Indolyl-quinuclidinols inhibit ENOX activity and endothelial cell morphogenesis while enhancing radiation-mediated control of tumor vasculature.
There is a need for novel strategies that target tumor vasculature, specifically those that synergize with cytotoxic therapy, in order to overcome resistance that can develop with current therapeutics. A chemistry-driven drug discovery screen was employed to identify novel compounds that inhibit endothelial cell tubule formation. Cell-based phenotypic screening revealed that noncytotoxic concentrations of (Z)-(+/-)-2-(1-benzenesulfonylindol-3-ylmethylene)-1-azabicyclo[2. 2.2]octan-3-ol (analog I) and (Z)-(+/-)-2-(1-benzylindol-3-ylmethylene)-1-azabicyclo[2.2.2]octan-3-ol (analog II) inhibited endothelial cell migration and the ability to form capillary-like structures in Matrigel by > or =70%. The ability to undergo neoangiogenesis, as measured in a window-chamber model, was also inhibited by 70%. Screening of biochemical pathways revealed that analog II inhibited the enzyme ENOX1 (EC(50) = 10 microM). Retroviral-mediated shRNA suppression of endothelial ENOX1 expression inhibited cell migration and tubule formation, recapitulating the effects observed with the small-molecule analogs. Genetic or chemical suppression of ENOX1 significantly increased radiation-mediated Caspase3-activated apoptosis, coincident with suppression of p70S6K1 phosphorylation. Administration of analog II prior to fractionated X-irradiation significantly diminished the number and density of tumor microvessels, as well as delayed syngeneic and xenograft tumor growth compared to results obtained with radiation alone. Analysis of necropsies suggests that the analog was well tolerated. These results suggest that targeting ENOX1 activity represents a novel therapeutic strategy for enhancing the radiation response of tumors.
Geng
Ling
L
Department of Radiation Oncology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
Rachakonda
Girish
G
Morré
D James
DJ
Morré
Dorothy M
DM
Crooks
Peter A
PA
Sonar
Vijayakumar N
VN
Roti
Joseph L Roti
JL
Rogers
Buck E
BE
Greco
Suellen
S
Ye
Fei
F
Salleng
Kenneth J
KJ
Sasi
Soumya
S
Freeman
Michael L
ML
Sekhar
Konjeti R
KR
D002465:Cell Movement / Q000187:drug effects; D048430:Cell Shape / Q000187:drug effects; D002478:Cells, Cultured; D004353:Drug Evaluation, Preclinical; D042783:Endothelial Cells / Q000187:drug effects / Q000502:physiology; D004730:Endothelium, Vascular / Q000166:cytology*; D006801:Humans; D007211:Indoles; D008565:Membrane Proteins / Q000037:antagonists & inhibitors; D009369:Neoplasms / Q000098:blood supply / Q000628:therapy; D009389:Neovascularization, Pathologic / Q000188:drug therapy* / Q000532:radiotherapy; D011490:Protein Disulfide Reductase (Glutathione) / Q000037:antagonists & inhibitors*; D011812:Quinuclidines / Q000494:pharmacology* / Q000627:therapeutic use; D014157:Transcription Factors / Q000037:antagonists & inhibitors*
D007211:Indoles; D008565:Membrane Proteins; D011812:Quinuclidines; D014157:Transcription Factors; C030374:indole; D011490:Protein Disulfide Reductase (Glutathione)