Immune checkpoint inhibitors may work in brain cancers

New evidence that immune checkpoint inhibitors may work in glioblastoma and brain metastases was presented today by Dr Anna Sophie Berghoff at the ESMO Symposium on Immuno-Oncology 2014 in Geneva, Switzerland.
The novel research shows that brain metastases have dense concentrations of tumour infiltrating lymphocytes, providing an immunoactive environment. Moreover, both primary and secondary brain cancers often exhibit high expression of the immunosuppressive factor programmed cell death ligand 1 (PDL1), which can be inhibited by new treatments, thus activating the immune system.
Berghoff, resident at the Department of Medicine I, Comprehensive Cancer Centre–CNS Tumours Unit, Medical University of Vienna, Austria, said: “Patients with glioblastoma and brain metastases have very few treatment options and usually die within a short period of time.”
Immune checkpoint inhibitors are a new group of cancer treatments that work by boosting the patient’s immune response to the tumour. The immune system operates differently in the brain in comparison to other organs. “Our study was designed to find out whether the immune system is activated and working in brain tumours, which would provide the foundation for immune checkpoint inhibitors to work,” Berghoff explained.
The study included 117 patients with glioblastoma and 116 patients with brain metastases. Using immunohistochemistry the researchers looked for the presence of T-cells --also called tumour infiltrating lymphocytes-- in the tumours and whether they were accentuated in different areas of the tumour. T-cells are the main effector cells of the immune response and can be boosted by immune checkpoint inhibitors. They also looked for PDL1 --an immunosuppressive protein that influences responses to immune checkpoint inhibitors.
The researchers found that patients with glioblastoma had fewer T-cells, and therefore less activation of the immune system, than patients with brain metastases who had high concentrations of T-cells. They also found that PDL1 was common in both glioblastoma and brain metastases, with glioblastoma showing particularly high PDL1 positivity.
Berghoff said: “We saw that these brain tumour types have a different interaction with the immune system. The glioblastoma actively suppresses the immune system and there is little immune response. In contrast the brain metastases do a little less suppression of the immune system and there are a lot more tumour infiltrating lymphocytes.”
Berghoff said the findings demonstrate that the immune system interacts with glioblastoma and brain metastases, which is evidence that immune checkpoint inhibitors may work: “We have arguments for conducting clinical studies with immune checkpoint inhibitors in patients with glioblastoma and brain metastases. In both tumour types we commonly see high expression of PDL1, an immunosuppressive factor which can be inhibited with new treatments. By inhibiting the suppression you can activate the immune system which in theory would work in brain cancers.”
She continued: “We know that immune checkpoint inhibitors are more effective in immunoactive microenvironments. In brain metastases we see dense infiltration with T-cells which provides a good background for immune checkpoint inhibitors.”
Small preliminary studies have shown efficacy of immune checkpoint inhibitors in melanoma brain metastases. However, melanoma is only the third most common brain metastases, the most common being non-small-cell lung cancer. Immune checkpoint inhibitors are active in extracranial metastasised lung cancer but it is unknown whether this holds true for patients with brain metastases. Data on immune checkpoint inhibitors in glioblastoma exists only in mice.
Berghoff said: “Our study shows that T-cells and PDL1 expression are present in glioblastoma and brain metastases. This means that the targets for novel drugs that activate the immune system against cancer cells are present and brain tumours may be effectively treatable with such drugs.”
She concluded: “Our data strongly support the launch of clinical trials with immune checkpoint inhibitors, especially the ones targeting the PD1/PDL1 axis, in patients with glioblastoma and brain metastases. Indeed, some early studies are being designed and started at the moment. In addition, profiling of other immune checkpoint molecules and modes of immune escape in brain tumours need to be identified to prepare for the development of next generation immunomodulators.”
Commenting on the implications of the findings for patients with glioblastoma and brain metastases, Professor Martin J. van den Bent, of the Neuro-Oncology Unit, Erasmus Medical Centre, Rotterdam, the Netherlands, said: “The investigators found different immune reactions to the malignant process in the brain that were related to the type of cancer. It is quite interesting that the immune system does play a role in brain metastases as well. The findings indicate that therapeutic interventions for brain cancers that use the immune system should be explored.
Van den Bent noted that brain metastases are not a homogenous group but vary depending on the primary tumour. He said: “I would guess that the type of immune reaction to brain metastases will differ between the various tumour types. We know that the mechanism with which metastases arise can be completely different between the various diseases.”

