⁶⁸Ga-DOTA-NT-20.3 Neurotensin Receptor 1 PET Imaging as a Surrogate for Neuroendocrine Differentiation of Prostate Cancer

Abstract

PSMA-negative neuroendocrine prostate cancer (NEPC) is likely to be a lethal subtype of prostate cancer (PCa) with limited clinical diagnostic and therapeutic options. High expression of neurotensin receptor subtype 1 (NTR1) associated with neuroendocrine differentiation of PCa, which makes NTR1 a potential target for NEPC. In this study, NTR1-targeted tracer 68 Ga-DOTA-NT-20.3 was synthesized and evaluated by determining its affinity to androgen-dependent (LNCap) and androgen-independent (PC3) xenografts.Methods: 68 Ga-DOTA-NT-20.3 was labeled with an automated iQS-theranostics synthesizer module and its stability, labeling yield, and radiochemical purity were analyzed by radio-HPLC. Receptor binding affinity was evaluated in NTR1-positive PC3 cells by competitive binding assay. The biodistribution of 68 Ga-DOTA-NT-20.3 in vivo was evaluated in PC3 and LNCap xenografts by micro-PET imaging. NTR1 expression was identified by immunohistochemistry and immunofluorescence. Results: 68 Ga-DOTA-NT-20.3 was synthesized successfully with a yield rate of 88.07 ± 1.26 %, radiochemical purity ≥ 99% and favorable stability. The NTR1 affinity (IC50) for 68 Ga-DOTA-NT-20.3 was 7.59 ± 0.41 nM. Micro-PET/CT in PC3 xenografts showed high contrast images with intense tumor uptake, which revealed specific NTR1 expression. The tumor showed significant radioactivity (4.95 ± 0.67 percentage of injected dose per gram of tissue [%ID/g]) at 1h, which fell to 1.95 ± 0.17 %ID/g (P < 0.01, t = 8.72) after specific blockage by neurotensin.LNCap xenografts had no significant accumulation (0.81 ± 0.06 %ID/g) of 68 Ga-DOTA-NT-20.3 at 1 h. In contrast, 68 Ga-PSMA-11 was mainly concentrated in LNCap xenografts (8.60 ± 2.11 %ID/g), with no significant uptake in PC3 tumors (0.53 ± 0.05 %ID/g), consistent with the in vitro immunohistochemistry findings. Biodistribution showed rapid clearance from the blood and main organs (brain, heart, lung, liver, muscle, bone) with significantly high tumor/liver (4.41 ± 0.73) and tumor/muscle ratios (12.34 ± 1.32) at 60 min post-injection. Conclusion: 68 Ga-DOTA-NT-20.3 can be efficiently prepared with a high yield and radiochemical purity. Its favorable biodistribution and prominent NTR1 affinity make 68 Ga-DOTA-NT-20.3 a potential radiopharmaceutical for the detection of PSMA-negative PCa and identification of neuroendocrine differentiation.

Neuron-derived neurotensin promotes pancreatic cancer invasiveness and gemcitabine resistance via the NTSR1/Akt pathway

“…We demonstrated that NTS is mainly produced by neuronal cells (Figure 11, Supplementary Figure 1) and acts via a paracrine mechanism to stimulate the invasiveness of PDAC. The importance of neural plasticity in cancer formation has been revisited recently [46][47][48]. As pancreas is an organ being innervated by different types of neurons, it is soaked in a microenvironment fulfilled with abundant neurotrophic factors, which help the initiation, promotion and progression of PDAC [46].…”

Evaluation of gastrin-releasing peptide receptor, prostate-specific membrane antigen, and neurotensin receptor 1 as potential biomarkers for accurate prostate cancer stratified diagnosis

“…The PC-3 cell line is characteristic of endocrine PCa and expresses high levels of neuroendocrine markers [ 35 ], consistent with our observations in two patients with neuroendocrine PCa, who were negative for PSMA and positive for GRPR and NTR1. Wu et al [ 36 ] also speculated that high expression of NTR1 is associated with neuroendocrine differentiation of PCa, which makes NTR1 a potential target for neuroendocrine PCa, and PSMA imaging may have false negative in NEPC patients, but targeted NTR1 imaging may make up for the deficiency of PSMA, but their research was limited to cells and animals study. And our findings were mainly based on patient samples.…”

PET/CT and Conventional Imaging for the Assessment of Neuroendocrine Prostate Cancer: A Systematic Review

“…In this scenario, it has been proposed that specific forms of NEPC, depending on their origin, can be imaged with different radiopharmaceuticals based on preclinical evidence [41,43,46,47]. Moreover, new tracers able to evaluate the presence of NEPC or its progression from CRPC are continuously developed and hopefully will help in the assessment of the disease [34,[48][49][50]. Lastly, some interesting insights on the role of these new radiopharmaceuticals for the evaluation of treatment response with innovative drugs specific to NEPC have been reported [51].…”