Immunohistochemical detection of poly(ADP-ribose) polymerase inhibition by ABT-888 in patients with refractory solid tumors and lymphomas

Cancer Biol Ther. 2009 Nov;8(21):2004-9. doi: 10.4161/cbt.8.21.9917. Epub 2009 Nov 25.


Purpose: Targeting the poly (ADP-ribose) polymerase (PARP) pathway for cancer treatment has been an active area of pre-clinical and clinical research. We aimed to determine whether the PARP inhibitor ABT-888 hits its therapeutic target in tumors by immunohistochemistry during a Phase 0 trial conducted at the National Cancer Institute.

Experimental design: The expression of poly (ADP-ribose) (PAR) and full size PARP-1 were quantitatively examined by immunohistochemistry in paraffin-embedded tumor biopsies at baseline and 3-24 h after a single oral dose (25 or 50 mg) of ABT-888.

Results: Baseline PAR levels were moderate to high in three patients with non-Hodgkin lymphomas, and one each with small cell lung cancer, squamous cell carcinoma of the tongue and melanoma; low in two patients with cutaneous T-cell lymphoma and one with adenocarcinoma of external ear canal. A significant decrease in PAR (median decrease 30.2, range -13.1 to -69.8) was achieved after drug administration (n = 6 pairs; p = 0.03), whereas an increase in PARP-1 expression was observed in five of the six tumors. This resulted in a decrease in the ratio of PAR to PARP-1 in tumor biopsies (median -6.76, range -0.41 to -22.59; p = 0.03).

Conclusions: ABT-888 hits its therapeutic target by significantly reducing PAR levels and the ratio of PAR to PARP-1 in human tumor cells detected by immunohistochemistry. Baseline tumor PAR levels vary considerably among patients who entered this phase 0 study. This underscores a need to investigate baseline PAR levels in association with response in future preclinical and clinical studies.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Benzimidazoles / pharmacology*
  • Blotting, Western
  • Cell Line, Tumor
  • Drug Resistance, Neoplasm
  • Enzyme Inhibitors / pharmacology*
  • Humans
  • Immunohistochemistry
  • Lymphoma / drug therapy*
  • Lymphoma / enzymology
  • Lymphoma / pathology
  • Neoplasms / drug therapy*
  • Neoplasms / enzymology*
  • Neoplasms / pathology
  • Poly (ADP-Ribose) Polymerase-1
  • Poly(ADP-ribose) Polymerase Inhibitors*
  • Poly(ADP-ribose) Polymerases / biosynthesis


  • Benzimidazoles
  • Enzyme Inhibitors
  • Poly(ADP-ribose) Polymerase Inhibitors
  • veliparib
  • PARP1 protein, human
  • Poly (ADP-Ribose) Polymerase-1
  • Poly(ADP-ribose) Polymerases