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Before we dive into the definition of immunotherapy, let’s see what is an immune system. Let’s get in to it!
An immune system consists of cells around our body who keeps pathogens at bay from attacking our body. It a really crucial system which moves around our body to detect any damage. They collect somewhere in the body to form lymph nodes, these nodes swell up when pathogens attacks our body. They keep patrolling throughout the body- our nose, our internal organs or limbs for not only pathogens but also abnormal growth. It eventually takes the course of cancer.
Yes, you guessed it right. We can use our immune system to fight off cancer. In our immune system, we have plethora of cells partaking in the immune response. We will read about some main cells now.
- Some cells deploy rapid response to cancer such as macrophages, microcytes, etc. that fall under innate immunity.
- Some cells like B-cells react slowly to invasion and cancer but their response is permanent or long term. They are called adaptive immunity because they adapt or evolve to solve the danger coming.
For cancer immunotherapy, there is a critically important cells called T-cell and dendritic cells. Think of T cell as the student in a school where they do not know what to do yet. Whereas dendritic cell acts a teacher or educator of the whole immune system. They teach the T-cells to find and kill the cancer by displaying a piece of cancer cells on its receptor to the T-cells.
Presenting the piece of cancer cells to the T-cells in a very specific way and conversion of immature T-cells in to killer T-cells to hunt down those nasty cancer cells is the core of manipulating the immune system for cancer immunotherapy.
How cancer cells evade T-cells?
Over the years, cancer cells have evolved to escape or counter the attack from T-cells. They have receptors specifically for those on T-cells which tells them to stand down. In turn, the T-cells shuts down whatever they are doing and the cancer invasion resumes.
Many scientists have developed drugs to prevent these from happening. These checkpoint blockade drugs interfere in the interaction of cancer and T-cells and prevent the latter’s inhibition.
What if T-cells fail to recognize cancer cells ?
Many things could fail in the whole process. Among them is inability of the T-cells to recognize and kill the cancer cells. What if dendritic cells did not educate it properly ? To counter this issue, scientists have figured out ways. Instead of dendritic cells to educate the T-cells, scientists have ways to engineer them in the laboratories.
They extract those T-cells out of the body and educate them by providing new receptors. New receptors empowers the T-cells with new way to find, recognize and kill the cancer cells. It is known as Chimeric Antigen Receptors(CAR). What they do is in case T-cell receptors fail to recognize the cancer cells, the CAR can replace it and eliminate the cancer cells.
What is Oncolytic Virus Immunotherapy ?
In some cases, it turns out dendritic cells aren’t able to take up pieces of cancer cells or CAR T-cell therapy isn’t viable option. Basically, our innate immunity system isn’t working properly. What other ways can we tackle this?
On occasions such as above, we can use something called “Oncolytic Viruses”. These viruses infect the cancer cells and slowly destroy them. There’s a class of preferential viruses that have the ability to infest tumor cells. When they destroy cancer cells, a small number becomes inflamed which brings the dendritic cell and makes it easier for it to take up pieces on the receptors. In turn, it educates the T-cells and convert them into killer T-cell.
So if the lesion is at the dendritic cells, it can be fixed by oncolytic virus immunotherapy.
Are cancer vaccines worth it ?
What if we replace the idea of using the cancer pieces to present it to T-cells with presenting them through cancer vaccines? Vaccines are great. Just like small pox was treated with vaccines and now it is completely eradicated.
This section of cancer immunotherapy is still in its early stage so to say. Many clinical trials are on going but few haven’t responded very well to it as of now.
There are several variables in these situations. It includes patient’s medical history, pre-existing immunity, genetics, gut conditions and so on. Such vital information are considered when deciding what type of cancer immunotherapy to go for. Gut microbiome and lifestyle are few factors that seem quite insignificant but play a crucial role in making the procedure a success.
Scientists are making great strides in this field to develop less invasive treatment options with minimal side effects. Coming to the side effects, side effects of immunotherapy is quite different from that of radiation or chemotherapy. This is why they should be tackled in different ways.
