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MRE11 deficiency increases sensitivity to poly(ADP-ribose) polymerase inhibition in microsatellite unstable

Eduardo Vilar1, Catherine M Bartnik, Stephanie L Stenzel

  • 1Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, Michigan, USA.

Cancer Research
|February 9, 2011
PubMed

Insights

Microsatellite instability (MSI) colorectal cancers with MRE11 mutations are sensitive to PARP-1 inhibitors. This suggests potential new treatments for MSI colorectal cancer (CRC) patients.

Area of Science:

  • Oncology
  • Molecular Biology
  • Genetics

Background:

  • Microsatellite instability (MSI) occurs in ~15% of colorectal cancers (CRC).
  • Defective DNA mismatch repair can lead to mutations in double-strand break (DSB) repair genes like MRE11.
  • MRE11 mutations are correlated with MSI status in CRC cell lines and primary tumors.

Purpose of the Study:

  • To investigate the hypothesis that MRE11 deficiency sensitizes CRC cells to poly(ADP-ribose) polymerase-1 (PARP-1) inhibition.
  • To evaluate the efficacy of the PARP-1 inhibitor ABT-888 in CRC cell lines with varying MRE11 mutational status and MSI.
  • To experimentally validate the role of MRE11 in conferring sensitivity to PARP-1 inhibition.

Main Methods:

  • Assessed MRE11 mutational status in 17 CRC cell lines and 46 primary tumors.
  • Administered PARP-1 inhibitor ABT-888 to CRC cell lines and measured cytotoxicity.
  • Utilized short hairpin RNA (shRNA) to knockdown MRE11 in a wild-type/microsatellite-stable (MSS) cell line (SW-480).
  • Transfected a cell line with mutant MRE11 to create a second experimental model.

Main Results:

  • Found a strong correlation between MRE11 mutational status and MSI in CRC.
  • Observed preferential cytotoxicity to ABT-888 in MSI CRC cell lines with MRE11 mutations.
  • Demonstrated a significant correlation between MRE11 expression levels and ABT-888 cytotoxicity (R² = 0.915, P < 0.001).
  • Experimental models showed proliferation changes in response to ABT-888, but a clear drug-response effect was not consistently observed, suggesting additional genetic factors.

Conclusions:

  • MSI colorectal tumors with MRE11 deficiency exhibit heightened sensitivity to PARP-1 inhibition.
  • MRE11 mutations may represent a predictive biomarker for PARP-1 inhibitor therapy in CRC.
  • Further clinical investigation of PARP-1 inhibitors in MSI CRCs is warranted.

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