Chapter 17

Genetics of Cancer   1  --   Introduction  to Cancer Biology

I.  Cancer

   Cancer is a group of diseases caused by loss of cell cycle control. 


   Cancer is associated with abnormal uncontrolled cell growth.


   Carcinogens are substances which cause cancer by mutating DNA.


Many genes that can mutate to cause cancer control the cell cycle or DNA maintenance (repair).


II.  Control of the cell cycle

Origin of cancer:

Cancer begins from the growth of a single abnormal cell.

A mutation occurs allowing a cell to undergo cell division when it would not normally divide.

Division produces more abnormal cells.


Mutations can occur:

In somatic cells    => sporadic cancer only affecting the individual

In germline cells  => mutations that are inherited


Germline mutations usually require second somatic mutation also.


Telomeres affect the cell cycle


III. Characteristics of cancer cells

Divide continually (given space and nutrients)

Heritable mutations: cells with mutations have daughter cells which inherit the same mutations.


Dedifferentiated: cells lose their specialized identity

Different appearance: reflects dedifferentiation

Lack contact inhibition: will divide in a crowd of cells and pile on top of each other

Induce angiogenesis (local blood vessel formation)

Increased mutation rate

Invasive:  squeeze into any space available

Metastasize:  cells move to new location in the body


Cell division rates of normal and cancer cells

Cancer can progress slowly over years