title: Inhibition of Rac1 activity induces G1/S phase arrest through the GSK3/cyclin D1 pathway in human cancer cells.
abstract: Rac1 has been shown to regulate the cell cycle in cancer cells. Yet, the related mechanism remains unclear. Thus, the present study aimed to investigate the mechanism involved in the regulation of G1/S phase transition by Rac1 in cancer cells. Inhibition of Rac1 by inhibitor NSC23766 induced G1/S phase arrest and inhibited the proliferation of A431, SW480 and U2-OS cells. Suppression of GSK3 by shRNA partially rescued G1/S phase arrest and inhibition of proliferation. Incubation of cells with NSC23766 reduced p-AKT and inactivated p-GSK3α and p-GSK3β, increased p-cyclin D1 expression and decreased the level of cyclin D1 protein. Consequently, cyclin D1 targeting transcriptional factor E2F1 expression, which promotes G1 to S phase transition, was also reduced. In contrast, constitutive active Rac1 resulted in increased p-AKT and inactivated p-GSK3α and p-GSK3β, decreased p-cyclin D1 expression and enhanced levels of cyclin D1 and E2F1 expression. Moreover, suppression of GSK3 did not alter p-AKT or Rac1 activity, but decreased p-cyclin D1 and increased total cyclin D1 protein. However, neither Rac1 nor GSK3 inhibition altered cyclin D1 at the RNA level. Moreover, after inhibition of Rac1 or GSK3 following proteasome inhibitor MG132 treatment, cyclin D1 expression at the protein level remained constant, indicating that Rac1 and GSK3 may regulate cyclin D1 turnover through phosphorylation and degradation. Therefore, our findings suggest that inhibition of Rac1 induces cell cycle G1/S arrest in cancer cells by regulation of the GSK3/cyclin D1 pathway.
authors.affiliation: Department of Pharmaceutics, Tangdu Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710038, P.R. China.
authors.forename: Linna
authors.initials: L
authors.lastname: Liu
authors.affiliation: Department of Clinical Oncology, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China.
authors.forename: Hongmei
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Department of Pharmaceutics, Tangdu Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710038, P.R. China.
authors.forename: Lei
authors.initials: L
authors.lastname: Shi
authors.affiliation: Department of Pharmaceutics, Tangdu Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710038, P.R. China.
authors.forename: Wenjuan
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Department of Pharmaceutics, Tangdu Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710038, P.R. China.
authors.forename: Juanli
authors.initials: J
authors.lastname: Yuan
authors.affiliation: Department of orthopedics, Tangdu Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710038, P.R. China.
authors.forename: Xiang
authors.initials: X
authors.lastname: Chen
authors.affiliation: Department of Pharmacology, School of Pharmacy, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China.
authors.forename: Juanjuan
authors.initials: J
authors.lastname: Liu
authors.affiliation: Department of Pharmaceutics, Tangdu Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710038, P.R. China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Pharmacology, School of Pharmacy, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China.
authors.forename: Zhipeng
authors.initials: Z
authors.lastname: Wang
mesh_terms: D000634:Aminoquinolines / Q000494:pharmacology; D059447:Cell Cycle Checkpoints / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D019938:Cyclin D1 / Q000187:drug effects* / Q000378:metabolism; D050687:E2F1 Transcription Factor / Q000187:drug effects / Q000378:metabolism; D059585:G1 Phase Cell Cycle Checkpoints / Q000187:drug effects*; D038362:Glycogen Synthase Kinase 3 / Q000187:drug effects* / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D051057:Proto-Oncogene Proteins c-akt / Q000187:drug effects / Q000378:metabolism; D011743:Pyrimidines / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D020830:rac1 GTP-Binding Protein / Q000037:antagonists & inhibitors* / Q000378:metabolism
chemical_list: D000634:Aminoquinolines; C530104:CCND1 protein, human; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; C487513:NSC 23766; D011743:Pyrimidines; C107953:RAC1 protein, human; D019938:Cyclin D1; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; D051057:Proto-Oncogene Proteins c-akt; D038362:Glycogen Synthase Kinase 3; C448021:glycogen synthase kinase 3 alpha; D020830:rac1 GTP-Binding Protein