Cell Plasticity And How It Relates To Heterogeneity In Cancer

Almost all modern treatments for cancer face one major problem – recurrent disease. Even when tumor seems to be completely removed, there are high chances that in several years the disease will simply come back, usually in a more aggressive form. It is hypothesized that this phenomenon is linked to variability in cancer cells.

Some of them are more resistant to treatments and can successfully survive in the body, thus giving rise to new islands of cancer later on. Also, many scientists believe that many of these resistant cells belong to a special population of so-called cancer stem cells that survive the treatment simply because they differ significantly from the cells of tumor. These cells, at later stage, can convert into cancer cells again.

Functional and phenotypic heterogeneity occur in a tumor's cancer cells due to environmental differences, genetic chance and various reversible changes taking place in the cancer cell population. It is not known which clinical behaviors are explained by the stem-cell model and which cancers follow this model. There are studies done on deep sequencing and lineage tracing that could provide information about the cancer stem cells and  how they accounts for disease progression and therapy resistance.

They also hope to find a way to slow down the progression of cancer so that patients to not experience metastasis.

What is Cell Plasticity?

Plasticity is the ability of stem cells and certain other cells to take on the characteristics of other cells. For example, when the stem cells from the bone marrow are transplanted into the lungs, they can become lung cells. Scientists think that they may be able to stimulate stem cells to repair tissues that are diseased in the lungs, heart and other vital organs. This type of treatment is still in the very early stages of development and it is referred to as stem cell therapy. While it will take years before this approach is put into clinical practice, the hopes are high that this new method may help to create treatments for cancer and other serious diseases.

Embryos have a high number of stem cells, as cell plasticity is necessary for a fetus to grow and develop. Human embryonic stem cells were first grown in the laboratory in 1998.

See Also: Anti-Angiogenic Therapy: Pros And Cons For Cancer Treatment

What is Heterogeneity?

In medicine and genetics, the term heterogeneity refers to variations in phenotypes. The phenotype of an organism is its physical appearance. For example, things like eye color, hair color and height are all phenotypic features. However, it also describes things like disease history and overall health, both of which go down to the cellular level and this is where heterogeneity becomes linked to phenotypes. If you have a gene that is mutated, this could also be part of the phenotype because it can result in a disease that affects overall health and disease history.

Genotype refers to a person's heritable genetic identity, the set of genes. Through personal genome sequencing, personalized genomic information can be obtained. In some cases, the term genotype also refers to an individual's set of genes or a mutation that increases the risk of disease, such as diabetes or heart disease.

Cell Plasticity, Stem Cells And Heterogeneity In Cancer

Stem cells are found in people of all ages. This is the type of cells that has the ability to renew themselves. In their original form, they are non-specialized and do not serve any particular function in the body. But they have the plasticity and can, therefore, adopt the characteristics of other cells. These cells are critical for growth in the developing embryo because stem cells are responsible for generating all parts of the body. Stem cells are generally located in the bone marrow in adults. As a result of activity or aging, they replace cells that have weakened or died.

Stem cells have substantial differentiation and self-renewing abilities. Embryonic stem cells can differentiate into three germ layers, and while developing, they are able to trigger the development of all cell types.

Cancer stem cells are involved in progression of various tumors

When it comes to cancer developing and progressing to a cancer that spreads to other areas of the body, there are two established scientific models at present time. They include the cancer stem cell model and the clonal evolution theory.

In the clonal evolution theory, it is believed that successive mutations continue to build up in the cells resulting in clonal outgrowth and generation of particular types of cells that thrive in the particular micro-environment. Different cancer cells might have slightly different genotype, thus contributing to cancer heterogeneity.

In the cancer stem cell model, it is believed that certain cancer cells have properties of stem cells, i.e. they have big potential for differentiation and renewal. As a result, the majority of cells in the tumor originate from these cells, even though functionally and phenotypically they are quite different from each other and from parental stem cells.  

It is not entirely clear where cancer stem cells come from. As evidence mounts concerning cell plasticity, it is suggested that aggressive forms of cancer stem cells can be made for the first time inside a tumor.

See Also: Deadliest Cancers We Still Have To Beat

Others, however, think that cancer recruits normal healthy stem cells and transforms them into cancerous.

Cancer stem cells is an attractive therapeutic target

Regardless of the precise mechanism, it is clear that targeting cancer stem cells is the key to successful cancer treatment. Conventional treatments do little to harm these cells, thus leaving the escape route for the disease. Targeting stem cells instead of usual cancer cells would allow to kill “parental” cells of cancer and thus limit or even stop the further progression of disease.

Right now, scientists are just starting to understand how cell plasticity and heterogeneity are related when it comes to cancer. Hopefully, in the near future, this research will pave the road to new, much more effective, cancer therapeutics.