They also discovered that cancer cells in tissue culture have less sensitivity to contact inhibition than equivalent normal cells. That seems likely to be part of the explanation of the increased invasiveness of cancer cells.
Other researchers later used the phrase "contact inhibition" to mean reduced rates of cell growth and mitosis in crowded tissue cultures.
Wikipedia article on Contact Inhibition
"Talk" section of this article; author not given, but he's someone you know.
YouTube video animation on Contact Inhibition
This was shown at the beginning of the lecture on October 5th, but without the audio. Please watch it again and listen to the narration.