Researchers at the National Institute of Biology are exploring new avenues for more effective treatment of glioblastoma, the most aggressive form of brain cancer. They have discovered different biomarkers that could be used as drug targets in the future.

In Slovenia, approximately 100 patients are diagnosed with glioblastoma annually, which makes it a rare disease. Nevertheless, it represents a major health challenge due to its high mortality rate, with patients typically surviving only a year and a half. Current treatment strategies only slightly extend patients' life expectancy.

Slovenian researchers in the cancer biology group at the National Institute of Biology (NIB), led by Barbara Breznik, have discovered various biological markers in glioblastoma tumour cells that could potentially be used as drug targets in the future.

They found that the tumour is flooded with inactive immune cells, opening up potential for immunotherapies. They are also developing 3D cellular models that mimic tumours in the brain.

The breakthrough discoveries were made as part of numerous international projects and networks in which the team actively participates. As Breznik explains, Slovenia can be competitive in such research precisely because of these international connections.

"In Slovenia, we have excellent study programmes, very innovative ideas, and, with the new premises, comparable infrastructure. However, it's true that we often encounter obstacles in research funding, which means that foreign countries frequently overtake us in implementation."

The researchers will present their findings at the first international conference within the COST Net4Brain network, which is taking place at NIB from 4 to 6 September. The event will feature renowned Slovenian and international experts who will attempt to set guidelines for future research and highlight the urgency of finding treatments for rare forms of cancer as well.

Challenging treatment

According to Breznik, treating patients with glioblastoma is complicated by several factors, including rapid spread and resistance to existing treatments. Individual cancer cells from the tumour mass skilfully penetrate the surrounding brain tissue, meaning the cancer is usually already in very late stages when discovered. Additionally, some cells - so-called glioblastoma stem cells in niches along the tumour vasculature - can reactivate after treatment.

Another significant challenge is the great diversity in tumour characteristics between different patients and even the diversity of cells within an individual patient's tumour. Researchers at NIB are therefore striving to find molecular targets in cells that are as commonly expressed as possible, thus enabling treatment for as many patients as possible.

"We always have the goal of finding some kind of universal target present in all cancer cells," Breznik says. Research worldwide is even moving towards finding common targets for different types of cancer, potentially using a drug currently used to treat skin cancer or melanoma to treat glioblastoma as well.

Breznik however warns that discovering a universal target for glioblastoma will likely not be possible, so breakthroughs are mainly anticipated in the field of personalised medicine. This approach would involve studying the molecular composition of each patient's tumour and preparing treatment tailored specifically for them.

Lab tumour modelling

To better understand the tumour environment and its biological conditions, Slovenian researchers are developing 3D cellular models of tumours, which are a better approximation of human conditions than just classical cell culture in single layers.

The creation of 3D models begins with obtaining cells from glioblastoma patients, which is the result of collaboration with the University Medical Centre Ljubljana, the Institute of Oncology, and the Faculty of Medicine in Ljubljana. "We then insert the cells into bioreactors or culture media with various nutrients and factors that guide cell development. We achieve the important three-dimensional structure through rotation," Breznik explains.

The end product is spheroids just a few millimetres in size, containing between 100,000 and 200,000 tumour cells. These models, which are extremely similar to human tumours, can then be used to study cancer biology or the effects of various therapies.

Using the immune system

One such therapy is immunotherapy, which has proved successful in recent years for other types of cancer. It uses cells from our own immune system to attack cancer cells, specifically natural killer cells in the blood that kill damaged cells and those infected with viruses. "In our brain tumour models, we are currently finding that natural killer cells are very effective at removing tumour cells that are resistant to conventional treatment," Breznik says.

The potential effectiveness of cell and immunotherapy for brain tumours is promising, as the brain was long considered an area without an immune system presence. Today, we know that the immune and central nervous systems are intertwined. Immune cells enter brain tumours and can comprise up to 50% of tumour tissue. However, the problem is that an immunosuppressive environment is created, which prevents the functioning of immune cells and consequently also of cell and immunotherapies.

Breznik's team's research provides fundamental knowledge about brain cancer. The path to new drugs or therapies is long and relies primarily on the interest of the pharmaceutical industry.

"In Slovenia, we do collaborate with the pharmaceutical industry, but Slovenian pharma companies are not focused on developing innovative biological drugs in oncology," she explains. Nevertheless, the institute's discoveries, also due to the involvement in the international research environment, will serve as a springboard for further breakthroughs in the treatment of what is currently incurable glioblastoma.