NF1 and neoplasm: Interestingly, the focal cAMP reduction achieved by forced expression of PDE4A1 in the cortex of neurofibromatosis-1 (NF1) genetically engineered mouse (GEM) model is sufficient to induce gliomagenesis in a mouse model of NF1, and conversely, rolipram dramatically inhibits in vivo optic glioma growth and tumor size in the model [134].