Reduction of intracellular pH inhibits constitutive expression of Cyclooxygenase‐2 in human colon cancer cells

Pirkebner, Daniela; Fuetsch, Michaela; Wittmann, Walter; Weiß, H.; Haller, Thomas; Schramek, Herbert; Margreiter, Raimund; Amberger, Albert

doi:10.1002/jcp.10408

Cited by 11 publications

(10 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Lotspeich (22), in his pioneering studies, was the first to show that the response to metabolic acidosis was more catholic than recognized despite lacking an understanding of underlying signaling pathways (2); in this regard, NH 4 Cl-induced metabolic acidosis and transient ERK activation may induce renal hyperplasia (22), whereas TROinduced sustained ERK activation may inhibit proliferation (20,35,36,41) and even in PPAR␥-negative cells (35,41). Such a model may also explain how extracellular acidosis (transient MAPK activation) upregulates tumorgenic cyclooxgenase-2 expression (38) while sustained intracellular acidosis [although difficult to achieve by reducing extracellular pH in normal (18) and, especially, in more alkaline tumor cells (41)] can inhibit expression of cyclooxgenase-2 in colon cancer cells (31). These studies, as well as the present findings, suggest potentially important but ill-defined relationships between acute and sustained MAPK activation and pH i in regulating growth in normal as well as malignant cells.…”

Section: Discussionmentioning

confidence: 99%

Troglitazone's rapid and sustained activation of ERK1/2 induces cellular acidosis in LLC-PK₁-F⁺cells: physiological responses

Oliver

Friday

Turturro

et al. 2005

American Journal of Physiology-Renal Physiology

View full text Add to dashboard Cite

We studied the signal pathway through which troglitazone (TRO) acts in inducing cellular acidosis in LLC-PK1-F+ cells in relation to ammoniagenesis and DNA synthesis. Cells were grown to confluent monolayers in 30-mm chambers and monitored for intracellular pH (pHi) by the BCECF assay and activated ERK by phospo-ERK1/2 antibodies. TRO induces a severe cellular acidosis (pHi 6.68 ± 0.10 vs. 7.28 ± 0.07 time control at 4 min, P < 0.01), whereas phospho-ERK1/2 to total ERK1/2 ratio increases 3.4-fold ( P < 0.01). To determine whether ERK1/2 was activated by cellular acidosis or TRO was acting via MEK1/2 to activate ERK1/2, cells were pretreated with specific inhibitors of MEK1/2 activity, PD-098059 and U-0126, followed by the addition of TRO or vehicle. With MEK1/2 activity inhibited, TRO treatment failed to activate ERK1/2. Preventing ERK1/2 activation abrogated the TRO-induced cellular acidosis and maintained the pHi within the low normal range (7.06 ± 0.11). To determine whether blocking ERK activation prevents TRO's inhibitory effect on NHE activity, cells were acid-loaded and the recovery response was monitored as ΔpHi/ t over a 4-min recovery period. TRO inhibited NHE activity by 85% ( P < 0.01), whereas blocking ERK activation restored the response. We measured activated ERK levels and pHi after 3- and 18-h exposure to TRO or extracellular acidosis (pHe = 6.95) to determine whether ERK activation was sustained. Whereas both TRO and extracellular acidosis increased activated ERK and decreased pHi after 3 h, only TRO sustained this response at 18 h. Furthermore, both enhanced ammoniagenesis and decreased DNA synthesis reflected the effect of TRO to induce and sustain a cellular acidosis.

show abstract

Section: Discussionmentioning

confidence: 99%

Troglitazone's rapid and sustained activation of ERK1/2 induces cellular acidosis in LLC-PK₁-F⁺cells: physiological responses

Oliver

Friday

Turturro

et al. 2005

American Journal of Physiology-Renal Physiology

View full text Add to dashboard Cite

show abstract

“…Genomic DNA free RNA was isolated with the SV total RNA isolation system (Promega, Madison, WI) according to the manufacturer's protocol. Reverse transcription-PCR (RT-PCR) was done as described earlier (20). The following 14-3-3j -specific primers was used: forward 5V -AGAGCGAAACCTGCTCTCAG-3V and reverse 5V -GGCATCTCCTTCTTGCTGAT-3V .…”

Section: Methodsmentioning

confidence: 99%

14-3-3σ Expression Is an Independent Prognostic Parameter for Poor Survival in Colorectal Carcinoma Patients

Perathoner

Pirkebner

Brandacher

et al. 2005

Clinical Cancer Research

Self Cite

View full text Add to dashboard Cite

Purpose: 14-3-3σ is an intracellular, dimeric, phosphoserine binding protein that is expressed in epithelial cells and involved in cancer development. In this study, we examined the expression of 14-3-3σ and evaluated its clinical significance in colorectal carcinoma. Experimental Design: Expression of 14-3-3σ was analyzed by Western blot in nine colorectal carcinoma cell lines, eight paired colorectal carcinoma tissues, and normal mucosas. Immunohistochemistry was used to evaluate expression of 14-3-3σ in tissues of 121 colorectal carcinoma patients and to correlate it with clinical parameters. Results: Western blot analysis of colorectal carcinoma cell lines and tissues revealed strong 14-3-3σ expression in four of eight cell lines and 14-3-3σ overexpression in carcinomas compared with normal mucosa in six of eight colorectal carcinoma tissue pairs. Immunohistochemical analysis revealed 14-3-3σ overexpression in 38.8% of colorectal carcinoma samples. Furthermore, highly positive immunoreactivity was significantly correlated with tumor differentiation (P < 0.001) and pT stage (P < 0.003). In Kaplan-Meier analysis, 14-3-3σ overexpression was associated with a significantly decreased survival time compared with negatively stained or low stained cases (P < 0.0096). In multivariate regression analysis, 14-3-3σ expression emerged as a significant independent parameter (P < 0.037). Conclusions: These results provide evidence that 14-3-3σ expression increases during carcinoma progression in a subset of colorectal carcinoma. The overexpression of this antigen identifies patients at high risk. It is tempting to suggest that 14-3-3σ overexpression either promotes tumor proliferation and/or prevents apoptotic signal transduction in colorectal carcinoma. Thus, targeting 14-3-3σ might be a new therapeutic strategy in colorectal carcinoma.

