High expression of ALDH1 and SOX2 diffuse staining pattern of oral squamous cell carcinomas correlates to lymph node metastasis

One of the major factors involved in the prognosis of oral squamous cell carcinoma (OSCC) patients is metastasis. Recent progress in cancer stem-like cell/cancer-initiating cell (CSC/CIC) research indicates that CSCs are related to metastasis. Aldehyde dehydrogenase 1 (ALDH1) and SRY-related HMG-box gene 2 (SOX2) have recently been shown to be putative CSC markers for several human malignancies. The aim of this study was to determine the association of ALDH1 and SOX2 expression in oral squamous cell carcinoma (OSCC) with lymph node metastasis. Immunohistochemical staining of ALDH1, SOX2 and Ki67 was performed in 80 OSCC tissues. High expression rates of ALDH1 (2%40%) were found to be related to lymph node metastasis (P = 0.0017). Interestingly, we found that SOX2 staining could be classified into two patterns: (i) peripheral staining pattern; and (ii) diffuse staining pattern. The diffuse staining pattern showed a significant correlation with lymph node metastasis (P < 0.001). No correlation was found between Ki67 staining and lymph node metastasis (P = 0.4724). The ALDH1 positive staining rates in metastatic lymph nodes were higher than that in corresponding primary OSCC tissues. These results indicate that high expression rates of ALDH1 and SOX2 diffuse staining patterns might be novel prediction markers for OSCC lymph node metastasis.