Regulating the Cell Cycle

Biology 392Chapter 10-3

Cancer• One in three people will develop cancer.

• One in four people will die of cancer.

• In 2005, about 1.4 million new cases of cancer were diagnosed.

• More than 1500 Americans die each day of cancer.

• Over 1,000,000 cases of skin cancer will be diagnosed yearly.

• Cancer is the leading cause of death among Americans under the age of 85.

US Mortality, 2003

1. Heart Diseases 685,089 28.0

2. Cancer 556,902 22.7

3. Cerebrovascular diseases 157,689 6.4

4. Chronic lower respiratory diseases 126,382 5.2

5. Accidents (Unintentional injuries) 109,277 4.5

6. Diabetes mellitus 74,219 3.0

7. Influenza and pneumonia 65,163 2.7

8. Alzheimer disease 63,457 2.6

9. Nephritis 42,453 1.7

10. Septicemia 34,069 1.4

Source: US Mortality Public Use Data Tape 2003, National Center for Health Statistics, Centers for Disease Control and Prevention, 2006.

Rank Cause of DeathNo. of deaths

% of all deaths

* For those free of cancer at beginning of age interval. Based on cancer cases diagnosed during 2000 to 2002.

Source: DevCan: Probability of Developing or Dying of Cancer Software, Version 6.0 Statistical Research and Applications Branch, NCI, 2005. http://srab.cancer.gov/devcan

Lifetime Probability of Developing Cancer, by Site, Men, 2000-2002*

‡ Includes invasive and in situ cancer cases† All Sites exclude basal and squamous cell skin cancers and in situ cancers except urinary bladder .

Site Risk

All sites† 1 in 2

Prostate 1 in 6

Lung and bronchus 1 in 13

Colon and rectum 1 in 17

Urinary bladder‡ 1 in 28

Non-Hodgkin lymphoma 1 in 46

Melanoma 1 in 52

Kidney 1 in 64

Leukemia 1 in 67

Oral Cavity 1 in 73

Stomach 1 in 82

Lifetime Probability of Developing Cancer, by Site, Women, US, 2000-2002*

Site Risk

All sites† 1 in 3

Breast 1 in 8

Lung & bronchus 1 in 17

Colon & rectum 1 in 18

Uterine corpus 1 in 38

Non-Hodgkin lymphoma 1 in 55

Ovary 1 in 68

Melanoma 1 in 77

Pancreas 1 in 79

Urinary bladder‡ 1 in 88

Uterine cervix 1 in 135

Source: DevCan: Probability of Developing or Dying of Cancer Software, Version 6.0 Statistical Research and Applications Branch, NCI, 2005. http://srab.cancer.gov/devcan

* For those free of cancer at beginning of age interval. Based on cancer cases diagnosed during 2000 to 2002.† All Sites exclude basal and squamous cell skin cancers and in situ cancers except urinary bladder .‡ Includes invasive and in situ cancer cases

What is Cancer?• Disorder in which some of the body’s

cells lose the ability to control growth• 100’s of different types• Do not respond to internal &/or

external signals • Continuously divide – forming masses

of cells called tumors. • Cancer cells can break from a tumor

and spread throughout the body (metastasize)

Skin Cancer

What’s happening in the petri dish?

How does this represent the healing process?

This is normal the cells eventually stop

What causes the cell cycle to continue? Is it automatic? Does it ever

stop?

A sample of cytoplasm is removed from a cell in mitosis.

The sample is injected into a second cell in G2 of interphase.

As a result, the second cell enters mitosis.

Hypothesis: Substance X will cause a cell to start mitosis

Substance X = CYCLIN cellular protein that regulates the timing

of the cell cycle in eukaryotic cells; helps create spindle

Cell Cycle Regulators

• INTERNAL• Proteins that

respond to signals inside the cell

• Checkpoints during the cell cycle:– Make sure all DNA

has been properly made

– Make sure all chromosomes have attached to a spindle

• EXTERNAL• Proteins that

respond to events outside the cell

• Speed up or slow down cell cycle

• Respond to environment and “crowding”

Cell Cycle Regulators

Three Checkpoints

G1

G2

Mitosis (metaphase)

Causes of CancerEnvironment sun, chemicalsNot exercising obesity is linked to severalGenetics (but not necessarily inherited)Mutations in genes that regulate cell cycle

Example:p53 gene responsible for halting the cell cycle

until all chromosomes have replicated properly Defects in this gene leads to cancer

Progression of Cancer

Kinds of Cancers

• SOLID TUMORS• Carcinomas originate from surface

cells (skin, wall of intestine, surface of organs)

• Sarcomas bone, cartilage, fat, muscle• “LIQUID” TUMORS• Leukemias circulate in blood stream,

from blood• Lymphomas developed in lymph

system

2006 Estimated US Cancer Deaths*

ONS=Other nervous system.Source: American Cancer Society, 2006.

Men291,270

Women273,560

26% Lung & bronchus

15% Breast

10% Colon & rectum

6% Pancreas

6% Ovary

4% Leukemia

3% Non-Hodgkin lymphoma

3% Uterine corpus

2% Multiple myeloma

2% Brain/ONS

23% All other sites

Lung & bronchus 31%

Colon & rectum 10%

Prostate 9%

Pancreas 6%

Leukemia 4%

Liver & intrahepatic 4%bile duct

Esophagus 4%

Non-Hodgkin 3%

lymphoma

Urinary bladder 3%

Kidney 3%

All other sites 23%

Cancer Treatments

• Surgery – remove the affected cells• Radiation – high-dose X-rays kill

cells• Chemotherapy – drugs kill cells• Hormone Therapy – hormones stop

cell growth

Cancer Prevention

• The best way to prevent cancer is to avoid things that can cause cancer.

• Ultraviolet radiation in sunlight can damage genes that control the cell cycle.

• Chemicals in cigarette smoke also affect how cell growth and division is regulated.

Video links

• http://video.about.com/cancer/Chemotherapy.htm

• http://video.about.com/cancer/Chronic-Myeloid-Leukemia.htm

• http://video.about.com/cancer/CyberKnife-Radiosurgery.htm

• http://video.on.nytimes.com/index.jsp?fr_story=cde8a179a490d9a9fe977c6df92fb8fe3b88a538– (lung cancer and CT scans)