(Back to the Cancer for Dummies main page for additional topics)
7 May 2011
This week’s question comes from Andrew Ulvestad in Chicago, Illinois:
Dumb cancer question: I always thought cancer cells were created by miscopying parts of the DNA. There’s some probability for this to happen, so (in the long run frequency interpretation) as you get older this happens more. Why, then, are some cancers only present in young people (I have in mind testicular cancer)?
According to the National Cancer Institute, “Testicular cancer occurs most often in men between the ages of 20 and 39, and is the most common form of cancer in men between the ages of 15 and 34.” It is important to note that TC does not only show up in young people, as it occasionally affects men outside of the 20-40 age range. (1)
But why does testicular cancer usually affect the 20-40 age range? As I discussed in a previous article, cancer is an age-related disease and that age range is atypical for cancer. Cancer is predominantly a disease of those with several more decades of age.
I had to take a plunge into PubMed to answer this question. The current view of WHY testicular cancer (TC) affects men in the 20-40 year old range is because one of the ingredients for development of full-blown TC is the presence of high levels of androgens (male sex hormones) like testosterone. This working hypothesis manifests because the typical age of onset closely mirrors the age at which androgen levels are highest in men, and is backed up by molecular studies of isolated TC cells. (2)
Beyond cells in a petri dish, a recent paper just came out that identified certain gene variants that could predispose men to TC. The genes in question? Ones that produce androgens. (3) This data further strengthens the androgen-TC link.
I’ve written about the similarities and differences between childhood cancer and adult cancers. While most adult cancers can be thought of as a gradual accumulation of genetic “hits”, or mutations, childhood cancer can occur because naturally occurring hiccups in development can sometimes leave cells several steps closer to becoming cancerous.
This process is likely what happens with testicular cancer, as a fair number of boys are born with Carcinoma in Situ (CIS), a normally benign defect in testicle development. (2) The flood of testosterone in puberty could act as the final ingredient needed to pushes some CIS into testicular cancer. As most developments in cancer progression, this process could take years to manifest after the androgen stimuli, which would account for the 20-40 year old TC range.
Thanks for writing!
1) National Cancer Institute: http://www.cancer.gov/cancertopics/factsheet/Sites-Types/testicular
2) Rajpert-De Meyts E: http://www.ncbi.nlm.nih.gov/pubmed?term=16540528
3) Vastermark et al, 2011: http://www.ncbi.nlm.nih.gov/pubmed/20880698