EVALUATION OF CANCER-STEM CELLS IN DIFFERENT MODELS OF PANCREATIC DUCTAL ADENOCARCINOMA

Pancreatic ductal adenocarcinoma (PDAC) is a lethal disease, mainly due to late diagnosis and its intrinsic resistance to available treatments. Similarly to many solid cancers, PDAC contains a rare population of highly tumorigenic ‘stem-like’ cells (CSC, cancer-stem cells), which have been shown to possess distinct features as compared to more differentiated cells composing the bulk of a tumour. While more differentiated cells are thought to succumb to the effects of chemotherapy, CSCs survive drug treatments and cause relapses by rapidly repopulating tumours. However, CSCs represent only a small fraction (1-5%) of neoplastic cells in tumour, which makes their study challenging. Previous studies have shown that pancreatic CSCs can be enriched in vitro as anchorage-independent spherical colonies expressing stem cell markers (e.g., CD133 and autofluorescence). In vitro three-dimensional (3D) cultures, including organoids, are emerging as novel systems to study tissue development and organogenesis. Here, we report the characterization of CSCs in pancreatic tumour cultures established from patient derived xenograft (PDX) of PDAC. We established organoid cultures from four PDX-tumours and showed that they are epithelial cultures enriched for cells expressing stem cell markers (e.g., autofluorescence) and displaying high expression of pluripotency-associated genes as compared to their corresponding more differentiated monolayer cell cultures. Most importantly, following transplantation in immunodeficient mice, organoids were capable of recapitulating the morphological heterogeneity of the parental tumour. Our results highlight the enhanced stemness potential of PDAC organoids and their potential value as an in vitro model system to study CSCs. 3D systems have recently emerged as advanced drug screening platforms as, unlike the 2D cell cultures, organoids more adequately mimic the cell and tissue architecture observed in vivo. Our preliminary data show that PDAC organoids are more resistant than conventional monolayer cell cultures to standard chemotherapy with gemcitabine and abraxane aligning them with the resistance/sensitivity profile usually observed in vivo. Thus, pancreatic organoids can be used to model PDAC and as drug screening platforms to predict clinical responses and personalised cancer treatments.