First successful treatment of cancer with a nanosytem

Anthony Marrelli

Argus

A team of researchers in California and Massachusetts have developed a “cocktail” of different nanometer sized particles that work in concert within the bloodstream to locate, adhere to and kill cancerous tumours.

Michael Sailor, researcher at the University of California (UC), says that “this study represents the first example of the benefits of employing a cooperative nanosystem to fight cancer”. He is the primary author of a paper describing the results.

In their study, they developed a system containing two different nanomaterials the size of only a few nanometers, or a thousand times smaller than the diameter of a human hair, that can be injected into the bloodstream. One nanomaterial was designed to find and adhere to tumours in mice, while the second nanomaterial was fabricated to kill those tumours.

These scientists and others had previously designed nanometer-sized devices to attach to diseased cells or deliver drugs specifically to the diseased cells while ignoring healthy cells. However the functions of those devices, the researchers discovered, often conflicted with one another.

“For example, a nanoparticle that is engineered to circulate through a cancer patient’s body for a long period of time is more likely to encounter a tumour,” said Sangeeta Bhatia, a physician, bioengineer and a professor of Health Sciences and Technology and a co-author of the study.

“However, that nanoparticle may not be able to stick to tumour cells once it finds them. Likewise, a particle that is engineered to adhere tightly to tumours may not be able to circulate in the body long enough to encounter one in the first place.”

Currently, when a single drug does not work in a patient with cancer, a doctor will commonly administer a cocktail containing several drug molecules. That strategy can be very effective in the treatment of cancer, where the rationale is to attack the disease on as many fronts as possible.

Drugs may sometimes work together on a single aspect of the disease, or they may attack separate functions. In either case, drug combinations can provide a greater effect than either drug alone.

Treating tumours with nanoparticles in the same way has been challenging because immune cells called mononuclear phagocytes identify them and yank them from circulation, preventing the nanomaterials from reaching their target.

The first particle being used is a gold nanorod “activator” that accumulates in tumours by seeping through its leaky blood vessels. The gold particles cover the whole tumour and behave like an antenna by absorbing otherwise benign infrared laser irradiation, which then heats up the tumour.

In the experiment, after the nanorods had circulated in the bloodstream of mice that had epithelial tumours for three days, the researchers used a weak laser beam to heat the rods that attached to the tumours.

This sensitized the tumours, and the researchers then sent in the second nanoparticle type, composed of either iron oxide nanoworms or doxorubicin-loaded liposomes. This “responder” nanoparticle is coated with a special targeting molecule specific for the heat-treated tumour.

Think of them like soldiers attacking an enemy base, the gold nanorods are the Special Forces, who come in first to mark the target. Then the Air Force flies in to deliver the laser-guided bomb. The devices are designed to minimize collateral damage to the rest of the body.

While one type of nanoparticle improves detection of the tumour, the other is designed to kill the tumour. This study is important because it is the first example of a combined, two-part nanosystem that can produce sustained reduction in tumour volume in live animals.