Regulating the Cell Cycle

Biology 392Chapter 10-3

Cancer• One in three people will develop cancer.

• One in four people will die of cancer.

• More than 1500 Americans died each day of cancer this year.

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

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

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)

Can you die from skin cancer?

What’s happening in the petri dish?Section 10-3

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?

Cell Cycle RatesCells do not move through the cell cycle at the same rate

• Cells in a developing embryo replicate rapidly- 3 minutes• Average time of cell cycle- 20 hours• Lining of esophagus- 2-3 days• Lining of small intestine- 1-2 days• Lining of large intestine- 6 days• Red blood cells-120 days• White blood cells- 10hrs-decades

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 = CYCLINSection 10-3

CyclinCyclin cellular protein that regulates the timing of the cell cycle in eukaryotic cells; help create spindle

Cell Cycle Regulators• INTERNALINTERNAL

• Proteins that respond to signals inside the cell

• Checkpoints during interphase:Make sure all DNA has

been properly madeMake sure all

chromosomes have attached to a spindle

• EXTERNALEXTERNAL• Proteins that respond to

events outside the cell• Speed up or slow down cell

cycle• Respond to environment

and “crowding”

Cell Cycle Regulators

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 is a precursor to cancer

Progression of Cancer

Kinds of Cancers• SOLID TUMORSSOLID TUMORS• Carcinomas originate from surface cells

(skin, wall of intestine, surface of organs)• Sarcomas bone, cartilage, fat, muscle• ““LIQUID” TUMORSLIQUID” TUMORS• Leukemias circulate in blood stream, from

blood• Lymphomas developed in lymph system

2006 Estimated US Cancer Deaths*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%

Treatments

• Surgery – remove the affected cells• Radiation – high-dose X-rays kill cells• Chemotherapy – drugs kill cells• Hormone therapy – hormones stop cell

growth

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)