Arsenic trioxide inhibits viability of pancreatic cancer stem cells in culture and in a xenograft model via binding to SHH-Gli

Jin-bin Han,^1,2 Feng Sang,³ Jin-jia Chang,^1,4 Yong-qiang Hua,^1,2 Wei-dong Shi,^1,2 Li-hua Tang,^1,2 Lu-ming Liu<sup>1,2

1</sup>Department of Integrative Oncology, Fudan University Shanghai Cancer Center, Shanghai, ²Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, ³The Center for AIDS Research of the First Affiliated Hospital of Henan University of TCM, Zhengzhou, ⁴Department of Medical Oncology, Fudan University Shanghai Cancer Center, Shanghai, People's Republic of China

Objective: Overexpression of the sonic hedgehog (SHH) signaling pathway is an essential characteristic of pancreatic cancer stem cells (PCSCs) and arsenic trioxide (ATO) is described as a SHH inhibitor. This study evaluates whether ATO has the potential to inhibit viability of PCSCs via binding to SHH-Gli proteins.
Methods: Cell counting kit-8 and flow cytometry were used for analyzing apoptosis in cells in vitro. The animal model was an athymic nude mouse model bearing subcutaneous xenografts of SW1990 pancreatic cancer cells. The terminal deoxynucleotidyl transferase dUTP nick end labeling assay and immunohistochemistry were used for tumor tissue analysis. The interaction between Gli1 and ATO was examined by a confocal system and an ultraviolet absorption spectrum assay.
Results: ATO induced apoptosis in pancreatic cancer cells, especially CD24⁺CD44⁺ cells in vitro. Combination treatment of ATO and low dose gemcitabine inhibited tumor growth by 60.9% (P = 0.004), and decreased the expression of CD24, CD44, and aldehyde dehydrogenase 1 family, member A1 significantly in vivo. ATO changed the structure of the recombinant Gli1 zinc finger peptides in a cell-free condition and the binding action of ATO to recombinant Gli1 was observed in cultured pancreatic cancer cells.
Conclusion: ATO may have the potential to inhibit viability of PCSCs via binding to SHH-Gli proteins in vitro and in vivo.

Keywords: pancreatic cancer, stem cells, gemcitabine, arsenic trioxide, sonic hedgehog, Gli