Question 15

[behii208456]

How can the metabolism, breaking down into simpler blocks make a non-carcinogenic compound carcinogenic? if so please give an example.

[nat6089]

metabolism/breakdown process of carcinogenic cells will also affect the surrounding cells thus making them carcinogenic. Similarly, a non carcinogenic compound when broken down releases substances than can be toxic and affect surrounding cells.

Examples: non-heterocyclic aromatic amines when produced as product of breakdown it increases the carcinogenic property.

[klr861276]

If the liver enzymes metabolized some molecule other than the suspected carcinogen being studied into a carcinogen, wouldn't this just skew the test, producing a carcinogenic effect that is not attributable to the original carcinogen alone?

[admin]

A procarcinogen is a substance that is not carcinogenic, but becomes carcinogenic when metabolized. Most known procarcinogens are activated by the cytochrome P450 enzymes in the liver. The enzymes convert the compound into a more water soluble form, so that they may be excreted. So, “breakdown into simpler parts” is not always the case; here “metabolism” is known as biotransformation. Sometimes, biotransformation produces carcinogenic compounds. For example, if electrophiles are produced, they can bind to DNA, which is nucleophilic. A classic example of a procarcinogen is the biotransformation of benzo[a]pyrene into an epoxide, and then into a diol expoxide that can covalently bind DNA.

[admin]

If a random endogenous molecule was metabolized by the liver enzymes into a carcinogen (not likely), then this would also happen on the reference plate (one containing liver enzymes and bacteria, but without the test substance). Since the number of colonies on the reference plate is subtracted from the number on the assay plate, then one would conclude that the substance is not a carcinogen.