Blunting brain tumor growth with immune activation

Pharmacologically stimulating immune cells in the brain can reduce the proliferation of cancer-forming stem cells in a mouse model of brain cancer, reports a study published online this week in Nature Neuroscience. This study also identifies a potential therapeutic drug to combat one of the most aggressive forms of brain tumor, called glioblastoma.

Malignant brain tumors are often resistant to conventional therapies because of the presence of tumor-forming stem cells called brain tumor initiating cells (BTICs). BTICs are stem-like cells that can self-renew. In patients with gliobastomas, BTICs are often surrounded by immune cells, such as microglia and macrophages that that constantly survey the central nervous system tissue and provide the first line of immune defense.

V. Wee Yong and colleagues examined the immune cells derived from brain tumors in patients for their effects on BTIC growth. They found that patient-derived immune cells perform poorly in mitigating BTIC expansion. However, microglia and macrophages from non-brain tumor patients reduced the growth of BTICs. Yong and colleagues then tested a library of small molecule compounds and identified a drug called amphotericin B (AmpB), that works by activating macrophages and microglia to lessen BTIC proliferation. When AmpB was administered to mice with human patient-derived BTICs, there was a nearly doubled survival age and significantly reduced brain tumor growth.

Although AmpB is an anti-fungal medication already approved by the US Food and Drug Administration, the drug is known to have severe - and potentially lethal - side effects of fever induction and multiple organ failure when used in high intravenous doses. Further studies are needed to determine the safety and feasibility of using AmpB and similar immune-activating drugs as potential gliobastoma treatments.