Radiotherapy is widely used to treat human cancer. Patients locally recurring after radiotherapy, however, have increased risk of metastatic progression and poor prognosis. The clinical management of post-radiation recurrences remains an unresolved issue. Tumors growing in pre-irradiated tissues have an increased fraction of hypoxic cells and are more metastatic, a condition known as tumor bed effect. Here we demonstrate that tumor cells growing in a pre-irradiated bed, or selected in vitro though repeated cycles of severe hypoxia, retain an invasive and metastatic capacities when returned to normoxia. HIF activity, while it facilitates metastatic spreading of tumors growing in a pre-irradiated bed, is not essential. Through gene expression profiling and gain and loss of function experiments, we identified the matricellular protein CYR61 and aVb5 integrin, as proteins cooperating to mediate these effects. Inhibition of aVb5 integrin suppressed invasion and metastasis induced by CYR61 and attenuated metastasis of tumors growing within a pre-irradiated field. These results represent a conceptual advance to the understanding of the tumor bed effect and identify CYR61 and aVb5 integrin as proteins that co-operate to mediate metastasis. They also indicate aV integrin inhibition a potential therapeutic approach for preventing metastasis in patients at risk for post-radiation recurrences, which can be promptly tested in the clinic.
CYR61 and alphaVbeta5 integrin cooperate to promote invasion and metastasis of tumors growing in preirradiated stroma.
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View SamplesThe Wnt signaling pathway is deregulated in over 90% of human colorectal cancers. Catenin, the central signal transducer of the Wnt pathway, can directly modulate gene expression by interacting with transcription factors of the TCF/LEF-family. In the present study we investigate the role of Wnt signaling in the homeostasis of intestinal epithelium using tissue-specific, inducible beta-catenin gene ablation in adult mice. Block of Wnt/beta-catenin signaling resulted in rapid loss of transient-amplifying cells and crypt structures. Importantly, intestinal stem cells were induced to terminally differentiate upon deletion of beta-catenin resulting in a complete block of intestinal homeostasis and fatal loss of intestinal function. Transcriptional profiling of mutant crypt mRNA isolated by laser capture micro dissection confirmed those observations and allowed to identify genes potentially responsible for the functional preservation of intestinal stem cells.
Wnt/beta-catenin is essential for intestinal homeostasis and maintenance of intestinal stem cells.
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View SamplesTo investigate the impact of ablating Bcl9/Bcl9l on tumorigenesis, 6-8- week-old mice were exposed first to a single dose dimethylhydrazine (DMH, 44 mg/kg body weight), which is metabolized in the liver to carcinogenic azoxymethane (AOM), followed by 7 days oral administration of 2 % dextrane sulfate sodium (DSS) in the drinking water. This regimen results in the emergence of dysplastic adenomas, which progress to differentiated adenocarcinomas that are morphologically similar to human colorectal adenocarcinomas and typically harbor -catenin stabilizing mutations of GSK3 phosphorylation sites. Accordingly, these tumors present hallmarks of active Wnt signaling such as accumulation of nuclear -catenin and expression of Wnt target genes.
Bcl9/Bcl9l are critical for Wnt-mediated regulation of stem cell traits in colon epithelium and adenocarcinomas.
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View SamplesTo assess potential changes in Wnt signaling more comprehensively, EDTA-dissociated colon epithelial cells from three pools of wild-type and Bcl9/Bcl9l-mutant mice were subjected to an exploratory comparative gene expression profiling.
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