Real Time Ultrasound Molecular Imaging of Prostate Cancer with PSMA-targeted Nanobubbles

Contrast-enhanced ultrasound with microbubbles has shown promise in detection of prostate cancer (PCa), but sensitivity and specificity of detection remain challenging. Targeted nanoscale contrast agents with improved capability to accumulate in tumors may result in prolonged signal enhancement and improved detection of PCa with ultrasound. Here we report on a new nanobubble contrast agent that specifically targets prostate specific membrane antigen (PSMA) overexpressed in most prostate tumors. The PSMA-targeted bubbles (PSMA-NB) were utilized to simultaneously image dual flank PCa tumors (PSMA-positive PC3pip and PSMA-negative PC3flu) to examine whether the biomarker can be successfully detected and imaged using this probe in a mouse model. Results demonstrate that active targeting of NBs to PSMA rapidly and selectively enhances tumor accumulation and is critical for tumor retention of the contrast agent. Importantly, these processes could be visualized and quantified, in real time, with standard clinical ultrasound. Such demonstration of the immense yet underutilized potential of ultrasound in the area of molecular imaging can open the door to future opportunities for improving sensitivity and specificity of cancer detection using parametric NB-enhanced ultrasound imaging.