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Updated: Feb 27, 2026

Establishment of a Clinic-based Biorepository
Published on: May 29, 2017
Phosphorylated ribosomal protein S6 correlation with p21 expression and inverse association with tumor size in oral
Juan C de Vicente1,2, Ignacio Peña1, Juan P Rodrigo3,2
1Department of Oral and Maxillofacial Surgery, Hospital Universitario Central de Asturias (HUCA), Oviedo, Asturias, Spain.
Background:
The purpose of this study was to investigate the clinical relevance of phosphorylated ribosomal protein S6 (p-S6), a surrogate marker of mammalian target of rapamycin (mTOR) activation, and p21 in a series of 125 patients with oral squamous cell carcinomas (OSCCs).
Methods:
Immunohistochemical analysis was performed to ascertain the phosphorylation status of p-S6 at Ser235/236 and Ser240/244, p21, and p53 protein expression.
Results:
Expression of phosphorylated S6 protein on either serine 235/236 or serine 240/244 was detected in 83% and 88% tumors, respectively, and both of them were inversely and significantly correlated with the tumor size and local infiltration. Positive p21 expression was found in 91.5% of the cases, and was inversely correlated with tumor size. In OSCC, p21 expression correlates with p-S6 levels, a surrogate marker of mTOR activation, independently of p53 status.
Conclusion:
Expression of both p21 and p-S6 was found to inversely associate with tumor size but not survival outcomes in patients with OSCC.
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