Oral squamous cell carcinoma (OSCC) is the eighth most prevalent cancer worldwide. In recent large-scale studies, by immunohistochemistry and cluster analysis, several markers were associated with patient survival in various tumors. The aim of this study was to analyze the expression profiles of 23 proteins that have been linked to the inhibition (Bcl-2, Bcl-x, Bcl-xL, Bcl-2-related protein A1, BAG-1, and survivin) and promotion (Bak, Bax, Bim/Bod, Bim-Long, Bad, Bid, PUMA, Apaf-1, caspase-2,

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... spase-3, caspase-6, caspase-7, caspase-8, caspase-9, caspase-10, Smac/DIABLO, and cytochrome c) of apoptosis in OSCC. Methods: Two-hundred and twenty nine cases of OSCC, arranged in a tissue microarray, were immunohistochemically analyzed, and the results were quantified on an automated imaging system. The data were analyzed using a random forest clustering method. Results: Overall protein expression patterns defined two chief clusters: an anti-apoptotic cluster (142 cases) and a pro-apoptotic cluster (29 cases). These groups could not be explained by any clinical or pathological characteristic, and overall and disease-free survival did not differ between them. Conclusions: Although there was no association with survival, the cluster analysis demonstrated specific protein profiles that could be of interest for using targeted therapies: in one of the clusters, the expression of pro-apoptotic proteins was more prominent, demonstrating a pro-apoptotic profile and highlighting the importance of apoptosis during OSCC development.