Can you be injected with cancer

Immunotherapy for cancer

What is Immunotherapy?

Immunotherapy against cancer comprises various methods and active ingredients that help direct the body's own immune system against cancer. The so-called immuno-oncology thus provides a fourth pillar of cancer therapy - alongside operations, radiation and chemotherapy.

The idea of ​​using the immune system to fight cancer is not new. But many hurdles had to be overcome for the implementation. Simply activating the immune system as part of immunotherapy is tricky and could have significant side effects. Immunotherapy must always maintain the balance so that the immune reaction is not too violent. And immunotherapy must ensure that the immune activity is directed as specifically as possible against cancer cells.

In most cases, immunotherapy is only used for cancer when the classic treatment fails. How successful it is depends on many factors. One of them is the form of cancer. Two examples: In metastatic non-small cell lung cancer, immunotherapy extends the patient's lifespan by an average of several months. In advanced black skin cancer (malignant melanoma), patients who otherwise would have died quickly with a high probability may even gain several years.

However, only some of those treated respond to immunotherapy. For others it doesn't work at all. Because the same form of cancer also varies from patient to patient. Everyone has their own cancer.

Immunotherapy: Cell Biology Background

Normally, sick or overaged cells of the body die on their own. Doctors call this programmed cell death “apoptosis”. It is different with cancer cells. They continue to divide and displace healthy tissue.

As part of immunotherapy, white blood cells are stimulated to render cancer cells harmless: T cells and natural killer cells are supposed to fight cancer in the same way as other invading pathogens.

Cancer cells trick the immune system

But this is not so easy. Pathogens have molecules (antigens) on their surface that mark them as foreign and make them vulnerable to the immune system. Cancer cells, on the other hand, emerged from the body's own cells. Their antigens identify them as members of the body. So they remain undetected by the immune system and multiply - a tumor develops.

Other cancer cells are recognized by the immune cells, but they manipulate or weaken the immune system. For example, by presenting inhibiting signal molecules to the T cells on their surface so that they no longer attack.

Immunotherapy - balance between activation and moderation

Cancer cells therefore use very different regulatory mechanisms to outsmart the immune system. Scientists summarize the various strategies under the term “immune escape mechanisms”. Accordingly, there are also different approaches to what exactly is done in immunotherapy to make the cancer cells vulnerable:

Immunotherapy with cytokines
Cytokines are the body's own messenger substances that, among other things, regulate the activity of the immune system. Their artificial counterparts are not tailor-made to treat specific tumors, but have a general effect on the immune system.

With the help of interleukin-2, for example, the activity of the immune system can be boosted. Interferon, in turn, slows the growth and division of cells - this also works with cancer cells.

disadvantage: Compared to newer methods of immunotherapy, cytokines do not work in a targeted manner. They are only successful with a few types of tumor.

Immunotherapy with monoclonal antibodies
Antibodies are Y-shaped protein molecules that attach themselves precisely to the specific antigens of a cell. They mark diseased cells and pathogens for the immune cells so that they can eliminate them. Such monoclonal antibodies can also be produced artificially.

On the one hand, they can be used to diagnose cancer. Equipped with fluorescent or radioactive particles, they help to make cancer cells in the blood or cancerous tumors and metastases in the body visible.

Monoclonal antibodies are also used directly as immuno-oncological therapeutics. If they attach themselves to the tumor, this is a signal for the immune system to tap into it. They can also be used to send cell poison or radioactive substances to the cancer cells in a targeted manner so that they perish.

And there is another application method: Monoclonal antibodies act as immunotherapy by inhibiting certain signaling pathways that are important for tumor growth. There are also immunotherapeutic antibodies that prevent the formation of blood vessels that supply the tumor. The development of an immunotherapy using monoclonal antibodies has already been successful for special types of cancer.

disadvantage: Immunotherapy using monoclonal antibodies only works for tumors that have very specific surface features that do not or hardly occur in healthy cells. Even if the tumor is poorly supplied with blood vessels or is very large, the treatment is not effective because not enough antibodies reach their target.

Immunotherapy with therapeutic cancer vaccinations
In contrast to vaccinations that protect against cancer (e.g. the HPV vaccination), therapeutic cancer vaccinations with so-called tumor vaccines are supposed to work against existing tumors.

In this type of immunotherapy, T cells are targeted to cancer cells. In one variant, so-called dendritic cells act as "agitators". Their job in the body is to alert the T cells to enemies. To do this, they present the T cells with certain antigens that are typical of the respective enemy. In the meantime it has been possible to equip the dendritic cells with antigens which are characteristic of special cancer cells and which otherwise do not occur in the body. The T cells then attack the tumor cells and destroy them.

Immunotherapy in the form of a cancer vaccination could revolutionize cancer therapy in the long term. It can be tailored to the individual tumor so that each patient receives their individual tumor vaccine.

When vaccinating with tumor vaccines, the vaccine is injected into cancer patients under the skin or directly into the lymph nodes.

disadvantage: So far, the successes have been moderate, it is difficult to produce the necessary components of the vaccination in the necessary quantities. Many approaches for cancer vaccines are still in the research stage and far from being used.

Immunotherapy with immune checkpoint inhibitors
Immune checkpoint inhibitors are special antibodies that belong to the latest generation of active substances in immuno-oncology. They aim at certain immune checkpoints, which act as brakes on the immune system - they do not act directly on the cancer cells themselves. With their help, excessive immune reactions are prevented in healthy, which would damage the healthy tissue.

Some tumors can trigger this braking function. On their surface, they carry molecules that match certain T-cell receptors that function like switching heads. Upon contact, the T cell is inactivated and does not act against the cancer cell.

Immune checkpoint inhibitors release these brakes again. In turn, they occupy the critical surface molecules of the cancer cells. They can no longer operate the T-cells' switch-off buttons and the T-cells can take action against them.

disadvantage: This form of immunotherapy is not a “silver bullet”. Sometimes it takes a few weeks for them to work. In addition, not all patients respond to them and the immune system can overreact when they are used.