Spotlight on Young Researchers: Glioblastoma and the challenge of getting cancer drugs to reach the brain

BACK TO RESEARCH WITH IMPACT: FNR HIGHLIGHTS

Glioblastoma is the most aggressive form of brain tumours in adults. The incidence is about 4 per 100.000 people and the average survival after diagnosis is about 14 months with current treatments. The tumour’s location represents a major challenge – few drugs make it past the blood brain barrier. Researchers are working on designing a novel kind of drug that could help do just that.

Glioblastomas are aggressive, fast growing tumours and display extensive invasion into the normal brain. Standard treatment includes tumour resection, followed by combined radio- chemotherapy, but the beneficial outcome is minimal. Compared to cancer in other organs, the brain location represents a major challenge because few drugs are able to enter and have a beneficial effect.

“There have been major advances in characterising Glioblastoma on a molecular level, which has improved the diagnosis and classification of gliomas such as Glioblastoma, and treatment research for this type of brain tumour. Many challenges remain, such designing new therapeutic agents that can diffuse into brain tissues,” explains Biochemist and molecular biologist Hugo Dosquet, researcher at the Luxembourg institute of Health (LIH).

Obstacles and resistance

Drugs have a very hard time crossing the blood brain barrier (BBB) – and if they do not reach their target, they are useless. On top of this, Glioblastomas show strong adaptive behaviour (known as tumour plasticity), often forming what looks like tentacles, reaching far into the brain. These are major limitations for an efficient drug response.

“Drugs face tumour molecular specificity and drug resistance. Science advances in terms of drug delivery and innovation are needed to generate specific and effective drugs for these tumours.”

As part of his PhD, Hugo is collaborating with several other scientists on a project aiming to do just that: designing a novel kind of drug, inspired by a stem cell maintenance mechanism.

This is where we jump into the technical molecular biology details – if you are fine with the scientific terms associated with this research topic, read more in our ‘peer to peer’ section below.

Hugo Dosquet is in the 3^rd year of his PhD in the NORLUX Lab at the Luxembourg Institute of Health (LIH). His project is one of 18 projects in the “Cancer Biology – CANBIO” PRIDE Doctoral Training Unit (DTU), coordinated by Prof Simone Niclou at the LIH and funded by the FNR.

MORE ABOUT HUGO DOSQUET & HIS RESEARCH

On choosing Luxembourg as a research destination

“I decided to come to Luxembourg for the international environment that I enjoyed during my university curriculum, where I had the opportunity to perform internships in France, Spain and New Zealand. As a non-English native speaker, the international environment is a priority for me to evolve for a future scientific career. Dr. Simone Niclou proposed me a PhD project ambitious and promising to have a real scientific impact, so I decided to take up the torch. The CANBIO programme also provided a real opportunity to travel, to establish relationships and assist at conferences to meet the scientific community. Those advantages offered in Luxembourg were good enough to accept the Luxembourg weather! Unfortunately, because of the COVID-19 pandemic, most of the travel and exchange opportunities were lost.”

On what drives him as a scientist

“Like many biologists, I wanted to decipher the basic life mechanism. My curiosity drives me to understand at molecular scale how an organ composed by cells could act to respond to environmental stimuli. Research of new therapeutic agents has always been the main axis of my different student experiences. My university studies covered three different fields: organic chemistry, bioinformatics and molecular biology, enabling me to diversify my point of view and research axis.”

THE SCIENCE: PEER TO PEER

What the field has been able to do so far to improve treatment

“Major advances in molecular characterisation have been achieved to improve the diagnosis and classification of gliomas including Glioblastoma (WHO CNS 2007, 2016 and TCGA 2008) and thus enhance Glioblastoma treatment research. Among Glioblastoma samples, 90 % of samples are IDH wildtype. In IDH wildtype glioblastoma samples, the most frequent genetic alterations affect RTK, RB and P53 signalling pathways. Receptors tyrosine kinase (RTK) overexpression such as EGFR lead to an increase of RTK pathway activity and increased proliferation and survival. Several RTK inhibitors (RTKi) were thus envisaged to reduce RTK activity, however clinical trials using RTKi failed to benefit GBM patients.”

Challenge: Decreasing RTK signalling pathway

“Conventional RTKi widely used in other cancers such as Erlotinib do not provide efficient treatment effect for GBM patients. RTKi used as monotherapy and on therapy combination with Temozolomide did not shown major benefits for GBM patients. The main challenge is to design new therapeutic agent able to decrease RTK signalling pathway activity and diffuse into brain tissues.”

A novel drug inspired by stem cell maintenance mechanisms

“An endogenous protein termed LRIG1 downregulates several RTK signalling pathways and level of expression as RTKs. LRIG1 is a transmembrane protein, however the extracellular part (sLRIG1) is able to reduce the cell growth of several GBM models in vitro and in vivo. Nevertheless, the mechanism of action and the minimal active residue of sLRIG1 is unknown.

“Thus, my research undertakes to identify which part of sLRIG1 protein is able to bind RTKs and thus reduce the cell proliferation. A second goal is to decipher the molecular mechanism of how LRIG1 interacts with RTK and affects downstream signalling events, including receptor internalisation and downregulation.”

A molecular tool to detect interactions between RTK and adaptor proteins

“In collaboration with the lab of Dr. Andy Chevigné (LIH), I set up a complementary molecular tool detecting the interaction between adaptor proteins Grb2 and CBL with RTKs (NanoBit technology). The interaction between RTK and adaptor proteins is the main access for RTK signalling pathway. This model looks to be sensible to RTKi known to inhibit this interaction and the RTK signalling pathway. Next step will be to investigate the effect of various LRIG1 constructs on this interaction.”

Oh AXL

“Our previous work identified AXL as a new target of LRIG1. AXL is a well-known RTK involved in cancer resistance therapy with anti-EGFR drugs. We have shown that long term treatment with sLRIG1 downregulates AXL. However, rather unexpectedly, my recent data suggest that co-expression of AXL and sLRIG1 results in an increase of AXL at the membrane. This poses new questions and leads us to investigate in a potential new kind of LRIG1-AXL interaction mechanism.”   

“In my PhD project, I found an efficient and carrying support from my NorLux team colleagues for daily experiment. However to complete support expertise, we are collaborating with internal and external research groups: Dr. Andy Chevigné from the Immuno-Pharmacology and Interactomics research group (LIH, DII), Dr. Christiane Hilger and Dr. Annette Kühn from Molecular and Translational Allergology research group (LIH, DII) and Pr. Mirko Schmidt from Technical University of Dresden, Germany. Pr. Serge Haan (UL) has been instrumental in supporting me for in silico analyses of protein engineering and protein-protein interaction studies using various bioinformatic tools.”

Focus on LRIG1 of the LIG protein family

“LRIG1 belongs to the LIG protein family. LRIG1 holds the largest LRR domain sequence compared to the other LIG family members, as well as three Immunoglobulin like domains. Its LRR domain is about 50 kDa, around 400 aa. In the literature, LRR protein domains mainly play a role to bind interactors (ligand, protein targets). Highly suspected to be involved in the interaction with RTKs, my PhD project also aims to identify if the LRR domain includes the minimal active residue involved in the inhibition GBM cell growth. I am following a complementary strategy between in silico and in vitro experiments. In vitro experiment is organised by the production of sLRR in a conditioned media to treat GBM cells and In silico to design future variants of sLRR helped by other LRR protein domains.”

Photos: Hugo Dosquet