Cell Communities: ~Tissues, Stem Cells, and Cancer

Question 1

What happens when stem cells divide

Answer 1

one cell remains a stem cell, but the other cell
differentiates. The non-stem cell further differentiates and proliferates to produce cells that form tissues

Question 2

When stem cells divide, what do they depend on which cell they become

Answer 2

Depends on which signal they recieve and the type of stem cell from which they derive

Question 3

What is a totipotent stem cell

Answer 3

A fertilized egg

Question 4

Pluripotent stem cells

Answer 4

Totipotent stem cells that eventually turn into pluripotent stem cells.
-They can divide and form many different types of cells but cannot revert to a fertilized egg
-A pluripotent cell cannot form an entire organism
-These are in embryos and called embryonic stem (ES)
cells

Question 5

Stem cells eventually become more specialized and become what

Answer 5

Adult stem cells

Question 6

Adult stem cells are what and can form limited diversity of cells

Answer 6

Multipotent

Question 7

Adult stem cells can do what

Answer 7

Replenish dead or damaged cells but cannot form whole tissues or organs

Question 8

Different types of tissues renew at different rates, what else happens

Answer 8

-Some renew frequently (epithelium)
-Some renew when stressed (liver)
-Some renew rarely or never (neurons)

Question 9

Reduced renewal rates limit tissue regeneration, meaning what

Answer 9

some damaged tissues cannot be repaired

Question 10

Limited tissue regeneration has a lack of

Answer 10

a lack of proper signaling events and a lack of proper stem cell types

Question 11

Differentiated cells which have undergone maximal renewal (Hayflick limit, ~50 doublings) will cease to renew which causes what

Answer 11

-Lack of active telomerase, induction of senescence
-Limits longevity of cells which may have accrued too many mutations

Question 12

Why is there such tight regulation of proliferation and differentiation in cells?

Answer 12

These signaling events and resulting gene expression are related to the tumor cell formation

Question 13

Tumor cells replicate uncontrollably, which means tissues grow when they should not

Answer 13

-Gene expression in tumors is usually dysfunctional such that the cells are not performing any real function
-Tumors infringe upon surrounding tissues and/or spread
to other parts of the body

Question 14

Because ES cells are pluripotent, they are a
potential source of what

Answer 14

cells to regenerate tissues

Question 15

Stem cells can be cultured in vitro to produce what

Answer 15

organoids, which are structures that closely resemble organ structure

Question 16

Embryonic stem cells can become any cell or tissue if provided the right signals and can grow new organs to replace lost or damaged organs, what is the problem?

Answer 16

-Ethics
-Embryonic stem cells are
acquired from embryos

Question 17

Induced pluripotent stem (iPS) cells offer what

Answer 17

a strategy to avoid embryo destruction
which can be accomplished by manipulating the expression of 3-4 genes / small RNAs

Question 18

Many multicellular organisms contain multiple tissues, what do tissues do?

Answer 18

-Tissues perform specific functions and make up organs
-Plants and animals both have tissues that perform specific functions, but tissue types differ

Question 19

What are the steps to getting cancer?

Answer 19

initiation, promotion, progression,

Question 20

What happens in initiation stage of cancer

Answer 20

first heritable mutation / mut. set tending
to favor proliferation and/or survival

Question 21

What happens in the promotion stage of cancer

Answer 21

decreased apoptosis + increased
proliferation over time, favors more cells with the initiated mutation to accrue (perhaps further
mutating)

Question 22

What happens in the progression stage of cancer

Answer 22

initiated cells accrued new cancer-
favoring mutations, enlarged palpable mass (tumor)

Question 23

What is metastasis

Answer 23

When tumors spread to other tissues

Question 24

What is malignancy

Answer 24

The tumor may invade surrounding tissue

Question 25

Mutations can be inherited but cancer isn’t but what can be inherited

Answer 25

A higher risk of cancer may be inherited due to inheritance of mutations

Question 26

As you live, you acquire additional mutations

Answer 26

-Some may occur in other proto-oncogenes or tumor suppressor genes
-The more of these mutations that occur, the higher the risk they may occur in the same cell, and the greater the risk of cancer developing

Question 27

What built in processes that work to prevent cancer

Answer 27

-The cell cycle & senescence: cells should only proliferate when they receive a proper signal
-DNA repair mechanisms: if DNA damage is detected, repair it
-Apoptosis: if DNA damage cannot be repaired, kill the cell
-immune Surveillance: the immune system recognizes tumor cells as foreign or “non-self” and destroys them

Question 28

What are genes related to cancer

Answer 28

-Proto-oncogenes, Tumor suppressor genes

Question 29

What are proto-oncogenes

Answer 29

-Proto-oncogenes encode proteins to promote replication (usually have a viral homolog)
-Mutations cause these proteins to always be active and gain of function mutations
- Oncogenes are formally cancer favoring genes in viruses

Question 30

What are tumor suppressor genes

Answer 30

-Tumor suppressor genes are expressed when cellular damage is detected
-Mutations cause these proteins to be inactive – called loss of function mutations
-If you inherit one bad copy and the second copy mutates, it may be observed via restriction enzymes as a loss of heterozygosity
-Mutations in both types of genes contribute to cancer

Question 31

What is the p53 gene

Answer 31

p53 gene is BOTH a tumor suppressor gene and a possible proto-oncogene due to Dominant-Negative Mutant p53