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The easiest carcinogenic thing for me to grasp is radiation, as it directly messes with DNA. Then it seems there are other compounds that simply mimic hormones, but these shouldn't necessarily cause cancer, right? Then there are things that can accelerate mitosis or mess with other processes, which can inadvertently mess with DNA. So my question is, in general, how many different flavors of carcinogens are there? I know there are a lot, but can someone list a good few? Maybe some examples? I'm most interested in how plastics and things like smoke cause cancer. I think a few examples would be best in aiding my understanding. Thank you!

Edit: I also just realized this is not the Chemistry Stack Exchange, I think I am more interested in the chemistry side of this question, but it might need to be migrated.

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    $\begingroup$ Have you read the WP article on carcinogens? Do you have any specific questions that aren't answered there or by a google search? $\endgroup$
    – MattDMo
    Jan 10, 2014 at 21:00
  • $\begingroup$ More Wikipedia articles to peruse: mechanism of carcinogenic behavior of tobacco smoke components (primarily by mutating DNA); Possible mechanisms of asbestos carcinogenicity. In general, my strategy is to look at the list of common carcinogens and follow the links to the carcinogen pages, and look to see if there is any info there on the mechanism of carcinogenicity. $\endgroup$
    – A. Kennard
    Jan 11, 2014 at 11:29
  • $\begingroup$ Another interesting mechanism that can contribute to carcinogenicity via disruption of the DNA's structure and subsequent reading of the DNA is DNA intercalation. $\endgroup$
    – Martin Dinov
    Jan 11, 2014 at 16:45
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    $\begingroup$ The user wants the question to be migrated to Chemistry SE $\endgroup$
    – The Last Word
    Jun 17, 2014 at 10:07
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    $\begingroup$ this is not a chemistry question.. this is a biological question but a broad question. It should not be migrated to ChemistrySE. The OP can narrow down the question and add some details- it is perfectly on topic $\endgroup$
    – WYSIWYG
    Jun 17, 2014 at 11:33

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"So my question is, in general, how many different flavors of carcinogens are there?" As mentioned in the comments, almost all carcinogens act by damaging DNA. In general there are three ways to do this:

Alkylation, a good example is pyridine. These compounds covalently modify the DNA and either cause a mutation by misincorporation during DNA replication (where the wrong base is incorporated across from the alkylated base), or by generation of double strand breaks during DNA replication that result in a mutations during the repair process (the details of which are not in-scope here).

Intercalation, my favourite example being ethidium bromide. These compounds literally insert themselves between the bases of the double helix, where they cause "fork collapse" during DNA replication, and the ensuing repair process mutates the DNA.

Ionization through radicals. Yes, carcinogens can generate radicals that will generate DNA damage. A good example is doxorubicin, which is a highly effective chemotherapeutic, but also a carcinogen in its own right. Some heavy metals can also generate radicals under the right circumstances. These compounds typically oxidize the bases of DNA, and result in broad misincorporation during DNA replication. Radicals can also result in breakage of the phosphodiester backbone, which cause mutations during repair. This mechanism is taken advantage of in some methods for studying the primary and secondary structure of RNA molecules, and in "foot printing" methods. Incidentally, it is this mechanism of carcinogenesis that causes antioxidants to be associated with the prevention of cancer. Compounds like vitamin C soak up the radicals generated by the carcinogen (or radiation), thereby preventing the damage from occurring.

An interesting point: pyrimidine dimers, which are generated whenever you get a sunburn, are a carcinogenic form of DNA damage somewhere between the ionization and alkylation mechanisms. UV light induces a redox reaction that results in covalent linkage of two neighboring pyrimidines. A dedicated repair process can cause a mutation at the site of the dimer.

However, the take home point is that the DNA damage itself is not usually the mechanism of mutation! Mutation occurs when the damage is repaired, either as part of a dedicated repair process, or by (non)homologous recombination after a stall in DNA replication.

I hope this answers your question. It is a complicated subject, and I doubt I covered everything here.

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  • $\begingroup$ There are no papers available which prove a carcinogenic effect of ethidium bromide. It is clearly mutagen and teratogen because of its ability to interact with DNA. It is used as a cure for trypanosoma in cattle. The dangers of EtBr are widely exaggerated. $\endgroup$
    – Chris ♦
    Jun 17, 2014 at 21:19
  • $\begingroup$ They are indeed widely exaggerated! However, it is an intercalator. Nonetheless, intercalation is a mechanism for inducing mutations. For example, coal dust is carcinogenic due to this mechanism. $\endgroup$
    – Richard Rymer
    Jun 17, 2014 at 21:30
  • $\begingroup$ But you have to differentiate between a mutagen and a cancerogen. Mutagens have indirect effects via hampering around with gene expression, while cancerogens act directly. $\endgroup$
    – Chris ♦
    Jun 17, 2014 at 21:48
  • $\begingroup$ Doesn't get a little existential though? I mean the actual carcinogen by your definition is a repair polymerase that slams in the wrong base. I agree that it is important to point out what compounds are dangerous, and which are not, but at the end of the day, an intercalator is a potential mutagen, and everything else is context. $\endgroup$
    – Richard Rymer
    Jun 17, 2014 at 21:50
  • $\begingroup$ You are probably right. $\endgroup$
    – Chris ♦
    Jun 18, 2014 at 7:08

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