A novel 3-dimensional culture system uncovers growth stimulatory actions by TGFβ in pancreatic cancer cells

Transforming Growth Factor-beta (TGF beta) exerts cell type-specific and context-dependent effects. Understanding the intrinsic actions of TGF beta on cancer cells in pancreatic ductal adenocarcinoma (PDAC) is a prerequisite for rationalizing clinical implementation of TGF beta targeted therapies. Since the tumor microenvironment can affect how cancer cells respond to TGF beta, we employed a novel 3-dimensional (3D) culturing system to recapitulate stromal and extracellular matrix interactions. We show here that TGF beta stimulates the growth of several human and murine pancreatic cancer cell lines (PCCs) when embedded in a 3% collagen IV/laminin-rich gelatinous medium (MatrigelTM) over a solidified layer of soft agar. Moreover, in this novel 3D model, concomitant treatment with TGF beta 1 and epidermal growth factor (EGF) enhanced PCC growth to a greater extent than either growth factor alone and conferred increased chemoresistance to cytotoxic compounds. These cooperative growth-stimulatory effects were blocked by pharmacological inhibition of either the TGF beta type I receptor with SB431542 or the EGF receptor with erlotinib. Co-incubation with SB431542 and erlotinib enhanced the efficacy of gemcitabine and cisplatin in PCCs and in primary cell cultures established from pancreata of genetically-engineered mouse models of PDAC. These findings suggest that concomitant inhibition of TGF beta and EGF signaling may represent an effective therapeutic strategy in PDAC, and that this 3D culturing system could be utilized to test ex vivo the therapeutic response of pancreatic tumor biopsies from PDAC patients, thereby providing a functional assay to facilitate personalized targeted therapies.