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"Spot Navigation" for Tumors: a Radiolabeled Protein for Pinpoint Cancer Diagnostics

Many cancers—lung, ovarian, breast, kidney—share a common feature: they overexpress a protein called EpCAM on their surface. It's the perfect target. If you can find EpCAM, you can find the tumor.

We already had a tool: a protein called DARPin Ec1, labeled with technetium-99m. It worked—it lit up EpCAM-positive tumors in clinical trials. But there was a catch: It also accumulated in healthy organs, creating a background noise.

Now, a team from Tomsk Polytechnic University and Siberian State Medical University, together with colleagues from the Institute of Bioorganic Chemistry RAS (Moscow), figured out how to clean up the signal.

🧪 The fix:

They tweaked the "tail" of the protein—the part where the radioactive label attaches. They added short peptide chelators: Gly-Gly-Gly-Cys (G3C) or Glu-Glu-Glu-Cys (E3C) , stitched onto the C-terminus of DARPin.

🔬 The result:
▫️ Both variants kept their high affinity for EpCAM (Kd = 8–10 nM).
▫️ The background signal drastically reduced.
▫️ Tc-Ec1-G3C gave the best contrast. Tumors lit up; healthy tissue stayed dark.

According to the researchers, this version is ready for clinical trials. It's a sharper tool for oncologists—better visualization means better detection, better staging, better decisions.

Published in Molecular Pharmaceutics (IF 4.5)

🔗 Read the paper