Acidic Environment Leads to ROS-Induced MAPK Signaling in Cancer Cells

Abstract

Tumor micromilieu often shows pronounced acidosis forcing cells to adapt their phenotype towards enhanced tumorigenesis induced by altered cellular signalling and transcriptional regulation. In the presents study mechanisms and potential consequences of the crosstalk between extra- and intracellular pH (pHe, pHi) and mitogen-activated-protein-kinases (ERK1/2, p38) was analyzed. Data were obtained mainly in AT1 R-3327 prostate carcinoma cells, but the principle importance was confirmed in 5 other cell types. Extracellular acidosis leads to a rapid and sustained decrease of pHi in parallel to p38 phosphorylation in all cell types and to ERK1/2 phosphorylation in 3 of 6 cell types. Furthermore, p38 phosphorylation was elicited by sole intracellular lactacidosis at normal pHe. Inhibition of ERK1/2 phosphorylation during acidosis led to necrotic cell death. No evidence for the involvement of the kinases c-SRC, PKC, PKA, PI3K or EGFR nor changes in cell volume in acidosis-induced MAPK activation was obtained. However, our data reveal that acidosis enhances the formation of reactive oxygen species (ROS), probably originating from mitochondria, which subsequently trigger MAPK phosphorylation. Scavenging of ROS prevented acidosis-induced MAPK phosphorylation whereas addition of H2O2 enhanced it. Finally, acidosis increased phosphorylation of the transcription factor CREB via p38, leading to increased transcriptional activity of a CRE-reporter even 24 h after switching the cells back to a normal environmental milieu. Thus, an acidic tumor microenvironment can induce a longer lasting p38-CREB-medited change in the transcriptional program, which may maintain the altered phenotype even when the cells leave the tumor environment.

Novel Paraoxonase 2-Dependent Mechanism Mediating the Biological Effects of the Pseudomonas aeruginosa Quorum-Sensing Molecule N -(3-Oxo-Dodecanoyl)- l -Homoserine Lactone

“…4A). Furthermore, p38 is phosphorylated in response to intracellular acidification (35). Therefore, we hypothesized that the phosphorylation of these kinases by 3OC12 treatment would be dependent on PON2.…”

Colorectal Carcinogenesis: Connecting K-RAS–Induced Transformation and CREB Activity In Vitro and In Vivo

“…A nonsense (NC) construct served as a control. The cell monolayer was incubated overnight at 37 C in complete medium and puromycin-resistant colonies were selected in medium supplemented with 3 mg puromycin/mL. Individual clones were picked after 3 weeks and subsequently expanded in individual wells.…”

“…Briefly, 5 Â 10 3 cells per well in 96-well plates were seeded in complete medium without phenol red and incubated at 37 C for the time points indicated before XTT reagent (Cell Proliferation Kit II) was added for 4 hours according to the manufacturer's instructions. Cell proliferation was quantified by determination of the absorbance of the oxidized XTT solution at 570 nm using an ELISA reader system (Dynex).…”

“…After incubation for 18 hours at 37 C, nonmigrated cells of the top insert were completely removed, whereas cells on the bottom insert surface were lysed with the CellTiter-Glo (Promega), before the ATP content was measured in a luminometer (Berthold). For invasion assays, the polycarbonate membranes were coated with Matrigel (30 mg/well; BD).…”

Src-mediated aryl hydrocarbon and epidermal growth factor receptor cross talk stimulates colon cancer cell proliferation

“…5, C and D, both anti-MMP7 and anti-HBEGF antibodies abolished TCDDinduced ERK1/2 phosphorylation. Concentrations of GM6001, GM6001NC, anti-MMP7, and anti-HBEGF used in these experiments were those previously shown to inhibit transactivation of EGFR in colon cancer cell lines (7,9,35,44). In addition, because generation of reactive oxygen species (ROS) may be required for transactivation of EGFR (35), we examined the actions of Tiron, a ROS scavenger.…”