MAP2K1 and cancer: Thus, with respect to signaling in cancer cells, after inhibiting the Ras-MEK 1/2-ERK 1/2 kinase cascade (Figure 4), the cardiac peptides can inhibit DNA synthesis secondarily by ERK 1/2 kinases' mediated decrease in DNA synthesis or possibly directly since they have been shown by immunocytochemical studies [57,58] to enter the nucleus where they can inhibit DNA synthesis.