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ATM- and ATR-mediated response to DNA damage induced by a novel camptothecin, ST1968

Valentina Zuco1, Valentina Benedetti, Franco Zunino

  • 1Fondazione IRCCS Istituto Nazionale dei Tumori, via Venezian 1, 20133 Milan, Italy.

Cancer Letters
|January 1, 2010
PubMed

Insights

This study reveals that DNA damage response pathways, ATM-Chk2 and ATR-Chk1, play protective roles against camptothecin ST1968. Inhibiting checkpoint kinases like ATM or Chk1 can enhance cancer cell death, improving drug efficacy.

Area of Science:

  • Molecular Biology
  • Cancer Research
  • Cell Biology

Background:

  • DNA damage response (DDR) and checkpoint activation influence sensitivity to DNA-damaging agents.
  • Camptothecins are a class of anticancer drugs that induce DNA damage.
  • Understanding differential cellular responses to DDR is crucial for optimizing cancer therapy.

Purpose of the Study:

  • To investigate the DNA damage response to the novel camptothecin ST1968 in two distinct tumor cell lines (A2780 and KB).
  • To elucidate the roles of ATM-Chk2 and ATR-Chk1 pathways in mediating cellular responses and sensitivity to ST1968.
  • To explore the potential of inhibiting checkpoint kinases to enhance camptothecin efficacy.

Main Methods:

  • Treatment of A2780 (ovarian carcinoma) and KB (squamous carcinoma) cells with camptothecin ST1968 or ionizing radiation.
  • Analysis of DNA damage response pathways, including ATM-Chk2 and ATR-Chk1 activation.
  • Assessment of cell cycle perturbations, cell death modalities (apoptosis, senescence, mitotic catastrophe), and effects of kinase inhibition (ATM, Chk1).

Main Results:

  • A2780 cells showed ATM-Chk2 activation and early apoptosis, while KB cells exhibited ATR-Chk1 activation, G(2)/M arrest, senescence, and delayed apoptosis, suggesting a defective ATM pathway in KB cells.
  • UV-induced DNA damage activated ATR-Chk1 similarly in both cell lines, leading to early apoptosis.
  • Inhibition of ATM enhanced ST1968-induced apoptosis in A2780 cells but not KB cells.
  • Inhibition of Chk1 enhanced apoptosis in KB cells but not A2780 cells.
  • Camptothecin-induced apoptosis in A2780 cells was p53-dependent but not ATM-related.

Conclusions:

  • The camptothecin ST1968 activates either ATM-Chk2 or ATR-Chk1 pathways depending on the cellular context, with both pathways conferring a protective role.
  • Cell death modality is not the critical determinant of sensitivity to camptothecins.
  • Inhibition of checkpoint kinases (ATM, Chk1) holds promise for improving the efficacy of camptothecins in cancer treatment.

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