Abrogation of ionizing radiation-induced G2 checkpoint and inhibition of nuclear export by Cryptocarya pyrones

Area of Science:

• Cell Biology
• Molecular Biology
• Pharmacology

Background:

• The G(2) checkpoint prevents cells with DNA damage from entering mitosis.
• G(2) checkpoint inhibitors can enhance cancer cell killing by radiation and chemotherapy, especially in p53-deficient cells.
• Existing inhibitors target checkpoint kinases or phosphatases.

Purpose of the Study:

• To identify novel G(2) checkpoint inhibitors using a phenotypic cell-based assay.
• To explore alternative mechanisms for abrogating the G(2) checkpoint.
• To investigate plant extracts for potential therapeutic compounds.

Main Methods:

• Phenotypic cell-based screening of plant extracts.
• Identification and characterization of Z-Cryptofolione and Cryptomoscatone D2.
• Assessment of nuclear export inhibition.
• Evaluation of radiosensitizing potential and toxicity.

Main Results:

• Z-Cryptofolione and Cryptomoscatone D2 were identified as potent G(2) checkpoint inhibitors from plant extracts.
• These compounds, along with related pyrones, were found to inhibit nuclear export.
• Leptomycin B, a known nuclear export inhibitor, also potently inhibited the G(2) checkpoint.
• The identified compounds showed toxicity to unirradiated cells, limiting their radiosensitizing potential.

Conclusions:

• Inhibition of nuclear export is a viable alternative strategy for abrogating the G(2) checkpoint.
• This finding warrants further research into developing less toxic nuclear export inhibitors.
• Novel plant-derived compounds offer new avenues for G(2) checkpoint modulation.