MAPK3 and colorectal carcinoma: As an NMUR2 agonist (SBL-NMU-17) has NMUR2 affinity and potency comparable to the shorter form of NMU [17] and no other receptor binding of unmodified NMU is expected, the proteolytic instability of NMU-9 in CRC cell culture could be a culprit of a weak calcium mobilisation signal or a lack of ERK1/2 signalling activation.