In this regard, we found a significant correlation between p21 and the mTORC1 activation marker phospho-S6, with 85% double-positive cases, which is in good accordance to our previous work unprecedentedly uncovering an alternative mechanism of p21 expression regulation by the mTORC1/4E-BP1 pathway that was operative in over 70% of HNSCC [26] as well as OSCC [30] and linked to a good prognosis [26,41]. The gene discussed is CDKN1A; the disease is head and neck squamous cell carcinoma.