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Vascular Endothelial Growth Factor Receptor-1 (VEGFR1) Is Synthetic
Lethal to Aberrant β-Catenin Activation in Colon Cancer

In a targeted RNA interference screen of the human kinome, VEGFR1/Flt1 was identified as a positive regulator of Wnt/β-catenin signaling and found to be synthetic lethal in the context of aberrant Wnt activation, such as that found in colon cancer. Even in the presence of siRNA targeting VEGFR1, immunofluorescence analysis showed nuclear translocation of β-catenin upon stimulation with Wnt. Thus, VEGFR1 likely regulates Wnt signaling at the level of posttranslational modification of β-catenin and represents a potential therapeutic target for treatment of Wnt/β-catenin-addicted cancers. Cover Image and Blurb from Clin Cancer Res 2009; 15(24): 7529-37.
Figure 1
High-throughput RNA interference screen for kinase modulators of Wnt signaling. Screen results including hits at various significance thresholds. Log(normalized photon flux) represents bioluminescence reporter signal intensity normalized for cell viability and a control nontargeting sequence placed on each plate to facilitate experiment-wide analysis. Values are plotted for siRNA against all 691 kinase targets. Log(normalized photon flux) values of <-0.37 and >0.38 score as significant based on high stringency criteria (α ≤ 0.0027; red). Values between -0.37 and -0.25, and between 0.38 and 0.26, score as significant based on lower stringency criteria (α ≤ 0.046; orange). Red triangles, hits scored at α ≤ 0.0027 in both experiment-wide and plate-by-plate analyses; blue triangle, VEGFR1/Flt1. Red circles, hits that score as significant based on high stringency criteria in experiment-wide analysis only and not in plate-by-plate analysis.
Figure 2
Inhibition of VEGFR TK activity is synthetic lethal in β-cat–addicted colon cancer cells, acting through downregulation of Wnt/β-catdependent transcriptional activation. (A) Inhibition of VEGFR TK activity selectively diminishes the viability of SW480 (filled circle) and KM12L4a (filled triangle) colon cancer cells, but not Wnt3a-stimulated STF293 cells (open square), control STF293 cells (open diamond), or non-colon cancer HeLa cells (open circle). Each cell type was treated with increasing concentrations of Inh II for 72 h before cell viability analysis with the use of an MTS assay. Data, mean ± SE of fold untreated absorbance values from two independent experiments (n = 3 each) for each concentration for each cell line. (B) reporter concentration response in STF293 cells stimulated with Wnt3a after pretreatment with increasing concentrations of Inh II. The bioluminescence photon flux was normalized to cell viability with the use of a resazurin dye-based fluorescence assay and plotted as fold untreated normalized photon flux ± propagated SE (n = 3 per concentration). Inset, in HEK293T cells transfected with pTOPFLASH, Inh II strongly attenuated β-cat-dependent transcription induced by Wnt3a (white bars) but showed a statistically significant lower effect on basal transcriptional activity in the absence of Wnt3a (black bars). The bioluminescence photon flux was normalized to cell viability with the use of a resazurin dye-based fluorescence assay and plotted as fold initial, fold untreated normalized photon flux ± propagated SE (n = 3 per concentration). *, P < 0.05, Student's t test. Two-way ANOVA also found statistically significant effects of both Wnt treatment (P < 0.05) and drug concentration (P < 0.001). (C) Inhibitory effect of 48-h exposure to increasing concentrations of Inh II on constitutively active β-cat-dependent signaling in SW480 (gray bars) and KM12L4a (black bars) colon carcinoma cells transfected with pTOPFLASH. Data, mean fold-initial, fold-untreated photon flux ± propagated SE (n = 3 per concentration). *, P < 0.05; **, P < 0.01, Student's t-test.
Reference:	Naik S, Dothager RS, Marasa J, Lewis CL, Piwnica-Worms D. Vascular Endothelial Growth Factor Receptor-1 Is Synthetic Lethal to Aberrant {beta}-Catenin Activation in Colon Cancer. Clin Cancer Res 2009; 15(24): 7529-37.	PubMed Link	Cover Image and Blurb

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