What are substances that cancer cells produce

Author: Dr. med. habil. Gesche Tallen, last changed: 03.04.2019

In the following, the essential processes in a healthy cell are compared with the respective cancer characteristic.

Cell communication

For their division and normal maturation, healthy cells are dependent on certain factors that stimulate and control their growth and their specialization in certain tasks. These so-called growth factors are the body's own proteins (protein e). They regulate cell growth by, on the one hand, controlling certain processes inside a cell and, on the other hand, also controlling communication between different cells. Growth factors develop their effect by first attaching (“docking”) to the wall of a cell at a certain point (at a so-called receptor) from the outside. This creates a stimulus that the receptor passes on like a message to numerous messenger proteins and biocatalysts (enzymes) in the cell. This message (signal) passes through several stations one after the other (signal cascade) and activates certain genes that ensure normal cell growth.

Cancer cells don't need these signals to divide. Instead, they divide completely independently, but usually do not mature in the process. This means that diseased, non-functional tissue is constantly being created, which takes away space and nutrients from the surrounding healthy tissue, thereby damaging it.

Cancer characteristic: cancer cells grow uncontrollably.

Cell growth regulation and cell aging

Healthy cells respond to certain signals that tell them when to stop dividing or when it is time to get old, that is, to stop dividing and die. In this way, there is a healthy balance between young and old cells in the body tissue. In cancer cells, this balance is broken - they do not react to growth-inhibiting signals, but instead divide infinitely often. Causes for such dysregulations in the cell cycle, which can cause a cell to degenerate, are often changes in the structure (mutations) and / or its activity, so-called epigenetic changes in one or more genes (s. below: genetic mutationestruggles) [TAL2017].

Cancer characteristic: cancer cells divide infinitely often - they do not age.

Cell death (apoptosis)

Programmed cell death (apoptosis, from Greek: apoptosis - falling leaves in autumn ”) is a natural process in cell metabolism that takes place in every healthy organism. It is a kind of built-in "suicide program" of the cell, which is triggered by certain signals (for example certain damage in the cell) and then leads to controlled cell breakdown. Through this endogenous apoptosis, the body succeeds in getting rid of dangerous, diseased and superfluous cells. However, cancer cells can ignore these death orders.

Cancer trait: Cancer cells are immortal.

Genetic changes and tumor stem cells

With each cell division, the genetic material (deoxyribonucleic acid, DNA) doubles and is then distributed between the two daughter cells. During this duplication or copying process, errors can occur or existing errors can be passed on to the daughter cells, in which they then cause further genetic changes (mutations). In the event of a mutation, a DNS component can be lost, incorrectly replaced or incorrectly added, for example.

As a result, wrong genetic information is passed on to the daughter cells the next time the cell divides. A healthy cell is usually able to recognize such errors in the genetic material and then to repair them or to look for the damage with apoptosis (s.above) to react. It becomes dangerous when the mutations affect genes that control cell growth or that are involved in DNA repair or programmed cell death (so-called guardians of the genome: tumor suppressor genes or proto-oncogenes).

This is the case in many cancer or cancer precursor cells. Cell growth can no longer be kept in check here, defects can no longer be properly repaired and cell death can no longer be triggered. Instead, the diseased cells multiply unchecked, passing on their damage to the daughter cells, and these in turn to their daughter cells and so on. This creates a constant supply of malignant cells. These starting cells are also called in cancer research "Tumor stem cells". They were described for the first time in connection with characteristic proteins on the cell surface of leukemia cells. In children and adolescents with certain cancers, such properties of tumor stem cells are used today, for example, to detect a minimal residual disease. In this way, relapses of the disease can be recognized in good time and possibly treated early before there is a visible relapse.

Tumor stem cells can remain in a kind of sleep state for a long time. Since chemotherapy and radiation therapy mainly affect cells that are currently dividing, tumor stem cells are relatively insensitive to these treatments in this phase. Such dormant tumor stem cells are probably partly responsible if an apparently destroyed tumor begins to grow again after a long period of time. Researchers are therefore working on therapies that should first "wake up" dormant tumor stem cells in order to then treat them with common therapeutic agents. So far, such developments are still at the very beginning.

Cancer characteristic: Cancer cells have abnormal genetic changes that promote tumor growth.

Energy metabolism and blood vessel formation

The formation of new blood vessels (angiogenesis) in healthy tissues in children and adolescents is usually based on the need for oxygen and other nutrients that normal body growth requires. The new blood vessels sprout from existing vessels. However, once it has reached a certain size, cancerous tissue needs an additional supply of blood and nutrients in order to be able to continue to grow. This is why cancer cells have the property of causing new blood vessels to form (so-called tumor neo-angiogenesis). So they can feed themselves adequately.

Cancer characteristic: Cancer cells form their own blood vessels in order to supply themselves with oxygen / energy (neoangiogenesis).

Defense Mechanisms

Normally, the body's own defense system (immune system) recognizes and fights changed, sick and other foreign cells in order to protect the organism from them.

Cancer cells can, however, develop “tricks” with which they can escape these defense mechanisms: On the one hand, they can weaken the body's own defense reaction, but on the other hand they can also specifically evade the immune system. However, it is not enough to “strengthen” one's immune system, for example with vitamins or other food additives, to effectively prevent or fight cancer. Instead, research groups are currently working on identifying the “tricks” of cancer cells in order to specifically prevent their evasive maneuvers and to help the immune system recognize the cancer cells as bad and then successfully eliminate them.

Cancer characteristic: Cancer cells can usually not be attacked by the body's own defense cells.

Inflammatory mechanisms

It is known that inflammation irritates normal, healthy tissue surrounding it. This sends signals to cell messengers that call up scavenger cells (macrophages) to remove the damage. If, however, the irritation does not cease and the inflammation becomes chronic, then the activity of all the messenger substances involved can lead to such overactivity that this has a detrimental effect on the irritated tissue. This is because such overactivity of the body's own defense system can lead to the release of harmful substances. These substances favor cancer characteristics such as genetic damage, impaired growth regulation and defective cell death mechanisms (so.).

In addition, constantly growing cancerous tissue irritates its surroundings and in this way can contribute to the overactivity of the immune system with the corresponding consequences. Therefore, and because macrophages are found in some cancerous tissues, cancer researchers now assume that chronic inflammation can also fundamentally contribute to the development and spread of cancer. In connection with cancer in children and adolescents, however, this cancer characteristic is still the subject of basic research.

Cancer trait: Cancer cells stimulate inflammation, which promotes tumor growth.

Spread / metastasis

Except for blood cells and lymphocytes, body cells do not migrate, but belong to a solid organ tissue in the organism. However, cancer cells can get to other organs, for example via the blood and / or lymphatic system, where they grow and form daughter tumors (metastasize) and in this way spread throughout the body (metastasis).

Cancer trait: cancer cells spread unchecked.