title: LKB1 catalytically deficient mutants enhance cyclin D1 expression.
abstract: Mutations in the serine-threonine tumor-suppressor kinase LKB1 are responsible for Peutz-Jeghers syndrome, characterized by hamartomatous proliferation and an increased risk of developing cancer. Mutations in lkb1 have also been identified in sporadic cancers, suggesting a wider role for LKB1 in cancer that is not limited to hamartomatous polyposis syndromes. Here, we show that LKB1 catalytically deficient mutants, when introduced into DLD1p21-/-p53-/- colorectal cancer cells, allowed for progression of cells through to S phase of cell cycle and elicited the expression of Rb, cyclin E, and cyclin A2 whereas the introduction of LKB1 lead to G1 cell cycle arrest independent of p21(WAF/CIP1) and/or p53 expression. Furthermore, we show that LKB1 catalytically deficient mutants activate the expression of cyclin D1 through recruitment to response elements within the promoter of the oncogene. In addition to compromising the tumor-suppressor function of LKB1, our findings highlight an emerging role for LKB1 catalytically deficient mutants, a gain of oncogenic properties.
authors.affiliation: Department of Biochemistry and Molecular Biology, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada.
authors.forename: Kristine D
authors.initials: KD
authors.lastname: Scott
authors.forename: Suchita
authors.initials: S
authors.lastname: Nath-Sain
authors.forename: Meghan D
authors.initials: MD
authors.lastname: Agnew
authors.forename: Paola A
authors.initials: PA
authors.lastname: Marignani
mesh_terms: D000091162:AMP-Activated Protein Kinase Kinases; D000230:Adenocarcinoma / Q000235:genetics / Q000378:metabolism*; D015153:Blotting, Western; D002453:Cell Cycle / Q000502:physiology; D049109:Cell Proliferation; D002471:Cell Transformation, Neoplastic / Q000378:metabolism*; D015179:Colorectal Neoplasms / Q000235:genetics / Q000378:metabolism*; D019938:Cyclin D1 / Q000096:biosynthesis*; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000172:deficiency; D005434:Flow Cytometry; D006801:Humans; D047468:Immunoprecipitation; D009154:Mutation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection; D016159:Tumor Suppressor Protein p53 / Q000172:deficiency
chemical_list: D050759:Cyclin-Dependent Kinase Inhibitor p21; D016159:Tumor Suppressor Protein p53; D019938:Cyclin D1; D017346:Protein Serine-Threonine Kinases; C109790:STK11 protein, human; D000091162:AMP-Activated Protein Kinase Kinases