Context-Dependent Spatial and Functional Roles of CD44 Across Pancreatic Ductal Adenocarcinoma States

Background/Objectives: Pancreatic ductal adenocarcinoma (PDAC) comprises distinct cellular states characterized by different differentiation programs and therapeutic responses. How a cell-surface receptor adapts its function across these states remains poorly understood. Here, we investigated whether the spatial organization and functional output of CD44 vary across PDAC cellular states. Methods: CD44 expression and spatial distribution were examined in human PDAC tissues and PDAC cell models representing different differentiation states. The functional roles of CD44 were investigated using genetic depletion, transcriptomic analysis, migration and invasion assays, and xenograft and orthotopic models. Hyaluronan (HA) responsiveness and downstream signaling were assessed following exogenous HA stimulation, and the therapeutic effects of HA synthesis inhibition with 4-methylumbelliferone (4-MU) were evaluated alone or in combination with gemcitabine. Results: In differentiated PDAC tissues and classical PDAC models, CD44 was predominantly localized to the basolateral membrane and spatially segregated from E-cadherin at cell-cell junctions, consistent with a role in epithelial organization and cell-matrix interactions. In contrast, poorly differentiated PDAC tissues and basal-like models exhibited increased CD44 abundance, E-cadherin loss, and redistribution of CD44 along the cell periphery. Genetic depletion of CD44 preferentially impaired malignant phenotypes in basal-like models. Mechanistically, basal-like cells exhibited enhanced CD44-dependent responsiveness to extracellular HA, accompanied by activation of EMT-associated signaling and destabilization of E-cadherin. Inhibition of HA synthesis with 4-MU preferentially suppressed basal-like PDAC models and enhanced gemcitabine sensitivity, with these effects further supported in orthotopic models. Conclusions: These findings suggest that the functional output of CD44 in PDAC is influenced not only by its expression level but also by cellular context and spatial organization. The context-dependent responsiveness of the HA-CD44 axis may contribute to functional heterogeneity among PDAC states and represents a potential therapeutic vulnerability of basal-like PDAC.