Prognostic significance of SOX18 expression in non-small cell lung cancer

Recent studies have demonstrated the involvement of SOX18 transcription factor in blood and lymphatic vessel development, as well as in wound healing processes. SOX18 expression has been noted in cancer cells of various tumours, including lung cancer. However, the exact role of SOX18 expression in non-small cell lung cancer (NSCLC) remains to be determined. The present study, therefore, assessed its expression in 198 cases of NSCLC, consisting of 94 adenocarcinomas (AC), 89 squamous cell carcinomas (SQC) and 15 large cell carcinomas (LCC). The analysis utilized immunohistochemistry (IHC) and, in 42 cases, molecular methods. SOX18 expression was also determined in NSCLC cell lines (NCI-H1703, NCI-H522 and A549) and in normal lung fibroblasts (IMR-90). SOX18 was found to be expressed in nuclei, as well as in the cytoplasm of cancer cells, in the majority of studied cases. SOX18 mRNA expression was significantly lower in NSCLC than in non-malignant lung tissue (p<0.0001). However, SOX18 protein expression levels were higher in NSCLC tissues (p<0.005) and in the examined lung cancer cell lines. No SOX18 expression was noted in the IMR-90 cell line. In paraffin sections, a positive correlation between the Ki-67 antigen and nuclear SOX18 expression (r=0.17, p<0.05) was noted. In univariate survival analysis, cytoplasmic SOX18 expression correlated with poor patient outcome in the whole study and in AC cohorts (both p<0.05). Based on these results, SOX18 may be involved in the progression of NSCLC.