CD44 and neoplasm: Osteopontin (OPN), a multifunctional cytokine that results from phosphorylation, contributes to the pathogenesis of various malignant conditions through different signaling pathways, including the EGFR/ERK/MMP-9 and CD44/Akt/NF-ĸB pathways; furthermore, OPN promotes cell survival, proliferation, and invasiveness in conjunction with tumor angiogenesis [13].