MAPK8 and cancer: OPN interacts with various integrins as well as other co-receptors collectively and activates downstream complex signaling cascades, such as PI3K/Akt, p38/MAPK/ERK, JNK, Ras/Raf/MEK/ERK, JAK/STAT and TIAM1/Rac1 pathways, thereby inducing the oncogenic gene expression in various cancer cells [11,15].