title: Intrinsic chemoresistance to gemcitabine is associated with constitutive and laminin-induced phosphorylation of FAK in pancreatic cancer cell lines.
abstract: BACKGROUND
  One of the major reasons for poor prognosis of pancreatic cancer is its high resistance to currently available chemotherapeutic agents. In recent years, focal adhesion kinase (FAK), a central molecule in extracellular matrix (ECM)/integrin-mediated signaling, has been thought to be a key determinant of chemoresistance in cancer cells. In this study, we aimed to determine the roles of FAK phosphorylation in the intrinsic chemoresistance of pancreatic cancer cell lines.
  
  
  RESULTS
  Our results showed that, the level of constitutive phosphorylation of FAK at Tyr397 correlated with the extent of intrinsic resistance to Gemcitabine (Gem) in four pancreatic cancer cell lines. Moreover, in Panc-1 cells, which had high expression of pFAK, specific inhibition of constitutive FAK phosphorylation by either RNAi or FRNK overexpression decreased the phosphorylation of Akt, reduced the levels of survivin expression and Bad phosphorylation at Ser136 and increased Gem-induced cytotoxicity and apoptosis. However, in AsPC-1 cells with a low level of pFAK, neither FAK RNAi nor FRNK overexpression affected Gem-induced cell apoptosis. We further found that laminin (LN) induced FAK and Akt phosphorylation in a time-dependent manner, increased the levels of survivin and pBad (pS136) and decreased Gem-induced cytotoxicity and apoptosis in AsPC-1 cells; Specific inhibition of LN-induced FAK phosphorylation by either FAK RNAi or FRNK overexpression suppressed the effects of LN on AsPC-1 cells. Moreover, inhibition of constitutive FAK phosphorylation in Panc-1 cells and LN-induced FAK phosphorylation in AsPC-1 cells by a novel and more specific FAK phosphorylation inhibitor PF-573,228 showed similar results with those of FAK phosphorylation inhibition by FAK RNAi or FRNK overexpression.
  
  
  CONCLUSIONS
  In conclusion, our research demonstrates for the first time that both constitutive and LN-induced FAK phosphorylation contribute to increased intrinsic chemoresistance to Gem in pancreatic cancer cell lines and these effects are partly due to the regulation of Akt and Bad phosphorylation and survivin expression. Development of selective FAK phosphorylation inhibitors may be a promising way to enhance chemosensitivity in pancreatic cancer.
authors.affiliation: Department of Pathology, Peking Union Medical College Hospital, Chinese Academy of Medical Science, Beijing, PR China. whw14093@163.com
authors.forename: Wu
authors.initials: W
authors.lastname: Huanwen
authors.forename: Liang
authors.initials: L
authors.lastname: Zhiyong
authors.forename: Shi
authors.initials: S
authors.lastname: Xiaohua
authors.forename: Ren
authors.initials: R
authors.lastname: Xinyu
authors.forename: Wang
authors.initials: W
authors.lastname: Kai
authors.forename: Liu
authors.initials: L
authors.lastname: Tonghua
mesh_terms: D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology*; D017209:Apoptosis; D001483:Base Sequence; D015153:Blotting, Western; D045744:Cell Line, Tumor; D017931:DNA Primers; D003841:Deoxycytidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000378:metabolism*; D006801:Humans; D007797:Laminin / Q000378:metabolism*; D010190:Pancreatic Neoplasms / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D010766:Phosphorylation; D034622:RNA Interference; D000093542:Gemcitabine
chemical_list: D000964:Antimetabolites, Antineoplastic; D017931:DNA Primers; D007797:Laminin; D003841:Deoxycytidine; D051416:Focal Adhesion Protein-Tyrosine Kinases; D000093542:Gemcitabine