Tumor-initiating cells (T-ICs) are a subpopulation of chemoresistant tumor cells that have been shown to cause tumor recurrence upon chemotherapy. Identification of T-ICs and their related pathways are therefore priorities for the development of new therapeutic paradigms. We established chemoresistant hepatocellular carcinoma (HCC) xenograft tumors in immunocompromised mice in which an enriched T-IC population was capable of tumor initiation and self-renewal. With this model, we found CD24 to be upregulated in residual chemoresistant tumors when compared with bulk tumor upon cisplatin treatment. CD24(+) HCC cells were found to be critical for the maintenance, self-renewal, differentiation, and metastasis of tumors and to significantly impact patients' clinical outcome. With a lentiviral-based knockdown approach, CD24 was found to be a functional liver T-IC marker that drives T-IC genesis through STAT3-mediated NANOG regulation. Our findings point to a CD24 cascade in liver T-ICs that may provide an attractive therapeutic target for HCC patients.

Liver tumor-initiating cells (T-ICs) are capable of self-renewal and tumor initiation and are more chemoresistant to chemotherapeutic drugs. The current therapeutic strategies for targeting stem cell self-renewal pathways therefore represent rational approaches for cancer prevention and treatment. In the present study, we found that Lup-20(29)-en-3b-ol (lupeol), a triterpene found in fruits and vegetables, inhibited the self-renewal ability of liver T-ICs present in both hepatocellular carcinoma (HCC) cell lines and clinical HCC samples, as reflected by hepatosphere formation. Furthermore, lupeol inhibited in vivo tumorigenicity in nude mice and down-regulated CD133 expression, which was previously shown to be a T-IC marker for HCC. In addition, lupeol sensitized HCC cells to chemotherapeutic agents through the phosphatase and tensin homolog (PTEN)-Akt-ABCG2 pathway. PTEN plays a crucial role in the self-renewal and chemoresistance of liver T-ICs; down-regulation of PTEN by a lentiviral-based approach reversed the effect of lupeol on liver T-ICs. Using an in vivo chemoresistant HCC tumor model, lupeol dramatically decreased the tumor volumes of MHCC-LM3 HCC cell line-derived xenografts, and the effect was equivalent to that of combined cisplatin and doxorubicin treatment. Lupeol exerted a synergistic effect without any adverse effects on body weight when combined with chemotherapeutic drugs. Conclusion: Our results suggest that lupeol may be an effective dietary phytochemical that targets liver T-ICs. (HEPATOLOGY 2011;53:160-170)

Anti-CD47 antibody treatment could complement chemotherapy which may be a promising therapeutic strategy for the treatment of HCC patients.