Anti-PLAU monoclonal antibody, clone FQ7385(3)

Ribosome-inactivating stresses possess a potent regulatory activity against tumor cell progression. In this study, we demonstrated that macrophage inhibitory cytokine-1 (MIC-1) and its associated signals determined the colon cancer cell response to the chemical ribotoxic stress. The ribotoxic stress agent anisomycin-induced MIC-I gene expression which was involved in the ribotoxin-induced apoptotic pathway. MIC-I was also a critical inducer of apoptosis-related gene products such as activated urokine-type plasminogen activator (PLAU) and PLAU receptor (uPAR). When MIC-1 or PLAU action was repressed in the tumor cells, the chemical ribotoxic stress triggered a survival-related MAP kinase such as ERK. Mechanistically, gene expression of apoptosis-mediator MIC-I was enhanced by activating transcription factor 3 (ATF-3) via the p38 MAP kinase signaling pathway. Moreover, both promoter activity and mRNA stability of MIC-1 gene were up-regulated by ribotoxic anisomycin via the p38 MAP kinase signaling pathway. In conclusion, ribotoxic anisomycin-induced MIC-I expression via p38-ATF3 pathway and subsequent apoptosis while suppressing survival ERK signal in the colon cancer cells. The results of this study provide mechanistic insight into tumor cell decision for death or survival pathways in response to ribosome-disrupting stresses from chemotherapeutics. (C) 2009 Elsevier Inc. All rights reserved.

Senescent cells have lost their capacity for proliferation and manifest as irreversibly in cell cycle arrest. Many membrane receptors, including G protein-coupled receptors (GPCRs), initiate a variety of intracellular signaling cascades modulating cell division and potentially play roles in triggering cellular senescence response. GPCR kinases (GRKs) belong to a family of serine/threonine kinases. Although their role in homologous desensitization of activated GPCRs is well established, the involvement of the kinases in cell proliferation is still largely unknown. In this study, we isolated GRK4-GFP expressing HEK293 cells by fluorescence-activated cell sorting (FACS) and found that the ectopic expression of GRK4 halted cell proliferation. Cells expressing GRK4 (GRK4(+)) demonstrated cell cycle G1/G0 phase arrest, accompanied with significant increase of senescence-associated-beta-galactosidase (SA-beta-Gal) activity. Expression profiling analysis of 78 senescence-related genes by qRT-PCR showed a total of 17 genes significantly changed in GRK4(+) cells (>= 2 fold, p < 0.05). Among these, 9 genes - AKT1, p16(INK4), p27(KIP1), p19(INK4), IGFBP3, MAPK14, PLAU, THBS1, TP73 - were up-regulated, while 8 genes, Cyclin A2, Cyclin D1, CDK2, CDK6, ETS1, NBN, RB1, SIRT1, were down-regulated. The increase in cyclin-dependent kinase inhibitors (p16, p27) and p38 MAPK proteins (MAPK14) was validated by immunoblotting. Neither p53 nor p21(Waf1/Cip1) protein was detectable, suggesting no p53 activation in the HEK293 cells. These results unveil a novel function of GRK4 on triggering a p53-independent cellular senescence, which involves an intricate signaling network.