title: Modulation of PKM alternative splicing by PTBP1 promotes gemcitabine resistance in pancreatic cancer cells.
abstract: Pancreatic ductal adenocarcinoma (PDAC) is an aggressive and incurable disease. Poor prognosis is due to multiple reasons, including acquisition of resistance to gemcitabine, the first-line chemotherapeutic approach. Thus, there is a strong need for novel therapies, targeting more directly the molecular aberrations of this disease. We found that chronic exposure of PDAC cells to gemcitabine selected a subpopulation of cells that are drug-resistant (DR-PDAC cells). Importantly, alternative splicing (AS) of the pyruvate kinase gene (PKM) was differentially modulated in DR-PDAC cells, resulting in promotion of the cancer-related PKM2 isoform, whose high expression also correlated with shorter recurrence-free survival in PDAC patients. Switching PKM splicing by antisense oligonucleotides to favor the alternative PKM1 variant rescued sensitivity of DR-PDAC cells to gemcitabine and cisplatin, suggesting that PKM2 expression is required to withstand drug-induced genotoxic stress. Mechanistically, upregulation of the polypyrimidine-tract binding protein (PTBP1), a key modulator of PKM splicing, correlated with PKM2 expression in DR-PDAC cell lines. PTBP1 was recruited more efficiently to PKM pre-mRNA in DR- than in parental PDAC cells. Accordingly, knockdown of PTBP1 in DR-PDAC cells reduced its recruitment to the PKM pre-mRNA, promoted splicing of the PKM1 variant and abolished drug resistance. Thus, chronic exposure to gemcitabine leads to upregulation of PTBP1 and modulation of PKM AS in PDAC cells, conferring resistance to the drug. These findings point to PKM2 and PTBP1 as new potential therapeutic targets to improve response of PDAC to chemotherapy.
authors.affiliation: Department of Biomedicine and Prevention, University of Rome Tor Vergata, Rome, Italy.|Department of Science Medical/Chirurgic and Translational Medicine, University of Rome La Sapienza, Rome, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Calabretta
authors.affiliation: Laboratory of Neuroembryology, Fondazione Santa Lucia, Rome, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Bielli
authors.affiliation: Department of Biomedicine and Prevention, University of Rome Tor Vergata, Rome, Italy.|Department of Science Medical/Chirurgic and Translational Medicine, University of Rome La Sapienza, Rome, Italy.
authors.forename: I
authors.initials: I
authors.lastname: Passacantilli
authors.affiliation: Department of Clinic and Molecular Medicine, University of Rome La Sapienza, Rome, Italy.
authors.forename: E
authors.initials: E
authors.lastname: Pilozzi
authors.affiliation: Department of Surgery, Philipps-University Marburg, Marburg, Germany.
authors.forename: V
authors.initials: V
authors.lastname: Fendrich
authors.affiliation: Department of Science Medical/Chirurgic and Translational Medicine, University of Rome La Sapienza, Rome, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Capurso
authors.affiliation: Department of Science Medical/Chirurgic and Translational Medicine, University of Rome La Sapienza, Rome, Italy.
authors.forename: G Delle
authors.initials: GD
authors.lastname: Fave
authors.affiliation: Department of Biomedicine and Prevention, University of Rome Tor Vergata, Rome, Italy.|Laboratory of Neuroembryology, Fondazione Santa Lucia, Rome, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Sette
mesh_terms: D017398:Alternative Splicing / Q000502:physiology*; D000964:Antimetabolites, Antineoplastic / Q000627:therapeutic use*; D021441:Carcinoma, Pancreatic Ductal / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D045744:Cell Line, Tumor; D003841:Deoxycytidine / Q000031:analogs & derivatives* / Q000627:therapeutic use; D018572:Disease-Free Survival; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D034441:Heterogeneous-Nuclear Ribonucleoproteins / Q000502:physiology*; D006801:Humans; D010190:Pancreatic Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D038941:Polypyrimidine Tract-Binding Protein / Q000502:physiology*; D011770:Pyruvate Kinase / Q000235:genetics*; D000093542:Gemcitabine
chemical_list: D000964:Antimetabolites, Antineoplastic; D034441:Heterogeneous-Nuclear Ribonucleoproteins; C450006:PTBP1 protein, human; D003841:Deoxycytidine; D038941:Polypyrimidine Tract-Binding Protein; D011770:Pyruvate Kinase; D000093542:Gemcitabine