Objective:To investigate the mechanism of aberrant Sonic hedgehog (Shh) signaling which contributes to acquired resistance to gemcitabine of pancreatic cancer cells SW1990. Methods:Gemcitabine-resistant pancreatic cancer cells SW1990-GEM were induced by increasing drug dosage intermittently. Quantitative real-time PCR and Western blot assay were used to evaluate the relative expression level of PIAS1 in SW1990 cells and SW1990-GEM cells. The ability of PIAS1 promoting acquired resistance to gemcitabine through up-regulating Shh signaling was evaluated by cell proliferation,soft agar colony formation assay and nude mice tumor transplantation assay. Results:SW1990-GEM (resistant strains) showed a high expression level of PIAS1. The overexpression of PIAS1 was involved in the increased cell proliferation and tumor formation ability of SW1990-GEM cells. Knockdown of PIAS1 in SW1990-GEM reduced the activity of Shh signaling thereby decreasing the drug resistance ability of this strain. Conclusion:PIAS1 is the key factor for acquired resistance to gemcitabine in pancreatice cancer cell SW1990 by up-regulating Shh signaling.