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Characterization, chemical optimization and anti-tumour activity of a tubulin poison identified by a p53-based
Oliver D Staples1, Jonathan J Hollick, Johanna Campbell
1Department of Surgery and Molecular Oncology, University of Dundee, Ninewells Hospital and Medical School, Dundee, Scotland, UK.
Abstract:
A robust p53 cell-based assay that exploits p53's function as a transcription factor was used to screen a small molecule library and identify bioactive small molecules with potential antitumor activity. Unexpectedly, the majority of the highest ranking hit compounds from this screen arrest cells in mitosis and most of them impair polymerization of tubulin in cells and in vitro. One of these novel compounds, JJ78:1, was subjected to structure-activity relationship studies and optimized leading to the identification of JJ78:12. This molecule is significantly more potent than the original hit JJ78:1, as it is active in cells at two-digit nanomolar concentrations and shows clear antitumor activity in a mouse xenograft model as a single agent. The effects of nocodazole, a well established tubulin poison, and JJ78:12 on p53 levels are remarkably similar, supporting that tubulin depolymerization is the main mechanism by which JJ78:12 treatment leads to p53 activation in cells. In summary, these results identify JJ78:12 as a potential cancer therapeutic, demonstrate that screening for activators of p53 in a cell-based assay is an effective way to identify inhibitors of mitosis progression and highlights p53's sensitivity to alterations during mitosis.
Insights
Researchers screened for p53 activators and found compounds that inhibit mitosis by disrupting tubulin polymerization. The optimized compound JJ78:12 shows potent antitumor activity and activates p53, highlighting a novel therapeutic strategy.
Area of Science:
- Oncology
- Molecular Biology
- Biochemistry
Background:
- The p53 protein is a critical tumor suppressor.
- Developing novel cancer therapeutics targeting cell division is essential.
Purpose of the Study:
- To identify small molecules with antitumor activity using a p53 cell-based assay.
- To investigate the mechanism of action of identified compounds.
Main Methods:
- Screening of a small molecule library using a p53 transcription factor assay.
- In vitro and cellular tubulin polymerization assays.
- Structure-activity relationship studies and in vivo efficacy testing in a mouse xenograft model.
Main Results:
- The screen identified compounds that inhibit mitosis and impair tubulin polymerization.
- Optimized compound JJ78:12 demonstrated potent activity at nanomolar concentrations.
- JJ78:12 exhibited significant antitumor activity as a single agent in vivo.
- JJ78:12's mechanism involves tubulin depolymerization, leading to p53 activation.
Conclusions:
- JJ78:12 is a promising novel cancer therapeutic candidate.
- p53-based screening can effectively identify mitosis inhibitors.
- p53 is sensitive to mitotic alterations, offering therapeutic insights.
