Krüppel‐like factor 6 interferes with cellular transformation induced by the H‐ ras oncogene

Abstract

KLF6 is a member of the Krüppel-like factor family of transcription factors, with diverse roles in the regulation of cell physiology, including proliferation, signal transduction, and apoptosis. Mutations or down-regulation of KLF6 have been described in several human cancers. In this work, we found that KLF6-knockdown resulted in the formation of transformed foci and allowed the spontaneous conversion of NIH3T3 cells to a tumorigenic state. We further assessed the role of KLF6 in the context of oncogenic Ras. We showed that KLF6 was up-regulated by H-Ras(G12V) expression in a Jun N-terminal kinase (JNK)-dependent manner, correlated with enhanced klf6 promoter activity. We found that ectopic KLF6 expression induced a G1-phase cell cycle arrest, thereby decreasing the cell proliferation rate. In addition, constitutive KLF6 expression impaired H-Ras(G12V)-mediated loss of density-dependent growth inhibition and anchorage-independent growth. Moreover, growth of H-Ras(G12V)-driven tumors was reduced in mice challenged with cells stably expressing KLF6. KLF6 expression correlated with the up-regulation of p21, whereas neither p53 induction nor apoptotic cell death was detected. Further, p21 knockdown impaired KLF6-induced cell cycle arrest. These findings provide novel evidence highlighting KLF6 function in response to malignant transformation, suggesting the relevance of KLF6 in controlling cell proliferation and hindering tumorigenesis.

Antibacterial and Cytotoxic Activity of Compounds Isolated fromFlourensia oolepis

“…CCRF-CEM acute lymphoblastic leukemia (ALL) [ 16 ] and K562 chronic myeloid leukemia (CML) [ 17 ] cells and their MDR P-glycoprotein overexpressing variants [ 18 , 19 ], CEM/ADR5000 and Lucena 1, respectively, were a generous gift from Dr. T. Efferth (Institute of Pharmacy and Biochemistry, Johannes Gutenberg University, Mainz, Germany) and Dr. V. Rumjanek (Instituto de Bioquímica Médica Leopoldo de Meis, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil), respectively. The HEK293T non-tumor derived cell line [ 20 ] and human isolated mononuclear cells (PBMC) were also tested. Leukemic and PBMC cells were grown in Roswell Park Memorial Institute (RPMI) 1640 medium (Invitrogen Life Technologies, CA, USA) while the HEK293T cell line was grown in Dulbecco's Modified Eagle's medium (DMEM, Invitrogen Life Technologies, CA, USA), both of these media supplemented with 10% heat-inactivated fetal bovine serum (FBS, PAA Laboratories, Pasching, Austria), 2 mM glutamine (Invitrogen Life Technologies, CA, USA), and penicillin (100 units/mL) streptomycin (100 μ g/mL) (Invitrogen Life Technologies, CA, USA).…”

Polo-like Kinase 1 Inhibition as a Therapeutic Approach to Selectively Target BRCA1-Deficient Cancer Cells by Synthetic Lethality Induction

“…iRFP-C1 was a gift from Michael Davidson and Vladislav Verkhusha (National Magnetic High Field Laboratory, Tallahassee, FL; Addgene plasmid #54786; ref. 14); shBRCA1 (TRCN0000010305, Sigma-Aldrich) was cloned into pLKO.1-TRC vector through EcoRI and AgeI restriction sites; and shSCR-pLKO.1 was described previously (15). shSCR-plenti (TR30021) and shPLK1-plenti (TL320457 A) were acquired from Origene.…”

Krüppel-Like Factor 6 Is Required for Oxidative and Oncogene-Induced Cellular Senescence

“…KLF6 is reputed as tumor suppressor since numerous reports demonstrate its frequent genomic loss or down-regulation, implying a functional inactivation, in a broad range of human cancers such as glioblastoma, hepatocellular carcinoma, gastric carcinoma, colorectal, prostate, ovarian, breast, and non-small-cell lung cancers (Narla et al, 2001; Kimmelman et al, 2004; Kremer-Tal et al, 2004; Narla et al, 2007; Bureau et al, 2009; DiFeo et al, 2009; Tetreault et al, 2013). In addition, previous reports from our laboratory showed that KLF6 down-regulation leads to spontaneous transformation of NIH3T3 fibroblasts (Trucco et al, 2014). Also, KLF6 ectopic expression impaired H-Ras G12V -mediated cell growth and transformed phenotype (Trucco et al, 2014).…”

“…In addition, previous reports from our laboratory showed that KLF6 down-regulation leads to spontaneous transformation of NIH3T3 fibroblasts (Trucco et al, 2014). Also, KLF6 ectopic expression impaired H-Ras G12V -mediated cell growth and transformed phenotype (Trucco et al, 2014).…”