The mechanism is here published in Cell! Basically, if one lives in a Enriched Environment like 唱着红歌or神清气爽, his hypothalamus generates BDNF and regulates sympathoneural β-adrenergic signaling and leptin level, which inhibits tumor. Environmental and Genetic Activation of a Brain-Adipocyte BDNF/Leptin Axis Causes Cancer Remission and Inhibition http://www.cell.com/retrieve/pii/S0092867410005659