What is Targeted Therapy?

Targeted therapy is a form of cancer treatment still being heavily researched. The idea is to target cancer cells and prevent them from growing or forming at all. Targeted therapy is meant to kill cancer cells while leaving healthy cells unharmed. Targeted therapy is not yet ready to be used for wide public use. Researches believe it may one day replace chemotherapy as the main form of cancer treatment. Researchers want targeted therapy to successfully locate cancer cells so the instructions those cells contain can be altered. DNA tells cells how to behave and sometimes those instructions involve cancer causing cell mutations. Targeted therapy has the ability to block carcinogenesis (process of healthy cells becoming cancerous) and block angiogenesis to tumors (the production of new blood vessels).

Cells can be removed from the body to have their DNA altered and then placed back in the body. When the immune system comes across these altered genes they are viewed as foreign. Foreign substances in the body are attacked by the immune system. Other target therapies are concerned with boosting the immune system so it can react to cancer cells on its own. Cancer vaccines attempt to get the immune system to remember it has to attack cancer cells once doctors inject a vaccine that tells the immune system to do it the first time. Marking cancer cells is a big part of targeted therapy. When radioisotopes or cytokines mark cancer cells they can more easily be located by doctors and the immune system. Targeted therapy offers less severe side effects than chemotherapy and radiation treatment. It is still being studied and tested in clinical trials. Research is slow moving because it is so difficult to find ways to insert new DNA into cells removed from a patient.

Uses of Targeted Therapy

Targeted therapy is used to stop the growth and formation of cancerous cells. Inhibiting enzymes are used in targeted therapy to change the function of cancer cells. They also are meant to teach the immune system to attack cancer cells that may appear in the future. Angieogensis can be effected by targeted therapy. This will result in tumors not being able to attract blood vessels. If tumors fail to receive blood from the vessels it will not be able to survive. Without blood vessels feeding it, a tumor will not be able to become malignant and infect other areas of the body.

Trastuzumab is a target therapy drug known to shrink tumors, especially in breast cancer. Sorafenib is a drug that has proven to be effective in treating tumors forming in the liver. Other lymphomas and leukemia have been treated with targeted therapies such as cytokines and cancer vaccines. Pemetrexed is a drug that has showed signs of successfully treating non-small cell lung cancer and has been approved to treat large cell carcinoma of the lungs. 

Types of Targeted Therapy

There are various method of targeted therapy and they all treat pati inents unique ways. The main idea behind the target therapies discussed here has to do with controlling cells so they act in a certain way. Cells are controlled so they react in a manner that will not allow cancer to survive. They also try and teach the immune system to attack cancer cells that are marked by antigens or cytokines in the body. Monoclonal antibodies, radioisotope therapy, cancer vaccines, gene therapy, and cytokines are all types of targeted therapy treatment. While acting uniquely, the ultimate goal of each is similar, control cells so they do not spread cancer throughout the body.

Monoclonal Antibodies

Monoclonal antibodies (MAbs) serve to kill unhealthy cells. They are produced naturally as well as by researchers in labs. MAbs can bind to cancer cells and serve as markers for the immune system to locate cancer cells. There are two types of monoclonal antibodies, naked MAbs, and conjugated MAbs.

·         Naked MAbs do not contain any drugs. They serve as markers for the immune system to find cancer cells. Some may block the production of new blood vessels near tumors.

·         Conjugated MAbs may contain either chemotherapy, radiation or toxins. They release drugs into cancer cells once they have found and binned to them. Conjugated MAbs do not harm healthy cells.

Radioisotope Therapy

Radioisotope therapy can be used to locate cancer cells, treat thyroid cancer and prevent bone metastasis. Radio iodine is injected into the blood stream. Once inside, the iodine is attracted to cancer cells. When viewing an imaging test, the glowing radiation is easy to locate and the location of cancer cells will be given away.

Oral-iodine can be used to find and then treat thyroid cancer. When radioisotope therapy is injected into a patient, any damage to bones will be located. The radioisotope therapy can locate and stop the metastasis of bone cancer using two radioisotope drugs, strontium-89, and samarium. In 2003, the FDA approved the use of monoclonal antibodies and radiation together. This combination of targeted therapy drugs has been used to treat non-Hodgkin lymphoma.

Cancer Vaccines

Cancer vaccines attempt to cure viruses and infections before they become cancerous. True cancer vaccines try and teach the immune system to kill cancer cells that are present in the body. Without a cancer vaccine, the immune system would not know to attack cancer cells because they were created naturally in a patient's body.

·         Tumor cell vaccines are either autologous or allogeneic. Autologous vaccines use cancer cells from the same patient being placed back inside with chemicals or genes added to them. The foreign substances will start an attack by the immune system. Allogeneic vaccines use cells from other people to be placed inside a patient. This is a less expensive yet less effective method.

·         Antigen Vaccines use one or a few antigens to boost the immune system. Researchers have disceovred they can mass produce antigens that have specific instructions such as attacking specific cancer cells.

·         Dendritic cell vaccines break down into presenting antigens that the immune system can easily spot. Once the immune system spots these antigens, T cells from the immune system will attack the cancer cells antigens bind to. Dendritic cell vaccines is believed to be one of the closest vaccines to being complete and ready for public use.

·         DNA vaccines are characterized by placing new DNA into antigens that will then be placed back in the body after having been extracted. The DNA code in the antigens will tell the antigens to keep creating more antigens so the immune system will continue to kill cancer cells. This will prevent the immune system from returning to it's pre-vaccine state.

·         Vector based vaccines are characterized by the usage of viral vectors carrying antigens or DNA. Viral vectors have the ability to enter DNA into cells. Researchers are hopeful they will be able to place the proper DNA on viral vectors which will carry the DNA to cancer cells.

Gene Therapy

Gene therapy is based on the idea of changing or removing genes before they have the chance to develop into cancer and make someone sick. This can be achieved by changing the instructions given by DNA in cancer cells. Once the cells have new DNA, the old DNA that instructed the cells to mutate will be lost. Gene therapy is difficult to achieve because researchers have not found the most effective to change a cells DNA. Researchers are hopeful they will be able to use virus vectors to get new DNA instructions into cancer cells. Liposomes are fat bubbles that carry DNA. These fat bubbles may also be useful in transporting DNA to cancer cells. It will be difficult to get the liposomes to come into contact with cancer cells, they will have to be directly injected into a tumor.

Cytokines

Cytokines are protein secretions from immune system cells. They generally serve as markers so the immune system can locate cancer cells. Cytokines produce more identical cytokines. Cytokines can be combined with radiation, toxins or chemotherapy to kill cancer cells once they have located them. They do not harm healthy cells when they release drugs after having binned with a cancer cells. Researchers have the ability to produce cytokines in a lab. This is where they are given drugs to kill cancer cells. They have the ability to slow tumor growth by ceasing the production of new blood vessels feeding tumors. Cytokines have been successful in treating multiple myeloma, chronic myelogenous leukemia, hairy cell leukemia, and malignant melanoma. Too many cytokines will lead to a condition called cytokine storm. When too many cytokines are present fever, fatigue, nausea, swelling, and redness may occur. This was first discovered in a clinical trial that led to the hospitalization of some volunteers.

Benefits of Targeted Therapy

Targeted therapy will offer many benefits over current cancer treatments once it is ready to be used publicly. Some of those benefits include:

·         Preventing cells from becoming cancerous.

·         Preventing the need for surgery in some cases.

·         Teaching the immune system to fight cancer.

·         Less painful treatment.

·         Treatment with far less side effects.

·         Shrinking tumors without surgery.

·         Overall strengthening of the immune system.