The E3 Ligase CHIP Mediates p21 Degradation to Maintain Radioresistance

Area of Science:

• Oncology
• Molecular Biology
• Radiotherapy

Background:

• Lung cancer exhibits resistance to radiotherapy, contributing to its high mortality rate.
• The C-terminus of Hsc70-interacting protein (CHIP), an E3 ubiquitin ligase, plays a role in stress-induced protein degradation.

Purpose of the Study:

• To investigate the role of CHIP in regulating lung cancer cell radiosensitivity.
• To elucidate the molecular mechanisms by which CHIP influences cellular response to ionizing radiation.

Main Methods:

• RNA interference (RNAi) to knockdown CHIP expression in human lung cancer cell lines.
• CRISPR/Cas9 gene editing to delete the p21 gene (CDKN1A).
• In vitro and cell-based assays to study protein ubiquitylation and degradation.

Main Results:

• CHIP knockdown increases lung cancer cell sensitivity to ionizing radiation.
• CHIP knockdown reduces the degradation of p21, enhancing IR-induced senescence.
• CHIP overexpression promotes radioresistance by increasing p21 degradation.
• p21 is identified as a direct ubiquitylation substrate of CHIP, requiring HSP70.

Conclusions:

• The CHIP-HSP70-p21 ubiquitylation/degradation pathway regulates lung cancer cell radiosensitivity.
• Inhibition of CHIP enhances radiosensitivity by stabilizing p21, suggesting a novel therapeutic strategy.
• Targeting this axis may improve radiotherapy efficacy in non-small cell lung cancer.