4-(N)-stearoyl- Gemcitabine (C18GEM) is more effective than Gemcitabine (GEM) in the inhibition of pancreatic ductal adenocarcinoma cancer stem cells’ (PDAC CSCs) growth. Cell viability analysis of PDAC parental (P) cells and CSCs treated with 50 μM of GEM or C12GEM, or C18GEM for 72 h in two-dimensional (2D) conditions (A) or for 7 days in Matrigel- and collagen I-rich extracellular matrix (ECM) (B). Cell viability was measured by Resazurin Cell Viability Assay Kit, as described in Materials and Methods. Values are the means (±SE) of at least three independent biological replicates. Statistical legend: p < 0.05 (*), p < 0.01 (**), or p < 0.001 (***), as indicated by bar in figure; p < 0.05 (+), p < 0.01 (++), or p < 0.001 (+++) collagen I versus Matrigel in each cell line for each drug; p < 0.05 (†), p < 0.01 (††), or p < 0.001 (†††) CSCs versus parental (P) cells in the two ECMs for each treatment.