Cancer stem cell generation during epithelial-mesenchymal transition is temporally gated by intrinsic circadian clocks

AbstractEpithelial-mesenchymal transition (EMT) is a key event preceding tumor cell metastasis that increases cell invasiveness and cancer stem cell (CSC)  populations. Studies suggest that genes used in generating circadian rhythms also serve in regulating EMT. To test the role of circadian clocks in cellular EMT events two cancer cell lines were compared, one that has a well-established circadian clock, C6 from rat glioma, and one that does not, MC F-7 from human breast tumor. MCF-7 tumorsphere cultures were tested for evidence of circadian rhythms because of previously reported circadian rhythm enhancement in C6 tumorspheres shown by elevated rhythm amplitude and increased expression of circadian clock gene Per2. Bioluminescence imaging of Pe r2 gene expression in MCF-7 tumorspheres revealed a previously unconfirmed circadian clock in this important cancer research model. Inducing CSC generation through EMT in C6 and MCF-7 monolayer cultures revealed circadian oscillations in the size of the post-EMT CSC population, confirming that cir cadian rhythms are additional processes controlling this stage of cancer progression. EMT was verified by distinct cellular morphological changes and expression of stem cell proteins OCT4, nestin, MSI1, and CD133 along with EMT-related proteins ZEB1, vimentin, and TWIST. Quantifying single-cell eve nts and behaviors through time-lapse imaging indicated the post-EMT population size was determined largely by circadian rhythms in epithelial...
Source: Clinical and Experimental Metastasis - Category: Cancer & Oncology Source Type: research