tumors and hormone-independent tumors (DMBA No. 1).
Main Results:
- A novel protein kinase-dependent phosphorylation was identified in the nuclei of hormone-dependent DMBA-induced mammary carcinoma following cAMP stimulation.
- 17beta-estradiol was found to inhibit this cAMP-induced phosphorylation.
- No significant effect on nuclear phosphorylation patterns was observed in hormone-independent mammary tumors (DMBA No. 1) with either cAMP or estrogen treatment.
Conclusions:
- The antagonistic effects of cAMP and estrogen on mammary tumor growth appear to be mediated by specific actions on nuclear protein phosphorylation.
- These phosphorylation events are closely linked to the hormone-dependency status of mammary tumors.