The experience in
free radical biology and medicine shows the crucial role of redox signalling in
carcinogenesis. The cells and tissues of healthy mammals are characterised by a low level of
reactive oxygen species (ROS) and some constant (reference) level of reducing equivalents. Increasing of ROS above the critical level provokes
genomic instability. The present study describes universal methodology for direct imaging of tissue redox activity in
carcinogenesis, which allows a differentiation of
cancer development from normal condition. The experiments were conducted on:
neuroblastoma-bearing mice;
colon cancer-bearing mice; and healthy mice. The tissue redox activity was visualised in vivo by
nitroxide-enhanced magnetic resonance imaging (MRI) on anesthetised animals. The method is based on
nitroxide redox cycle, coupled with appearance/disappearance of MRI signal. The half-life (τ1/2) of
nitroxide-enhanced MRI signal in the respective tissue was used as a diagnostic marker. The study provides direct evidence that healthy and
cancer-bearing mammalian tissues are characterised by different redox activities - a basis for
cancer diagnosis. The tissues (
cancer and 'normal') of
cancer-bearing mammals were characterised by a long-lived MRI signal (τ1/2>14 min), indicating a high oxidative activity. The tissues of healthy organism were characterised by a short-lived MRI signal (τ1/2=1-3 min), indicating a high reducing activity. The study shows that tissue redox activity is a sensing platform for imaging of
cancer using
nitroxide-enhanced MRI. It also suggests that 'normal' tissues of
cancer-bearing organism are susceptible to oxidative damage.