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Analysis of Circadian Properties and Clock Regulation of Glioma and Breast Cancer Stem Cells

Sharma, Vishal Premdev
http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1416521259

Abstract Details

2014, Doctor of Philosophy (Ph.D.), Bowling Green State University, Biological Sciences.
Increased cancer risk is linked to disruption of circadian rhythms. Cancer stem cells (CSCs) are a known cause of cancer aggressiveness, but their circadian properties have not been described. In this study we describe the circadian properties of C6 rat glioma tumorspheres and MCF-7 human breast CSCs. We discovered circadian rhythms in gene expression within C6 glioma tumorspheres enriched in CSCs and found that the circadian clock is particularly robust in medium lacking any growth factors. A method is introduced for identifying individual CSCs in culture for single-cell analysis. CSCs in monolayer, attached cell cultures failed to show a circadian rhythm in nuclear localization of mPER2 protein, suggesting that cell interactions or the tumor-like microenvironment within tumorspheres enable circadian timing. The MCF-7 cancer cell line, derived from an epithelial breast tumor, has been widely studied because of its aggressiveness and high percentage of CSCs. Although several cancer cell lines have distinct circadian rhythms in gene expression, the reason why many other lines apparently lack circadian clocks remains unclear. Similarly, circadian rhythms of cells within tumors are also often poorly organized or absent. Considering the cell heterogeneity of cancer cell lines, including CSCs within these lines, it seemed likely that some of the cells could retain a functional circadian clock. To test this idea, we probed the circadian properties of MCF-7 cultures with a reporter gene that expresses a functional mPER2 protein fused with firefly luciferase under the control of the mouse Per2 promoter. MCF-7 cells grew as small clusters in medium containing fetal bovine serum or one containing growth factors stimulating CSC proliferation. The percentage of clusters expressing the mPer2 gene was surprisingly high, and at least 60% of these expressed a circadian rhythm. Reporter gene expression and Per2 mRNA were elevated in response to growth factors that prevent CSC differentiation. Despite previous reports suggesting otherwise, these results indicate that circadian clocks could have a functional role in MCF-7 breast cancer cells and that these clocks were previously undetected. Alternatively, the mouse mPer2 transfection may have rescued MCF-7 cells from an arrhythmic state. The presence of circadian rhythms in C6 and MCF-7 cultures enriched in CSCs suggests that there may be links between circadian clock genes and genes that inhibit CSC differentiation. These interactions should be tested further and might be used to develop novel therapeutic approaches for suppressing tumor growth by targeting CSCs.
Michael Geusz, Ph.D. (Advisor)
Rogers Scott, Ph.D. (Committee Member)
Moris Paul, Ph.D. (Committee Member)
Maltese William, Ph.D. (Committee Member)
Anzenbacher Pavel, Ph.D. (Other)
142 p.
Biology; Cellular Biology; Molecular Biology
Cancer Stem Cell; Circadian rhythms; Glioma; C6; Breast cancer; MCF-7; Hes-1; Bmi-1

Recommended Citations

Citations

  • Sharma, V. P. (2014). Analysis of Circadian Properties and Clock Regulation of Glioma and Breast Cancer Stem Cells [Doctoral dissertation, Bowling Green State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1416521259

    APA Style (7th edition)

  • Sharma, Vishal. Analysis of Circadian Properties and Clock Regulation of Glioma and Breast Cancer Stem Cells. 2014. Bowling Green State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1416521259.

    MLA Style (8th edition)

  • Sharma, Vishal. "Analysis of Circadian Properties and Clock Regulation of Glioma and Breast Cancer Stem Cells." Doctoral dissertation, Bowling Green State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1416521259

    Chicago Manual of Style (17th edition)

bgsu1416521259
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© 2014, all rights reserved.
This open access ETD is published by Bowling Green State University and OhioLINK.