Description:
Abstract Introduction: Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal malignancies with a propensity for metastasis and drug resistance. To overcome this and improve the outcome of patients with PDAC, there is an urgent need to elucidate the molecular mechanisms of metastasis in which cancer stem cells (CSCs) may play a role. Prrx1, a homeobox transcription factor has been identified by us, as a key molecule involved in pancreatic development, regeneration and early carcinogenesis (Reichert et al. Genes and Development 2013). Furthermore, we have reported recently that Prrx1 isoform switching governs EMT-MET plasticity to regulate PDAC invasion and metastasis (Takano et al. Genes and Development 2016). Herein, we examined that the correlation between the two Prrx1 isoforms and putative CSC markers to investigate the role of Prrx1 on pancreatic CSC functions. Materials and Methods: Mouse pancreatic ductal cell lines were isolated and established from Pdx1Cre mice (normal pancreatic ductal cells), Pdx1Cre;KrasG12D/+ mice (PanIN cells), Pdx1Cre;KrasG12D/+;p53R175H/+ mice (primary and metastatic PDAC cells). Either Prrx1a and Prrx1b was overexpressed by lentiviral transduction in each cell line with controls. Prrx1 knockdown was done in primary PDAC cells and their matched liver metastatic cells by two isoform specific siRNAs. We immunophenotyped putative pancreatic CSCs using antibodies against CSC markers (CD133, CD44, CD24 and Epcam) by flow cytometry. These subpopulations of cells were evaluated in 3D cultures, invasion assays and single-pancreatosphere formation assays. Additionally, we evaluated the expression of pancreatic CSC markers in Prrx1a and Prrx1b overexpressing and knockdown cells by qRT-PCR and flow cytometry. Results: CD133High cells and CD44HighCD24High cells are expressed highly in metastatic PDAC cells compared to primary PDAC cells. CD133High cells form spheroid cysts and CD133Low cells form spindle-shaped cells in 3D culture. CD133High cells demonstrate more invasiveness and higher self-renewal capacity compared to CD133 Low cells. The percentage of CD133High cells, CD44HighCD24High cells and EpCAMHigh cells are increased significantly in Prrx1a overexpressing primary PDAC cells. However, these cells are decreased in Prrx1a knockdown metastatic cells. Contrary to this, these subpopulation of cells are significantly decreased in Prrx1b overexpressing primary PDAC cells, and increased in Prrx1b knockdown metastatic cells. These data suggest that Prrx1a might regulate pancreatic CSC functions in metastatic PDAC cells. Conclusion: Prrx1a may be associated with a subpopulation of pancreatic cancer cells that have features of cancer stem cells. This may influence metastatic properties of pancreatic cancer cells to the liver. Citation Format: Shigetsugu Takano, Maximilian Reichert, Hideyuki Yoshitomi, Basil Bakir, Koushik K. Das, Steffen Heeg, Shingo Kagawa, Hiroaki Shimizu, Masayuki Ohtsuka, Katsunori Furukawa, Masaru Miyazaki, Anil K. Rustgi.{Authors}. Prrx1 isoforms regulate pancreatic cancer stem cell functions during pancreatic cancer progression. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2016 May 12-15; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2016;76(24 Suppl):Abstract nr B30.