Cancer module 4- stem cells

Question 1

What is a totipotent stem cell?

Answer 1

This is the highest type of SC in the body. These cells can become any human cell in the body. These are the sperm and egg cells. Think that totipotent= totally potent!

Question 2

What is a pluripotent stem cell?

Answer 2

This is the next highest type of SC. It is also known as the embryonic stem cells because they give rise to all the cells of the embryo, such as the mesoderm, ectoderm and endoderm.

Question 3

what is a multipotent stem cell?

Answer 3

These stem cells give rise to many different types of cells, but they must be closely related to each other. For example, the multipotent stem cells give rise to the cells of the hematopoietic system and mammary gland cells.

Question 4

What are unipotent stem cells?

Answer 4

These are the lowest type of SC. These cells can only give rise to one type of cell.

Question 5

What are the characteristics of a stem cell?

Answer 5

1. They must be able to self-renew and maintain the life of the cells they produce.
2. They must not be differentiated, or specialised into any particular cell type.

Question 6

What is self-renewal defined as?

Answer 6

Self renewal is proliferation without differentiation.

Question 7

Are stem cell proliferation regulation mechanisms unique to only stem cells?

Answer 7

No. These proliferation regulation pathways are the same ones used to tell normal cells to proliferate in the body too.

Question 8

Do stem cells have multi-lineage differential potential?

Answer 8

Yes. This means that the SC can give rise to many different cell types in the body.

Question 9

What state do stem cells usually exist in the body?

Answer 9

They are typically in a quiescent or sleeping state. Then, they are stimulated to proliferate when needed.

Question 10

Since stem cells are often dividing, are there any protective process to maintain genomic integrity in place?

Answer 10

Yes. Maintenance of genomic integrity in stem cells is essential so that abnormal DNA is not transferred to cellular progeny.

Question 11

Does the regulation of stem cells remain exactly the same throughout life?

Answer 11

No. The regulation of stem cells is always changing and is specific to age. Thus it is always changing through life.

Question 12

What is the relationship between stem cell growth and cancer cell growth?

Answer 12

The factors and pathways used by the body to increase stem cell growth is the same as those used to increase cancer cell growth.

Question 13

What happens to the regulation of stem cell growth during aging?

Answer 13

During aging, the proliferation of stem cells is decreased significantly, and thus the proliferation of cancer cells is also decreased. This leads to decreased cancer growth and thus aging is considered a protective factor.

Question 14

Which of the two hypothesis explain the origin of cancer:
A) Do mutations to oncogenes in normal cells activate self-renewal or
B) Do mutations to stem cells result in them become cancerous.

Answer 14

The answer is possibly both. Different cancers arise from either of these two theories. Colon cancer originates from mutations to its epithelial stem cells.
Leukemia originates from mutated, fully differentiated haematopoietic cells.

Question 15

Does a tumour contain a mass of identical cancer cells?

Answer 15

No. A tumour consists of many different types of cancer cells that do different things.

Question 16

Describe the cancer stem cell model.

Answer 16

The cancer stem cell model proposes that not all cancer cell types found in a tumour can actually self-renew. It suggests that only the tumour stem cells, a select group of cancer cells can self-renew. All other cancer cells in the tumour are just accessory.

Question 17

Which cancer type does not follow the cancer stem cell model?

Answer 17

Melanoma.

Question 18

Describe the clonal evolution model.

Answer 18

The clonal evolution model proposes that all cells in a tumour have the capacity for self-renewal. All the cancer cells in the tumour have mutated, and differing genomes. As a result, the cancer cells that survive and reproduce will be the ones with the best genomes that enable them to survive in that particular environment. It is often described as cancer cell darwinism.