Q: What do you think of alternating electric fields as a therapy option?
A: Therapy with alternating electric fields is currently being used and offered to patients. This means that patients who have survived well through radiochemotherapy should also be offered treatment with alternating electric fields.
However, what happens in this process is not as well understood as with other therapies. It is assumed that the cell cycle, i.e., cell division, is altered by disrupting the mitotic spindle. But you can imagine, and this is now speculation, but quite sound speculation I believe, that alternating electric fields also cause a certain amount of confusion in the previously described networks. But this still needs to be investigated in more detail.
It is not implausible. We know that such alternating electric fields disturb the organization of cell organelles. And we also know that for this communication, we need fairly good order and also organization. This would definitely be a starting point on the way to understanding why this therapy potentially shows a certain effect in some patients.
Nerve cell precursors
Q: Scientists from the UKHD and the DKFZ have discovered a new glioblastoma spreading strategy and have learned that the tumor cells imitate the properties and movement patterns of nerve cells. They are labeling the results a “milestone in the field of cancer neuroscience.” Could you explain a bit more?
A: Glioblastoma does not grow on its own as a solid mass, but instead, the entire brain is affected by the disease. The question of how the tumor’s individual cells move the main tumor mass from afar, how they get there, how they continue to be supplied, and what their interaction partners are – an entirely new light has been shed on all of this in our work.
The development of tumor cell mobility has been recognized as a remnant of brain development. The tumor cells have retained properties that the precursor cells for nervous-system development require for an organized nervous system to emerge from just a few cells. This means that the tumor cells copy or eventually retain properties of the nerve-cell precursors that, unlike mature nerve cells, are mobile to a fairly high degree.
Mobility here means that it can advance along a network, despite said network being very densely packed. This also means that certain processes, such as releasing and then continuing to move again, must function and that the communication regarding the original disease must be maintained.
First, we understand what the different glioblastoma cell types do, which molecular properties are associated with which behaviors, and which cell type (namely the swarming cells) is responsible for the invasive tumor growth. In contrast, the network-forming cell type, which only develops from these, is responsible for the resistance.
Interrupting communication
Q: Which starting points for new therapies do you see?
A: In terms of new therapies, these movement phenomena are one good starting point. The other starting point – I find this one much more interesting – is that the programming steps that these tumor cells use [are] no longer needed. This is because our mature nervous system no longer requires this program, which was necessary for the mobility of cells in development.
Our central nervous system exhibits little cell movement. This is to do with programs of nervous-system development that are switched off in the mature nervous system. But they are then reactivated or remain active in the tumor cells. This process reveals potential starting points for therapy.
Addressing the movement of cells, that has been investigated for the last 20 years, but it seems to have an extraordinarily high number of side effects, because these movement mechanisms are also important for other, healthy cells in the body. For example, digestive mechanisms and other proliferation mechanisms, on mucous membranes, in the blood system, in the bone marrow, are then affected and no longer function.
There is another possible approach: the more-or-less specific interaction between the nerve cells and the tumor cells also offers starting points for therapies, from our point of view. The key word is epilepsy treatment. We know that people with brain tumors suffer badly, or worse than usual, from epileptic seizures. This was often regarded purely as a pressure problem. There is a disruptive element in the brain, and this causes the electrical activity in the brain to become disorganized. For some people, this can lead to seizures in certain situations.
The communication between tumor cells and nerve cells takes place via transmission substances, e.g., through the neurotransmitter glutamate. Now you can consider whether a “surplus” of communication, such as an excessively strong stimulus, can trigger epileptic seizures.
In this work, we demonstrate that by interrupting this communication, we can also prevent the movement of these cells and the growth, the proliferation, of these cells.
Q: What is the significance of parvoviruses for therapy?
A: The major topic for cancer is immunotherapy. And one option for performing immunotherapies lies with viruses. Parvoviruses are a plausible therapy for proliferating cells.
Parvoviruses are usually administered locally. This means that a surgical cavity is infected with the viruses and the tumor cells that remain after an operation will then hopefully be killed off by these viruses.
This is the first step and the immediate effect of virus therapy. The attempt is made to kill off cells in the same way as with a medication. The advantage of viruses is the high specificity, i.e., only dividing cells will be attacked. In addition, parvoviruses are so small that they can also spread well and circulate through the brain.
The second reason for immunotherapy is that when killing off cells with viruses, antigens are often released that otherwise would not be, depending on the virus. But it’s the case with parvoviruses. They integrate with the virus’s genetic material. When cells rupture, certain proteins are then revealed, hybrids of viruses and the human genome, and these are attractive to the immune system.
There is a whole range of studies on this subject. However, there are currently no randomized studies that directly compare the therapies. But the expectation is that the use of parvoviruses could be a good addition to therapy.
One limitation that should be mentioned is that the use of viruses may be beneficial for some patients, but it will not have an effect in every patient. What is exciting about parvoviruses is that these viruses can be injected via the bloodstream and still achieve a good effect in the brain.