Treating Glioblastoma With a Trojan Horse

Vladimirs Piļipenko had been working for more than a decade at the University of Latvia (on the topic of brain, namely neurodegenerative diseases) when he decided it was time for a change. He submitted a proposal and received a postdoctoral grant in Estonia, at the Laboratory of Precision and Nanomedicine (run by Professor Tambet Teesalu), University of Tartu. Since December 2024, Vladimirs continues his research of the brain, but in a different angle – looking for solutions to the most aggressive form of brain cancer, glioblastoma.

Glioblastoma is extremely difficult to treat

Currently, glioblastoma is extremely difficult to treat due to several unique characteristics of the disease. First, anticancer therapies essentially cannot be delivered to the brain and reach the tumor. This is due to the blood-brain barrier (BBB), a protective barrier that shields the brain from toxins and other potentially harmful substances, but at the same time significantly limits the delivery of therapeutic agents to the central nervous system. Second, brain tumor produces stem cells that are highly resistant to therapeutic agents. And third, tumor environment can turn off the immune defenses of the patient.

To overcome these barriers, Piļipenko and the research team at Teesalu lab are working with lipid nanoparticles (LNPs). These nanocarriers have been used in cancer research for over 30 years, yet the first therapeutic agent based on LNP technology (Onpattro®) was only approved in 2018. LNPs gained global attention during the COVID-19 pandemic, when they were used to deliver messenger RNA (mRNA) encoding the SARS-CoV-2 spike protein, providing cells with genetic instructions that trained the immune system to recognize the virus.

To treat glioblastoma, Piļipenko and coworkers develop precision-guided LNPs to deliver to tumors small interfering nucleic acids (siRNAs). These nucleic acids can turn off specific cancer genes, for example those involved in tumor promotion or therapy resistance while sparing the healthy cells. For the LNPs to release their therapeutic cargo in malignant glioblastoma cells, they need to cross the vascular and tissue barriers and penetrate deep into the brain. So how can LNPs be delivered to the brain?

Trojan horses

The answer may lie in glioblastoma-specific homing peptides, short chains of amino acids that can be discovered using a variety of screening technologies. The Teesalu lab is a global leader in the discovery and characterization of such homing peptides, including peptides that target the brain and brain tumors. Chemically coupling the LNPs with a brain-homing and -penetrating peptides can enhance the accumulation of the nanoparticles in the brain. Pilipenko compares the peptide-guided peptide-LNP formulations to a Trojan horses.

Homing peptide-mediated targeting of LNPs is first evaluated in cultured human neuroblastoma cells, which are specifically recognized by the brain-targeting peptide. Piļipenko genetically engineered these cancer cell lines to produce a fluorescent signal when exposed to a specific enzyme encoded by mRNA delivered by the LNPs. When the targeted LNPs enter the cells and release their cargo, the resulting fluorescence provides a quantitative readout of LNP delivery efficiency. The same approach can then be evaluated in genetically modified reporter mice available in Teesalu lab.

Piļipenko and colleagues intravenously administer the sterile LNP formulation and detect fluorescent signals in the target tissues 5–7 days later. For formulations that demonstrate efficient delivery, nucleic acid cargoes designed to silence cancer-promoting genes can then be encapsulated in the LNPs and coupled to the brain-specific peptides. Their ability to knock down target genes can subsequently be evaluated in vitro and in vivo. This is precisely the work Piļipenko and his colleagues are currently undertaking: producing the LNPs, encapsulating the nucleic acid cargoes, coupling the particles to brain-specific peptides, and testing their delivery and gene-silencing activity in cellular systems and glioblastoma models.

Although Piļipenko’s initial project focuses on glioblastoma, the LNP platform he has developed could potentially be applied to other brain diseases, including neurodegenerative disorders. Combining a tailored LNP platform with tissue-specific homing peptides represents a promising approach for achieving more precise delivery to diseased tissues and could have broader applications across multiple disease areas. This line of research is also being pursued through grant proposals aimed at further developing peptide-guided LNP technologies for brain disease applications.

This article is written by Annette Maria Hermaküla. This article was funded by the European Regional Development Fund through Estonian Research Council.

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