Increase in tumour permeability following TGF-β type I receptor-inhibitor treatment observed by dynamic contrast-enhanced MRI

BACKGROUND: To enhance the success rate of nanocarrier-mediated chemotherapy combined with an anti-angiogenic agent, it is crucial to identify parameters for tumour vasculature that can predict a response to the treatment of the anti-angiogenic agent. METHODS: To apply transforming growth factor (TGF)-β type I receptor (TβR-I) inhibitor, A-83-01, to combined therapy, dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) was carried out in mice bearing colon 26 cells using gadolinium (Gd)-DTPA and for its liposomal formulation to evaluate changes in tumour microvasculature following A-83-01. Tumour vascular parameters from DCE-MRI were compared with histological assessment and apparent diffusion coefficient of water in tumour generated by diffusion-weighted MRI. RESULTS: Contrary to evaluations reported for anti-angiogenic agents, A-83-01 treatment increased the initial area under the Gd concentration–time curve (IAUGC(60)), volume transfer constant (K(trans)) and fractional plasma volume (v(p)) significantly within 24 h, that was positively related to α-smooth muscle actin-positive pericyte coverage and tumour cell proliferation, and was correlated inversely with the apparent diffusion coefficient. The vascular function of the tumour improved by A-83-01 treatment was well assessed on post-liposomal Gd-DTPA-enhanced MR images, which predicted delivery of a liposomal drug to the tumour. CONCLUSION: These findings suggest that DCE-MRI and, in particular, K(trans) and v(p) quantitation, provide important additional information about tumour vasculature by A-83-01 treatment.