The naked mole rat's lifespan of 30 years is remarkable, as is its natural resistance to cancer. Researchers have now identified a mechanism responsible for the latter: high levels of high-molecular-mass hyaluronan secreted from fibroblasts, which accumulates because of decreased activity of hyaluronan-degrading enzymes. Suppression of hyaluronan synthesis (or promotion of its degradation) renders the animal susceptible to cancer. Evolutionarily, hyaluronan is thought to increase skin elasticity, which enables the animals to live underground.