show abstract

“…pHi was also one of the factors thought to control the rate of cell proliferation and invasion (18,19). In many tumor cell lines pHi was more alkaline than in normal cell lines (9).…”

Section: Discussionmentioning

confidence: 99%

“…Using confocal laser microscopy and BCECF labeled cells Pirkebner et al reported identical pH values in the cytosol and the nucleus (18). In contrast, a 0.3-0.5 pH unit higher pH in the nucleus than in the cytosol was found using SNARF-1 as pH indicator (25).…”

mentioning

confidence: 99%

Na+/H+ exchanger blockade inhibits the expression of vascular endothelial growth factor in SGC7901 cells

Zhang²,

Zhu³

2009

Oncol Rep

View full text Add to dashboard Cite

IntroductionAngiogenesis is tightly regulated by pro-angiogenic and antiangiogenic balance. In tumorigenesis, this balance is derailed (1), thereby triggering tumor growth, invasion, and metastasis (2). The 'angiogenic switch' (3) is triggered by oncogenemediated tumor expression of angiogenic proteins such as vascular endothelial growth factor (VEGF) (1). VEGF plays a critical role in many aspects of cancer biology. VEGF and VEGF receptor (VEGFR) expression has been detected in a variety of solid tumors, including those of gastrointestinal tract (4,5). The acquired ability to maintain elevated intracellular pH (pHi) despite the growth in a progressively acidic extracellular milieu confers selective advantage to transformed malignant cells (6). The microenviroment within solid tumors is slightly acidic, and manipulation of this extracellular acidity to cause intracellular acidification might be used to increase selective antitumor effects of some anticancer drugs (7). An alkaline pHi is a fundamental step in the acquisition of a malignant phenotype (8). On the contrary, cytosolic hyperacidification is a generalized event in programmed cell death at different stages of the apoptotic process (9). The primary regulator of pHi is the Na + /H + exchanger (NHE) of which there are 8 known isoforms (10). The involvement of the ubiquitous pHi regulator NHE in tumorigenesis is well documented; more recently, signaling pathways involved in the activation of NHE have been explored in cells with malignant phenotype (11,12).Our previous study in leukemia cells indicated that there is a correlation between modulation of pHi and the expression of VEGF (13). Considering VEGF and its receptors play more important roles in solid tumors than in leukemia, it is an agent involved in the relationship between pHi and VEGF expression in solid tumors. However, there is little data on this relationship. In an attempt to integrate these subfields, the study therefore explores the effect of inhibition of NHE on the expression of VEGF mRNA and VEGF protein in human SGC7901 gastric cancer cell line. The purpose of this study was to determine whether NHE inhibition can decrease the expression of VEGF in SGC7901 cell line. If NHE inhibition could decrease the expression of VEGF in SGC7901 cells, it would inhibit tumor angiogenesis. The study allows consideration of NHE inhibitors as potential anti-tumor agents. Materials and methodsReagents and chemicals. RPMI-1640 was obtained from Gibco Co. Nigericin, 5-(N-ethyl-N-isopropyl) amiloride (EIPA), 3-(4,5-dimethyl-thiazoyl-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and amiloride were obtained from Sigma Co. (Vienna, Austria). The pH-sensitive fluorescent probe 2',7'-biscarboxyethyl-5(6)-carboxyfluorescein acetoxymethyl ester Mixed isomers (BCECF-AM) was obtained from Calbiochem Co. Primers were obtained from Shanghai Sangon Biotechnology. TRIzol Reagent, Superscript II ONCOLOGY REPORTS 23: 79-87, 2010

show abstract

Reduction of intracellular pH inhibits constitutive expression of Cyclooxygenase‐2 in human colon cancer cells

Cited by 11 publications

References 32 publications

Troglitazone's rapid and sustained activation of ERK1/2 induces cellular acidosis in LLC-PK₁-F⁺cells: physiological responses

Troglitazone's rapid and sustained activation of ERK1/2 induces cellular acidosis in LLC-PK₁-F⁺cells: physiological responses

14-3-3σ Expression Is an Independent Prognostic Parameter for Poor Survival in Colorectal Carcinoma Patients

Na+/H+ exchanger blockade inhibits the expression of vascular endothelial growth factor in SGC7901 cells

Contact Info

Product

Resources

About

Reduction of intracellular pH inhibits constitutive expression of Cyclooxygenase‐2 in human colon cancer cells

Cited by 11 publications

References 32 publications

Troglitazone's rapid and sustained activation of ERK1/2 induces cellular acidosis in LLC-PK1-F+cells: physiological responses

Troglitazone's rapid and sustained activation of ERK1/2 induces cellular acidosis in LLC-PK1-F+cells: physiological responses

14-3-3σ Expression Is an Independent Prognostic Parameter for Poor Survival in Colorectal Carcinoma Patients

Na+/H+ exchanger blockade inhibits the expression of vascular endothelial growth factor in SGC7901 cells

Contact Info

Product

Resources

About

Troglitazone's rapid and sustained activation of ERK1/2 induces cellular acidosis in LLC-PK₁-F⁺cells: physiological responses

Troglitazone's rapid and sustained activation of ERK1/2 induces cellular acidosis in LLC-PK₁-F⁺cells: physiological responses