Protein fragment linked to a light-emitting molecule was able to pick out tumors in mice two days after treatment.

 Investigators report finding a small protein that specifically recognizes tumors responding to chemotherapy. They showed that the protein when tagged with a light-emitting molecule can be used to visualize response in mice just two days after starting therapy.

The researchers focused not on tumor size but molecular and cellular changes in responding tumors. From billions of peptides, they identified one that specifically bound to tumors responding to therapy. They attached a light-emitting molecule to this peptide and injected the labeled peptides into mice that had been implanted with human tumors.

Using imaging cameras that detect light in the near-infrared range, the investigators observed that tumors responding to therapy were brighter than nonresponding tumors. The peptide detected response in a wide range of tumors such as in the brain, lungs, colon, prostate, and breast within two days of initiation of treatment, they say.

The next step will be to move the technology into humans. The imaging technique used in mice is not sensitive enough to penetrate deeply into human tissues, so the researchers are adapting the method to use PET.

“This imaging peptide will enter clinical trials within about 18 months,” says senior investigator Dennis Hallahan, M.D., the Ingram professor of cancer research and chair of radiation oncology at Vanderbilt University Medical Center.

The study included researchers at Vanderbilt University and Vanderbilt-Ingram Cancer Center. The findings appear online ahead of print in Nature Medicine.

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