title: Endogenous, hyperactive Rac3 controls proliferation of breast cancer cells by a p21-activated kinase-dependent pathway.
abstract: Uncontrolled cell proliferation is a major feature of cancer. Experimental cellular models have implicated some members of the Rho GTPase family in this process. However, direct evidence for active Rho GTPases in tumors or cancer cell lines has never been provided. In this paper, we show that endogenous, hyperactive Rac3 is present in highly proliferative human breast cancer-derived cell lines and tumor tissues. Rac3 activity results from both its distinct subcellular localization at the membrane and altered regulatory factors affecting the guanine nucleotide state of Rac3. Associated with active Rac3 was deregulated, persistent kinase activity of two isoforms of the Rac effector p21-activated kinase (Pak) and of c-Jun N-terminal kinase (JNK). Introducing dominant-negative Rac3 and Pak1 fragments into a breast cancer cell line revealed that active Rac3 drives Pak and JNK kinase activities by two separate pathways. Only the Rac3-Pak pathway was critical for DNA synthesis, independently of JNK. These findings identify Rac3 as a consistently active Rho GTPase in human cancer cells and suggest an important role for Rac3 and Pak in tumor growth.
authors.affiliation: Department of Immunology, The Scripps Research Institute, La Jolla, CA 92037, USA.
authors.forename: J P
authors.initials: JP
authors.lastname: Mira
authors.forename: V
authors.initials: V
authors.lastname: Benard
authors.forename: J
authors.initials: J
authors.lastname: Groffen
authors.forename: L C
authors.initials: LC
authors.lastname: Sanders
authors.forename: U G
authors.initials: UG
authors.lastname: Knaus
mesh_terms: D001943:Breast Neoplasms; D002455:Cell Division; D004247:DNA / Q000096:biosynthesis; D005260:Female; D015971:Gene Expression Regulation, Enzymologic / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D008856:Microscopy, Fluorescence; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D056921:Nuclear Receptor Coactivator 3; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors; D014162:Transfection; D014407:Tumor Cells, Cultured; D020741:rho GTP-Binding Proteins / Q000235:genetics
chemical_list: D015534:Trans-Activators; D014157:Transcription Factors; D004247:DNA; D056921:Nuclear Receptor Coactivator 3; D017346:Protein Serine-Threonine Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D020741:rho GTP-Binding Proteins