Targeting Homologous Recombination in Notch-Driven C. elegans Stem Cell and Human Tumors

Area of Science:

• Developmental biology
• Cancer research
• Radiation oncology

Background:

• Mammalian NOTCH1-4 receptors are implicated in human cancers, but their precise roles are unclear.
• The NOTCH pathway is crucial for cell fate decisions and tissue development.
• Cancer radiotherapy effectiveness can be limited by tumor cell resistance mechanisms.

Purpose of the Study:

• To investigate the role of NOTCH signaling in tumor response to radiotherapy using a C. elegans model.
• To elucidate the molecular mechanisms underlying NOTCH-driven tumor radiosensitivity.
• To determine if findings in C. elegans translate to human cancer models.

Main Methods:

• Utilized a temperature-sensitive gain-of-function C. elegans NOTCH mutant (glp-1(ar202)).
• Induced tumor formation at a permissive temperature (25°C) and analyzed radiation response.
• Investigated DNA repair pathways and cell cycle progression post-irradiation.
• Validated findings in human cancer cell line models.

Main Results:

• NOTCH activation in C. elegans induced a tumor phenotype with rapid G2/M cell cycle arrest after irradiation.
• Tumor cells exclusively attempted DNA repair via homology-driven repair (HDR).
• Failure of HDR led to mitotic cell death, indicating a radiosensitizing effect.
• Inactivation of HDR significantly increased radiosensitivity in these tumors.
• The observed NOTCH-driven radiation response mechanisms were conserved in human cancer models.

Conclusions:

• NOTCH signaling dictates a specific tumor cell response to radiotherapy, involving cell cycle arrest and reliance on HDR for DNA repair.
• Targeting HDR presents a potential strategy to enhance radiotherapy efficacy in NOTCH-driven cancers.
• The C. elegans model provides valuable insights into fundamental cancer biology and radiation response applicable to human malignancies.