CANCERCANCER

And Cell DivisionAnd Cell DivisionGlencoe Chapter 2Glencoe Chapter 2

What is Cancer?What is Cancer?• The division of normal cells is controlled. New cells are

only formed for growth or to replace dead ones. Cells that are old or not functioning properly normally self destruct and are replaced by new cells.

• However, cancerous cells do not self destruct and continue to divide rapidly producing millions of new cancerous cells.

• Cancerous cells divide repeatedly out of control even though they are not needed, they crowd out other normal cells and function abnormally. They can also destroy the correct functioning of major organs.

• A cancerous cell arises from the mutation of a normal gene and duplicates itself during cell division.

Stages of CancerStages of Cancer• 1) Minor proliferation of cells in one area - “cancer in situ”

• 2) Growth of cells and recruitment of blood vessels etc. to support growth - “tumor”

• 3) Invasion/destruction of neighboring tissue -“malignant tumor”

• 4) Spread of cells to new organs - “metastasis”

Cancer StatisticsCancer Statistics • Cancer is one of the most common diseases in

the developed world:• Average 1 in 4 deaths are due to cancer• There are over 100 different forms of cancer• 1 in 17 deaths are due to lung cancer• Lung cancer is the most common cancer in

men• Breast cancer is the most common cancer in

women

Cancer Cell vs. Normal CellCancer Cell vs. Normal Cell

2 Types of Cancerous Tumors2 Types of Cancerous Tumors

• Benign tumours do not spread from their site of origin, but can crowd out (squash) surrounding cells eg brain tumour, warts.

• Malignant tumours can spread from the original site and cause secondary tumours. This is called metastasis. They interfere with neighbouring cells and can block blood vessels, the gut, glands, lungs etc.

Causes of CancerCauses of Cancer

• Tobacco Smoke• Diet• Radiation• Work Related Chemicals• Medicines• Microbes and Bacteria• Pollution

Tobacco smoke Tobacco smoke • Smoking causes 30% of fatal cancers: lung, upper

respiratory tract, esophagus, bladder, pancreas; probably stomach, liver, kidney; implicated in chronic myelocytic leukemia; maybe colon, rectum

• Malignancy depends on frequency of smoking, tar content, duration of habit

• Passive inhalation of second-hand smoke causes as many deaths as air pollution

• Understanding Lung Cancer• http://www.medicalnewstoday.com/sections/lung_

cancer/videos.php

Normal Lung vs. Cancerous LungNormal Lung vs. Cancerous Lung

Skin CancersSkin Cancers

Irregular Moles

Irregular skin marks can be cancerous

Diet: ~ 20-30% of fatal Diet: ~ 20-30% of fatal cancers cancers

• Animal (saturated fat) in general and red meat in particular: colon and rectum; implicated in prostate cancer

• Salt: high intake may lead to stomach cancer; in very young children in Southeast Asia leads to cancer of the nasopharynx

• Hot drinks increase risk of esophageal cancer • Eating too few vegetables and fruits is associated with higher

cancer rates, perhaps by the absence of antioxidants to neutralize free radicals

• Some natural chemicals may block cell proliferating signals from steroids, e.g. estrogens

• Overeating is linked to certain cancers: breast and prostate • Obesity is a cause of cancer of the endometrium and contributes

to postmenopausal breast cancer; increases risk for cancers of the colon, kidney, and gallbladder

• Alcohol in large quantity, especially with smoking, increases risk of cancer of upper respiratory and digestive tracts

Radiation: ~ 2% of fatal cancers Radiation: ~ 2% of fatal cancers • High frequency UV-B rays damage DNA; cause 90%

of skin cancers • Radon - radioactive gas is emitted from the earth in

some locations • Low frequency electric and magnetic fields: perhaps

a small risk for childhood leukemia • Radio-frequencies - no empirical evidence for

increased risk • Nuclear radiation - a potential risk for those few

exposed• CANCER 101 Video

• http://www.medicalnewstoday.com/sections/lung_cancer/videos.php

Work, medications, microbes: Work, medications, microbes: ~ 5% of fatal cancers~ 5% of fatal cancers

• Work: asbestos, benzene, formaldehyde, diesel exhaust

• Radiation and chemotherapy; clinical usefulness outweighs risks of cancer

• Some immunosuppressive drugs can cause lymphoma • Estrogens increase risk of endometrial and breast

cancer • Steroids to treat aplastic anemia associated with rare

cases of liver cancer• Microbes • Viruses: human papillomavirus, hepatitis, Epstein-Barr,

and HIV • Bacteria: Helicobacter pylori by causing stomach ulcers

Pollution: ~ 2% of fatal Pollution: ~ 2% of fatal cancers cancers

• Urban air pollution seems to increase the risk for smokers but not non-smokers

• Long-term exposure to high levels of air pollution increases risk 50%

Reproductive and gynecological Reproductive and gynecological factors: ~ 4% of fatal cancers factors: ~ 4% of fatal cancers

• Early age of starting menstration, late age at first pregnancy, and late age at menopause tend to increase the risk for breast cancer

• Number of offspring is inversely correlated with cancer of the endometrium, ovary, and breast • (less children-less cancer)

Treating cancerTreating cancer• “Watchful waiting” - appropriate for many cancer in

situs and prostrate cancer.• Many never become serious.

• Surgery - can cure isolated tumors. • Chemotherapy - required when cancer metastasizes

or is inoperable (brain)• Radiation - can be used before or after metastasis.• Vaccines - experimental therapy to get immune

system to fight cancer.

• Standard treatment - surgery followed by chemo.

Socioeconomic differences Socioeconomic differences

• Poverty is associated with a risky lifestyle: higher rates of smoking, alcohol consumption, poor nutrition, and exposure to certain infectious agents

• More affluent seem to be prone to cancers of the breast and prostate

• Racial differences can be traced to lifestyle: diet and environmental exposure

• Genetic variability is higher within than between races

OTHER OTHER

• ??? Plastic Bottles??? • Do they cause cancer?• http://www.videonewslive.com/view/19646

1/some_plastic_bottles_can_cause_cancer