“The debate on the penetration through the intact blood brain barrier and how significant that is for treatment effectiveness is still on the table,” continued van den Bent. “But the general understanding is that any therapy that

Nano-Syringe Delivers Combination, Targeted Brain Cancer Therapy

Nanomedicine researchers at the Methodist Neurological Institute and Rice University have developed a way to selectively kill brain cancer cells by using a tiny syringe to deliver a combination of chemotherapy drugs directly into the cells. These findings will be published in the April 24 issue of the American Chemical Society journal ACS Nano.

Patients with glioblastoma multiforme (GBM), the most common and aggressive malignant primary brain tumor, typically have a prognosis of 14-month median survival time despite medical interventions, which currently include surgery, chemotherapy and radiation.
The Rice-Methodist group developed the hydrophilic carbon cluster (HCC) antibody drug enhancement system (HADES), named after the Greek god of the underworld. Through a 20-nanometer syringe, which is 2 million times smaller than a coffee mug, this nanovector successfully delivered a combination of three chemotherapy drugs into GBM cells in vivo, resulting in a high kill rate.
"Without our nano-delivery system, we know that current drug delivery would be highly toxic to patients if we tried to deliver all three of these drugs at once," said David Baskin, M.D., neurosurgeon at the Methodist Neurological Institute, who began his nanomedicine research in 2004 with the late Nobel laureate and Rice chemist Richard Smalley. "But delivered in combination using these nano-syringes, our research demonstrated extreme lethality, with at least a three-fold increase in the number of dead cancer cells following treatment. The nano-syringes selectively deliver these drugs only to cancer cells, and appear not to be toxic to normal neurons and other non-cancerous brain cells."
HCCs are nanovectors with protective antioxidant properties, capable of transporting and delivering drugs and bioactive molecules. In order to bring the drug carriers close enough to the cancer cells and successfully deliver the chemotherapy combination, three different antibodies were combined with the HCC to allow the nanoparticle to stick to the cell membrane. The drugs stayed inside the HCC until it attached to the cell membrane. Once binding occurred, the drugs were released into the fatty (lipid) environment in the membrane. The chemical properties of the chemotherapy drugs inside the HCC are such that they prefer to accumulate in areas with high concentrations of lipids and avoid areas with high water content, such as the extracellular space.
"A new and exciting advance is that now we have a carrier with protective properties, unlike previous nanotubes which were shown to be toxic," said Martyn Sharpe, the paper's lead author and a scientist with the Methodist NI's department of neurosurgery. "Some of the chemotherapy agents used in this research traditionally perform poorly with GBMs. Now that we've shown a successful kill rate of these cells in vivo, we're looking at treating human tumors that will be grown in immune-compromised mice models."
As personalized medicine continues to evolve, Baskin says this research could also be significant for other forms of cancer, including breast and head and neck cancers.

**Published in "SCIENCE DAILY"

Novel compound halts tumor spread, improves brain cancer treatment in animal studies

