Leveraging an NQO1 Bioactivatable Drug for Tumor-Selective Use of Poly(ADP-ribose) Polymerase Inhibitors

Area of Science:

• Oncology
• Molecular Biology
• Pharmacology

Background:

• Therapeutic drugs targeting DNA repair, such as poly(ADP-ribose) polymerase (PARP) inhibitors, often lack tumor selectivity, limiting their efficacy.
• Tumor cells can exhibit resistance mechanisms to DNA repair inhibitors, necessitating novel therapeutic strategies.

Purpose of the Study:

• To investigate the synergistic antitumor activity of combining PARP inhibitors with β-lapachone.
• To elucidate the underlying mechanisms of this synergy, focusing on NAD(P)H levels, NQO1 activity, and cell death pathways.
• To evaluate the therapeutic efficacy and tumor selectivity of the combination therapy in preclinical cancer models.

Main Methods:

• Combination therapy using PARP inhibitors and β-lapachone.
• Assessment of NAD(P)H levels and NQO1-dependent redox cycling.
• Measurement of oxygen consumption rate and reactive oxygen species (ROS) production.
• Analysis of DNA damage and repair inhibition.
• Investigation of cell death mechanisms (necrosis vs. apoptosis) via caspase activity.
• Evaluation in human orthotopic xenograft models of pancreatic and non-small-cell lung cancer.

Main Results:

• The combination of PARP inhibitors and β-lapachone demonstrated synergistic antitumor activity.
• Sustained NAD(P)H levels were observed, refueling NQO1-dependent futile redox drug recycling.
• Increased oxygen consumption and ROS generation led to significant DNA lesions unrepaired due to PARP inhibition.
• In NQO1-positive cancers, the cell death mechanism shifted from necrosis to synergistic, tumor-selective, caspase-dependent apoptosis.
• Synergistic antitumor efficacy and prolonged survival were observed in pancreatic and non-small-cell lung cancer xenograft models.

Conclusions:

• The combination of PARP inhibitors and β-lapachone offers a tumor-selective approach for treating NQO1-positive cancers.
• This combination therapy enhances efficacy by inducing apoptosis and overcoming resistance mechanisms.
• The findings support the expanded use and improved efficacy of PARP inhibitors in human cancer therapy.