MAPK3 and cancer: Our observations described above, as well as previous reports of abundant expression of GHR and readily detectable RNA levels of GH in all four melanoma cells [13–19], in addition to our observation of distinct growth hormone regulation of JAK2, SRC, STAT5, STAT3, AKT, mTOR and ERK1/2 pathways [56–60] – all converge upon initiation and progression of EMT in several forms of cancer.