TP53 and cancer: The onco‐circular RNA circPVT1 exerts its role in HNSCC by acting as a sponge for the miRNA‐497‐5p, a tumor suppressor miRNA associated with p53 mutations in several cancers (Guo et al., 2013; Huang et al., 2015; Li et al., 2011; Verduci et al., 2017; Wang et al., 2015).