Cancer Immunotherapy: Cancer Vaccine Journey So Far

Combining the realms of cancer and vaccines might seem implausible at first glance. After all, cancer is characterized by the relentless growth and reproduction of cells, often leading to malignancy, while vaccines are devised to bolster the immune system against infections. However, delving into this intriguing interplay reveals a complex landscape where science strives to harness the immune system's prowess for cancer prevention and treatment

In the 18th century, smallpox was the biggest cause of death and was caused by the infection of the Variola virus. This disease killed nearly 1/3 of the world's population and was a pandemic of concern until Edward Jenner tried to use cowpox which was less fatal on humans to protect humans from smallpox. In 1796, he inoculated lesions from cowpox into a boy who then developed mouth fever for a few days but was healthy afterward. He then inoculated the boy with smallpox lesions but this time around, the boy didn't develop the smallpox disease. This was a risky experiment, and I am happy that I wasn't born at that time because that was surely going to be worse than the Covid-19 pandemic. Anyways, Edward Jenner became the father of immunology as he developed the principle of vaccination.^,

We know that we have been able to vaccinate ourselves against diseases but what about cancer. Let's quickly look at what happens when the disease gets into the body. When pathogens get into the body, they trigger responses from the innate and adaptive immune system in the body. When the adaptive immune system made up of the B-cells and T-cells recognizes a pathogen, they undergo Clonal proliferation which causes an increase in cells allowing them to kill the pathogens easily. Once the infection has been tackled, most of the cells die, while the rest remain as memory cells. These cells are going to be activated when the body encounters the pathogens again.

Vaccination against infections involves introducing pathogen components into the body, spurring immune response without causing illness. Antigens and adjuvants within vaccines stimulate the immune system, generating memory B-cells and T-cells. These cells become vigilant, ready to counteract the actual pathogen upon invasion.

When it comes to vaccination for cancer, there are two main approaches which are vaccinating people against viruses that can cause cancer or vaccinating cancer patients to enable their immune system to kill cancer cells. As you would guess that vaccines against viruses that cause cancer are similar to conventional vaccines, which means that after vaccination, the immune system of the people should be able to fight against cancer-causing viruses thereby reducing the prevalence of certain cancer types. For simple understanding, many strains of the Human papillomavirus (HPV) can trigger cancer of the uterine cervix. But then we now have to vaccinate cancer patients against human cells.

Cells in the body need to undergo mutation in their DNA for them to become cancerous and this mutation causes the cell to acquire certain characteristics to help stimulate growth and enable unlimited proliferation. In other for our cells to fight these cancer cells, they require natural killer cells and T-cells as both can identify stress in cells that exhibit abnormal peptides in their MHC-1 molecules or do not have any MHC molecule, as well as abnormal growth in cells. When T-cells cannot find the peptide or the MHC molecule, the natural killer cells does the job of killing them.

For cancer to be able to evade the immune system, the cells can secrete factors that would inhibit the activity of immune cells thereby causing the cancer cells to grow over time. With the vaccination of cancer patients, the immune system is thought to recognize the abnormal proteins on the surface of the cancer cell. These proteins are either found at the early stages of the growth, or in excess amounts as the cancer grows. These proteins are known as Neoantigens which are produced by cancer-specific DNA mutations. If the patient's immune systems are able to identify these proteins, then they will be able to fight the cancer cells.

Notably, the 2010 approval of Provenge sipuleucel-T marked a milestone as the first FDA-approved cancer vaccine for Metastatic Castration-Resistant Prostate Cancer.. However, the road to effective cancer vaccines remains lengthy, with research ongoing to harness the power of Neoantigens in the battle against cancer. While challenges persist, the strides made so far hold promises for a future where the immune system becomes a potent weapon against cancers.

Image Reference

Image 1 || Pexels || Medical Practitioner holding a Vial of Vaccine
Image 2 ||Creative Commons || Cancer vaccines already exist for some types of cancer.