Consistent with the “Two PIP Hypothesis”, levels of the SHIP1 product PI(3,4)P2 are increased in several leukemia cells lines [19], while increased amounts of PI(3,4)P2 in inositol polyphosphate 4-phosphatase type II (INPP4A/B) knockout mice are implicated in promoting tumor formation [20,21]. This evidence concerns the gene INPP5D and leukemia.