Georgia Tech/Jennifer Munson

Georgia Tech/Jennifer Munson

Georgia Tech/Jennifer Munson

Treating invasive brain tumors with a combination of chemotherapy and radiation has improved clinical outcomes, but few patients survive longer than two years after diagnosis. The effectiveness of the treatment is limited by the tumor's aggressive invasion of healthy brain tissue, which restricts chemotherapy access to the cancer cells and complicates surgical removal of the tumor. To address this challenge, researchers from the Georgia Institute of Technology and Emory University have designed a new treatment approach that appears to halt the spread of cancer cells into normal brain tissue in animal models. The researchers treated animals possessing an invasive tumor with a vesicle carrying a molecule called imipramine blue, followed by conventional doxorubicin chemotherapy. The tumors ceased their invasion of healthy tissue and the animals survived longer than animals treated with chemotherapy alone.
"Our results show that imipramine blue stops tumor invasion into healthy tissue and enhances the efficacy of chemotherapy, which suggests that chemotherapy may be more effective when the target is stationary," said Ravi Bellamkonda, a professor in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University. "These results reveal a new strategy for treating brain cancer that could improve clinical outcomes."
The results of this work were published on March 28, 2012 in the journal Science Translational Medicine. The research was supported primarily by the Ian's Friends Foundation and partially by the Georgia Cancer Coalition, the Wallace H. Coulter Foundation and a National Science Foundation graduate research fellowship.
In addition to Bellamkonda, collaborators on the project include Jack Arbiser, a professor in the Emory University Department of Dermatology; Daniel Brat, a professor in the Emory University Department of Pathology and Laboratory Medicine; and the paper's lead author, Jennifer Munson, a former Fulbright Scholar who was a bioengineering graduate student in the Georgia Tech School of Chemical & Biomolecular Engineering when the research was conducted.
Arbiser designed the novel imipramine blue compound, which is an organic triphenylmethane dye. After in vitro experiments showed that imipramine blue effectively inhibited movement of several cancer cell lines, the researchers tested the compound in an animal model of aggressive cancer that exhibited attributes similar to a human brain tumor called glioblastoma.
"There were many reasons why we chose to use the RT2 astrocytoma rat model for these experiments," said Brat. "The tumor exhibited properties of aggressive growth, invasiveness, angiogenesis and necrosis that are similar to human glioblastoma; the model utilized an intact immune system, which is seen in the human disease; and the model enabled increased visualization by MRI because it was a rat model, rather than a mouse."
Because imipramine blue is hydrophobic and doxorubicin is cytotoxic, the researchers encapsulated each compound in an artificially-prepared vesicle called a liposome so that the drugs would reach the brain. The liposomal drug delivery vehicle also ensured that the drugs would not be released into tissue until they passed through leaky blood vessel walls, which are only present where a tumor is growing.
Animals received one of the following four treatments: liposomes filled with saline, liposomes filled with imipramine blue, liposomes filled with doxorubicin chemotherapy, or liposomes filled with imipramine blue followed by liposomes filled with doxorubicin chemotherapy.
All of the animals that received the sequential treatment of imipramine blue followed by doxorubicin chemotherapy survived for 200 days -- more than 6 months -- with no observable tumor mass. Of the animals treated with doxorubicin chemotherapy alone, 33 percent were alive after 200 days with a median survival time of 44 days. Animals that received capsules filled with saline or imipramine blue -- but no chemotherapy -- did not survive more than 19 days.
"Our results show that the increased effectiveness of the chemotherapy treatment is not because of a synergistic toxicity between imipramine blue and doxorubicin. Imipramine blue is not making the doxorubicin more toxic, it's simply stopping the movement of the cancer cells and containing the cancer so that the chemotherapy can do a better job," explained Bellamkonda, who is also the Carol Ann and David D. Flanagan Chair in Biomedical Engineering and a Georgia Cancer Coalition Distinguished Cancer Scholar.
MRI results showed a reduction and compaction of the tumor in animals treated with imipramine blue followed by doxorubicin chemotherapy, while animals treated with chemotherapy alone presented with abnormal tissue and glioma cells. MRI also indicated that the blood-brain barrier breach often seen during tumor growth was present in the animals treated with chemotherapy alone, but not the group treated with chemotherapy and imipramine blue.
According to the researchers, imipramine blue appears to improve the outcome of brain cancer treatment by altering the regulation of actin, a protein found in all eukaryotic cells. Actin mediates a variety of essential biological functions, including the production of reactive oxygen species. Most cancer cells exhibit overproduction of reactive oxygen species, which are thought to stimulate cancer cells to invade healthy tissue. The dye's reorganization of the actin cytoskeleton is thought to inhibit production of enzymes that produce reactive oxygen species.
"I formulated the imipramine blue compound as a triphenylmethane dye because I knew that another triphenylmethane dye, gentian violet, exhibited anti-cancer properties, and I decided to use imipramine -- a drug used to treat depression -- as the starting material because I knew it could get into the brain," said Arbiser.
For future studies, the researchers are planning to test imipramine blue's effect on animal models with invasive brain tumors, metastatic tumors, and other types of cancer such as prostate and breast.
"While we need to conduct future studies to determine if the effect of imipramine blue is the same for different types of cancer diagnosed at different stages, this initial study shows the possibility that imipramine blue may be useful as soon as any tumor is diagnosed, before anti-cancer treatment begins, to create a more treatable tumor and enhance clinical outcome," noted Bellamkonda.

**Source: Georgia Institute of Technology Research News