Cancer

• Deregulation of cell cycle• Loss of control of mitosis• Result of mutation• Over 200 types of cancer exists• (Number of cancer cases will double by

2050, as an increasing proportion of U.S. population reaches older ages)

United States Cancer Death Rates

United States Cancer Death Rates

United States Cancer Death Rates

Characteristics of Cancer(no matter what type)

• Uncontrolled cell growth- most significant characteristic of all cancer cells

• Loss of cell differentiation (specialization)– Ex. Skin cell no longer produces another skin cell

• Invasion of normal tissues, occupying space that should contain normal cells

• Metastasis or spread to multiple sites

Stages of Cancer

1. Initiation (Stage I)

2. Promotion (Stage II)

3. Progression (Stage III)

Initiation of Cancer(Transformation)

Series of gene mutations damages DNA

• Proto-oncogenes change to oncogenes (“on” switches for tumors or masses)

• Caused by: combination of mutations– Allow tumor (abnormal

cells) to begin

• Initiation does not directly result in cancer, it results in a precancerous cell.

• Heredity acts only as an initiator, not a promoter

Promotion of Cancer• Cells are stimulated to grow &

divide when they normally would not.

• Growth is gradual • Carcinogens – agents that

both initiate & promote cancer– Viruses – Chemicals – Radiation

• Benign cells – Masses of partially transformed

cells, confined & encapsulated– Cells exhibit dysplasia-growth

patterns char. of cancer cells

Normal Cells

Dysplastic Cells

Progression of Cancer

• Cells become less differentiated• Cells invade other tissue• Move to other areas of the body• Called malignant cells