ATM-dependent CHK2 activation induced by anticancer agent, irofulven

Area of Science:

• Oncology
• Molecular Biology
• Cell Biology

Background:

• Irofulven (HMAF) is a novel anticancer agent derived from illudin S.
• It shows efficacy against various tumors and induces DNA damage, MAPK activation, and apoptosis.
• Understanding its precise molecular mechanisms is crucial for optimizing cancer therapy.

Purpose of the Study:

• To elucidate the role of ATM and CHK2 kinases in irofulven-induced DNA damage response.
• To investigate the contribution of CHK2 activation to irofulven's anti-cancer effects, specifically S phase arrest.

Main Methods:

• Utilized ovarian cancer cells, human fibroblasts (ATM proficient/deficient, ATR.kd expressing), and colon cancer cell lines (HCT116, CHK2 knockout).
• Employed RNA interference (siRNA for ATM) and expression of kinase-dead CHK2.
• Assessed kinase activation (ATM, CHK2), phosphorylation of downstream targets (NBS1, SMC1, p53), and cell cycle progression (S phase arrest).

Main Results:

• Irofulven activated CHK2 kinase in ovarian cancer cells, but not CHK1.
• ATR kinase did not significantly contribute to irofulven-induced CHK2 activation.
• CHK2 activation by irofulven was mediated by ATM kinase, evidenced by ATM phosphorylation and inhibition upon ATM siRNA.
• CHK2 activation was essential for irofulven-induced S phase arrest, impacting NBS1, SMC1, and p53 phosphorylation.
• p53 phosphorylation at Ser20 was CHK2-dependent following irofulven treatment.

Conclusions:

• Irofulven activates the ATM-CHK2 DNA damage signaling pathway in cancer cells.
• CHK2 activation plays a critical role in mediating the S phase cell cycle arrest induced by irofulven.
• These findings highlight the ATM-CHK2 axis as a key target for irofulven's anticancer activity.