IL1B and cancer: Similarly, IL-1 was shown to upregulate Atrogin-1 expression through the phosphorylation of p38 MAPK.413 Additionally, JNK can inhibit muscle formation by phosphorylating MRF4, which suppresses the expression of late-selective myogenic genes, thus adversely affecting myogenesis.438 These findings underscore the crucial function of the MAPK signaling pathway in the manifestation of cancer cachexia.