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Updated: Jul 2, 2026
A Multiplexed Luciferase-based Screening Platform for Interrogating Cancer-associated Signal Transduction in Cultured Cells
Published on: July 3, 2013
Assay development for high throughput screening of p21(Waf1/Cip1) protein expression in intact cells using
T Grand-Perret1, M Cik, J Arts
1Oncology Discovery Research, Johnson & Johnson Pharmaceutical R&D, Beerse, Belgium. tgrandpe@prdbe.jnj.com
Abstract:
The p21(Waf1/Cip1) protein represents a broad-acting cyclin-dependent kinase inhibitor that plays a key role in cell cycle regulation. Furthermore, p21(Waf1/Cip1) protein has been described as a direct participant in regulating genes involved in growth arrest, senescence and aging. In response to genotoxic insults (e.g., following chemotherapeutic treatment), p21(Waf1/Cip1) protein accumulates mainly through p53-mediated transcriptional activation and is also regulated at the post-transcriptional level. In tumor cells, p53 is frequently mutated leading to reduced p21(Waf1/Cip1) protein induction that may contribute to resistance to treatment by DNA-damaging agents. In order to identify compounds capable of restoring p21(Waf1/Cip1) protein level, we have developed a 96-multi-well plate-based high throughput screening assay in intact cells using the Applied Biosystems Fluorometric Microvolume Assay Technology (FMAT) macro-confocal system. Briefly, following incubation with test compounds, human MCF7 breast carcinoma cells were fixed and p21(Waf1/Cip1) protein was detected using anti-p21(Waf1/Cip1) monoclonal antibody and anti-mouse IgG conjugated to the red fluorescent dye Alexafluor 633. FMAT provides a set of raw images at a high magnification, in which fluorescence concentrated in a cell is detected as a specific signal. The mean fluorescence of a population of cells is calculated independently of the number of cells as with a classical FACS analysis. This is of particular interest for screening anticancer drugs that may affect cell number and therefore may impact on the readout. This assay was validated using reference compounds such as camptothecin and actinomycin D, known inducers of p21(Waf1/Cip1) protein.
Insights
Researchers developed a high-throughput screening assay to identify compounds that restore p21(Waf1/Cip1) protein levels, crucial for cell cycle regulation and cancer treatment resistance. This assay helps find new anticancer drugs by measuring p21 protein induction in cells.
Area of Science:
- Molecular Biology
- Cell Biology
- Cancer Research
Background:
- The p21(Waf1/Cip1) protein is a key inhibitor of cyclin-dependent kinases, regulating cell cycle, growth arrest, senescence, and aging.
- Genotoxic insults, like chemotherapy, increase p21(Waf1/Cip1) levels via p53 activation, but mutations in p53 can lead to treatment resistance in cancer cells.
- Restoring p21(Waf1/Cip1) levels is a potential strategy to overcome resistance to DNA-damaging chemotherapeutic agents.
Purpose of the Study:
- To develop a high-throughput screening (HTS) assay for identifying novel compounds that can restore p21(Waf1/Cip1) protein levels in cancer cells.
- To establish a reliable and efficient method for screening potential anticancer drugs that target the p21 pathway.
- To validate the assay's performance using known p21(Waf1/Cip1) inducers.
Main Methods:
- A 96-multi-well plate-based HTS assay was developed using human MCF7 breast carcinoma cells.
- The assay utilized Applied Biosystems Fluorometric Microvolume Assay Technology (FMAT) for detecting p21(Waf1/Cip1) protein levels via immunofluorescence.
- Cells were incubated with test compounds, fixed, and stained with anti-p21(Waf1/Cip1) antibody and fluorescently labeled secondary antibodies; fluorescence intensity was measured using FMAT.
Main Results:
- The FMAT assay successfully quantified p21(Waf1/Cip1) protein levels, with fluorescence signal correlating with protein concentration.
- The assay's robustness was confirmed by its ability to measure fluorescence independently of cell number, crucial for screening cytotoxic compounds.
- Validation with known inducers like camptothecin and actinomycin D demonstrated the assay's efficacy in detecting p21(Waf1/Cip1) induction.
Conclusions:
- A novel, validated HTS assay using FMAT technology has been established for screening compounds that modulate p21(Waf1/Cip1) protein levels.
- This assay provides a valuable tool for discovering novel anticancer therapeutics aimed at overcoming treatment resistance by restoring p21(Waf1/Cip1) expression.
- The assay's design is particularly suitable for identifying drugs that impact cell cycle regulation and induce tumor cell death.
