Viruses May Silence Cancer Therapy’s Side Effects

Viruses May Silence Cancer Therapy's Side Effects

The same virus that can level a potato crop may have a huge upside as a deadly weapon in the war on cancer.

Case Western Reserve University biomedical engineering professor Nicole Steinmetz, PhD, wants to use particles formed by plant viruses to carry crucial medicine directly to tumor sites. The approach aims to knock out patients’ malignant cells without ravaging healthy ones—sparing them the side effects of traditional chemotherapy, such as nausea, hair loss, fatigue and even congestive heart failure.

Steinmetz and her team are conducting preclinical studies to evaluate the promise of several such viruses. The virus particles, known as viral nanoparticles (VNPs), can be lethal to plants but are entirely nontoxic for humans.

“We aim to take highly potent drugs—not new drugs, necessarily, but ones that already are FDA-approved— and put them inside a nanoparticle that will deliver them only to the tumor,” Steinmetz explains.

She adds that VNPs are well suited to deliver cancer drugs because they can hold a full “payload” of medication. In addition, they can be designed to bond only to the cancer cells and not healthy surrounding cells. Another upside of using VNPs rather than synthetic delivery systems: They’re easily and cheaply produced using molecular plant-farming methods.

The agents under study—such as cowpea mosaic virus, potato virus X, tobacco mosaic virus and brome mosaic virus—have structures that vary from each other, and each could perform well depending on the medical need, Steinmetz explains.

The nanoparticles are tiny, by Steinmetz’s description, some 2,500 times smaller than the width of a human hair. After they’re extracted from plant leaves, ligands—molecules tasked with directing the VNP to cancer cells—are added to the formulation along with the actual drug.

While many scientists are exploring drug-delivery systems from man-made materials, Steinmetz happily hitches a ride on nature’s coattails: “There’s only so much research I can do in a lifetime, so I’m relying on nature for what it already does best. Viruses have evolved over millions of years to carry cargos to specific cells and tissues.”

The viruses have promise in a broad range of biomedical applications—they may lead to improved imaging methods and vaccines, as well as drug-delivery systems, for example. But Steinmetz notes extensive additional preclinical research, and then thorough study in people, is needed before VNPs can approach their clinical potential.