Pancreatic cancer is the fourth leading cause of all cancer-related death.  It is notoriously difficult to diagnose and has very limited therapeutic options.  Pancreatic ductal adenocarcinoma (PDAC) accounts for more than 80% of all forms of pancreatic cancer.  Understanding PDAC cell growth and motility is the key to developing effective drug therapeutics for treating PDAC.  To date, most in vitro PDAC studies have been conducted on two dimensional (2D) tissue-culture plastic dishes (TCP) that are unnaturally stiff (E > 1 GPa).  The ultrahigh stiffness of a 2D surface not only un-naturally polarizes the attached cells, but also causes the cells to behave differently due to abnormal mechano-sensing.  2D cell culture techniques are also inadequate in the study of tumor cells, which are highly influenced by the stromal tissues (i.e., desmoplasia, dense extracellular matrices deposited by activated pancreatic stellate cells) found in three-dimensional (3D) tumors.  It is also believed that desmoplasia communicates with pancreatic cancer cells to promote tumor progression and to hinder drug penetration and efficacy.  Although a few studies have explored the utility of 3D matrices, such as Matrigel(R), for PDAC research, the commercially available matrices are mechanically weak and contain ill-defined and un- controllable biochemical components that may confound the experimental results.  Our central hypothesis is that a synthetic tumor niche with dynamically and modularly adaptable properties can be used to elucidate the influence of extracellular matrix (ECM) cues on the growth, morphogenesis, and drug efficacy in PDAC cells.  Toward this end, we will develop synthetic hydrogels that can be reversibly stiffen/soften via cytocompatible light exposure (365-430nm) in a range relevant to PDAC.  In Aim 1, we will develop innovative dynamic desmoplasia-mimetic hydrogel matrix to encapsulate PDAC cells (e.g., PANC-1, COLO-357, and ASPC1) and study their growth, morphogenesis, and epithelial-mesenchymal transition (EMT).  In Aim 2, we will independently and reversibly modulate the biophysical and biochemical properties of cell-laden hydrogels in order to delineate the influence of various immobilized and soluble extracellular factors on PDAC cell fate processes.  We will also reveal the influence of these critical factors on drug resistance in PDAC.  The information obtained from this study will open new therapeutic options for treating the lethal PDAC.