A recent study found that loss of expression of bone morphogenetic protein 5 (Bmp5), which maps to distal chr 9, was associated with reduction in size and number of clonogenic keratinocyte stem cells and an increase in sensitivity to skin tumor promotion (Kangsamaksin and Morris 2011) suggesting that Bmp5 may underlie a portion of the effect of Psl1 on skin tumor promotion susceptibility. This evidence concerns the gene BMP5 and skin neoplasm.