- The leading cause of death in North America
- Strikes victims of all ages (more prevalent in old)
- Will become even more prevalent as the population ages
Molecular Basis of Cancer:
- Cancer is characterized by genetic and biochemical defects
- Biochemistry and molecular biology provide avenues for cures
- in one spot; can be surgically removed
- Not as fatal
- Not contained, and tends to spread (can’t be surgically removed)
o Fig 20-44 – Metastasis
Cells can grow as a benign tumor and break through the basal lamina to enter
blood vessels. The cells can escape from the blood vessels and move to other
tissues and start growing there too!
- Huge problem!
What is Tumor Angiogenesis?
- Small localized tumor -------Angiogenesis-------> Tumors that can grow and spread
o Small localized tumor will try to get access to blood vessels for nutrients. Once
connected to blood vessels for nutrients, are able to grow even quicker
How do we know that Cancer is a Genetic Disease?
- Susceptibility to cancer can be inherited
o Eg. Retinoblastoma (a cancer of the eye)
o Eg. Xeroderma pigmentosa (a cancer of the skin)
o Eg. Some forms of breast, prostate, ovarian, and intestinal cancer
- DNA damaging agents cause cancer
o Radiation- UV, X-Rays
o Chemical Mutagens (Ex. Benzene) What are some of the avoidable causes of cancer?
- Avoid agents that cause DNA damage
o Radiation (x-rays, UV), mutagens
- Chemicals that cause cells to divide- Tumour promoters
o Ex. Asbestos
o Are carcinogens but not mutagens
- Certain viruses
o Hepatitis (liver cancer)
o HPV (cervical cancer and others)
o HIV (Kaposi sarcoma, non-Hodgkins lymphoma)
Q: What is the single most preventable cause of cancer?
A. Genetic defect
E. High altitude flight
- 30% of all cancers can be attributed to smoking
o Smoking responsible for 90% of lung cancer
- Cigarette smoke contains 69 chemicals that are known to cause cancer
o Eg. Arsenic, Benzene, Formaldehyde, Radioactive Polonium-210
A single mutation is not sufficient to cause cancer
- THEREFORE: Cancer risk increases with age.
- Tumour progression involves successive rounds of mutation and selection
- At each round the descendent acquires another mutation allowing it to grow faster or in
- Fig 20-46
o Most cancers derive from a single abnormal cell where this first cell picks up a mutation
that allows it to grow a bit faster than other cells
o Second mutation may allow the cells to grow in the absence of the basal lamina
o Third mutation may allow the ells to penetrate the basal lamina
o ETC......... Properties of Cancer Cells
1. Divide in the absence of growth factors.
a. Do not respond normally to signals of cell division
2. Are immortal