Expert: Dana Krempels, Ph.D. - 9/13/2008

Question
Dear Dr. Krempels,

I know mammals can have cancer, but I don't know if simpler animals, unicellular organisms or plants develop diseases/mutations similar in features to cancer, especially a cellular metabolism oriented to growth rather then energy production.

Is cancer limited to a certain taxonomic category? If so, is there a deeper (genetic, biochemical?) explanation?

Thanks, R.C.

Answer
Dear R.C.,

Mammals are not the only animals that get cancer.  In fact, any vertebrate (except sharks--they are amazingly exempted) can get cancer.

I've not heard of cancers in non-vertebrates.  But plants can develop cancer-like (localized, not metastatic) tumors called galls, when exposed to certain viruses or parasites.

Cancers are a class of genetic diseases.  They start to form when a combination of mutations in a cell does two things:  (1) ceases to control cell proliferation/growth and (2) ceases to control programmed cell death, which occurs naturally when cells are triggered to die for various reasons.  Any organism that can have mutations like this can develop cancer-like lesions, but it actually takes quite a bit of time for the "right" combination of mutations to accumulate and cause cancer.  This is why the longer you live, the more likely you are to get cancer.

Small non-vertebrates, with their generally short lifespans, may simply not last long enough to get cancers.

I hope this helps.

Dana