Nanocarriers May Carry New Hope for Brain Cancer Therapy

Berkeley Lab Researchers Develop Nanoparticles That Can Carry Therapeutics Across the Brain Blood Barrier

Glioblastoma multiforme, a cancer of the brain also known as “octopus tumors” because of the manner in which the cancer cells extend their tendrils into surrounding tissue, is virtually inoperable, resistant to therapies, and always fatal, usually within 15 months of onset. Each year, glioblastoma multiforme (GBM) kills approximately 15,000 people in the United States. One of the major obstacles to treatment is the blood brain barrier, the network of blood vessels that allows essential nutrients to enter the brain but blocks the passage of other substances. What is desperately needed is a means of effectively transporting therapeutic drugs through this barrier. A nanoscience expert at Lawrence Berkeley National Laboratory (Berkeley Lab) may have the solution.

Ting Xu, a polymer scientist with Berkeley Lab’s Materials Sciences Division who specializes in self-assembling bio/nano hybrid materials, has developed a new family of nanocarriers formed from the self-assembly of amphiphilic peptides and polymers. Called “3HM” for coiled-coil 3-helix micelles, these new nanocarriers meet all the size and stability requirements for effectively delivering a therapeutic drug to GBM tumors. Amphiphiles are chemical compounds that feature both hydrophilic (water-loving) and lipophilic (fat-loving) properties. Micelles are spherical aggregates of amphiphiles.

In a recent collaboration between Xu, Katherine Ferrara at the University of California (UC) Davis, and John Forsayeth and Krystof Bankiewicz of UC San Francisco, 3HM nanocarriers were tested on GBM tumors in rats. Using the radioactive form of copper (copper-64) in combination with positron emission tomography (PET) and magnetic resonance imaging (MRI), the collaboration demonstrated that 3HM can cross the blood brain barrier and accumulate inside GBM tumors at nearly double the concentration rate of current FDA-approved nanocarriers.

“Our 3HM nanocarriers show very good attributes for the treatment of brain cancers in terms of long circulation, deep tumor penetration and low accumulation in off-target organs such as the liver and spleen,” says Xu, who also holds a joint appointment with the UC Berkeley’s Departments of Materials Sciences and Engineering, and Chemistry. “The fact that 3HM is able to cross the blood brain barrier of GBM-bearing rats and selectively accumulate within tumor tissue, opens the possibility of treating GBM via intravenous drug administration rather than invasive measures.

While there is still a lot to learn about why 3HM is able to do what it does, so far all the results have been very positive.”

Glial cells provide physical and chemical support for neurons. Approximately 90-percent of all the cells in the brain are glial cells which, unlike neurons, undergo a cycle of birth, differentiation, and mitosis. Undergoing this cycle makes glial cells vulnerable to becoming cancerous. When they do, as the name “multiforme” suggests, they can take on different shapes, which often makes detection difficult until the tumors are dangerously large. The multiple shapes of a cancerous glial cell also make it difficult to identify and locate all of the cell’s tendrils. Removal or destruction of the main tumor mass while leaving these tendrils intact is ineffective therapy: like the mythical Hydra, the tendrils will sprout new tumors.

Although there are FDA approved therapeutic drugs for the treatment of GBM, these treatments have had little impact on patient survival rate because the blood brain barrier has limited the accumulation of therapeutics within the brain. Typically, GBM therapeutics are ferried across the blood brain barrier in special liposomes that are approximately 110 nanometers in size. The 3HM nanocarriers developed by Xu and her group are only about 20 nanometers in size. Their smaller size and unique hierarchical structure afforded the 3HM nanocarriers much greater access to rat GBM tumors than 110-nanometer liposomes in the tests carried out by Xu and her colleagues.

“3HM is a product of basic research at the interface of materials science and biology,” Xu says. “When I first started at Berkeley, I explored hybrid nanomaterials based on proteins, peptides and polymers as a new family of biomaterials. During the process of understanding the hierarchical assembly of amphiphilic peptide-polymer conjugates, my group and I noticed some unusual behavior of these micelles, especially their unusual kinetic stability in the 20 nanometer size range.

We looked into critical needs for nanocarriers with these attributes and identified the treatment of GBM cancer as a potential application.”

Copper-64 was used to label both 3HM and liposome nanocarriers for systematic PET and MRI studies to find out how a nanocarrier’s size might affect the pharmacokinetics and biodistribution in rats with GBM tumors. The results not only confirmed the effectiveness of 3HM as GBM delivery vessels, they also suggest that PET and MRI imaging of nanoparticle distribution and tumor kinetics can be used to improve the future design of nanoparticles for GBM treatment.

“I thought our 3HM hybrid materials could bring new therapeutic opportunities for GBM but I did not expect it to happen so quickly,” says Xu, who has been awarded a patent for the 3HM technology.

A paper describing this research has been published in The Journal of Controlled Release. The paper is titled “Self-assembled 20-nm 64Cu-micelles enhance accumulation in rat glioblastoma.”

