Clinical and functional analysis of SOX9 in colorectal cancer.

Abstract

519 Background: Colorectal cancer (CRC) is the third leading cause of cancer-related deaths worldwide. CRC develops within the intestinal epithelium, which is constantly self-renewing, developmental genes could promote the initiation and progression of cancer. SOX9 transcription factor is expressed especially in intestinal stem cells and in Paneth cells, thus alterations in expression could greatly promote neoplasia. However, the clinical significance and functional role of SOX9 in CRC remains unclear. The aim of this study is to investigate the association of SOX9 expression with relapse in CRC patients and initiate functional studies by evaluating the effects of silencing SOX9 in stem cells properties such as colonospheres formation in HCT116 CRC cells. Methods: 97 FFPE biopsies from CRC patients in stage I (N = 34) and stage II (N = 63) were analyzed. Immunoreactivity of SOX9 was classified as low and high expression groups based on the percentage of positive nucleus and tissue staining intensity. SOX9 silencing was achieved using a specific siRNA and Lipofectamine-RNAiMax and confirmed by qPCR 24 h postransfection. 40,000 HCT116 and HCT116-siSOX9 cells were seeded under adherent and ultra-low attachment conditions for tumorigenesis assays. After 72 h colonospheres were seeded and quantified. ROC analysis was used to assess the clinical correlation of SOX9 with relapse. Experimental data were expressed as means and differences tested by t-Student. Results: Data showed that 12.3% of patients relapsed. Interestingly, all of them showed lower SOX9 expression (p ≤ 0.05), regardless of their relapse free survival. In functional analysis, SOX9-deficient HCT116 cells formed smaller and less-compacted spheroid when compared to non-transfected HCT116 (p ≤ 0.05). Nonetheless, cell proliferation and migration under adherent condition were similar between the groups. Conclusions: This study did not find association between SOX9 expression and relapse. So far, in vitro assays results suggest that silencing of SOX9 inhibits colonospheres formation in HCT116 cells. Further investigation will be performed in order to evaluate the functional importance of SOX9 in chemotherapy response.