title: The histone methyltransferase G9a as a therapeutic target to override gemcitabine resistance in pancreatic cancer.
abstract: Gemcitabine (GEM) resistance is a critical issue for pancreatic cancer treatment. The involvement of epigenetic modification in GEM resistance is still unclear. We established a GEM-resistant subline PANC-1-R from the parental PANC-1 pancreatic cancer cells and found the elevation of various chromatin-modifying enzymes including G9a in GEM-resistant cells. Ectopic expression of G9a in PANC-1 cells increased GEM resistance while inactivation of G9a in PANC-1-R cells reduced it. Challenge of PANC-1 cells with GEM increased the expression of stemness markers including CD133, nestin and Lgr5 and promoted sphere forming activity suggesting chemotherapy enriched cancer cells with stem-like properties. Inhibition of G9a in PANC-1-R cells reduced stemness and invasiveness and sensitized the cells to GEM. We revealed interleukin-8 (IL-8) is a downstream effector of G9a to increase GEM resistance. G9a-overexpressing PANC-1-R cells exhibited autocrine IL-8/CXCR1/2 stimulation to increase GEM resistance which could be decreased by anti-IL-8 antibody and G9a inhibitor. IL-8 released by cancer cells also activated pancreatic stellate cell (PSC) to increase GEM resistance. In orthotopic animal model, GEM could not suppress tumor growth of PANC-1-R cells and eventually promoted tumor metastasis. Combination with G9a inhibitor and GEM reduced tumor growth, metastasis, IL-8 expression and PSC activation in animals. Finally, we showed that overexpression of G9a correlated with poor survival and early recurrence in pancreatic cancer patients. Collectively, our results suggest G9a is a therapeutic target to override GEM resistance in the treatment of pancreatic cancer.
authors.affiliation: Graduate Institute of Clinical Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan.|Research Center for Environmental Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan.
authors.forename: Mei-Ren
authors.initials: MR
authors.lastname: Pan
authors.affiliation: National Institute of Cancer Research, National Health Research Institutes, Tainan 704, Taiwan.
authors.forename: Ming-Chuan
authors.initials: MC
authors.lastname: Hsu
authors.affiliation: Department of Pathology, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung 807, Taiwan.
authors.forename: Chi-Wen
authors.initials: CW
authors.lastname: Luo
authors.affiliation: National Institute of Cancer Research, National Health Research Institutes, Tainan 704, Taiwan.|Division of Hematology/Oncology, Department of Internal Medicine, National Cheng Kung University Hospital, Tainan 704, Taiwan.
authors.forename: Li-Tzong
authors.initials: LT
authors.lastname: Chen
authors.affiliation: Institute of Clinical Medicine, College of Medicine, National Cheng Kung University, Tainan 704, Taiwan.|Department of Surgery, National Cheng Kung University Hospital, Tainan 704, Taiwan.
authors.forename: Yan-Shen
authors.initials: YS
authors.lastname: Shan
authors.affiliation: National Institute of Cancer Research, National Health Research Institutes, Tainan 704, Taiwan.|Institute of Basic Medical Sciences, National Cheng Kung University, Tainan 704, Taiwan.
authors.forename: Wen-Chun
authors.initials: WC
authors.lastname: Hung
mesh_terms: D000368:Aged; D000818:Animals; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D045744:Cell Line, Tumor; D002465:Cell Movement; D003841:Deoxycytidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm; D005109:Extracellular Matrix / Q000378:metabolism; D005260:Female; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D057809:HEK293 Cells; D006649:Histocompatibility Antigens / Q000378:metabolism*; D056466:Histone Demethylases / Q000378:metabolism; D011495:Histone-Lysine N-Methyltransferase / Q000378:metabolism*; D006801:Humans; D016209:Interleukin-8 / Q000378:metabolism; D008297:Male; D051379:Mice; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D009362:Neoplasm Metastasis; D014411:Neoplastic Stem Cells / Q000378:metabolism; D010190:Pancreatic Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D058954:Pancreatic Stellate Cells / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D023062:Receptors, Interleukin-8A / Q000378:metabolism; D000093542:Gemcitabine
chemical_list: D000964:Antimetabolites, Antineoplastic; C508606:CXCL8 protein, human; D006649:Histocompatibility Antigens; D016209:Interleukin-8; D034741:RNA, Small Interfering; D023062:Receptors, Interleukin-8A; D003841:Deoxycytidine; D056466:Histone Demethylases; C445405:EHMT2 protein, human; D011495:Histone-Lysine N-Methyltransferase; D000093542:Gemcitabine
keywords: drug resistance; interleukin-8; lysine demethylase; pancreatic stellate cell