CDKN1A and cancer: OSCC cells may acquire more malignant characteristics through exogenous OSCC cells-derived exosomes-induced activation of PI3K/Akt signaling pathways, since this signaling pathways are associated with cellular transformation, tumorigenesis, cancer progression, and drug resistance through the regulation of oncogene and gate keeper tumor suppressor gene expression (c-Myc, p53, p27Kip1, and p21cip1/WAF1).