One of the biggest problems experienced after full response cancer treatments is the risk of recurrence (recurrence) after many years. So what is the factor that causes cancer to reappear after many years?
Tumor dormancy is when cancer cells "sleep" undiagnosed for long periods of time. These types of cells bypass standard treatments and begin to divide again after many years, causing the cancer to recur.
Cancer types in which tumor sleep is frequently observed;
-breast cancer,
-prostate cancer,
- skin cancer (malignant melanoma) and
It is B cell lymphoma.
Sleeping cancer cells have 4 main features:
1. Growth at a slow rate,
2. Resistance to standard cancer treatments,
3. Bypassing the immune system and
4. Self-renewal
The control of cell growth is done by an advanced manager. They do not reproduce until the environmental conditions are suitable.
There are 3 types of tumor sleep mechanisms:
1) Cellular sleep: Cells are constantly kept at the G0 checkpoint. For this reason, they do not divide and do not reproduce.
2) Angiogenic sleep: Since cancer cells grow very quickly, they need to form vessels to provide nutrients after a while. However, some cells cannot form enough blood vessels. Growth rates stop, a constant balance occurs in the number of dying cells and growing cells. This balance is called angiogenic sleep.
3) Immunogenic sleep: Our immune system approaches tumors in 3 ways. They are elimination (destruction), Equilibrium (equilibrium) and escape sections. Some tumor cells learn and adapt to appear "friendly" to our immune system. In this way, it stays dormant for years. Standard cancer treatments and environmental factors can cause these cells to wake up and divide aggressively.
Why and how tumor cells fall asleep has not yet been answered. Recent studies show that epigenetic (genetic and environmental relationship) factors are effective. The fact that these cells are the same type of cells can be successful against tumor dormancy in targeted therapies developed against cancer stem cells.
Another problem is whether dormant cancer cells are still present in all patients who have been successfully treated for cancer.
In recent years, it has been discussed how a strategy should be developed against tumor sleep in cancer research.
There are basically two options;
1. Developing treatments that awaken dormant cancer cells or
2. Treatments that keep the tumor dormant?
In recent clinical studies, it has been observed that treatments that awaken the tumor from sleep cause the cancer cell to begin to divide more aggressively, and cancer cells with multi-drug resistance begin to develop. For this reason, the generally accepted view is to develop treatments that will keep the tumor dormant. Drugs targeting epigenetic factors show promise for this purpose.
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