Combination Treatment Targeting Glucose in Advanced Brain Cancer Shows Promising Results in Preclinical Study

UCLA scientists have discovered a potential combination treatment for glioblastoma, the deadliest form of brain cancer in adults. The three-year study led by Dr. David Nathanson, a member of UCLA’s Jonsson Comprehensive Cancer Center, found that the drug combination tested in mice disrupts and exploits glucose intake, essentially cutting off the tumor’s nutrients and energy supply. This treatment then stimulates cell death pathways—which control the cancer cells’ fate—and prevents the glioblastoma from getting bigger.

The combination treatment works by manipulating sugar metabolism with the FDA-approved drug erlotinib against one of the most common genetic alterations in glioblastoma, a cell surface protein known as EGFR. The researchers found that erlotinib treatment reduces sugar uptake in the majority of glioblastomas studied, thereby creating a metabolically vulnerable state for these brain tumors. The researchers then exploited this metabolic deficiency with an experimental drug called idasanutlin, which activates a protein called p53 to promote glioblastoma cell death and stimulate tumor regression in mice. Nathanson and his team also demonstrated that positron emission tomography, or PET, imaging can predict which tumors would respond best to this combination treatment.

BACKGROUND 

These findings build on previous research by Nathanson, who was a co-author of the initial study in 2013. That research showed that EGFR genetic alterations promote sugar uptake in glioblastomas. The researchers also found they could not directly attack sugar metabolism in the brain, due to potential side effects, since normal tissue requires sugar to survive.

Glioblastoma is one of the most lethal human cancers, with a median survival rate in adults of just 15 months after diagnosis.

METHOD

Researchers conducted the study using 19 human glioblastoma cells from different people. Some of the cells were implanted in the mice to analyze the effectiveness of the drug combination treatment. The researchers used PET imaging to predict which tumors would benefit from the drug combination.

The researchers also used an assay, or an assessment tool, developed by collaborators at Harvard University to measure how close a brain tumor cell is to the death threshold while targeting sugar metabolism.

IMPACT

The next stage of research will be to test the combination treatment on people with glioblastomas in clinical trials. Eventually, the researchers might design a new strategy involving the combination treatment that would attack and kill the glioblastoma altogether.

Study Suggests that Zika Virus Could Be Used to Treat Brain Cancer Patients

Recent outbreaks of Zika virus have revealed that the virus causes brain defects in unborn children. But in a study to be published September 5 in The Journal of Experimental Medicine, researchers from Washington University School of Medicine in St. Louis and the University of California, San Diego report that the virus could eventually be used to target and kill cancer cells in the brain.

Glioblastoma is the most common form of brain cancer and is frequently lethal; most patients die within two years of diagnosis. Just like normal, healthy tissues, the growth and development of glioblastomas is driven by stem cells that proliferate and give rise to other tumor cells. Glioblastoma stem cells are hard to kill because they can avoid the body’s immune system and are resistant to chemotherapy and radiation. But killing these cells is vital to prevent new tumors from recurring after the original tumor has been surgically removed.

“It is so frustrating to treat a patient as aggressively as we know how, only to see his or her tumor recur a few months later. We wondered whether nature could provide a weapon to target the cells most likely responsible for this return,” says Milan Chheda from Washington University School of Medicine in St. Louis.

One approach to killing cancer stem cells involves using viruses that specifically target tumor cells. Zika virus appears to disrupt fetal brain development by preferentially targeting neural stem and progenitor cells. The virus’ effects on adult brains—which contain fewer active stem cells that developing fetal brains—are generally much less severe.

“We hypothesized that the preference of Zika virus for neural precursor cells could be leveraged against glioblastoma stem cells,” says Michael Diamond, also from Washington University School of Medicine in St. Louis, who co-directed the study with Milan Chheda and with Jeremy Rich, from the University of California, San Diego and the Cleveland Clinic Lerner Research Institute.

The researchers found that Zika virus preferentially infected and killed patient-derived glioblastoma stem cells compared with other glioblastoma cell types or normal neural cells. When mice with aggressive glioma were injected with a mouse-adapted strain of Zika virus, the virus slowed tumor growth and significantly extended the animals’ lifespan.

