The hepatocellular carcinoma-initiating cells (HCICs) confer hepatocellular carcinoma (HCC) initiating, progression, and multi-drugs resistance. Here, we investigated icaritin on its efficacy to inhibit HCICs and its potential mechanism.
Studies of tumorsphere formation and tumor seeding ability were used to determine whether icaritin targets HCICs. Flow cytometry and qRT-PCR assays were conducted to evaluate HCC stem cells proportion. The activation of Interleukin-6 Receptors (IL-6Rs)/ Janus-activated kinases 2 (Jak2)/ Signal transducer and activator of transcription 3 (Stat3) signaling axis was detected with western blots and immunohistochemistry. Stat3 knockdown and overexpression experiments were used to decipher Stat3's critical role in icaritin effects. Finally, the in vivo activity of icaritin was measured with immunodeficient xenograft mouse models.
Icaritin inhibited primary and secondary formation of HCC tumorspheres. The pretreatment with icaritin decreased the proportion of EpCAM-positive (a HCICs marker) HCC cells and attenuated tumor incidence in immunodeficient mice. Icaritin reduced expression of IL-6Rs, attenuated phosphorylation of Jak2 and Stat3, and inhibited Stat3 regulated genes. The expression level of HCC stemness genes, including Bmi-1 and Oct4, decreased upon icaritin treatment. The inhibitory effect of icaritin on tumorsphere was increased by siRNA-mediated silencing of Stat3 and attenuated by overexpression of Stat3. In vivo, the growth of HCC cells PLC/PRF/5 and the patient derived recurrent cells Hep-12 were inhibited upon icaritin treatment accompanied with inactivation of Stat3 signaling.
Icaritin inhibits HCICs through suppressing IL-6Rs/Jak2/Stat3 axis. These findings provide support for the development of icaritin as a novel and effective agent for HCC.
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All authors have declared no conflicts of interest.