In vitro model of inflammatory, hypoxia, and cancer stem cell signaling in pancreatic cancer using heterocellular 3-dimensional spheroids

Introduction As one of the most aggressive cancers worldwide, pancreatic cancer is associated with an extremely poor prognosis. The pancreatic tumor microenvironment consists of cancer cells and other tumor associated cells. Cross-talk between these different cell types through various signaling molecules results in the development of a more aggressive and malignant phenotype. Additionally, due to the highly dysregulated vasculature of tumors, the inner tumor core becomes hypoxic and eventually necrotic. Therefore, there is a need for the development of a physiologically relevant in vitro model that recapitulates these dynamic cell-cell interactions and the 3-dimensional (3D) structure of pancreatic tumors. Methods Four different 3D co-culture spheroid models using different combinations of Panc-1 tumor cells, J774.A1 macrophages, and NIH-3T3 fibroblast cell lines were reproducibly developed using the hanging drop technique in order to mimic the tumor microenvironment and to evaluate the differences in expression of various inflammatory, hypoxia, and cancer stem cell markers, including IL-8, TNF-α, TGF-β, HIF-1α HIF-2α, SCF, and LDH-A. Additionally, immunofluorescence studies were employed to investigate whether these spheroids tested positive for a cancer stem cell population. Results Pronounced differences in morphology as well as expression of signalling markers were observed using qPCR, indicative of strong influences of co-culturing different cell lines. These models also tested positive for cancer stem cell (CSCs) markers based on immunofluorescence and qPCR analysis. Conclusion Our results demonstrate the potential of 3D co-culture spheroid models to capture the inflammatory and hypoxic markers of pancreatic tumor microenvironment. We further demonstrate the presence of cancer cells with stem cell markers, similar to actual pancreatic cancer tumor. These spheroids present excellent in vitro system to study tumor-immune-stromal cell interactions as well as test deliverability of potential therapeutics in the tumor microenvironment with accurate physical and physiological barriers.