Cancer cells are scary because of the following three characteristics.
Infinite proliferation
The blood, electrolytes, and cytokines in the body are the favorite nutrients of cancer cells. In the body, cancer cells can keep growing, keep dividing, and grow the next generation of cancer cells.
And, cancer cells require much less than normal cells for the substances they need to grow. After normal human cells grow and come into contact with each other, the movement and division activities have to stop and reach a stable state. Unlike cancer cells, their division and proliferation do not cease with mutual contact, which is why malignant tumors grow larger and larger in the human body.
Easy to metastasize
Normal cells do not live “alone,” they need to adhere in order to maintain structure and cell growth in the body. The “bridge” for cellular adhesion is a polymeric glycoprotein called fibronectin.
A significant decrease or absence of fibronectin between cancer cells disrupts the adhesion between cells, allowing them to “regain their freedom” and move elsewhere. In the course of metastasis, cancer cells secrete specific substances that dissolve and destroy surrounding tissue, opening the way for metastasis to spread. The first of these is to make sure that the cells are not too large or too small.
There are several common ways for cancer cells to metastasize:
- Lymphatic tract metastasis. Cancer cells invade the lymphatic vessels and first reach local lymph nodes, and continue to progress to adjacent or distant lymph nodes.
- Hematologic metastasis. Cancer cells directly invade blood vessels, or re-enter blood vessels via lymphatic vessels, and follow the blood flow to other sites. The most common sites of metastasis are the lung, brain, liver, and bone.
- Implantation metastasis. Cancer cells break through the plasma membrane of the organs and are shed from the surface of the tumor, spreading like “seeds” to the chest, abdomen, and cerebrospinal cavity, where implantation growth occurs.
Immune escape
When a bacteria or virus (“antigen”) enters the body, the immune system immediately recognizes the foreign substance and is quickly mobilized to destroy the invading enemy. The immune system is able to protect the cancer cells from being removed by the immune system.
This is because most tumors are weak in their ability to elicit an immune response (called “antigenicity” or “immunogenicity”) and do not induce a “response” from the immune system. Some cancer cells also disguise themselves as normal cells in the body so that they are not detected by the immune system.
To summarize, cancer cells are infinitely proliferative, easily metastasized, and escape immune surveillance, basic characteristics that explain many of the symptoms of cancer and why treatment is difficult.
Co-reviewed by Dr. Zhiyong Chen, Guangdong Provincial People’s Hospital, Guangdong Lung Cancer Institute
Co-Author: Department of Oncology, Renji Hospital, Shanghai Jiao Tong University Dr. Ma Yue