MAPK9 and neoplasm: Since the constitutive signaling of the RAF-MEK-Mitogen Activated Protein Kinase (MAPK) cascade plays an important role in sustaining tumor proliferation, we were also able to demonstrate that treatment with lonafarnib reduced the expression of phospho-ERK1/2 and phospho-SAPK/JNK, two effector molecules of MAPK pathway (Figure 1).