AM251 reverses TGF-β1-dependent decreases in E-cadherin expression.

<p>(A–C) RPTEC cells were incubated with 2 ng/ml TGF-β1 and/or 10 μM AM251, as indicated, for 24 h. (A) Total protein lysates were prepared and equal amounts of proteins (5 μg per sample) were separated by SDS-PAGE, followed by immunoblotting with an anti-E-cadherin antibody or an anti-GAPDH antibody as a loading control. (B) The results from (A) were quantified. Values are means ± SD of E-cadherin protein levels relative to those in cells with no treatment (TGF-β1(−) AM251(−)), from three independent experiments. (C) Total RNA was prepared and subjected to real-time RT-PCR to measure E-cadherin (<i>CDH1</i>) and <i>PPIA</i> mRNA levels. Values are means ± SD of the ratio of <i>CDH1</i> to <i>PPIA</i> mRNA levels, expressed relative to the ratio in cells with no treatment (TGF-β1(−) AM251(−)), from three independent experiments. Statistically significant differences are indicated (* <i>P</i> < 0.05, ** <i>P</i> < 0.01, Student’s <i>t</i>-test).</p

TGF-β signaling pathways and induction of EMT-related genes.

<p>Binding of TGF-β to the TGF-β receptor induces activation of SMAD2/3 and p38 MAPK via phosphorylation. The SMAD2/3 pathway directly activates EMT-related transcription factors including SNAIL1, whereas the p38 MAPK pathway activates these factors via AP-1. EMT related genes are then up- or downregulated.</p

AM251 suppresses <i>COL1A1</i> expression pre-induced by TGF-β1.

<p>(A and B) RPTEC cells were cultured in REGM medium containing 2 ng/ml TGF-β1 and/or 10 μM AM251, as indicated, for 24, 48, 72, or 96 h. Total RNA was prepared and subjected to real-time RT-PCR to measure <i>COL1A1</i> and <i>PPIA</i> mRNAs. Values are means ± SD of the ratio of <i>COL1A1</i> to <i>PPIA</i> mRNA levels, expressed relative to the ratio in the control (no treatment) (A) or <i>PPIA</i> mRNA levels relative to the control (no treatment) (B), from three independent experiments. Statistically significant differences from the control (A, without AM251; B, no treatment) are indicated (** <i>P</i> < 0.01, Student’s <i>t</i>-test). (C and D) RPTEC cells were incubated with 2 ng/ml TGF-β1 for 96 h in REGM medium containing REGM Single Quots and incubated with 2 ng/ml TGF-β1 and/or 10 μM AM251, as indicated, for the following 24 h in REGM medium. Total RNA was prepared and subjected to real-time RT-PCR to measure <i>COL1A1</i> and <i>PPIA</i>. Relative mRNA levels of <i>COL1A1</i> (C) and <i>PPIA</i> (D) were determined as described for (A) and (B), respectively.</p

AM251 inhibits the SMAD2/3 and p38 MAPK signaling pathways.

<p>(A) RPTEC cells were incubated with or without 2 ng/ml TGF-β1 in the presence or absence of 10 μM AM251 for 24 h. (A) Total RNA was isolated from three independent samples, pooled, and subjected to microarray analyses. Values for <i>SMAD2</i>, <i>SMAD3</i>, <i>MAPK11</i> (p38β), <i>MAPK12</i> (p38γ), <i>MAPK13</i> (p38δ), and <i>MAPK14</i> (p38) represent their gene expression changes in cells treated with TGF-β1. (B–D) RPTEC cells were incubated with or without 2 ng/ml TGF-β1 in the presence or absence of 10 μM AM251 for 1 h. (B) Total protein lysates were prepared, and equal amounts of protein (5 μg per sample) were separated by SDS-PAGE, followed by immunoblotting with anti-phopho-p38 (P-p38), anti-p38, anti-phospho-SMAD3 (P-SMAD3), or anti-SMAD3 antibodies. (C and D) The results from (B) were quantified. Values are means ± SD of phopho-p38 (C) or phospho-SMAD3 (D) levels relative to those in cells with no treatment (TGF-β1(−) AM251(−)), from three independent experiments. Statistically significant differences are indicated (** <i>P</i> < 0.01, Student’s <i>t</i>-test).</p

AM251 suppresses induction of <i>SNAILs</i>, <i>JUNB</i>, <i>FOSB</i>, <i>TGFR1</i>, and <i>TGFBs</i>.

<p>RPTEC cells were incubated with or without 2 ng/ml TGF-β1 in the presence or absence of 10 μM AM251 for 24 h. Total RNA was prepared and subjected to real-time RT-PCR to measure <i>PPIA</i> and <i>SNAIL1</i> (A), <i>SNAIL2</i> (B), <i>JUNB</i> (C), <i>FOSB</i> (D), <i>TGFBR1</i> (E), <i>TGFB2</i> (F), and <i>TGFB3</i> (G) mRNA levels. Values are means ± SD of the ratio of each gene to <i>PPIA</i> mRNA levels, expressed relative to the ratio in the control (no treatment), from three independent experiments. Statistically significant differences are indicated (* <i>P</i> < 0.05, ** <i>P</i> < 0.01, Student’s <i>t</i>-test).</p

AM251 reverses TGF-β1-induced changes in expression of EMT-related genes.

