MDR, multi-drug resistant gene, was reported by a Nature journel to be associated with lifespan determination. The report stated that more copy numbers of MDR was associated with 10-20% increase of life span in yeast, while just one copy of MDR was associated with reduction of life span more than 30%. The report also suggested that the high copy number of MDR might be the reason of long lived cancer cells.

There are three facts that should be noted: a) MDR knockout mice are useful tools of MDR research, this suggests that MDR is not essential to life; b) whether MDR copy numbers play any  role in lifespan determination could be solved by monitoring the lifespan of MDR knockout mice and MDR transgenic mice; c) the incidence of cancer should be monitored in MDR trangenic mice in comparison to wild type mice.