Melanoma Coverage from Every Angle

Radiolabeled Peptide Targeting Melanocortin-1 Receptor in Melanoma Imaging

By: Sarah Campen, PharmD
Posted: Tuesday, December 18, 2018

For the first time in humans, a radiolabeled peptide, 68Ga-DOTA-GGNle-CycMSHhex, has enabled researchers to view melanoma metastases with positron-emission tomography (PET). The peptide, with an imaging radionuclide attached, seeks out and binds to melanocortin-1 receptor (MC1R), a protein that is highly expressed on the surface of more than 80% of melanomas in humans. The study was published in Science Translational Medicine.

Basically, we attach the imaging radionuclide to the peptide, then the radiolabeled peptide finds MC1Rs on the melanoma through blood circulation, allowing us to use a PET machine to gather the signals from the radiolabeled peptide for melanoma imaging,” stated Yubin Miao, PhD, of the University of Colorado Denver, Aurora, in an institutional press release. “It’s a very sensitive way to see melanoma.”

The researchers are hopeful this development may eventually allow them to use the peptide as a delivery vehicle to transport a therapeutic radionuclide directly to melanoma cells marked with MC1Rs in patients with metastatic melanoma. The PET images of melanoma metastases suggest that MC1R is a valid molecular target for melanoma during both early development and advanced stages of disease, including later generations of daughter metastases. “The successful imaging of melanoma metastases in patients underscored the need to develop MC1R-targeting therapeutic peptides for treating patients with metastatic melanoma,” according to the investigators.

They were also able to replace the radiolabel with a fluorescent label to generate a new MC1R-targeting fluorescence imaging probe, known as Cy5.5-GGNle-CycMSHhex. They believe that combining the radiolabeled and fluorescent probes may improve surgical outcomes in melanoma through imaging-guided surgery.

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