CANCER

General• A general grouping of all diseases related to unregulated cell growth

• Cancers generally develop by an accumulation of mutations of the DNA

• Begin at the DNA level

Multi-hit hypothesis

• All cancers appear to be the result of multiple DNA damage events

• Each event causes that cell, and its descendents, to lose more and more control over the cell cycle

• Eventually, a tumor may form• Then, if the cancer begins to leave, survive,

and populate other regions of the body, we have metastasis - the growth of the tumor in other regions - this is cancer!

DNA damage

• Number of forms can lead to cancer1. Direct changes to the DNA

1. Point mutations

2. Insertions and Deletions

2. Relocation of DNA1. Translocation of chromosomes

2. Loss of chromosomes

3. Duplication of chromosomes

3. Viral and Transposon agents1. Viruses can insert into critical genes

2. So may transposones

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Two mechanisms of action - 1) disruption of function, as shown here, or 2) disruption of homeostasis - bone cancer and Ca2+

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Common feature of cancer cells

• Reduced dependence of extracellular signals• Less likely to undergo apoptosis• Unregulated cell division• Unstable - high mutation rate• Invasive - they lack cell-adhesion molecules• Survive in foreign tissues

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