AG-013736, a novel inhibitor of VEGF receptor tyrosine kinases, inhibits breast cancer growth and decreases vascular permeability as detected by dynamic contrast-enhanced magnetic resonance imaging.
Dynamic contrast-enhanced MRI (DCE-MRI) was used to noninvasively evaluate the effects of AG-03736, a novel inhibitor of vascular endothelial growth factor (VEGF) receptor tyrosine kinases, on tumor microvasculature in a breast cancer model. First, a dose response study was undertaken to determine the responsiveness of the BT474 human breast cancer xenograft to AG-013736. Then, DCE-MRI was used to study the effects of a 7-day treatment regimen on tumor growth and microvasculature. Two DCE-MRI protocols were evaluated: (1) a high molecular weight (MW) contrast agent (albumin-(GdDTPA)(30)) with pharmacokinetic analysis of the contrast uptake curve and (2) a low MW contrast agent (GdDTPA) with a clinically utilized empirical parametric analysis of the contrast uptake curve, the signal enhancement ratio (SER). AG-013736 significantly inhibited growth of breast tumors in vivo at all doses studied (10-100 mg/kg) and disrupted tumor microvasculature as assessed by DCE-MRI. Tumor endothelial transfer constant (K(ps)) measured with albumin-(GdDTPA)(30) decreased from 0.034+/-0.005 to 0.003+/-0.001 ml min(-1) 100 ml(-1) tissue (P<.0022) posttreatment. No treatment-related change in tumor fractional plasma volume (fPV) was detected. Similarly, in the group of mice studied with GdDTPA DCE-MRI, AG-013736-induced decreases in tumor SER measures were observed. Additionally, our data suggest that 3D MRI-based volume measurements are more sensitive than caliper measurements for detecting small changes in tumor volume. Histological staining revealed decreases in tumor cellularity and microvessel density with treatment. These data demonstrate that both high and low MW DCE-MRI protocols can detect AG-013736-induced changes in tumor microvasculature. Furthermore, the correlative relationship between microvasculature changes and tumor growth inhibition supports DCE-MRI methods as a biomarker of VEGF receptor target inhibition with potential clinical utility.
Wilmes
Lisa J
LJ
Department of Radiology, University of California San Francisco, San Francisco, CA 94143-1290, USA. lisa@mrsc.ucsf.edu
Pallavicini
Maria G
MG
Fleming
Lisa M
LM
Gibbs
Jessica
J
Wang
Donghui
D
Li
Ka-Loh
KL
Partridge
Savannah C
SC
Henry
Roland G
RG
Shalinsky
David R
DR
Hu-Lowe
Dana
D
Park
John W
JW
McShane
Teresa M
TM
Lu
Ying
Y
Brasch
Robert C
RC
Hylton
Nola M
NM
D000818:Animals; D000970:Antineoplastic Agents / Q000008:administration & dosage; D000077784:Axitinib; D001943:Breast Neoplasms / Q000098:blood supply / Q000188:drug therapy* / Q000473:pathology*; D002199:Capillary Permeability / Q000187:drug effects*; D049109:Cell Proliferation / Q000187:drug effects; D003287:Contrast Media; D005260:Female; D007093:Imidazoles / Q000627:therapeutic use*; D007191:Indazoles / Q000627:therapeutic use*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D051379:Mice; D008819:Mice, Nude; D009389:Neovascularization, Pathologic / Q000473:pathology* / Q000517:prevention & control*; D040262:Receptors, Vascular Endothelial Growth Factor / Q000037:antagonists & inhibitors; D016896:Treatment Outcome; D019061:src-Family Kinases / Q000037:antagonists & inhibitors
D000970:Antineoplastic Agents; D003287:Contrast Media; D007093:Imidazoles; D007191:Indazoles; D000077784:Axitinib; D040262:Receptors, Vascular Endothelial Growth Factor; D019061:src-Family Kinases