1. Cell Cycle Clock, Mitosis, and Cancer Biology

2. Cell Division – Mitosis of a Zygote

3. The Cell Cycle Clock
G0 -
Quiescence
Work but no Mitosis

4. The Cell Cycle Control System
is like a clock
regulated by both internal and external controls
has specific checkpoints where the cell cycle stops until a go-ahead signal is received

5. The Cell Cycle Control System
For many cells, the G1 checkpoint is the most important.
If a cell receives a go-ahead signal at the G1 checkpoint, it will usually complete the S, G2, and M phases and divide.
If the cell does not receive the go-ahead signal, it will exit the cycle, switching into a non-dividing state called the G0 phase

6. The Eukaryotic Cell Cycle is Regulated by a Molecular Control System
The frequency of cell division varies with the type of cell.
Not all cells divide at the same time, for the same reasons, or as frequent as other cells.
These differences result from genetic regulation at the molecular level.
This controls the RATE and TIMING of cell division.

8. Contact Inhibition
Cells do not normally grow or divide when in contact with other cells.
Ex: Cultured cells in a petri dish
will divide until they form a layer one cell thick and then stop when make contact w/ other cells.
Called contact inhibition of cell growth.
Cells can migrate in culture
Stop moving when touch other cells due to contact inhibition of cell movement.

9. Contact inhibition Does not occur in Cancerous Cells
Cancerous cells continue growing and moving when they touch other cells.
They pile up and they migrate to other parts of the body -- the cancer spreads.
Growth Factors
Chemical messages that control the cell cycle

10. Characteristics of Cancer Cells
Have lost the genetic ability to stop dividing
Cancer is heritable—Cancer cells give rise to cancer cells
Immortal
Not subject to contact inhibition
Metastasize: Spread into other tissues
Are De-differentiated
less specialized than the
cell it came from)

12. 2. Basal cell carcinoma
1. Normal cell growth
One
daughter
differentiates
Only one daughter
Cell divides
Both daughter
cells divide
Actively dividing cells
(basal cells)

13. Growth Factors Stimulate Cell Division
Diffuse through the body making contact with many different cells
Bind to Membrane Receptors, like a key fitting into a lock.
stimulate a pathway inside cell that leads to cell division.
Different cell types are stimulated by different growth factors.

14. Cancer: It’s all in the Genes
Proto-oncogenes:
“pre-cancer genes”
Genes that code for growth factors
Active in actively dividing tissues (e.g. skin)
Sometimes mutate into......
Oncogenes:
A mutated proto-oncogene
Genes that cause cancer
Produce too much growth factor
Over stimulate mitosis

15. Tumor Suppressor Genes
Code for Proteins that turn off cell division
p53 Gene
Codes for a protein that stops the cell cycle after G1
Half of all cancers involve a mutation of p53.

16. The Role of the Environment in Causing Cancer
Certain Viruses, toxins, or Radiation may lead to a p53 mutation
A 2nd p53 mutation may lead to one of the following cancers
Bladder, blood, brain, breast, colon, esophagus, liver, lung, spleen, thyroid, etc.

17. TMN System
T = Tumor Size
N = Lymph Node Involvement
M = Metastasis

18. Therapeutic Strategies for Treating Cancer
Slash – Surgical Removal
Burn – with Radiation
Poison – with Chemotherapy
Since cancer is uncontrolled cell division, all chemotherapeutic treatments involve the cell cycle.
Phase-specific chemotherapies
Prevent cells from entering S-phase
Block the S-phase
Block the M-phase (mitosis)

19. Cells Affected by Chemotherapy
Chemo may affect all dividing cells
Which cells divide rapidly?
Hair follicle cells
Skin cells
Cells lining digestive tract
Blood stem cells
What would be the side effects?

20. Common Warning Signs of Cancer: C.A.U.T.I.O.N.
C - change in bowel or bladder habits A - a sore that does not heal U - unusual bleeding or discharge T - thickening or lump in the breast or any part of the body I - indigestion or difficulty swallowing O - obvious change in a wart or mole N - nagging cough or hoarseness