Hello, my name is Lynn Enquist,
I'm a professor of molecular biology at Princeton University.
Today, I want to continue my discussion of virology in cancer biology.
In particular, I want to talk to you about
DNA viruses that are associated with transformation in
tumor formation and focus on
the early work that led to the discovery of tumor-suppressor genes.
If we recall from the previous lecture, on the left side of this slide
I discussed how retroviruses that cause
tumors were discovered, and our basic understanding of how they
cause cells to grow out of control, and how they came together
in the 1960s and '70s to give us this unified theory of cell growth control.
Today, I want to talk about the study of DNA virus transformation.
They didn't reveal much about oncogenes, but rather
they revealed how the cell cycle was regulated.
This started in the 1920s with
the discovery of some viruses that caused tumors in animals, in the 1930s,
discovering warts caused by a papilloma virus in rabbits,
in the late 1950s and early 1960s
how certain DNA viruses transform cells in vitro , and the discovery of polyoma virus.
The beginnings were the discovery of a virus that was
involved in the formation of papillomas in cottontail rabbits, it's called CRPV.
A papilloma is a benign epithelial tumor that essentially causes warts.
You can see on the head of this cottontail rabbit
these growths, these fibromas that were growing out.
It was benign, the tumors didn't directly kill the animal,
but they interfered with feeding and breathing and everything.
They were very obvious, and in 1933
Richard Shope and Weston Hurst discovered the fact that if they ground up these warts,
made cell-free filtrates and injected the filtered material into rabbits,
they could transmit the capacity to form these fibromas.
Once again, a filterable agent was involved in tumor formation.
At this time, they had a better understanding what a virus was
and so they figured out it must be due to a virus that caused this particular tumor.
Even though they were onto this very early,
it took at least 18 or 20 or so years to characterize what the virus was.