The principal extrarenal manifestation of autosomal dominant polycystic kidney disease (ADPKD) involves formation of liver cysts derived from intrahepatic bil e ducts. Autocrine and paracrine factors secreted into the cyst would be positio ned to modulate the rate of hepatic cyst growth. The aim of this study was to id entify potential growth factors present in human ADPKD liver cyst fluid. Cytokin e array and enzyme-linked immunosorbent assay analysis of human ADPKD liver cys t fluid detected epithelial neutrophil attractant 78, interleukin (IL)-6 (503 ±121 pg/mL); and IL-8 (4,488 ±355 pg/mL); and elevated levels of vascular end othelial growth factor compared with non-ADPKD bile (849 ±144 pg/mL vs. 270 pg /mL maximum concentration). ADPKD liver cyst cell cultures also released IL-8 a nd vascular endothelial growth factor, suggesting that cystic epithelial cells t hemselves are capable of secreting these factors. Western blotting of cultured c yst cells and immunostaining of intact cysts demonstrate that cysteine-X-cyste ine receptor 2, an epithelial neutrophil attractant 78 and IL-8 receptor, is ex pressed at the apical domain of cyst lining epithelial cells. Suggesting the cys tic epithelial cells may exist in hypoxic conditions, electron microscopy of the ADPKD liver cyst epithelium revealed morphological features similar to those ob served in ischemic bile ducts. These features include elongation, altered struct ure, and diminished abundance of apical microvilli. In conclusion, IL-8, epithe lial neutrophil attractant 78, IL-6, and vascular endothelial growth factor may serve as autocrine and paracrine factors to direct errant growth of ADPKD liver cyst epithelia. Interruption of these signaling pathways may provide therapeuti c targets for inhibiting liver cyst expansion. The principal extrarenal manifestation of autosomal dominant polycystic kidney disease (ADPKD) involves formation of liver cysts derived from intrahepatic bil e ducts. Autocrine and paracrine factors secreted into the cyst would be positio ned to modulate the rate of hepatic cyst growth. The aim of this study was to id entify potential growth factors present in human ADPKD liver cyst fluid. Cytokin e array and enzyme-linked immunosorbent assay analysis of human ADPKD liver cys t fluid detected epithelial neutrophil attractant 78, interleukin (IL) -6 (503 ± 121 pg / mL); and IL-8 (4,488 ± 355 pg / mL); and elevated levels of vascular endothelial growth factor compared with non-ADPKD bile (849 ± 144 pg / mL vs. 270 pg / mL maximum concentration) liver cyst cell cultures also released IL-8 a nd vascular endothelial growth factor, suggesting that cystic epithelial cells t hemselves are capable of secreting these factors. Western blotting of cultured c yst cells and immunostaining of intact cysts demonstrate that cysteine-X-cysteine ​​receptor 2, an epithelial neutrophil attractant 78 and IL-8 receptor, is ex pressed at the apical domain of cyst lining epithelial cells. Suggesting the cys tic epithelial cells may exist in hypoxic conditions, electron microscopy of the ADPKD liver cyst epithelium revealed morphological features similar to those ob served in ischemic bile ducts. These features include elongation, altered struct ure, and diminished abundance of apical microvilli. In conclusion, IL-8, epithe l neutrophil attractant 78, IL- 6, and vascular endothelial growth factor may serve as autocrine and paracrine factors to direct errant growth of ADPKD liver cyst epithelia. Interruption of these signaling pathways may provide therapeuti c targets for inhibiting liver cyst expansion.