Imaging method kills cancers cells, but spares healthy ones

BALTIMORE, MD – Cancer imaging experts at Johns Hopkins have developed a method for finding and killing malignant cancer cells while sparing healthy ones.

“Theranostic imaging” is a method that targets and tracks potent drug therapies directly and only to cancer cells. It relies on binding an inactive form of drug chemotherapy with an enzyme to specific proteins on tumor cell surfaces and detecting the drug’s absorption into the tumor. The binding of the highly specific drug-protein complex, or nanoplex, to the cell surface allows it to get inside the cancerous cell, where the enzyme activates the drug.

The study was published in the journal American Chemical Society Nano online on August 6. Senior study investigator Zaver Bhujwalla, Ph.D., a professor at the Johns Hopkins University School of Medicine and its Kimmel Cancer Center, notes that a persistent problem with current chemotherapy is that it attacks all kinds of cells and tissues.

In the theranostic imaging experiments, overseen by Bhujwalla and study co-investigator Martin Pomper, M.D., Ph.D, drugs were directed only to cancer cells with prostate-specific membrane antigen (PSMA) cell surface proteins.

“Our results show a non-invasive imaging approach to following and delivering targeted therapy to any cancer that expresses PSMA,” says Bhujwalla, who also serves as director of the Johns Hopkins In Vivo Cellular and Molecular Imaging Center (ICMIC), where the studies were developed.

Different concentrations of the drug nanoplex were tagged with radioactive and fluorescent molecules and mixed in the lab with prostate cancer tissue cells, some of which had extra PSMA and others which had none. Only cells with extra PSMA showed nanoplex uptake.

“Our theranostic imaging approach shows how the best methods of detection and treatment can be combined to form highly specialized, more potent and safer forms of chemotherapy,” says Pomper, who is currently working to identify other molecular targets. “With theranostic imaging, we can attack multiple tumor targets, making it harder for the tumor to evade drug treatment.”