Despite an increasing number of experimental therapies tested via clinical trials, about 90 percent of children with diffuse intrinsic pontine glioma (DIPG) die within two years of diagnoses. The last five years have revolutionized DIPG research, providing unprecedented insight into the biology of tumors, creation of pre-clinical models, and expanded use of brainstem biopsies. Molecular studies have yielded additional insight about DIPG, including that mutations in histone-encoding genes are associated with the vast majority cases. Biomarkers that point to DIPG – like the copies of DNA that tumors shed and leave behind in the bloodstream - could enable creation of liquid biopsies, compared with surgical approaches. The search for cures for DIPG will necessitate taking a multi-pronged approach, such as drug cocktails with or without radiation, to target multiple tumor strains.
More precise targets
The human genome contains roughly three billion letters of DNA. The exome, the protein-coding region of the genome, represents just 2 percent of this genetic code but contains most variants known to be related to disease. Using whole exome sequencing, researchers will be able to look at all the genes in the genome at once, identifying more precise targets needed to select the best off-the-shelf therapy or to guide new drug development.
Novel combination therapies
For 45 years, children with DIPG were treated like adults when, in reality, pediatric DIPG tumors behave differently. Pre-clinical models will be used to winnow the field of potential therapeutics to the candidates most likely to help children survive DIPG.
The preclinical tumor cells will be labeled with luciferase – enzymes that, like photoproteins, produce bioluminescence – permitting the researcher to see how DIPG tumors form, progress, and respond to treatment.
Because of the obligate partnerships between driver mutations and secondary mutations, the research team already knows that effective DIPG medicines will need more than one target. Combined drug regimes, including those created with proprietary technology, will be key to targeting myriad mutations in order to kill tumors where they are. Those drug combinations that demonstrate they can do their jobs – slowing tumor growth, increasing chances of survival, taming toxicity – will be selected for clinical application.
The protein NG2 may represent a good target for immune therapy. The protein is expressed in primitive cells that have not become specialized – meaning there may be an opportunity to intervene before it is driven to become a tumor cell.
Immunotherapy leverages T-cells, the immune system’s most able fighters, to help in the overall goal of extending patients’ survival. One of the most challenging aspects of pediatric brain tumors is the body does a very good job of shielding the brain from potential pathogens. Precise drug delivery means finding innovative ways for therapeutics to cross the blood-brain barrier in order to reach the tumor.