In this work we characterize the relaxivity, chemical stability, and tumor-specific uptake of a cancer-targeting T1-shortening contrast agent, Gd-DOTA-APC. We observe striking longitudinal relaxivity of up to 16.5 s-1/mM and 10.6 s-1/mM at 1.5T and 3.0T, respectively. High chemical stability was measured, with less than 0.1% free Gd3+ detected after dissolution of the agent in buffer. Finally, we observe tumor-specific T1-weighted signal enhancement following Gd-DOTA-APC delivery, sustained out to seven days after administration. These observations indicate that Gd-DOTA-APC holds potential as a safe and effective agent for targeted cancer imaging.