Development of a high-throughput cell-based reporter assay to identify stabilizers of tumor suppressor Pdcd4

Area of Science:

• Molecular Biology
• Cancer Research
• Biochemistry

Background:

• Programmed cell death protein 4 (Pdcd4) is a crucial tumor suppressor that inhibits protein translation.
• Pdcd4 stability is regulated by phosphorylation and subsequent proteasomal degradation under tumor-promoting conditions.
• Developing methods to monitor Pdcd4 stability is essential for identifying therapeutic interventions.

Purpose of the Study:

• To develop and validate a reporter cell system for monitoring Pdcd4 stability.
• To screen chemical and natural product libraries for compounds that stabilize Pdcd4.
• To identify novel Pdcd4 stabilizers for potential cancer therapy.

Main Methods:

• Cloning of Pdcd4's phosphorylation-dependent degradation domain into a luciferase reporter system.
• Optimization of the reporter system for high-throughput screening in a 384-well format.
• Screening of over 15,000 pure compounds and 135,000 natural product extracts, with confirmation assays.

Main Results:

• The reporter system accurately reflected Pdcd4 degradation under specific conditions.
• High-throughput screening identified 0.30% specific hits from pure compounds and 42 confirmed hits from natural products.
• Hits included inhibitors of known Pdcd4 degradation pathways, and one compound was identified as nonspecific.
• The Z' factor of 0.58 indicated high reliability for the screening assay.

Conclusions:

• A robust reporter cell system for monitoring Pdcd4 stability was successfully developed.
• The screening identified promising synthetic and natural compounds that stabilize Pdcd4.
• These Pdcd4 stabilizers represent potential novel therapeutic agents for cancer treatment by targeting protein translation.