Circulating tumor cells (CTCs) are present in the blood of people suffering from most cancers, but because of their rarity their presence is very difficult to spot. A number of technologies have been developed in the past to capture and count CTCs, but they tend to still have a number of limitations. The main problem is that because CTCs are so rare, a very large amount of blood is required to have a chance of finding enough of the cells to point toward a diagnosis. Scientists at Stanford University have now developed their own unique approach for capturing CTCs that relies on magnets that work directly inside blood vessels, avoiding taking blood samples altogether. They used the wire to capture free-floating tumor cells in the blood, a technique that soon could be used in humans to yield an earlier cancer diagnosis.

The wire, which is threaded into a vein, attracts special magnetic nanoparticles engineered to glom onto tumor cells that may be roaming the bloodstream if you have a tumor somewhere in your body. A flexible magnetic wire is inserted into a blood vessel via an IV catheter and allowed to spend some time inside while blood passes by. The magnetic particles swimming by the wire end up sticking to it, and if they have CTCs attached to them, those come along as well.

The technique, which has only been used in pigs so far, attracts from 10-80 times more tumor cells than current blood-based cancer-detection methods, making it a potent tool to catch the disease earlier. The technique could even help doctors evaluate a patient’s response to particular cancer treatments: If the therapy is working, tumor-cell levels in the blood should rise as the cells die and break away from the tumor, and then fall as the tumor shrinks. “It could be useful in any other disease in which there are cells or molecules of interest in the blood,” said Sanjiv “Sam” Gambhir, MD, PhD, professor and chair of radiology and director of the Canary Center at Stanford for Cancer Early Detection, who developed the wire with the help of his colleagues. “For example, let’s say you’re checking for a bacterial infection, circulating tumor DNA or rare cells that are responsible for inflammation — in any of these scenarios, the wire and nanoparticles help to enrich the signal, and therefore detect the disease or infection.”

A flexible wire

Gambhir said the technique could also be used to gather genetic information about tumors located in hard-to-biopsy places or to provide information about the efficacy of a cancer treatments. Perhaps most intriguingly, the magnetic wire may even stand to evolve into a treatment in and of itself. “If we can get this thing to be really good at sucking up cancer cells, you might consider an application where you leave the wire in longer term,” Gambhir said. “That way it almost acts like a filter that grabs the cancer cells and prevents them from spreading to other parts of the body.”

Now, Gambhir is working to ready the technique for humans, which involves approval for the nanoparticles. His lab is conducting toxicity studies in mice, paying close attention to what happens to leftover nanoparticles that don’t bind. So far, there are no signs of toxicity, and the extras decay over the course of a few weeks, he said. Gambhir is also looking into nanoparticles that are already FDA-approved, working to tweak them for use with the wire. Once approved for humans, the goal is to develop the technology into a multi-pronged tool that will boost detection, diagnosis, treatment and evaluation of cancer therapy.

Source: Stanford University