One of the chemicals that triggers the transformation of normal cells into cancer cells is called prostaglandin E2, which is derived from arachidonic acid.

The average American eats an excess of arachidonic acid indirectly and directly.  We eat an excess of refined and processed fast foods cooked in linoleic acid-rich oils such as corn, sunflower, safflower, cottonseed oils.  Some of the worst are french fries and chips.  Our bodies convert linoleic acid into arachidonic acid.   

We also eat arachidonic acid in fatty meats and farmed raised fish, such as tilapia and catfish, which almost exclusively are fed foods rich in linoleic acid.

Over 20% of our calories come from omega 6 rich refined oils and obese meat, which means that the modern diet is really the "PGE2/cancer diet."

We also consume about 20% of our calories from sugar and another 20% from refined carbohydrates with high glycemic indexes.   Research has demonstrated that cancer cells actually survive on sugar.  

For more Information:

http://www.toyourhealth.com/mpacms/tyh/article.php?id=1581