Novel PET Tracer for Prostate Cancer Shows Promise

Study is the first to provide evidence that proton-coupled amino acid transporters can be elevated in prostate cancer.

For the first time, scientists were able to demonstrate the potential of a novel PET tracer for imaging prostate cancer.

In a study published in the Journal of Nuclear Medicine, the investigators sought to compare the efficacy of the new tracer Carbon-11 labeled sarcosine (11C-sarcosine) with the widely-used tracer 11C-choline in 2 mouse models.

The investigators also performed the first PET/CT scan with 11C-sarcosine of a human with prostate cancer, according to a press release.

Prostate cancer is the second leading cause of cancer death among men, according to the CDC. Approximately 1 of 7 men will be diagnosed with prostate cancer during his lifetime. Sarcosine plays a critical role in the aggressive nature and progression of the disease, entering cells via proton-coupled amino acid transporters (PAT)—–which are overexpressed in selected tissues and solid tumors.

“Given the link between 11C-sarcosine cell uptake and PAT transport, the study provides the first evidence that PAT expression can be elevated in prostate cancer,” investigator Morand Piert, MD, said in the release.

In preclinical models, the results of the study showed the tumor-to-background ratios obtained from 11C-sarcosine PET were significantly elevated compared with 11C-choline. Furthermore, 11C-sarcosine produced high-contrast images in human prostate cancer case, according to the release.

The investigators then conducted independent target metabolite analyses and found significant increases of sarcosine, glycine, and choline tissue levels from benign prostate tissue to localized prostate cancer and subsequently metastatic disease.

The findings suggest 11C-sarcosine PET may be a viable tracer for prostate cancer imaging, the authors said. Additionally, 11C-sarcosine could be an important trace for identifying and characterizing other cancers.

“To our knowledge, this is the first radiotracer to interrogate the activity of PATs, which play a role as multi-purpose carriers with distinct roles in different cells,” Piert said. “In the brain, these transporters are involved in the neuronal amino acid transport. In the intestinal tract, certain PATs play a role as nutrient and drug transporter.

“Furthermore, PAT expression increases the cell proliferation. In cancer, PAT function has been related to the amino acid-sensing engine that drives activation of the mammalian target of rapamycin complex 1 (mTORC1), which is an important target for existing and new anti-cancer drugs.”

Although the findings show promise, the authors said more research needs to be done.

“Based on the known metabolism of sarcosine in cancer, we postulate that elevated 11C-sarcosine uptake is a negative prognostic marker and may potentially be useful to monitor mTORC1-targeted cancer treatments,” Piert concluded.