ATF2 loss promotes 5-FU resistance in colon cancer cells via activation of the ATR-Chk1 damage response pathway

Area of Science:

• Oncology
• Molecular Biology
• Cancer Research

Background:

• The role of Activating Transcription Factor 2 (ATF2) in colon cancer (CC) is debated, with low expression linked to invasive tumors and potential therapy resistance.
• 5-Fluorouracil (5-FU) is a primary CC treatment, but its efficacy is limited by drug resistance.
• The specific role of ATF2 in 5-FU response in CC remains unclear.

Purpose of the Study:

• To investigate the role of ATF2 in 5-FU resistance in colon cancer.
• To elucidate the molecular mechanisms by which ATF2 influences response to 5-FU chemotherapy.

Main Methods:

• Utilized CRISPR-Cas9 to generate ATF2-knockout (KO) HCT116 (wild-type p53) and HT29 (mutant p53) colon cancer cell lines.
• Assessed 5-FU response, DNA damage response (DDR) pathway activation (p-ATR, p-Chk1, γ-H2AX), apoptosis, and ATF2-ATR interaction using in vitro, in vivo (CAM model), and in silico methods.
• Employed Chk1 inhibitors and ATF2-silencing in p53-deficient cells to confirm findings.

Main Results:

• Loss of ATF2 conferred dose- and time-dependent 5-FU resistance in HCT116 cells, characterized by activated DDR (elevated p-ATR, p-Chk1, γ-H2AX).
• HT29 ATF2-KO cells showed contradictory results with low p-Chk1, apoptosis induction, but no DNA damage changes.
• ATF2-silenced HCT116 p53-/- cells did not activate DDR upon 5-FU treatment.
• ATF2 binds ATR upon 5-FU treatment, inhibiting Chk1 phosphorylation, a function disrupted in ATF2-negative cells.

Conclusions:

• ATF2 functions as a novel scaffold in the DDR pathway, crucial for maintaining 5-FU sensitivity.
• ATF2-negative colon cancer cells exhibit high 5-FU resistance due to efficient ATR/Chk1-mediated DNA damage repair.
• Mutant p53 may override the tumor-suppressive role of ATF2 in colon cancer therapy response.