Absence of Nuclear p16 Is a Diagnostic and Independent Prognostic Biomarker in Squamous Cell Carcinoma of the Cervix

Abstract

The tumor-suppressor protein p16 is paradoxically overexpressed in cervical cancer (CC). Despite its potential as a biomarker, its clinical value and the reasons for its failure in tumor suppression remain unclear. Our purpose was to determine p16 clinical and biological significance in CC. p16 expression pattern was examined by immunohistochemistry in 78 CC cases (high-grade squamous intraepithelial lesions (HSILs) and squamous cell carcinomas of the cervix –SCCCs). CC cell proliferation and invasion were monitored by real-time cell analysis and Transwell® invasion assay, respectively. Cytoplasmic p16 interactors were identified from immunoprecipitated extracts by liquid chromatography-tandem mass spectrometry, and colocalization was confirmed by double-immunofluorescence. We observed that SCCCs showed significantly more cytoplasmic than nuclear p16 expression than HSILs. Importantly, nuclear p16 absence significantly predicted poor outcome in SCCC patients irrespective of other clinical parameters. Moreover, we demonstrated that cytoplasmic p16 interacted with CDK4 and other unreported proteins, such as BANF1, AKAP8 and AGTRAP, which could sequester p16 to avoid nuclear translocation, and then, impair its anti-tumor function. Our results suggest that the absence of nuclear p16 could be a diagnostic biomarker between HSIL and SCCC, and an independent prognostic biomarker in SCCC; and explain why p16 overexpression fails to stop CC growth.

Understanding the Molecular Mechanism of miR-877-3p Could Provide Potential Biomarkers and Therapeutic Targets in Squamous Cell Carcinoma of the Cervix

“…Therefore, changes in protein location could be also considered as molecular alterations, and thus, potential biomarkers. Indeed, we [ 103 ], and others [ 104 , 105 , 106 , 107 , 108 , 109 ], have reported the likely clinical relevance of the subcellular location of some proteins in several tumors. Similarly, we emphasize here for the first time the relevance of the subcellular location of ZNF177 as a potential diagnostic and prognostic biomarker in SCCC.…”

Cervical cancer risk profiling: molecular biomarkers predicting the outcome of hrHPV infection

“…Therefore, although the overexpression of p16 will lead to increased inhibition of CDK4/6, it may not be able to induce its anti-tumor activity in the cytoplasm after HPV persistent infection and disease progression. This was recently described by Mendaza et alwho determined that the absence of nuclear p16, as a result of cytoplasmic sequestration, may be an indicator of progression from HSIL to cervical cancer, and poor outcomes [110]. Thus, further research is needed to clarify the subcellular localization of this protein and the meaning of these findings in terms of its utility as a tumor suppressor and as a biomarker for the disease.…”

“…Thus, demonstrating its utility in distinguishing high-grade cervical lesions [109]. In practice, p16 staining could be used ancillary in cervical cytology and histology [110][111][112]. In a population-based screening setting it could be performed on an additional slide from the same scrape, from which cytology was made, using commercially available kit (CINtecPlus, Roche mtm Laboratories, Germany).…”

Immunohistochemical Expression of P16 in Low Grade Urothelial Carcinoma

“…The dynamic interaction of cyclins, cyclin-dependent kinases (CDKs) and its inhibitors regulate cell cycle progression. Those participating in the G1/S phase change, such as cyclin D1 and E, and CDK-inhibitors such as P16 are the best predictive indicators for survival, relapse, and advancement 6 . The P16 allele acts as a tumor suppressor at chromosome 9P21, an area which is frequently mutated in different tumors 7, by negative regulation of the G1/S phase of the cell cycle with a number of malignancies showing P16 deletion.…”