1. The Cell Cycle and Cancer

4. Checkpoints in the Cell Cycle
In normal healthy cells, there are proteins that send messages to the nucleus to stay in interphase if:
Signals from surrounding cells say to not divide
DNA has not been replicated or is damaged on certain genes
Finite number of divisions – cellular apoptosis

5. 1. Chemical Signals from surrounding cells help tell a cell when to start and stop dividing.
There are not enough nutrients to allow proper growth
All cellular space is currently covered – called contact inhibition, as all cells only grow to a certain density

7. 2. DNA has not been replicated or is damaged
Before a cell divides, the DNA is checked to make sure it has replicated correctly. (If DNA does not copy itself correctly, a gene mutation occurs.
DNA replication animation:click on DNA picture

8. Key Gene Mutations Oncogenes, mutant alleles of a proto-oncogenes
Oncogenes encode proteins that stimulate proliferation or inhibit apoptosis
Tumor-suppressor genes (TSGs), also called
“gatekeepers”, which encode for regulators of various cell-cycle checkpoints
“caretakers”, which encode proteins responsible for detecting and repairing mutations

9. Cell Cycle Controls
Timing is controlled by cyclic variations in the concentrations of certain proteins – cyclins
Checkpoints are included to stop the cycle in the event of catastrophic damage or incomplete steps.

10. DNA mutations disrupt the cell cycle.
Mutations may be caused by:
1. radiation
2. smoking
3. Pollutants
4. chemicals
5. viruses

11. 3. Finite Number of Divisions
The regulated death of a cell that is no longer useful (e.g. white blood cells post-infection) or has lost its ability to function efficiently is called apoptosis.
What happens when damage to a cell impairs its ability to commit apoptosis and it divides and divides and divides?
You get Cancerous cells

12. The Beginning of Cancerous Growth
National Cancer Institute
Understanding Cancer and Related Topics
Understanding Cancer
The Beginning of Cancerous Growth
Cancers grow more quickly
where cells divide frequently.
Cancerous growths are called tumours.
Underlying tissue
NCI Web site:

13. Invasion and Metastasis
National Cancer Institute
Understanding Cancer and Related Topics
Understanding Cancer
Invasion and Metastasis
Cancer cells can invade surrounding tissues and blood vessels.
They can also be transported by the circulatory system to other parts of the body (metastasis).
Cancer cells then grow at the new locations.
NCI Web site:

14. METASTASIS
The transfer of disease from one organ or part of an organ to another not directly connected with it Video link below:

15. Malignant versus Benign Tumors
National Cancer Institute
Understanding Cancer and Related Topics
Understanding Cancer
Malignant versus Benign Tumors
Malignant cells invade neighboring tissues, enter blood vessels, and metastasize to different sites.
Benign tumor cells grow only locally and cannot spread by invasion or metastasis.
Time
NCI Web site:

16. Cancer is a disease of the cell cycle
Cancer is a disease of the cell cycle. Some of the body’s cells divide uncontrollably and tumors form.
Tumors in Liver
Tumor in Colon

17. While normal cells will stop dividing if there is a mutation in the DNA, cancer cells will continue to divide with mutation.

18. Due to DNA mutations, cancer cells ignore the chemical signals that start and stop the cell cycle. They also no longer communicate well with neighboring cells

19. Differences between Benign and Malignant tumors
BENIGN MALIGNANT
Often encapsulated Non encapsulated
Well differentiated Poorly differentiated
Low mitotic rate High mitotic rate
Noninvasive Invasive
Non-metastasising Metastasising

20. Why Cancer Is Dangerous
National Cancer Institute
Understanding Cancer and Related Topics
Understanding Cancer
Why Cancer Is Dangerous
Melanoma (skin cancer) cells can travel through the circulatory system.
The cancer that spreads to the liver would be called metastatic melanoma, not liver cancer.
Liver
Melanoma (initial tumor)
NCI Web site:

21. Cervical Cancer Screening
National Cancer Institute
Understanding Cancer and Related Topics
Understanding Cancer
Cervical Cancer Screening
Normal
Pap smear
But even earlier stages of cancer can be detected by screening cells.
Biopsies similarly look at cells inside suspected tumours.
Normal Pap smear
Abnormal Pap smear
Abnormal
Pap smear
NCI Web site:

22. Cancer Cells Look Different
National Cancer Institute
Understanding Cancer and Related Topics
Understanding Cancer
NCI Web site:

23. SUMMARY Normal Cell Division DNA is replicated properly.
2. Chemical signals start and stop the cell cycle.
3. Cells communicate with each other so they don’t become overcrowded.
Cancer Cells
Mutations occur in the DNA when it is replicated.
2. Chemical signals that start and stop the cell cycle are ignored.
3. Cells do not communicate with each other and tumors form.

25. Apoptosis
The material of the cell is recycled by the body.