Good things happen to happy mice

The late Dr. Randy Pausch said in his famous Last Lecture, “We cannot change the cards we are dealt, just how we play the hand.” Dr. Pausch was referring to the 10 tumors in his liver and the fact that his doctors had told him he had only three to six months of good health left. He then went on to do plyometric push-ups in front of the crowd to illustrate in what good health he was at the time, despite his prognosis.

Similarly, you’ve heard that even if you’re facing a worst-case scenario, your attitude, ultimately, is what matters: “Think positive,” “Good things happen to good people,” and “Mind over Matter.” This all sounds well and good, but is there any scientific evidence to prove that attitude and mental state can make a difference? Let’s ask our friends, the mice.

Although it’s impossible to have a conversation with a mouse that’s facing a worst-case scenario, such as a terminal cancer diagnosis, we can put mice in an environment, which, based on everything we know about mouse behavior, could be considered a “Disney World” for laboratory mice. I can’t help but imagine and wonder about such a world: Would there be miniature humans greeting the mice at the front gates with great smiles and wearing little fur coats?

Back to the issue at hand, would a Disney World for laboratory mice alter the course of a disease? According to research done by investigators at the University of Auckland, The Ohio State University, and the Weill Medical College of Cornell University, the answer is yes. The group used three different cancer models to put this hypothesis to the test: C57BL/6J-ApcMin/J, a model of human colon cancer, and two syngeneic cancer models using B16 melanoma cells or MC38 colon cancer cells. The researchers monitored tumor incidence and progression of three different cancer models housed either in an “enriched environment” (see photo above) or a standard environment. They found that all three models in the “Happiest Laboratory Mouse Place on Earth” exhibit reduced tumor growth and increased remission!

Well, we all know that you don’t publish in Cell without a mechanism. The researchers had one: They found that the enriched environment up-regulates expression of hypothalamic brain-derived neurotrophic factor (BDNF), which in turn down-regulates leptin expression. They proposed that the BDNF/leptin axis may have therapeutic significance for cancer.

Whether or not an enriched environment makes mice “happier” is arguable, but I think the researchers’ findings provide an excellent argument for why we all need more vacations!