This blog post examines how immune surveillance and CTL-based immunotherapy can address the side effects and limitations of existing cancer treatments, and what contributions they can make toward conquering cancer in the future.
Throughout history, across cultures, humanity’s fear of cancer and efforts to overcome it have persisted. Cancer manifests in diverse forms, and its treatment methods have steadily evolved. While understanding was limited and treatment nearly impossible in the past, modern medicine has achieved remarkable progress. Initially, surgery to remove tumors was the primary approach, but today, attempts to treat cancer using more sophisticated techniques are increasingly common.
At the current level of medical technology, it is often difficult to remove widely spread cancer cells through surgery alone, leading to a heavy reliance on chemotherapy or radiation therapy. However, these treatments have limitations as they attack not only cancer cells but also healthy cells. Targeting rapidly dividing cells, these therapies cause side effects that weaken or destroy normal cells that divide quickly, such as bone marrow cells or hair follicle cells. Consequently, patients experience severe side effects such as decreased physical strength, hair loss, and weakened immunity.
To address these issues, developing anticancer therapies that precisely target and destroy only cancer cells has become a major challenge in immunology. In this process, humanity is exploring ways to more effectively utilize the functions of the naturally occurring immune system. Our body’s immune system performs the function of detecting and eliminating abnormal cells or external invaders, known as immune surveillance. Immune surveillance recognizes and eliminates not only invading bacteria but also mutated cells expressing new antigens, namely cancer cells. However, cancer cells proliferate and mutate very rapidly, enabling them to outgrow the limitations of the immune system.
Therefore, tumor immunologists are conducting research to harness anti-tumor immune responses as the next generation of anticancer drugs, considering these characteristics. Immunotherapy, which selectively eliminates cancer cells, is attracting significant attention because, unlike conventional treatments, it can minimize damage to normal cells.
Anti-tumor immune responses are primarily mediated by T cells. When T cells recognize tumor antigens expressed on tumor cells and become activated, both CD4+ T cells and CD8+ T cells recognize these antigens and take on the role of attacking the tumor cells. In particular, CD8+ T cells differentiate into tumor-specific cytotoxic T lymphocytes (CTLs), playing a crucial role in directly eliminating tumor cells. Antigen-presenting cells (APCs) are vital for the formation of these CTLs, and recent research has highlighted dendritic cells (DCs) as the most potent APCs.
A research team led by Professor Thomas Brocker at Ludwig-Maximilian University in Germany discovered that these DCs play a crucial role in activating the CTL response. DCs are highly effective at phagocytosing tumor cell antigens and then presenting them to T cells to induce the CTL response. This research is expected to significantly contribute to the advancement of anti-tumor immunotherapy in the future.
Therapies utilizing immune surveillance and CTLs are highly innovative because, unlike conventional chemotherapy or radiation therapy, they can maximize therapeutic efficacy by targeting only cancer cells. Furthermore, the recently studied field of Tumor Immunotherapy can be broadly categorized into three types: passive immunity, active immunity, and immune enhancement.
Passive immunotherapy involves administering pre-activated T lymphocytes or antibodies to the patient. This method directly strengthens the patient’s immune system to attack cancer cells. Recently, methods using the patient’s own T lymphocytes, cultured and then re-administered, are also being researched. Active immunity involves administering vaccines containing antigens to patients to induce an immune response, and this approach is also the subject of extensive ongoing research. Furthermore, immune enhancement therapy suppresses cancer cells’ ability to evade the immune system and promotes immune responses to effectively eliminate cancer.
Thus, therapies utilizing immune surveillance and CTLs have established themselves as a crucial research field aiming to overcome the limitations of existing cancer treatments. This article has examined the diverse characteristics and principles of anti-tumor immunity and tumor immunotherapy, which are currently attracting significant attention. While these therapies remain in the research phase, current findings are opening possibilities for future cancer treatment.
In the future, it is anticipated that these immunotherapies will advance further, minimizing side effects and enabling effective cancer treatment. Humanity’s relentless challenge against cancer will continue, and someday, the day will come when cancer is completely overcome.
