Silibinin strongly inhibits the growth kinetics of colon cancer stem cell-enriched spheroids by modulating interleukin 4/6-mediated survival signals
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Sushil Kumar1,*, Komal Raina1,2*, Chapla Agarwal1,2 and Rajesh Agarwal1,2
1 Department of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences,
2 University of Colorado Cancer Center, University of Colorado Anschutz Medical Campus, Aurora, Colorado
* These Authors Contributed equally and share first authorship
Rajesh Agarwal, email:
Keywords: colorectal cancer, silibinin, cancer chemoprevention, cancer stem cells
Received: May 1, 2014 Accepted: June 5, 2014 Published: June 6, 2014
Involvement of cancer stem cells (CSC) in initiation, progression, relapse, and therapy-resistance of colorectal cancer (CRC) warrants search for small molecules as ‘adjunct-therapy’ to target both colon CSC and bulk tumor population. Herein, we assessed the potential of silibinin to eradicate colon CSC together with associated molecular mechanisms. In studies examining how silibinin modulates dynamics of CSC spheroids in terms of its effect on kinetics of CSC spheroids generated in presence of mitogenic and interleukin (IL)-mediated signaling which provides an autocrine/paracrine amplification loop in CRC, silibinin strongly decreased colon CSC pool together with cell survival of bulk tumor cells. Silibinin effect on colon CSC was mediated via blocking of pro-tumorigenic signaling, notably IL-4/-6 signaling that affects CSC population. These silibinin effects were associated with decreased mRNA and protein levels of various CSC-associated transcription factors, signaling molecules and markers. Furthermore, 2D and 3D differentiation assays indicated formation of more differentiated clones by silibinin. These results highlight silibinin potential to interfere with kinetics of CSC pool by shifting CSC cell division to asymmetric type via targeting various signals associated with the survival and multiplication of colon CSC pool. Together, our findings further support clinical usefulness of silibinin in CRC intervention and therapy.
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