Abstract A21: Inhibition of Sonic Hedgehog Pathway by small molecule inhibitors: Targeting colon cancer stem cells

Abstract

Abstract The existence of Cancer Stem Cells (CSCs) has been proven extensively in recent years. CSCs have been positively identified in, and isolated from colon cancer. They have been found to be resilient to therapy and are highly metastatic and it has been suggested that this could be attributed to the presence of CSCs expressing cell surface CD133. An active Hedgehog-Gli pathway has been detected in human colon carcinoma cells as well as their stem cells. Sonic Hedgehog (Shh) inhibitors such as cyclopamine have been successful in the treatment of other cancer types. CSCs were isolated from HT29 and DLD1 cells using the CD133 surface protein and these cells were further characterized via their expression of key stem cell markers using fluorescence microscopy. These markers included c-Myc, KLF4 and alkaline phosphatase, all of which showed elevated expression levels in the CSC fraction. The growth pattern of CSCs in comparison to non-CSCs was analyzed using cell-impedance (xCELLigence) assays, with clear differences noted in their growth rates. Adhesion assays revealed that although CSCs have a lower proliferation rate, their adhesive potential proved to be greater, possibly due to them being highly metastatic. The effects of the Shh inhibitors cyclopamine and SANT-2 on cellular adhesion of colon CSCs were compared to the Shh pathway control molecule tomatidine, and a marked decrease in adhesion potential was noted. With regard to cell invasion, this was significantly decreased when CSCs were treated with the small molecule inhibitors. In cell migration/scratch assays a similar trend was seen, wherein cell migration was retarded by Hh pathway inhibition. Using confocal microscopy, the cell surface expression of Shh and CD133 was observed following treatment with cyclopamine and while found to significantly reduce Shh expression, CD133 expression remained unaffected. Considering these in vitro results small molecule inhibitors targeting the Shh pathway appear to be promising therapeutic tools for the treatment of metastatic colon CSCs. Citation Format: Aadilah Omar, Clement Penny, Paul Ruff. Inhibition of Sonic Hedgehog Pathway by small molecule inhibitors: Targeting colon cancer stem cells [abstract]. In: Proceedings of the AACR International Conference: New Frontiers in Cancer Research; 2017 Jan 18-22; Cape Town, South Africa. Philadelphia (PA): AACR; Cancer Res 2017;77(22 Suppl):Abstract nr A21.