Spraying an anticancer gel onto the surgery site after tumor removal can help reduce cancer spread.
Researchers at the University of California, Los Angeles (UCLA) are leading the team that is developing the gel, which comes in the form of a sprayable solution.
Their aim is that one day, surgeons will be able to spray the solution onto sites of tumor removal directly after surgery.
The solution, which quickly forms a biodegradable gel, contains nanoparticles laden with drugs that "wake up" the immune system.
Tests of the substance on mice that had undergone surgery to remove advanced melanoma tumors yielded promising results.
Half the mice remained tumor-free for at least 60 days following treatment.
The scientists say that not only did the treatment help prevent cancer recurrence at the site of surgery, but it also helped stop tumors forming in other parts of the body.
A study report on their work now features in the journal Nature Nanotechnology.
Cancer is dangerous because it spreads
According to the World Health Organization (WHO), "cancer is a leading cause of death worldwide." They estimate that cancer will cause 9.6 million deaths in 2018.
"One of the trademarks of cancer is that it spreads," explains co-senior study author Zhen Gu, a professor of bioengineering at UCLA's Samueli School of Engineering.
The process of cancer spread is called metastasis. It is the main reason that people die of cancer, and it is a great challenge to treatment developers.
For many people, a diagnosis of cancer leads to treatment that involves surgery.
Nearly 95 percent of those with early-stage breast cancer, for instance, will need surgery. For people with brain tumors, surgery is often the "first line of treatment."
However, despite surgical advances in the past 10 years, the cancer often returns.
Healing gel slowly releases anticancer drugs
The sprayable gel encapsulates calcium carbonate nanoparticles charged with antibodies that attack a protein called CD47.
One of the ways that cancer cells avoid the immune system is by releasing CD47, which sends out a "don't eat me" signal.
While the gel is helping the wound at the tumor site to heal, it slowly releases the antibody-charged nanoparticles into the body.
Lead study author Dr. Qian Chen, who works as a researcher in Prof. Gu's laboratory, explains that they decided to make the nanoparticles out of calcium carbonate because the compound dissolves slowly in the slightly acidic environment of surgical wounds.
Calcium carbonate also enhances the activity of immune cells called macrophages, Dr. Chen adds.
Bring on the macrophages and T cells
Macrophages are among the most abundant types of cell that the immune system summons to tumor sites, and they stay there for "all stages of tumor progression."
These white blood cells help rid the body of foreign objects and cellular waste by literally eating them. Their name comes from the Greek for "big eaters."
"We also learned," Dr. Chen continues, "that the gel could activate T cells in the immune system to get them to work together as another line of attack against lingering cancer cells."
There are still several steps to complete before the gel is ready for human trials.
Further testing in animals will help decide the "optimal doses." This will involve trying out different combinations of nanoparticles, drug loads, and treatment frequencies.
"This sprayable gel shows promise against one of the greatest obstacles in curing cancer."
Prof. Zhen Gu