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Updated: Feb 2, 2026
Purification of Ubiquitinated p53 Proteins from Mammalian Cells
Published on: March 21, 2022
Pifithrin-α enhancing anticancer effect of topotecan on p53-expressing cancer cells
Jianli Guo1, Qin Tang2, Qingling Wang1
1School of Life Science and Biotechnology, Dalian University of Technology, Dalian 116024, China.
Abstract:
p53 is generally known as an effective anti-cancer molecular, but it is lost or mutated in more than 50% of human tumors. It is still a controversial issue whether the activity of p53 really benefits for treating cancers, we wondered what would happen if the endogenous p53 was inhibited before treated with topotecan (TPT) on p53 positive tumor cells. In this study, pifithrin-α (PFTα), a p53 inhibitor, was used 2 h before treated with TPT on three kinds of cancer cell lines including MCF7, BGC823 and HepG2 cells. The IC50s of TPT for MCF7, BGC823 and HepG2 cells after 10 μΜ PFTα pretreated, was 4.8 to 14.4 folds lower than the effect of TPT alone. It was demonstrated that PFTα decreases the p-p53 levels and p-p53 activity, not affects p53 expression in p53 positive tumor cells. PFTα enhanced anticancer effect of TPT on cells was found mainly by two ways. Firstly, it increased the TPT accumulation in cells and nucleus and promoted the inhibition of TPT on activity of Topo I, and induced more DNA damage. Secondly, PFTα decreased formation of p53/mdm2 complex responsible for p53 degradation by inhibiting the protein expression of mdm2, so p53 degradation was decreased in cytoplasm and p53 accumulation was increased in nucleus, which induced more cells undergo apoptosis. So, the crosstalk between p53 and TPT played a pivotal role for enhancing anticancer effects of PFTα and TPT on p53 positive cancer cells. These findings provide a new idea for drug design and combination chemotherapy of cancers.
Insights
Inhibiting p53 with pifithrin-α (PFTα) before topotecan (TPT) treatment significantly enhances TPT
Area of Science:
- Oncology
- Molecular Biology
- Cancer Therapeutics
Background:
- The tumor suppressor protein p53 is frequently lost or mutated in human cancers.
- The role of p53 activity in cancer treatment remains controversial.
- Topotecan (TPT) is a chemotherapy drug whose efficacy may be influenced by p53 status.
Purpose of the Study:
- To investigate the effect of inhibiting endogenous p53 on the efficacy of topotecan (TPT) in p53-positive cancer cells.
- To elucidate the mechanisms by which p53 inhibition enhances TPT's anticancer effects.
Main Methods:
- Three p53-positive cancer cell lines (MCF7, BGC823, HepG2) were treated with pifithrin-α (PFTα), a p53 inhibitor, followed by TPT.
- Cell viability was assessed by calculating IC50 values.
- Mechanisms investigated included drug accumulation, Topo I inhibition, DNA damage, p53/mdm2 complex formation, and apoptosis induction.
Main Results:
- Pretreatment with PFTα significantly reduced the IC50 of TPT by 4.8 to 14.4 folds in tested cell lines.
- PFTα decreased phosphorylated p53 levels and activity without affecting total p53 expression.
- PFTα enhanced TPT efficacy by increasing TPT accumulation, promoting Topo I inhibition, inducing DNA damage, and increasing nuclear p53 levels via mdm2 inhibition, leading to enhanced apoptosis.
Conclusions:
- Inhibiting p53 with PFTα potentiates the anticancer effects of TPT in p53-positive cancer cells.
- The enhanced efficacy is mediated by increased TPT-induced DNA damage and apoptosis.
- These findings suggest a novel strategy for combination chemotherapy involving p53 inhibition.
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