Download Cancer supplement

Cancer
Chapter 4 Supplement
Cancer - important facts
• Cancer is uncontrolled cell growth
• It requires several steps to form
• It is very different depending on which
tissues are affected
• It is a leading cause of death in the U.S.
and other developed nations (Behind
cardiovascular disease)
Cancer and Cell Division
• Cancer
disrupts
cellular
controls on cell
division
• Remember
Interphase (G1,
S, G2) and
Mitotic phase?
Figure 3.30
Cancer and Cell Division
• Normally, checkpoints keep cells from
passing from one stage of the cell cycle to
the next (e.g. S phase  G2)
• Cancer causes cells to lose the ability to
stop cell division at these checkpoints and
so the cells divide continuously and
beyond control
How Mutations lead to cancer
• Mutations disrupt normal controls over cell
growth and division
• Uncontrolled growth increases error rates
• Thus cancers often begin where “stem
cells” are dividing rapidly and are very
rare in cells that do not divide.
• Where would you expect more cancers to
occur: in the heart or in the colon?
Cancer Stages
• Cancer develops in steps:
– Abnormal cell – genetic mutations cause
uncontrolled growth
– Primary tumor – mass of cells develops, often
in one area
– Metastasis – cells from tumor enter blood
stream
– Secondary tumor(s) – these cells take up
residence in other parts of the body, forming
new tumors there
Development of Cancer Metastasis
• Invasion – abnormal cells grow into
surrounding tissues
• Penetration – cells enter the bloodstream
• Escape – cells leave bloodstream to for
secondary tumor
Cell Division and Tumors
• Tumors (neoplasms):
– enlarged mass of cells
– abnormal cell growth and division
1. Malignant tumor:
– Spreads into surrounding tissues (invasion)
– Can start new tumors (metastasis)
2. Benign tumor:
– Contained (no invasion)
– not life threatening (but may become
malignant)
Cancer and Genes
• Genes that when mutated tend to cause
cancer come in two types
• Oncogenes
– Dominant (only one mutation needed to lose
control of growth)
• Tumor suppressor genes:
– Recessive (need two mutated copies)
– Examples: BRCA1, Rb1
Cancer and Genes
• The key to cancer: Whether the first
mutation is inherited, like BRCA1, or
spontaneous, cells need to accumulate
more than one key mutation to become
malignant.
• However, each mutation makes the
accumulation of further mutations more
likely.