Cancer is the leading cause of death in South Korea, and conventional surgery, radiation, and chemotherapy have their limitations. Recently researched virus-based therapies selectively attack only cancer cells and can be used in combination with immunotherapy to maximise the effectiveness of treatment. Future challenges include safety and addressing the risk of mutations.
Cancer and modern health issues
Cancer is one of the most serious diseases in modern society, with millions of people diagnosed worldwide every year. Even in Korea, cancer is the number one cause of death, and its severity is increasing year by year. Especially since lifestyle and environmental factors are known to play an important role in the development of cancer, many people are paying attention to cancer prevention. Smoking, excessive alcohol consumption, unbalanced diet, lack of exercise, chronic stress, and environmental factors such as air pollution are the main factors that increase the risk of developing cancer.
In addition to regular health check-ups, preventive measures that can be taken in everyday life are recommended. Eating antioxidant-rich vegetables and fruits, not smoking, exercising regularly, and managing stress can reduce the risk of developing cancer. These lifestyle improvements contribute not only to preventing cancer but also to improving your overall health. However, because the causes of cancer are so complex and varied, it remains a challenge to completely prevent certain cancers, which is why the development and improvement of cancer treatments is so important.
Limitations of conventional cancer treatments and new approaches
Conventional cancer treatment methods are broadly divided into surgery, radiotherapy, and chemotherapy (cancer drugs). While these treatments are effective in removing cancer cells or inhibiting their growth, they can cause serious side effects for patients. Because radiotherapy and chemotherapy affect normal cells as well as cancer cells, patients can experience a variety of side effects, including hair loss, lowered immunity, fatigue, and digestive upset. In particular, some cancer cells become resistant to anticancer drugs over time, making treatment more difficult. In addition, in metastatic cancer, the cancer has spread to multiple organs and tissues, making it difficult to remove surgically and often impossible to cure completely.
For these reasons, scientists are investigating new treatment methods such as immunotherapy, gene therapy, and stem cell therapy to overcome the limitations of existing treatments. Immunotherapy, in particular, is a method of activating a patient’s immune system to directly attack cancer cells. Immune checkpoint inhibitors, for example, block the mechanisms by which cancer cells evade immune cells, allowing the immune system to more effectively eliminate cancer cells. Another emerging technology is CAR-T cell therapy, which involves manipulating a patient’s own T cells to target and attack only cancer cells. These new therapies have the potential to be combined with conventional chemotherapy or radiotherapy to maximise the effectiveness of cancer treatment.
New cancer therapies using viruses
Scientists have begun to look to viruses as a way to overcome the limitations of conventional therapies and eliminate cancer cells more effectively. This is because viruses have the potential to selectively attack cancer cells and not normal cells. Viruses have the ability to enter host cells, replicate and multiply their genetic material, and then destroy the host cell. Researchers are working to develop viruses that target cancer cells specifically.
By inserting a promoter into a virus that recognises a specific protein present only in cancer cells, the virus will replicate, multiply, and destroy cancer cells, while remaining inactive in normal cells. The resulting ‘guided munition’ virus can selectively attack cancer cells and can be used in two ways. The first is to inject the virus into a blood vessel. As the virus circulates through the body, it seeks out cancer cells, and when it encounters them, it replicates within them and destroys them. This method is effective even when the cancer has spread to multiple organs. Reoviruses are commonly used in this method.
The second method involves injecting a ‘guided munition’ virus directly into the cancer cells. This method can quickly focus on specific cancer cells and is particularly effective in cases where the cancer has not metastasised. Engineered vaccinia viruses and adenoviruses are commonly used, which multiply inside cancer cells and destroy them. Adenoviruses, in particular, naturally destroy the HPV virus, which causes cervical cancer, and some studies have shown that they are also effective in eliminating cancers such as breast, prostate, and squamous cell carcinoma.
The challenges and future of viral therapies
Despite the appeal of viral cancer therapy, a number of challenges remain. For one thing, injecting viruses through blood vessels may not reach all cancer cells due to immune system interference. On the other hand, direct injection into cancer cells can quickly eliminate cancer cells in a specific area, but may have limited effect on cancer cells that have spread to other parts of the body. The current study also found that the viruses did not spread well inside cancer cells, so viral therapies may be most effective when used in combination with conventional radiation and chemotherapy.
In 2012, the British medical journal Nature Medicine published clinical results showing that anti-cancer treatment with vaccinia viruses doubled the survival time of patients with late-stage cancer. The drug used in the study, Pexa-Vec, is an anti-cancer drug that genetically engineers vaccinia viruses so that they only multiply in cancer cells. The high-dose group of patients survived for an average of 14.1 months, while the low-dose group survived for only 6.7 months. This is an important example of how virus-based cancer treatments can actually work.
Virus-based cancer therapies are getting better as research continues. An anti-cancer viral therapy called T-Bec (Talimogene laherparepvec) is already FDA-approved and being used to treat melanoma (skin cancer), and it is expected that it could be applied to a wider range of cancers in the future. Furthermore, scientists are developing viruses that can modulate the microenvironment around cancer cells to inhibit their growth or activate immune cells around them.
The future of viral therapy and safety concerns
While viral therapies have great potential, they need to be carefully studied and tested for safety. Even if a virus is engineered to selectively attack only cancer cells, there is a risk of unexpected mutations or immune responses. There is also the possibility that the virus could spread uncontrolled or mutate within the body. More clinical trials and long-term studies are needed to address these issues.
Virus-based anticancer therapies have the potential to become an important alternative to cancer treatment in the future. In particular, the availability of personalised viral therapies will allow for personalised treatment tailored to each patient’s cancer type and condition. Once this technology is commercialised and proven safe, we may soon be able to conquer cancer once and for all.
