Granulin-Epithelin Precursor Is an Oncofetal Protein Defining Hepatic Cancer Stem Cells

Abstract

Background and AimsIncreasing evidence has suggested that hepatocellular carcinoma (HCC) might originate from a distinct subpopulation called cancer stem cells (CSCs), which are responsible for the limited efficacy of conventional therapies. We have previously demonstrated that granulin-epithelin precursor (GEP), a pluripotent growth factor, is upregulated in HCC but not in the adjacent non-tumor, and that GEP is a potential therapeutic target for HCC. Here, we characterized its expression pattern and stem cell properties in fetal and cancerous livers.MethodsProtein expression of GEP in fetal and adult livers was examined in human and mouse models by immunohistochemical staining and flow cytometry. Liver cancer cell lines, isolated based on their GEP and/or ATP-dependent binding cassette (ABC) drug transporter ABCB5 expression, were evaluated for hepatic CSC properties in terms of colony formation, chemoresistance and tumorigenicity.ResultsWe demonstrated that GEP was a hepatic oncofetal protein that expressed in the fetal livers, but not in the normal adult livers. Importantly, GEP+ fetal liver cells co-expressed the embryonic stem (ES) cell-related signaling molecules including β-catenin, Oct4, Nanog, Sox2 and DLK1, and also hepatic CSC-markers CD133, EpCAM and ABCB5. Phenotypic characterization in HCC clinical specimens and cell lines revealed that GEP+ cancer cells co-expressed these stem cell markers similarly as the GEP+ fetal liver cells. Furthermore, GEP was shown to regulate the expression of ES cell-related signaling molecules β-catenin, Oct4, Nanog, and Sox2. Isolated GEPhigh cancer cells showed enhanced colony formation ability and chemoresistance when compared with the GEPlow counterparts. Co-expression of GEP and ABCB5 better defined the CSC populations with enhanced tumorigenic ability in immunocompromised mice.ConclusionsOur findings demonstrate that GEP is a hepatic oncofetal protein regulating ES cell-related signaling molecules. Co-expression of GEP and ABCB5 further enriches a subpopulation with enhanced CSC properties. The current data provide new insight into the therapeutic strategy.

Doxorubicin and 5-fluorouracil resistant hepatic cancer cells demonstrate stem-like properties

“…Indeed, expression of Sox-2, Oct-3/4 and Nanog is involved in the self-renewal of undifferentiated embryonic stem cells (Niwa et al 2000;Mitsui et al 2003;Chambers et al 2003), and their proteins have been implicated in the tumorigenesis of adult germ cells (Hochedlinger et al 2005), with ectopic expression causing tumor formation such as oral squamous cell carcinoma Tsai et al 2011), lung cancer , breast cancer ) and glioma (Guo et al 2011). Such gene expression has been confirmed in HCC (Zou et al 2009;Yuan et al 2010) and HCSCs (Cheung et al 2011;Xu et al 2010). The expression of CD117, CD56 and AFP has been also reported in recurrent HCC (Xu et al 2010) and tumor-propagating cells (Colombo et al 2011).…”

“…The existence of cancer stem cells (CSCs) in malignant tumors has been proposed for some decades, and much evidence supports this hypothesis. Hepatic cancer stem cells (HCSCs) have been identified and isolated from HCCs (Rountree et al 2011;Mikhail and He 2011;Cao et al 2011;Cheung et al 2011;Jia et al 2012;Yoon 2012;Shen and Cao 2012;Piao et al 2012;, and characterized by specific properties such as expression of CD133 (Suetsugu et al 2006;Yin et al 2007;Ma et al 2007), CD44, CD133 (Zhu et al 2010), CD90 (Yang et al 2008), EpCAM (Epithelial cell adhesion molecule) (Yamashita et al 2008(Yamashita et al , 2009), CD13 (Haraguchi et al 2010), OV6 (Yang et al 2008) and ALDH (Aldehyde hydrogenase) (Ma et al 2008).…”

Tirapazamine Sensitizes Hepatocellular Carcinoma Cells to Topoisomerase I Inhibitors via Cooperative Modulation of Hypoxia-Inducible Factor-1α

“…Although surgery remains the treatment of choice for hepatocellular carcinoma, tumor size and hepatic functional reservation might restrict surgical ablation. Conventional radio/chemotherapies are generally not prescribed for advanced hepatocellular carcinoma due to their low efficacies (2). We and other groups (3,4) have found that the expression of HIF-1a is increased in most hepatocellular carcinomas and is associated with poor outcomes.…”

Granulin–Epithelin Precursor Renders Hepatocellular Carcinoma Cells Resistant to Natural Killer Cytotoxicity

“…Moreover, GEP blockade with antibody could inhibit the growth of established HCC in a mouse model (10). Recently, we showed that GEP was a hepatic oncofetal protein defining a cancer stem cell (CSC) population in HCC (11). CSCs are "roots" of cancers responsible for tumor initiation and progression; they are endowed with stem cell properties, including selfrenewal, differentiation, and chemoresistance.…”