The researchers then tested a mutant strain of Zika that is less virulent than naturally occurring strains of the virus. This “attenuated” strain, which is more sensitive to the body’s immune response, was still able to specifically target and kill glioblastoma stem cells and was even more effective when combined with a chemotherapy drug, temozolomide, that usually has little effect on these cells. “This effort represents the creative synthesis of three research groups with complementary expertise to attack a deadly cancer by harnessing the cause of another disease,” says Jeremy Rich. “Adults with Zika may suffer less damage from their infection, suggesting that this approach could be used with acceptable toxicity.”

“Our study is a first step towards the development of safe and effective strains of Zika virus that could become important tools in neuro-oncology and the treatment of glioblastoma,” says Diamond. “However, public health concerns will need to be addressed through pre-clinical testing and evaluations of the strains’ ability to disseminate or revert to more virulent forms.”

Immunotherapy for Glioblastoma Well Tolerated; Survival Gains Observed

A phase one study of 11 patients with glioblastoma who received injections of an investigational vaccine therapy and an approved chemotherapy showed the combination to be well tolerated while also resulting in unexpectedly significant survival increases, researchers at the Duke Cancer Institute report.

Patients treated with the study drug (dose-intensified temozolomide and vaccines) were continuously monitored for toxicity and adverse events. Study patients experienced known side effects with temozolomide, including nausea, lymphopenia, thrombocytopenia and fatigue.

There were no treatment limiting adverse events and no adverse events related to the cellular portion of the vaccine. One patient developed a grade 3 vaccine-related allergic reaction to the GM-CSF component of the vaccine. The patient was able to continue vaccinations in which the GM-CSF was removed and had no subsequent adverse events.

Although the trial was small and not designed to evaluate efficacy, four of the 11 study patients survived for more than five years following treatment with a combination of vaccine and the drug temozolomide, a first-line chemotherapy drug for glioblastoma. That outcome is uncommon for glioblastoma, a lethal brain cancer that has a median survival of nearly 15 months when treated with the current standard of care.

“This is a small study, but it’s one in a sequence of clinical trials we have conducted to explore the use of an immunotherapy that specifically targets a protein on glioblastoma tumors,” said Duke’s Kristen Batich, M.D., Ph.D., lead author of a study published online April 14 in the journal Clinical Cancer Research. “While not a controlled efficacy study, the survival results were surprising, and they suggest the possibility that combining the vaccine with a more intense regimen of this chemotherapy promotes a strong cooperative benefit.”

Batich and colleagues–including senior author John Sampson, M.D., Ph.D., chair of Duke’s Department of Neurosurgery — treated 11 patients as part of a single arm study to test the safety of using a dose-intensified regimen of temozolomide along with a dendritic cell vaccine therapy that selectively targets a cytomegalovirus (CMV) protein. CMV proteins are abundant in glioblastoma tumors, but are absent in surrounding brain cells.

In earlier clinical trials, the researchers used the dendritic cell vaccine to teach T-cells to attack tumor cells, and their data suggested these vaccines could be enhanced when primed by an immune system booster. A separate clinical trial found that higher-than-standard doses of temozolomide, combined with an immune-stimulating factor, also primed the immune system and enhanced the response of a different vaccine target.

The researchers built on those findings in the current study. They used a combination of the dendritic cell vaccine therapy and the immune-stimulating factor, which was administered as injections following dose-intensified regimens of temozolomide. The 11 patients received at least six vaccine treatments.

“Our strategy was to capitalize on the immune deficiency caused by the temozolomide regimen,” Batich said. “It seems counter-intuitive, but when the patient’s lymphocytes are depleted, it’s actually an optimal time to introduce the vaccine therapy. It basically gives the immune system marching orders to mount resources to attack the tumor.”

Batich said the approach significantly slowed the progression of patients’ tumors. Typically, glioblastoma tumors begin to regrow after standard treatment at a median of eight months, but for study participants, recurrence occurred at a median of 25 months.

“These are surprisingly promising clinical outcomes,” Sampson said. “However, it is important to emphasize that this was a very small study that used historical comparisons rather than randomizing patients to two different treatments, but the findings certainly support further study of this approach in larger, controlled clinical trials.”

The research team has received approval to launch a new study that will compare the standard dose of temozolomide vs. the dose-intensified regimen along with the vaccine in glioblastoma patients.