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G protein abnormalities in pituitary adenomas
1Institute of Endocrine Sciences, University of Milan, Ospedale Maggiore IRCCS, Milano, Italy. endosci@imiucca.csi.unimi.it
Molecular and Cellular Endocrinology
|October 23, 1998
Summary
Pituitary tumors often originate from a single mutated cell. Key genetic mutations in Gs alpha (gsp) and Gi2 alpha (gip2) protooncogenes drive tumor growth by altering cell signaling pathways.
Area of Science:
- Endocrinology
- Molecular Biology
- Oncology
Background:
- Pituitary adenomas, both secreting and nonsecreting, are typically monoclonal, arising from a single mutated cell.
- Genetic alterations, such as deletions in chromosome 11q13 (MEN-1 gene) and mutations in Gs and Gi2 proteins, are implicated in pituitary tumor development.
- These mutations can lead to constitutive activation of Gs alpha and Gi2 alpha proteins, functioning as protooncogenes (gsp and gip2).
Purpose of the Study:
- To investigate the role of specific genetic mutations in the development and behavior of pituitary tumors.
- To explore the oncogenic potential of Gs alpha (gsp) and Gi2 alpha (gip2) protooncogenes in pituitary adenomas.
- To understand how these genetic abnormalities influence cell growth, differentiation, and signaling pathways.
Main Methods:
- Screening of numerous genes for mutations in pituitary tumors.
- Analysis of allelic deletions and specific gene mutations, including those in Gs and Gi2 proteins.
- In vitro mutagenesis studies to assess the oncogenic potential of various G protein alpha subunits.
Main Results:
- The gsp oncogene is found in 30-40% of GH-secreting pituitary adenomas and other endocrine tumors, leading to increased cAMP production and sustained differentiated functions.
- The gip2 oncogene is identified in approximately 10% of nonfunctioning pituitary adenomas and other tumors, though its mitogenic role in pituitary cells requires further investigation.
- Mutations in Gq alpha, G12alpha, G13alpha, and Gz alpha have demonstrated oncogenic potential in vitro, but their natural occurrence in human pituitary tumors is yet to be confirmed.
Conclusions:
- Mutations in Gs alpha (gsp) and Gi2 alpha (gip2) protooncogenes are significant drivers of pituitary adenoma development and function.
- Constitutive activation of these proteins disrupts normal cell signaling, promoting uncontrolled growth.
- Further research is needed to confirm the role of other G protein alpha subunits in pituitary tumorigenesis.