S100 proteins in oral squamous cell carcinoma

Controversy exists in the literature regarding the differential expression of S100 protein members and their functional correlations in oral squamous cell carcinoma (OSCC). The aim of the present study was to systematically review the expression of S100 protein family members among OSCC and healthy controls and to evaluate whether S100 protein members serve as diagnostic marker in OSCC.

Indexed databases were searched up to and including October 2017. Case-control/cross-sectional studies in human diagnosed clinically and/or histologically with OSCC and evaluated the expression of S100 protein family among OSCC and healthy controls were included.

A total of 11 studies were included. Four studies were of good quality, 5 were of moderate and 2 were of poor quality. Five studies evaluated S100A2, A7 and A12 and showed overexpression of these protein levels in OSCC patients when compared to healthy controls. Three studies reported down-regulation of S100A1, A3, A6, A11, A13, A14, A16 and S100Z in OSCC patients as compared to healthy controls. Two studies reported overexpression of S100A9 and one study each reported overexpression of S100A4, A8, A10, and S100P in OSCCs as compared to healthy controls respectively.

It remains debatable whether up-regulation or down-regulation of specific S100 protein members serves as a diagnostic marker in OSCC. With the findings of the present systematic review, the threshold for diagnostic levels of S100 proteins cannot be proposed. In addition, S100A7 protein could act as a potential OSCC marker. However, further case-control studies with larger sample size are required to obtain strong conclusion in this regard.