Monoclonal Antibodies: Drugs to Treat Many Kinds of Cancers

Monoclonal antibodies are the type of targeted therapy drugs used to treat many kinds of cancers. The basis of this medicine is synthetic, lab-made antibodies that attack specific targets on cancer cells or boost the patient immune system’s ability to defend against it.

Key takeaways:
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    Monoclonal antibodies are one type of targeted cancer therapy drug.
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    Monoclonal antibodies are laboratory-engineered molecules that mimic the action of natural antibodies (protective proteins produced by the immune system).
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    Monoclonal antibodies attack the specific proteins (targets) on the cancer cell's surface.
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    Monoclonal antibodies are characterized by relatively mild side effects. However, in rare cases, this treatment can cause more serious side effects.

What exactly are the antibodies?

Antibodies (also known as immunoglobulins) are large protective proteins produced by the immune system. However, they are just a tiny part of this complex biological processes network, as the immune system is made up of millions of different molecules which interact with each other. These interactions ensure that human organisms would be protected from disease-causing agents, such as bacteria, fungi, viruses, toxins, etc.

One way how immune system identifies and neutralizes invaders is by using antibodies. An antibody can recognize a unique molecule on the pathogen's surface, called an antigen. After recognition, immunoglobulin binds to the antigen and serves as a flag that attracts disease-fighting immune system molecules or as a trigger that promotes cell destruction by other immune system processes.

In the same way, mutated cells are in our bodies. However, these damaged cells are often able to evade identification. Usually, they mask themselves by releasing specific signals that prevent antibodies from recognizing them. Hiding protects the cells from destruction, so they can continue to multiply and finally form cancer. Fortunately, thanks to the monoclonal antibodies drugs the cancer cells in the body can still be detected and killed.

Definition of monoclonal antibodies?

Monoclonal antibodies are laboratory-produced molecules designed to act like natural ones. However, these immunoglobulins are engineered to find and recognize only a specific target on a cancer cell. Thus, different types of monoclonal antibodies have to be produced to kill distinct cancer cells. This monoclonal antibody property is emphasized even by the word – monoclonal, which means that the specific immunoglobulin therapy has a lot of copies of one type of antibody, that can recognize only a particular target.

How do monoclonal antibodies do their job?

Although a specific monoclonal antibody drug can detect only one target, it can still be called a multi-tasker, because to disrupt a cancer cell it can act with different mechanisms. The way of work depends on the protein immunoglobulins are designed to attack. In the text below main possible monoclonal antibodies' ways of working are presented.

Blocking cell growth

Cancer cells usually have higher than normal amounts of proteins called growth factor receptors, which are located on their surface. These receptors send and receive signals which help the cell to survive, grow and multiply. Some monoclonal antibodies can find and attach to growth factor receptors. In this way, they block the receptors and they can no longer work properly. Ultimately the cancer cell no longer receives the signals needed for survival.

Delivering radiation or chemotherapy treatment

Because of a monoclonal antibody's ability to find and bind to the specific proteins on cancer cells' surface, they are sometimes engineered as a delivery vehicle for other treatments (called conjugated monoclonal antibodies). In this case, a monoclonal antibody is combined with different chemotherapy drugs or radioactive substances, to transport them directly to the cancer cell. This helps to minimize the effect of the drug on healthy cells.

Flagging cancer cells helps the patient’s immune system to find and kill them

As mentioned above, one way how immune system fights infection and destroys mutated cells is through antibodies. They are like flags denoting organisms or cells that immune system disease-fighting molecules have to destroy. Sometimes monoclonal antibodies are manufactured to attach to the cancer cells which the immune system cannot detect under normal circumstances. This helps to trigger a natural immunogenic reaction during which cancer cells are killed.

Inhibiting blood vessel growth

Blood flow is one of the most important factors ensuring nutrient supply for the tumors. That is why while growing and spreading throughout the body, cancer cells send signals that stimulate the formation of new vascular networks around them. Therefore, knowing that blood vessels are so important for cancer survival, monoclonal antibodies which block these signals are developed (anti-angiogenic monoclonal antibodies). For example, cancer cells in large quantities produce a protein called vascular endothelial growth factor (VEGF). This protein is a signaling molecule stimulating stem cells from the blood vessels to migrate near newly forming tumors and start to form a blood vessel network there. However, the anti-angiogenic monoclonal antibodies can recognize and attach to VEGF. Consequently, this monoclonal antibody and VEGF complexes are no longer recognized by stem cells as a signal that encourages them to form blood vessels.

Possible side effects

All drugs have side effects, and monoclonal antibodies are no exception. Depending on the type of immunoglobulin, their side effects can vary. The most common side effect of monoclonal antibodies is an allergic reaction which usually manifests with the symptoms like breathlessness, fever, chills, itchy rashes, flushes, and faintness. However, in rare cases, treatment with monoclonal antibodies can cause more serious side effects, e.g., infusion reactions, blood pressure, congestive heart failure, heart attacks, inflammatory lung disease, etc.

Still, there is no need to be afraid of these side effects, because their impact could be significantly decreased by constant monitoring of the organism's reactions and overall condition. Most importantly, monoclonal antibodies are considered the safest and most effective cancer treatment strategy for patients with both hematological malignancies and a wide range of solid tumors.

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