Cellular mechanism of action of 2-nitroimidazoles as hypoxia-selective therapeutic agents
Faisal Bin Rashed,
Diana Diaz-Dussan,
Fatemeh Mashayekhi,
Dawn Macdonald,
Patrick Nicholas Nation,
Xiao-Hong Yang,
Sargun Sokhi,
Alexandru Cezar Stoica,
Hassan El-Saidi,
Carolynne Ricardo,
Ravin Narain,
Ismail Hassan Ismail,
Leonard Irving Wiebe,
Piyush Kumar,
Michael Weinfeld
Affiliations
Faisal Bin Rashed
Department of Oncology, University of Alberta, Edmonton, Alberta, AB T6G 2R3, Canada
Diana Diaz-Dussan
Department of Chemical & Materials Engineering, University of Alberta, Edmonton, Alberta, AB T6G 2R3, Canada
Fatemeh Mashayekhi
Department of Oncology, University of Alberta, Edmonton, Alberta, AB T6G 2R3, Canada
Dawn Macdonald
Department of Oncology, University of Alberta, Edmonton, Alberta, AB T6G 2R3, Canada
Patrick Nicholas Nation
Department of Laboratory Medicine & Pathology, University of Alberta, Edmonton, Alberta, AB T6G 2R3, Canada
Xiao-Hong Yang
Department of Oncology, University of Alberta, Edmonton, Alberta, AB T6G 2R3, Canada
Sargun Sokhi
Department of Oncology, University of Alberta, Edmonton, Alberta, AB T6G 2R3, Canada
Alexandru Cezar Stoica
Department of Oncology, University of Alberta, Edmonton, Alberta, AB T6G 2R3, Canada
Hassan El-Saidi
Department of Oncology, University of Alberta, Edmonton, Alberta, AB T6G 2R3, Canada; Department of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Alexandria, El Sultan Hussein St. Azarita, Alexandria, Egypt
Carolynne Ricardo
Department of Oncology, University of Alberta, Edmonton, Alberta, AB T6G 2R3, Canada
Ravin Narain
Department of Chemical & Materials Engineering, University of Alberta, Edmonton, Alberta, AB T6G 2R3, Canada
Ismail Hassan Ismail
Department of Oncology, University of Alberta, Edmonton, Alberta, AB T6G 2R3, Canada; Biophysics Department, Faculty of Science, Cairo University, Cairo, Egypt
Leonard Irving Wiebe
Department of Oncology, University of Alberta, Edmonton, Alberta, AB T6G 2R3, Canada
Piyush Kumar
Department of Oncology, University of Alberta, Edmonton, Alberta, AB T6G 2R3, Canada; Corresponding author. Department of Oncology, University of Alberta, 116 St & 85 Ave, Edmonton, AB T6G 2R3, Canada.
Michael Weinfeld
Department of Oncology, University of Alberta, Edmonton, Alberta, AB T6G 2R3, Canada; Corresponding author. Department of Oncology, University of Alberta, 116 St & 85 Ave, Edmonton, AB T6G 2R3, Canada.
Solid tumours are often poorly oxygenated, which confers resistance to standard treatment modalities. Targeting hypoxic tumours requires compounds, such as nitroimidazoles (NIs), equipped with the ability to reach and become activated within diffusion limited tumour niches. NIs become selectively entrapped in hypoxic cells through bioreductive activation, and have shown promise as hypoxia directed therapeutics. However, little is known about their mechanism of action, hindering the broader clinical usage of NIs. Iodoazomycin arabinofuranoside (IAZA) and fluoroazomycin arabinofuranoside (FAZA) are clinically validated 2-NI hypoxic radiotracers with excellent tumour uptake properties. Hypoxic cancer cells have also shown preferential susceptibility to IAZA and FAZA treatment, making them ideal candidates for an in-depth study in a therapeutic setting. Using a head and neck cancer model, we show that hypoxic cells display higher sensitivity to IAZA and FAZA, where the drugs alter cell morphology, compromise DNA replication, slow down cell cycle progression and induce replication stress, ultimately leading to cytostasis. Effects of IAZA and FAZA on target cellular macromolecules (DNA, proteins and glutathione) were characterized to uncover potential mechanism(s) of action. Covalent binding of these NIs was only observed to cellular proteins, but not to DNA, under hypoxia. While protein levels remained unaffected, catalytic activities of NI target proteins, such as the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and the detoxification enzyme glutathione S-transferase (GST) were significantly curtailed in response to drug treatment under hypoxia. Intraperitoneal administration of IAZA was well-tolerated in mice and produced early (but transient) growth inhibition of subcutaneous mouse tumours.
