Source: Medscape Blogs
Author: Alok Khorana, MD

As clinicians, we know that patients with excellent support systems will (in general) do better than patients without.  I had personally always thought of this as being secondary to better reporting and oversight – for instance, a patient with a spouse is more likely to be brought in with a fever whereas a patient living by him/herself is more likely to try and ride it out, leading to more dangerous complications.

In a fascinating animal model study published in Cell, researchers led by Cao et al at identify even more of a therapeutic benefit for having such an “enriched environment”.  The authors show this by placing mice with different types of cancers (melanoma, colon cancer) in two different types of environments: one, the usual laboratory housing (5 mice per cage) and the other “enriched” with “groups (18-20 mice per cage) in large cages of 1.5 m x 1.5 m x 1.0 m supplemented with running wheels, tunnels, igloos, huts, retreats, wood toys, a maze, and nesting material”.

The results all clearly favored having an enriched environment:

“In the mice housed in enriched environment for 3 weeks prior to tumor implantation, the mean volume of the tumor was 43% smaller than those in the control housing (p < 0.05). For the 6 week groups, the tumor mass in EE mice was reduced by 77.2% p < 0.001). Notably, all mice in the control groups developed solid tumors, whereas 5% of mice with 3 weeks of enriched environment had no visible tumors, and this tumor-resistant group reached 17% with 6 weeks EE.” Indeed, even in tumors with established colon cancer, improving the environment improved survival!

These results could not be shown with physical activity (minus the other enrichment) alone.  Mechanistically, the authors identified a neurotrophic growth factor (BDNF) that may be responsible for this anti-tumor effect, potentially by mediating immunocompetence.  Of course, no one knows what in the environment induces BDNF to begin with.

Just a sign of how little we know about environmental influences (as opposed to microenvironmental) and yet how important it can be…

Alok A. Khorana, M.D., is Associate Professor and Vice-Chief, Division of Hematology/Oncology, at the James P. Wilmot Cancer Center, University of Rochester, Rochester, New York. His clinical and research programs focus on cancer-associated thrombosis and gastrointestinal cancers and are funded by the NIH and the V Foundation.