New research published in oncology science Glioblastoma is exploring a potential new approach to the treatment of brain tumors, a malignancy that remains extremely difficult to treat. The paper is titled “Selective blood-brain barrier penetration and tumor targeting of nitrosylcobalamin in glioblastoma: pharmacokinetics, tissue distribution, and synergistic activity with TRAIL and temozolomide.”
The study was led by first and corresponding author Joseph A. Bauer of Nitric Oxide Services, LLC and Cleveland Clinic Foundation Taussig Cancer Center. The research team investigated nitrosylcobalamin (NO-Cbl), a modified form of vitamin B12 that releases nitric oxide, to see if it could cross the blood-brain barrier (BBB) and accumulate selectively in glioblastoma tumors.
Glioblastoma multiforme (GBM) is one of the most lethal and treatment-resistant brain cancers. Even with surgery, radiation therapy, and chemotherapy, patients usually survive less than 15 months after diagnosis. One of the main reasons is the blood-brain barrier, a protective structure that blocks many drugs from reaching tumor tissue in the brain.
Trial of vitamin B12-based brain tumor treatment
To evaluate NO-Cbl, researchers used several experimental methods. These include testing the compound against cancer cells in the NCI-60 human tumor cell line panel, conducting pharmacokinetic studies in rats bearing glioblastoma tumors, and examining the effects of NO-Cbl in combination with other treatments in human glioblastoma cell lines.
The results showed that NO-Cbl has antitumor activity across a wide range of cancer types. Tumor cells originating from the central nervous system showed moderate sensitivity to treatment.
Cross the blood-brain barrier to target tumors
One of the most important findings of this study came from animal studies. After systemically administered, NO-Cbl successfully crossed the blood-brain barrier and preferentially accumulated within glioblastoma tissues.
The researchers also found evidence that the compound remains active within tumors for long periods of time. Nitrate levels in tumor tissue remained elevated for at least 24 hours after treatment, whereas nitrate levels in normal tissue decreased more rapidly. This pattern suggests that NO-Cbl is retained within the tumor and may deliver nitric oxide directly to the tumor microenvironment.
Figures 2 and 3 (pages 3-4) of the study show sustained levels of nitrate and cobalamin-related metabolites in brain tumor tissue compared to other organs, further supporting selective accumulation in glioblastoma.
Augmenting the effectiveness of existing glioblastoma treatments
The researchers also investigated whether NO-Cbl could improve the outcomes of established glioblastoma treatments.
In laboratory studies using U87 and D54 glioblastoma cells, combining NO-Cbl with either TRAIL or temozolomide inhibited tumor cell growth much more strongly than any treatment achieved alone. Additional analyzes confirmed synergistic interactions across multiple dose ranges.
“This pilot study demonstrates that NO-Cbl crosses the BBB, selectively accumulates in brain tumor tissue, and synergizes with established experimental glioblastoma treatments.”
Possibility of overcoming treatment resistance
According to the authors, NO-Cbl may also help address some of the biological mechanisms that allow glioblastoma tumors to resist treatment.
Previous studies referenced in the paper have shown that NO-Cbl can promote apoptosis through activation of caspase-8, suppress NF-κB survival signaling, and enhance TRAIL receptor signaling through S-nitrosylation. Together, these effects may increase the responsiveness of glioblastoma cells to treatment, including tumors that have acquired resistance to temozolomide.
Initial findings and further research to come
The authors emphasize that these findings come from a pilot translational study and that further research is needed before considering this approach for clinical use.
Future studies are expected to focus on orthotopic validation, optimizing dosing strategies, tracking nitric oxide activity over time, and investigating the underlying mechanisms in additional central nervous system tumor models.
Overall, this finding provides initial evidence that cobalamin-based nitric oxide donors may be a promising new strategy for glioblastoma treatment. By combining blood-brain barrier penetration, selective tumor targeting, and enhanced activity with existing therapies, NO-Cbl has the potential to improve drug delivery in one of the most challenging cancers in neuro-oncology and provide a new way to combat treatment resistance.
