Nanoparticles hit Cancer’s moving target

Though most cancer therapies treat tumors as monoliths, the cells evolve and change their behavior over time. For example, they can alter their gene expression pattern to escape from the primary tumor and spread throughout the body. Now, researchers have developed a nanoparticle that targets cancer cells at two different stages of metastasis, which could make it possible to prevent the disease from spreading. About 90% of cancer deaths are caused not by the initial tumor but by secondary tumors, or metastases, that often take root in the lungs, bone, liver, or brain. These metastatic cells commonly survive chemotherapy and are “buried in the large population of healthy cells in the body.
The team decorated a 100-nm-diameter liposome with ligands that target two surface proteins expressed on metastatic cancer cells after they have escaped from a tumor and are circulating in the bloodstream. Both proteins help circulating tumor cells exit the bloodstream at a new site so that they can establish a new tumor. One protein, selectin, helps cancer cells circulating in the blood start to roll along the inside surface of a blood vessel. The second protein, integrin, helps these rolling cells firmly attach to the blood vessel before exiting and seeding a new tumor. They injected fluorescently or radioactively labeled nanoparticles into the mice and saw that the nanoparticles hit the mark. They caught about 90% of the micrometastatic sites, small clusters of cancer cells 10 to 30 μm in size, Karathanasis says. It recognizes that tumors are not monolithic and that, within each tumor or within each patient, one might have tumors at different stages of development or metastatic spread,” he says. That brings nanotherapy design into better alignment with the current understanding of cancer biology.