Two-dimensional gel analysis of apoptosis-specific p53 isoforms induced by 2-methoxyestradiol in human lung cancer
T Mukhopadhyay1, J A Roth, S A Acosta
1Section of Thoracic Molecular Oncology, Department of Thoracic and Cardiovascular Surgery, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA.
Abstract:
The natural metabolic byproduct of estradiol, 2-methoxyestradiol (2-MeOE2), induces apoptosis in human lung cancer cells by a p53-dependent mechanism. The expression of wild-type p53 isoforms was investigated in H1299 non-small cell lung carcinoma cells induced into apoptosis by 2-MeOE2. H1299 cells lack endogenous p53 and undergo predominantly a G1 arrest when infected with a recombinant wild-type p53 adenovirus. However, when H1299 cells transfected with p53 were treated with 2-MeOE2, they underwent rapid and extensive apoptosis. H1299 cells expressing mutant his273 p53 were unaffected by 2-MeOE2, indicating a dependence of 2-MeOE2-mediated apoptosis on the presence of a functional p53. Analysis of wild-type p53 phosphoisoforms in H1299 cells by two-dimensional gel electrophoresis revealed that 2-MeOE2 induced a unique group of acidic p53 isoforms. Although most of the wild-type p53 in untreated H1299 cells migrated as at least five diffuse species with isoelectric points from pH 5.5-6.3, as many as nine additional forms migrating toward the acidic region with pI values from 4.4-5.3 were detected in 2-MeOE2-treated apoptotic cells. Two other agents known to induce apoptosis, vinblastine and actinomycin D, induced a similar pattern of acidic p53 species as that observed for 2-MeOE2. The results indicated that the induction of apoptosis in H1299 cells by 2-MeOE2 is dependent on the upregulation of specific p53 isoforms. Identification of the specific p53 phosphoisoforms induced by MeOE2 will be an important step in understanding the regulation and function of p53 in apoptosis.
Insights
2-methoxyestradiol (2-MeOE2) triggers programmed cell death in lung cancer cells by activating the p53 tumor suppressor. This compound specifically upregulates unique p53 protein forms, crucial for its apoptotic effect.
Area of Science:
- Molecular Biology
- Cancer Research
- Biochemistry
Background:
- Estradiol metabolite 2-methoxyestradiol (2-MeOE2) is known to induce apoptosis.
- The p53 tumor suppressor protein plays a critical role in regulating cell death.
- H1299 lung cancer cells lack endogenous p53, making them a useful model for studying p53-dependent pathways.
Purpose of the Study:
- To investigate the mechanism by which 2-MeOE2 induces apoptosis in human lung cancer cells.
- To determine the role of p53 and its isoforms in 2-MeOE2-mediated apoptosis.
- To identify specific p53 phosphoisoforms regulated by 2-MeOE2.
Main Methods:
- Transfection of H1299 cells with wild-type or mutant p53.
- Treatment of cells with 2-MeOE2, vinblastine, and actinomycin D.
- Two-dimensional gel electrophoresis to analyze p53 phosphoisoforms.
Main Results:
- 2-MeOE2 induced rapid and extensive apoptosis in H1299 cells expressing wild-type p53, but not in cells with mutant p53.
- 2-MeOE2 treatment led to the upregulation of unique acidic p53 phosphoisoforms.
- Vinblastine and actinomycin D induced similar patterns of acidic p53 species.
Conclusions:
- Apoptosis induction by 2-MeOE2 in lung cancer cells is dependent on the presence of functional p53.
- 2-MeOE2 modulates specific p53 phosphoisoforms, suggesting a novel regulatory mechanism.
- Further identification of these p53 isoforms is key to understanding p53 function in apoptosis.
