Jiang et al. [100] found that circMAPK1 (hsa_circ_0004872) encodes the novel protein MAPK1-109aa, functioning as a cancer suppressor by binding to MEK1 and preventing the phosphorylation of MAPK1, leading to the inhibition of MAPK1 activation and its related elements in the MAPK pathway (Figure 2n). The gene discussed is MAPK1; the disease is cancer.