Molecular Imaging of Monoamine Oxidase A Expression in Highly Aggressive Prostate Cancer: Synthesis and Preclinical Evaluation of Positron Emission Tomography Tracers

Abstract

The role of monoamine oxidase A (MAO-A) in the aggressiveness of prostate cancer (PCa) has been established in recent years. The molecular imaging of MAO-A expression could offer a noninvasive tool for the visualization and quantification of highly aggressive PCa. This study reports the synthesis and preclinical evaluation of 11 C-and 18 F-labeled MAO-A inhibitors as positron emission tomography (PET) tracers for proof-of-concept studies in animal models of PCa. Good manufacturing practice production and quality control of these radiotracers using an automated platform was achieved. PET imaging was performed in an LNCaP tumor model with high MAO-A expression. The tumor-to-muscle (T/M) uptake ratio of [ 11 C]harmine (4.5 ± 0.5) was significantly higher than that for 2-[ 18 F]fluoroethyl-harmol (2.3 ± 0.7) and [ 11 C]clorgyline (2.0 ± 0.1). A comparable ex vivo biodistribution pattern in all radiotracers was observed. Furthermore, the tumor uptake of [ 11 C]harmine showed a dramatic reduction (T/M = 1) in a PC3 tumor model with limited MAO-A expression, and radioactivity uptake in LNCaP tumors was blocked in the presence of nonradioactive harmine. Our findings suggest that [ 11 C]harmine may serve as an attractive PET probe for the visualization of MAO-A expression in highly aggressive PCa. These radiotracers have the potential for clinical translation and may aid in the development of personalized therapeutic strategies for PCa patients.

Small molecule probes for the specific imaging of monoamine oxidase A and monoamine oxidase B

“…The wide applications of this probe were demonstrated by detecting MAO-A levels in bladder cancer, neuroendocrine gastroenteropancreatic tumors, and pancreatic cancer [27][28][29]. Recently, the potential of 10 also showed its potential for visualizing MAO-A expression in highly aggressive prostate cancer (PCa) was also shown [30]. Although a limited uptake of 10 was observed in a PC3 tumor-bearing mouse model, PET images showed a marked accumulation of 10 in an LNCaP tumor-bearing model, and the tumor/muscle (T/M) uptake ratio value was 4.5 � 0.5 over a 75-90 min post-injection acquisition (Figure 5a).…”