title: Modulation of DNA damage response and induction of apoptosis mediates synergism between doxorubicin and a new imidazopyridine derivative in breast and lung cancer cells.
abstract: DNA damage response machinery (DDR) is an attractive target of cancer therapy. Modulation of DDR network may alter the response of cancer cells to DNA damaging anticancer drugs such as doxorubicin. The aim of the present study is to investigate the effects of a newly developed imidazopyridine (IAZP) derivative on the DDR after induction of DNA damage in cancer cells by doxorubicin. Cytotoxicity sulphrhodamine-B assay showed a weak anti-proliferative effect of IAZP alone on six cancer cell lines (MCF7, A549, A549DOX11, HepG2, HeLa and M8) and a normal fibroblast strain. Combination of IAZP with doxorubicin resulted in synergism in lung (A549) and breast (MCF7) cancer cells but neither in the other cancer cell lines nor in normal fibroblasts. Molecular studies revealed that synergism is mediated by modulation of DNA damage response and induction of apoptosis. Using constant-field gel electrophoresis and immunofluorescence detection of γ-H2AX foci, IAZP was shown to inhibit the repair of doxorubicin-induced DNA damage in A549 and MCF7 cells. Immunoblot analysis showed that IAZP suppresses the phosphorylation of the ataxia lelangiectasia and Rad3 related (ATR) protein, which is an important player in the response of cancer cells to chemotherapy-induced DNA damage. Moreover, IAZP augmented the doxorubicin-induced degradation of p21, activation of p53, CDK2, caspase 3/7 and phosphorylation of Rb protein. These effects enhanced doxorubicin-induced apoptosis in both cell lines. Our results indicate that IAZP is a promising agent that may enhance the cytotoxic effects of doxorubicin on some cancer cells through targeting the DDR. It is a preliminary step toward the clinical application of IAZP in combination with anticancer drugs and opens the avenue for the development of compounds targeting the DDR pathway that might improve the therapeutic index of anticancer drugs and enhance their cure rate.
authors.affiliation: Sharjah Institute for Medical Research, University of Sharjah, Sharjah, United Arab Emirates; College of Pharmacy, University of Sharjah, Sharjah, United Arab Emirates; Cancer Biology Department, National Cancer Institute and College of Medicine, Cairo University, Cairo, Egypt. Electronic address: relawady@sharjah.ac.ae.
authors.forename: Raafat A
authors.initials: RA
authors.lastname: El-Awady
authors.affiliation: Sharjah Institute for Medical Research, University of Sharjah, Sharjah, United Arab Emirates; College of Pharmacy, University of Sharjah, Sharjah, United Arab Emirates.
authors.forename: Mohammad H
authors.initials: MH
authors.lastname: Semreen
authors.affiliation: Sharjah Institute for Medical Research, University of Sharjah, Sharjah, United Arab Emirates; Cancer Biology Department, National Cancer Institute and College of Medicine, Cairo University, Cairo, Egypt.
authors.forename: Maha M
authors.initials: MM
authors.lastname: Saber-Ayad
authors.affiliation: Sharjah Institute for Medical Research, University of Sharjah, Sharjah, United Arab Emirates; College of Medicine, University of Sharjah, Sharjah, United Arab Emirates.
authors.forename: Farhan
authors.initials: F
authors.lastname: Cyprian
authors.affiliation: Sharjah Institute for Medical Research, University of Sharjah, Sharjah, United Arab Emirates.
authors.forename: Varsha
authors.initials: V
authors.lastname: Menon
authors.affiliation: Sharjah Institute for Medical Research, University of Sharjah, Sharjah, United Arab Emirates; College of Pharmacy, University of Sharjah, Sharjah, United Arab Emirates.
authors.forename: Taleb H
authors.initials: TH
authors.lastname: Al-Tel
mesh_terms: D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology / Q000627:therapeutic use*; D017209:Apoptosis / Q000187:drug effects*; D064007:Ataxia Telangiectasia Mutated Proteins / Q000187:drug effects / Q000378:metabolism; D001562:Benzimidazoles / Q000627:therapeutic use*; D001943:Breast Neoplasms / Q000188:drug therapy*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D004247:DNA / Q000187:drug effects / Q000378:metabolism; D004249:DNA Damage; D004260:DNA Repair / Q000187:drug effects*; D004317:Doxorubicin / Q000494:pharmacology / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy*; D010766:Phosphorylation; D011725:Pyridines / Q000627:therapeutic use*
chemical_list: D001562:Benzimidazoles; C000611844:N-tert-butyl-2-(3-(5-fluoro-1H-benzo(d)imidazol-2-yl)phenyl)imidazo(1,2-a)pyridin-3-amine; D011725:Pyridines; D004317:Doxorubicin; D004247:DNA; C576597:ATR protein, human; D064007:Ataxia Telangiectasia Mutated Proteins
keywords: Apoptosis; Cyclin-dependent kinase (CDK); DNA damage response; Doxorubicin; Drug discovery; p21