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Fig. 1. Stem cells and cancer phenotype. Slowly renewing stem cells that exist
within a niche may be subject to mutation, and to gene silencing or
upregulated expression. This might be one reason for the delay between an
effector stimulus and the cancer phenotype appearing, and might also explain
the heterogeneity of cells in tumours. If stem cells or their progenitors
escape from the regulation of specific genes, signalling pathways might
activate genes, resulting in their escaping from apoptosis and their
activating ß-catenin, and/or oncogenes and tumour suppression
pathways.
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