Introduction
Cancer Immunotherapy has been around since the early 1900s. However, it wasn’t until recently that we started seeing some major breakthroughs in the field. As of today, there are over 100 clinical trials ongoing worldwide that involve using vaccines against various types of cancers. These vaccines stimulate the immune system to recognize tumor cells as foreign invaders and attack them.
What Is Immunotherapy?
Immunotherapy is a treatment method that uses the body’s own immune system to fight cancer cells. In immunotherapy, the patient’s own white blood cells (T-cells) are removed from their bloodstream and then re-infused back into the patient. Let us discuss these in detail.
How Does Immunotherapy Work?
The first step in immunotherapy is removing the patient’s T-cells from their bloodstream. This is done using a procedure called leukapheresis. Leukapheresis involves drawing blood from the patient, separating out the white blood cells, and returning the red blood cells to the patient. After the T-cells are collected, they are sent to a lab where they are grown in special culture dishes.
Next, the T-cells are modified to express receptors that allow them to identify and attack specific types of cancer cells. Finally, the T-cells undergo genetic engineering to make sure they don’t cause autoimmune disease after being reintroduced into the patient.
- Checkpoint inhibitors – Checkpoint inhibitors are drugs that block certain points in the signaling pathways that normally prevent the immune system from attacking tumors. These drugs have been shown to increase survival rates in patients with some cancers.
- CAR T-cell therapy – CAR T-cell therapy is a type of treatment where doctors take white blood cells called T-cells and genetically modify them using viral vectors to target and destroy specific kinds of cancer cells.
- Oncolytic viruses – Oncolytic viruses are viruses that selectively kill cancer cells while leaving normal cells alone. Scientists are working to develop these viruses to specifically target and destroy cancer cells without harming healthy ones.
- Immune checkpoint inhibitors – Immune checkpoint inhibitors work by blocking molecules that prevent the immune system from being able to recognize tumor cells.
- PD-1/PDL-1 inhibitors – The PD-1 receptor binds to its ligand (PDL-1) on the surface of cancer cells. When this happens, the immune system becomes less likely to detect and eliminate cancer cells. Researchers are developing therapies that block the PD-1 pathway to enhance the effectiveness of existing treatments.
- CTLA-4 inhibitors – CTLA-4 is a protein expressed by immune cells that helps regulate their activity. A class of medications known as CTLA-4 inhibitors works by preventing the interaction between CTLA-4 and CD80/CD86, thereby stopping the downregulation of T-cell activation.
Lung Cancer Immunotherapy
Lung cancer is one of the leading causes of death among men and women all over the world. According to the American Lung Association, lung cancer kills more Americans than breast, colon, and prostate cancer combined. NSCLC accounts for 85% of cases while SCLC only represents 15%.
In recent years, researchers have made great strides in developing new treatments for lung cancer. One such treatment is known as PD-1/PD-L1 inhibitors. They work by blocking the interaction between PD-1 receptors and their ligands, PD-L1.
Pancreatic Cancer Immunotherapy
Pancreatic cancer is one of the deadliest forms of cancer. Nearly 40,000 people die each year due to pancreatic cancer. Diagnosing pancreatic cancer in its early stages is difficult, when patients already have the widespread disease you get to know about it. Unfortunately, even after surgery, chemotherapy, radiation therapy, and targeted therapies, many patients still experience recurrence of the disease.
Researchers have found that certain proteins play a role in the development of pancreatic cancer. One of these proteins is MUC16. MUC16 is a protein that helps maintain the integrity of the intestinal lining. When MUC16 levels increase, it may lead to the formation of precancerous lesions. Researchers believe that inhibiting MUC16 could prevent the growth of precancerous lesions and slow down the progression of pancreatic cancer.
Ovarian Cancer Immunotherapy
Ovarian cancer is difficult to detect during the earliest stages. Once detected, however, it is very responsive to chemotherapy.
One reason why ovarian cancer relapses are because the cancer cells develop resistance to chemotherapy. A team of scientists led by Dr. David Peeper discovered that a protein called CD47 plays a key role in chemoresistance. CD47 is a protein that acts as a marker for macrophages. Macrophages are white blood cells that engulf pathogens and debris.
When CD47 binds to macrophages, it prevents phagocytosis. Therefore, researchers believe that inhibiting CD47 could allow macrophages to engulf cancer cells and stop them from spreading throughout the body.
Prostate Cancer Immunotherapy
You can treat prostate cancer with surgical removal of the prostate gland also following hormone therapy. Unfortunately, many patients eventually relapse and require additional treatment.
Researchers have identified a protein called NKG2D that appears to play a role in prostate cancer. NKG2D is an important molecule that activates natural killer cells. Natural killer cells are white blood cells that kill infected or abnormal cells.
NKG2D is present on the surface of natural killer cells. When NKG2D binds to its ligand, it triggers the release of cytotoxic granules into the surrounding area. Cytotoxic granules contain perforins and granzymes which destroy nearby cells.
Bladder Cancer Immunotherapy
In bladder cancer, the immune system attacks the tumor cells by recognizing them as foreign invaders. When the immune system identifies a threat, it creates antibodies that attack the invader. These antibodies then travel throughout the body looking for any sign of infection. If they find something suspicious, they attach themselves to the surface of the infected cells and alert the body’s defenses.
Researchers have developed drugs called checkpoint inhibitors that help boost the activity of the immune system. Checkpoint inhibitors block the action of certain molecules that normally prevent the immune system from attacking the cancer cells. By blocking these checkpoints, the immune system becomes free to recognize and kill the cancer cells.
Checkpoint inhibitors are still in the testing stage in clinical trials for patients with advanced bladder cancer. Researchers hope that these drugs will improve survival rates and increase the quality of life for patients who suffer from bladder cancer.
Brain Cancer Immunotherapy
Brain cancer immunotherapy works by activating T-cells (immune system cells) to attack brain tumors. A patient’s own immune system naturally attacks foreign invaders, including viruses and bacteria. When these same T-cells activate inside the body, they become even more powerful. By infusing patients’ blood with their own immune system cells, doctors activate the T-cells to fight off the tumor cells.
The treatment involves two steps. First, doctors remove some of the patient’s white blood cells called lymphocytes. These cells help protect the body from infection and disease. Next, they use a drug to stimulate the remaining lymphocytes to multiply and mature. Once the drugs are, doctors collect the newly formed lymphocytes, put them back into the patient’s bloodstream, and then reinfuse the patient with his/her own lymphocytes.
This procedure is repeated over several weeks until enough lymphocytes are collected. Then, the lymphocytes are frozen and stored at -196 degrees Fahrenheit (-120 degrees Celsius). Doctors later thaw out the lymphocytes and reinfuse them back into the patient.
In addition to fighting brain cancer, this type of therapy may also be useful for treating other types of cancer.
Who Can Benefit From Immunotherapy?
Patients who have exhausted standard treatments may benefit from immunotherapy. Patients who have had chemotherapy, radiation therapy, surgery, or targeted therapies may not respond well to traditional treatments. Immunotherapy works best if you diagnose cancer early enough before cancer spreads throughout the body.
When Should I Consider Immunotherapy?
If you have exhausted standard treatments and have no other options left, consider immunotherapy. If you have advanced prostate cancer, immunotherapy may help slow down the progression of the disease.
Where Do We Go From Here?
There are currently several clinical trials underway investigating the use of immunotherapy for prostate cancer patients. Researchers hope to find ways to improve the effectiveness of immunotherapy while reducing its side effects.