Xu, Ferrara and Bankiewicz are the senior authors. Other authors, in addition to Forsayeth, are Jai Woong Seo, Joo Chuan Ang, Lisa Mahakian, Sarah Tam, Brett Fite, Elizabeth Ingham and Janine Beyer.

This research was funded by the National Institutes of Health and the UC Davis Research Investments in Science and Engineering.

Lawrence Berkeley National Laboratory

Football-shaped particles bolster the body's defense against cancer

Researchers at Johns Hopkins have succeeded in making flattened, football-shaped artificial particles that impersonate immune cells. These football-shaped particles seem to be better than the typical basketball-shaped particles at teaching immune cells to recognize and destroy cancer cells in mice.

"The shape of the particles really seems to matter because the stretched, ellipsoidal particles we made performed much better than spherical ones in activating the immune system and reducing the animals' tumors," according to Jordan Green, Ph.D., assistant professor of biomedical engineering at the Johns Hopkins University School of Medicine and a collaborator on this work. A summary of the team's results was published online in the journal Biomaterials on Oct. 5.

According to Green, one of the greatest challenges in the field of cancer medicine is tracking down and killing tumor cells once they have metastasized and escaped from a tumor mass. One strategy has been to create tiny artificial capsules that stealthily carry toxic drugs throughout the body so that they can reach the escaped tumor cells. "Unfortunately, traditional chemotherapy drugs do not know healthy cells from tumor cells, but immune system cells recognize this difference. We wanted to enhance the natural ability of T-cells to find and attack tumor cells," says Jonathan Schneck, M.D., Ph.D., professor of pathology, medicine and oncology.

In their experiments, Schneck and Green's interdisciplinary team exploited the well-known immune system interaction between antigen-presenting cells (APC) and T-cells. APCs "swallow" invaders and then display on their surfaces chewed-up protein pieces from the invaders along with molecular "danger signals." When circulating T-cells interact with APCs, they learn that those proteins come from an enemy, so that if the T-cells see those proteins again, they divide rapidly to create an army that attacks and kills the invaders.

According to Schneck, to enhance this natural process, several laboratories, including his own, have made various types of "artificial APCs" — tiny inanimate spheres "decorated" with pieces of tumor proteins and danger signals. These are then often used in immunotherapy techniques in which immune cells are collected from a cancer patient and mixed with the artificial APCs. When they interact with the patient's T-cells, the T-cells are activated, learn to recognize the tumor cell proteins and multiply over the course of several days. The immune cells can then be transferred back into the patient to seek out and kill cancer cells.

The cell-based technique has had only limited success and involves risks due to growing the cells outside the body, Green says. These downsides sparked interest in the team to improve the technique by making biodegradable artificial APCs that could be administered directly into a potential patient and that would better mimic the interactions of natural APCs with T-cells. "When immune cells in the body come in contact, they're not doing so like two billiard balls that just touch ever so slightly," explains Green. "Contact between two cells involves a significant overlapping surface area. We thought that if we could flatten the particles, they might mimic this interaction better than spheres and activate the T-cells more effectively."

To flatten the particles, two M.D./Ph.D. students, Joel Sunshine and Karlo Perica, figured out how to embed a regular batch of spherical particles in a thin layer of a glue-like compound. When they heated the resulting sheet of particles, it stretched like taffy, turning the round spheres into tiny football shapes. Once cooled, the film could be dissolved to free each of the microscopic particles that could then be outfitted with the tumor proteins and danger signals. When they compared typical spherical and football-shaped particles — both coated with tumor proteins and danger signals at equivalent densities and mixed with T-cells in the laboratory — the T-cells multiplied many more times in response to the stretched particles than to spherical ones. In fact, by stretching the original spheres to varying degrees, they found that, up to a point, they could increase the multiplication of the T-cells just by lengthening the "footballs."

When the particles were injected into mice with skin cancer, the T-cells that interacted with the elongated artificial APCs, versus spherical ones, were also more successful at killing tumor cells. Schneck says that tumors in mice that were treated with round particles reduced tumor growth by half, while elongated particles reduced tumor growth by three-quarters. Even better, he says, over the course of a one-month trial, 25 percent of the mice with skin cancer being treated with elongated particles survived, while none of the mice in the other treatment groups did.

According to Green, "This adds an entirely new dimension to studying cellular interactions and developing new artificial APCs. Now that we know that shape matters, scientists and engineers can add this parameter to their studies," says Green. Schneck notes, "This project is a great example of how interdisciplinary science by two different groups, in this case one from biomedical engineering and another from pathology, can change our entire approach to tackling a problem. We're now continuing our work together to tweak other characteristics of the artificial APCs so that we can optimize their ability to activate T-cells inside the body."

###

This work was supported by grants from the Johns Hopkins University Institute for NanoBioTechnology, the National Institute of Allergy and Infectious Diseases (AI072677, AI44129), the National Cancer Institute (CA108835) and the National Institute of Biomedical Imaging and Bioengineering (EB016721).

Source: http://www.hopkinsmedicine.org/news/media/releases/football_shaped_particles_bolster_the_bodys_defense_against_cancer