<p>RPTEC cells were incubated with or without 2 ng/ml TGF-β1 in the presence or absence of 10 μM AM251 for 24 h. Total RNA was isolated from three independent samples, pooled, and subjected to microarray analyses. Values represent gene expression changes upon treatment with TGF-β1. N.D., not detected.</p

GPR55 is not involved in EMT suppression in RPTEC cells.

<p>(A) RPTEC cells were incubated with 2 ng/ml TGF-β1 for 24 h. Total RNA was prepared and subjected to real-time RT-PCR to measure <i>GRP55</i> and <i>PPIA</i> mRNA levels. Values are means ± SD of the ratio of <i>GRP55</i> to <i>PPIA</i> mRNA levels, expressed relative to the ratio in the control (no treatment), from three independent experiments. (B) RPTEC cells were incubated with 2 ng/ml TGF-β1 in the presence or absence of the GRP55 antagonist CID16020046 (CID; Tocris Bioscience, Minneapolis, MN, USA) at the indicated concentrations and 10 μM AM251 for 24 h. Relative mRNA levels of <i>COL1A1</i> were determined as for (A). Statistically significant differences are indicated (* <i>P</i> < 0.05, ** <i>P</i> < 0.01, Student’s <i>t</i>-test).</p

CB1 is not involved in EMT suppression in RPTEC cells.

<p>(A) RPTEC cells were incubated with 2 ng/ml TGF-β1 for 24 h. Total RNA was prepared and subjected to real-time RT-PCR to measure CB1 (<i>CNR1</i>) and <i>PPIA</i> mRNA levels. Values are means ± SD of the ratio of <i>CNR1</i> to <i>PPIA</i> mRNA levels, expressed relative to the ratio in the control, from three independent experiments. (B) RPTEC cells were incubated with 2 ng/ml TGF-β1 and the CB1 agonist anandamide (ANA) at the indicated concentrations for 24 h. Relative mRNA levels of <i>COL1A1</i> were determined as for (A). (C) RPTEC cells were treated with control siRNA or a selective siRNA for <i>CNR1</i> (siCB1-1 or siCB1-2) for 72 h. Relative mRNA levels of <i>CNR1</i> were determined as for (A). (D) RPTEC cells were treated with control siRNA or selective siRNA for <i>CNR1</i> (siCB1-1 or siCB1-2) for 48 h and then incubated with 2 ng/ml TGF-β1 and 10 μM AM251 for another 24 h. Relative mRNA levels of <i>COL1A1</i> were determined as for (A). Statistically significant differences are indicated (** <i>P</i> < 0.01, Student’s <i>t</i>-test).</p

AM251 inhibits EMT with specificity.

<p>(A–C) RPTEC cells were incubated with or without 2 ng/ml TGF-β1 (TGF) in the presence or absence of 10 μM AM251 (AM) for 24 h. Total RNA was isolated from three independent samples, pooled, and subjected to microarray analyses. (A) Comparison of the microarray data was conducted on the data from AM251(−) TGF-β1(−) versus those from AM251(−) TGF-β1(+) conditions (red circles); and from AM251(+) TGF-β1(−) versus those from AM251(+) TGF-β1(+) conditions (blue circles). Numbers of upregulated (≥2-fold; left panels) and downregulated (≥2-fold; right panels) genes are depicted as Venn diagrams. (B) Hierarchical clustering analyses were performed using genes upregulated by ≥2-fold upon treatment with TGF-β1 by the centroid distance method. Yellow bars indicate that the values are similar to the averages of four different conditions. Red and blue bars indicate that the values are higher and lower than the averages, respectively, with the color strengths representing the degrees of the values. (C) Enrichment pathway analyses were conducted using genes with ≥2-fold change upon treatment with TGF-β1 and the MetaCore gene regulatory network database. The top 10 pathways are shown. PI3K, phosphoinositide 3-kinase; ILK, integrin-linked kinase; IGF, insulin-like growth factor; TNFα, tumor necrosis factor α; MAG, myelin-associated glycoprotein.</p

Imaging Mass Spectrometry Revealed the Accumulation Characteristics of the 2-Nitroimidazole-Based Agent “Pimonidazole” in Hypoxia

<div><p>Hypoxia, or low oxygen concentration, is a key factor promoting tumor progression and angiogenesis and resistance of cancer to radiotherapy and chemotherapy. 2-Nitroimidazole-based agents have been widely used in pathological and nuclear medicine examinations to detect hypoxic regions in tumors; in particular, pimonidazole is used for histochemical staining of hypoxic regions. It is considered to accumulate in hypoxic cells via covalent binding with macromolecules or by forming reductive metabolites after reduction of its nitro group. However, the detailed mechanism of its accumulation remains unknown. In this study, we investigated the accumulation mechanism of pimonidazole in hypoxic tumor tissues in a mouse model by mass spectrometric analyses including imaging mass spectrometry (IMS). Pimonidazole and its reductive metabolites were observed in the tumor tissues. However, their locations in the tumor sections were not similar to the positively stained areas in pimonidazole-immunohistochemistry, an area considered hypoxic. The glutathione conjugate of reduced pimonidazole, a low-molecular-weight metabolite of pimonidazole, was found in tumor tissues by LC-MS analysis, and our IMS study determined that the intratumor localization of the glutathione conjugate was consistent with the area positively immunostained for pimonidazole. We also found complementary localization of the glutathione conjugate and reduced glutathione (GSH), implying that formation of the glutathione conjugate occurred in the tumor tissue. These results suggest that in hypoxic tumor cells, pimonidazole is reduced at its nitro group, followed by conjugation with GSH.</p></div