Most know the word “cancer” as a negative thing. As a disease characterized by the body’s cells growing uncontrollably, cancer remains a significant cause of mortality worldwide. Cancer has become an ugly word, and you have a good reason if the thought of this disease instills fear and anxiety. After all, experts expect over 2,000,000 new cancer diagnoses and over 600,000 cancer-related deaths in the United States by the end of 2024.
Have you ever wondered about the intricate process of cancer development? It's not just a fatal disease, but a complex phenomenon that unfolds within the human body.
Cancer can begin in just about any cell in the body, and this explains why we have so many different types of cancer. Importantly, all types of cancer grow differently, so, for example, breast cancer and lung cancer need to be treated differently. Notably, every kind of cancer can have numerous subtypes and classes, which may also grow differently and respond to unique treatment approaches.
Most cancers start when normal biological processes go awry. The trillions of cells in our bodies grow and multiply regularly. The processes involved in cellular growth produce new cells that replace old or damaged cells as needed. When an abnormal cell multiplies instead of dying and being replaced, the accumulating abnormal cells can form a tumor. Most of the time, our bodies eliminate abnormal cells or those containing damaged DNA before they grow into cancer, but in instances where these protections break down, cancer develops.
The immune system also plays a role in preventing abnormal cells from developing into cancer. Through a three-phase process known as “immunoediting,” immune cells identify and kill cancer cells before they multiply and grow into tumors. The elimination phase, also called “immune surveillance,” involves the immune system detecting and eliminating tumor cells. Next is the equilibrium phase. A second phase of immunoediting, equilibrium, describes a scenario where a tumor and the immune system interact in a way that the cancer survives but does not grow. During the equilibrium phase, tumors are kept in check by various immune mechanisms. Finally, the third phase of immunoediting, escape, occurs when the cancer can entirely evade the immune response and begins to grow.
Cancer cells have evolved to act quite differently from healthy cells. For example, they grow without biological signals directing them to the fact that new cell growth is needed. Similarly, cancer cells evade biological signals telling them to stop growing or to die. Cancer cells can also communicate and signal to other parts of the body. For example, tumors can instruct blood vessels to expand into growing tumors to increase the delivery of blood and nutrients to support growth. Tumor growth and development will almost always involve a strategy to subvert normal immune responses.
Finally, it’s important to note that not all tumors are cancer. Benign tumors, which are not cancerous, don’t spread to other parts of the body and typically do not grow back once removed. On the other hand, cancerous tumors, known as malignant, can be more aggressive, growing faster and invading surrounding tissues.
Sources: CA, J Clin Inv, JAMA Oncol