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The proliferation of normal human fibroblasts is dependent upon negative regulation of p53 function by mdm2
J P Blaydes1, D Wynford-Thomas
1Department of Pathology, University of Wales College of Medicine, Cardiff, UK.
Abstract:
Loss of function of the tumour suppressor gene p53 is a key event in most human cancers. Although usually occurring through mutation, in some tumour types this appears to be achieved via an indirect mechanism involving inappropriate expression of a functional inhibitor, mdm2, which binds to the transactivation domain of p53. This interaction offers an ideal potential target for novel cancer therapies. However, therapeutic specificity may depend on the extent to which this p53-inhibitory action of mdm2 is also required by normal cells. Transgenic data have already established that mdm2 is needed to prevent embryonic lethality, but the situation in adult cells is still unclear. Here we show that micro-injection of normal human fibroblasts with an antibody directed against the p53-binding domain of mdm2 induces expression of p53-responsive genes, and furthermore results in p53-dependent growth arrest. We conclude that normal cell proliferation can be dependent on negative regulation of p53 by mdm2, a finding which raises an important note of caution for mdm2-directed cancer therapies.
Insights
Normal cell growth relies on the MDM2 protein inhibiting the tumor suppressor p53. Targeting this interaction for cancer therapy may impact healthy cells, necessitating caution.
Area of Science:
- Oncology
- Molecular Biology
- Cell Biology
Background:
- Loss of function of the tumor suppressor gene p53 is a critical step in human cancer development.
- MDM2 protein inhibits p53 activity by binding to its transactivation domain, representing a potential therapeutic target.
- The role of MDM2 in regulating p53 in normal adult cells remains largely uncharacterized.
Purpose of the Study:
- To investigate the necessity of MDM2's p53 inhibitory function for normal cell proliferation.
- To assess the potential impact of targeting the p53-MDM2 interaction on normal cell growth.
Main Methods:
- Micro-injection of normal human fibroblasts with an antibody targeting the p53-binding domain of MDM2.
- Analysis of p53-responsive gene expression.
- Assessment of cell growth arrest.
Main Results:
- Antibody-mediated inhibition of MDM2-p53 binding induced p53-responsive gene expression in normal fibroblasts.
- This inhibition resulted in p53-dependent growth arrest of normal cells.
- Normal cell proliferation is dependent on MDM2-mediated negative regulation of p53.
Conclusions:
- MDM2 plays a crucial role in regulating p53 activity in normal adult cells.
- Targeting the MDM2-p53 interaction for cancer therapy requires careful consideration due to its essential role in normal cell proliferation.
- This finding highlights a potential limitation for MDM2-directed cancer therapies.