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Function and dysfunction of the human oncoprotein MDM2
1Department of Biochemistry and Molecular Biophysics and the Massey Cancer Center, Medical College of Virginia, Virginia Commonwealth University, Richmond, VA 23298, USA. Spdeb@hsc.vcu.edu
Abstract:
The protein MDM2 coded by the human homologue of mouse double minute-2 (mdm2) gene frequently overexpresses in malignant human breast and other tumors. Artificial amplification of mouse mdm2 gene derived from a transformed murine cell line enhances tumorigenic potential of murine cells. These evidences suggest oncogenic properties of human or mouse MDM2. The tumorigenic property of MDM2 is not unexpected as MDM2 can inactivate several functions of the tumor suppressor p53. The protein also interacts with several cell cycle regulatory proteins that may contribute to its tumorigenic ability. Several spliced forms of MDM2 have been detected in cells that overexpress MDM2. The function of the proteins coded by these spliced forms is not well understood. Overexpression of full-length MDM2 from its cDNA arrests G1 to S phase transition of normal human or murine cells. Elimination of the growth inhibitory domains of the oncoprotein induces tumorigenesis. Some cancer-derived cell lines are partially insensitive to MDM2-mediated growth arrest. Normal cells can induce MDM2 in response to oncogenic challenges such as UV irradiation or estrogen treatment. Normal cells may induce full-length MDM2 in response to oncogenic challenges to protect against premature cell cycle progression. If the oncoprotein is defective in growth arrest or if the cells are insensitive to MDM2 mediated growth arrest, premature progression of cell cycle may lead to tumorigenesis. Elucidation of the growth regulatory functions of MDM2 may help develop new drug design for cancer treatment.
Insights
The double minute-2 (MDM2) oncoprotein promotes cancer by inactivating tumor suppressor p53 and regulating cell cycle progression. Understanding MDM2
Area of Science:
- Oncology
- Molecular Biology
- Cell Biology
Background:
- The double minute-2 (mdm2) gene product, MDM2, is frequently overexpressed in human cancers.
- MDM2 possesses oncogenic properties, partly due to its ability to inactivate the tumor suppressor p53.
- MDM2 interacts with cell cycle regulators, contributing to its tumorigenic potential.
Purpose of the Study:
- To investigate the oncogenic functions of MDM2.
- To understand the role of MDM2 in cell cycle regulation and tumorigenesis.
- To explore the implications of MDM2's growth regulatory functions for cancer drug development.
Main Methods:
- Analysis of MDM2 overexpression in tumors.
- Investigation of MDM2 gene amplification effects on cell transformation.
- Studies on MDM2's interaction with p53 and cell cycle proteins.
- Examination of MDM2-mediated cell cycle arrest (G1 to S phase transition).
Main Results:
- MDM2 overexpression and gene amplification enhance tumorigenic potential.
- MDM2 inactivates p53 and interacts with cell cycle proteins.
- Full-length MDM2 overexpression arrests cells at G1/S phase; domain elimination induces tumorigenesis.
- Some cancer cells exhibit insensitivity to MDM2-induced growth arrest.
Conclusions:
- MDM2 plays a significant role in cancer development through p53 inactivation and cell cycle dysregulation.
- Defects in MDM2-mediated growth arrest or cellular insensitivity contribute to tumorigenesis.
- Further elucidation of MDM2's growth regulatory functions could lead to novel cancer therapeutics.