Can Infections Cure Cancer?
The idea of treating cancer with microbes comes from the 19th century.
A 61-year-old man was brought to the hospital due to severe COVID-19. He was treated for 11 days and then discharged from the hospital. He had stage 3 lymphoma, an advanced form of cancer, developing in white blood cells. After 4 months, something extraordinary happened. The tumor was largely gone! The doctors reported it in a scientific journal, arguing that the coronavirus infection might’ve induced an anti-tumor defense in the body. No one exactly knows how, but this is not the first time an infection cured cancer.
The mysterious disappearance of tumors is mostly observed in lymphoma. Many articles report spontaneous cancer remission, but some repeatedly associate reduced tumor size with certain infections. For instance, another lymphoma patient was reported to recover from cancer after having a colon and lung infection at the same time. A 63-year-old woman with a malignant lymphoma fully recovered without chemotherapy, following the diagnosis of the ulcer-causing bacteria.
A robust immune system is a key to combat diseases, including cancer. Our defense system mainly works by distinguishing self from non-self patterns and attacking the ones who are unfamiliar. But there is a small problem here. Cancer cells aren’t foreign; they’re actually ours. Specific genetic changes can induce uncontrollable cell division, resulting in cancer formation. Although sometimes immune cells realize abnormal cell proliferation, tumors have brilliant escaping strategies from immune system attacks.
Smart cancer cells are not the only reason why the immune system is incapable of destroying them. Most treatments, such as radiotherapy and chemotherapy, weaken the immune system as a side effect. Besides, tumors affecting the bone marrow can reduce the number of immune cells in the body. Therefore, a spark -such as an infection- might be needed to wake up the defense system in the body.
In the past years, scientists put efforts into developing cancer treatments to increase the activity of the weakened immune system in patients. Cancer vaccines, immune system modulators, and immune cell transfer are examples of what is called immunotherapy. Immune system modulators are a broad range of molecules. They aim to enhance the immune system activity by increasing the number of cells or the amount of effector molecules secreted from those cells.
Remember the patients whose tumors spontaneously regressed after an infection. The microbes causing inflammation act like immune modulators, priming the defense system to fight tumors. It is not a mysterious recovery after all; it’s the power of the immune system!
Using microbes to treat cancers date back to the 19th century. The first known experimental treatment was performed in 1863: a female cancer patient was laid on a bed contaminated with a bacterium. As expected, following the infection, her tumor regressed. Unfortunately, however, she died because the doctors failed to control the infectious disease.
An American physician, William Coley, was the one who realized that the dose of bacteria is the key that makes microbes either poison or cure. He became the pioneer of cancer immunotherapy research. He mixed certain microbes that he first attenuated by applying heat. More than 1000 cancer patients received the ‘Coley’s toxin’ during his career. He had written more than 100 papers where he reported hundreds of successfully recovered cancer cases. Fever was the most common side effect of the therapy, but it was associated with cancer remission.
After his death, Coley’s toxin had been used as an immunotherapy for 30 more years. Although some medical associations heavily criticized him, some physicians continued to use his microbial formula to treat cancers and obtained favorable results.
Coley’s toxin isn’t used for tumor treatment anymore, but the idea of infecting cancer patients with microbes still lives on. The tuberculosis vaccine, BCG, has been used to treat severe bladder cancer for more than 30 years. The patients receive BCG, which contains live-attenuated bacteria, injected into their bladder. The treatment aims to induce infection and inflammation in the bladder, enhancing the immune system response. Approximately 70% of the bladder cancer patients receiving BCG go into remission. Furthermore, some bacterial strains are being tested for their therapeutic use against cancer in several clinical trials.
There is still not an absolute cure for tumors. Since all cancer types are highly complex and heterogeneous, they require different treatments. However, there is something to be sure of: a strong immune system along with the proper cancer treatment is crucial to wipe out those nasty cells. Infection-causing microbes as immune activators might be a promising candidate in the fight against cancer.
