Dataset Information

EpCAM-positive hepatocellular carcinoma cells are tumor-initiating cells with stem/progenitor cell features.

ABSTRACT:

Background & aims

Cancer progression/metastases and embryonic development share many properties including cellular plasticity, dynamic cell motility, and integral interaction with the microenvironment. We hypothesized that the heterogeneous nature of hepatocellular carcinoma (HCC), in part, may be owing to the presence of hepatic cancer cells with stem/progenitor features.

Methods

Gene expression profiling and immunohistochemistry analyses were used to analyze 235 tumor specimens derived from 2 recently identified HCC subtypes (EpCAM(+) alpha-fetoprotein [AFP(+)] HCC and EpCAM(-) AFP(-) HCC). These subtypes differed in their expression of AFP, a molecule produced in the developing embryo, and EpCAM, a cell surface hepatic stem cell marker. Fluorescence-activated cell sorting was used to isolate EpCAM(+) HCC cells, which were tested for hepatic stem/progenitor cell properties.

Results

Gene expression and pathway analyses revealed that the EpCAM(+) AFP(+) HCC subtype had features of hepatic stem/progenitor cells. Indeed, the fluorescence-activated cell sorting-isolated EpCAM(+) HCC cells displayed hepatic cancer stem cell-like traits including the abilities to self-renew and differentiate. Moreover, these cells were capable of initiating highly invasive HCC in nonobese diabetic, severe combined immunodeficient mice. Activation of Wnt/beta-catenin signaling enriched the EpCAM(+) cell population, whereas RNA interference-based blockage of EpCAM, a Wnt/beta-catenin signaling target, attenuated the activities of these cells.

Conclusions

Taken together, our results suggest that HCC growth and invasiveness is dictated by a subset of EpCAM(+) cells, opening a new avenue for HCC cancer cell eradication by targeting Wnt/beta-catenin signaling components such as EpCAM.

SUBMITTER: Yamashita T

PROVIDER: S-EPMC2828822 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BACKGROUND:The relationship between specific genome alterations and hepatocellular carcinoma (HCC) cancer stem cells (CSCs) remains unclear. In this study, we evaluated the relationship between somatic mutations and epithelial cell adhesion molecule positive (EpCAM+) CSCs. METHODS:Two patient-derived HCC samples (HCC1 and HCC2) were sorted by EpCAM expression and analyzed by whole exome sequence. We measured PCDH18 expression level in eight HCC cell lines as well as HCC1 and HCC2 by real-time quantitative RT-PCR. We validated the identified gene mutations in 57 paired of HCC and matched non-cancerous liver tissues by Sanger sequence. RESULTS:Whole exome sequencing on the sorted EpCAM+ and EpCAM- HCC1 and HCC2 cells revealed 19,263 nonsynonymous mutations in the cording region. We selected mutations that potentially impair the function of the encoded protein. Ultimately, 60 mutations including 13 novel nonsense and frameshift mutations were identified. Among them, PCDH18 mutation was more frequently detected in sorted EpCAM+ cells than in EpCAM- cells in HCC1 by whole exome sequences. However, we could not confirm the difference of PCDH18 mutation frequency between sorted EpCAM+ and EpCAM- cells by Sanger sequencing, indicating that PCDH18 mutation could not explain intracellular heterogeneity. In contrast, we found novel PCDH18 mutations, including c.2556_2557delTG, c.1474C>G, c.2337A>G, and c.2976G>T, were detected in HCC1 and 3/57 (5.3%) additional HCC surgical specimens. All four HCCs with PCDH18 mutations were EpCAM-positive, suggesting that PCDH18 somatic mutations might explain the intertumor heterogeneity of HCCs in terms of the expression status of EpCAM. Furthermore, EpCAM-positive cell lines (Huh1, Huh7, HepG2, and Hep3B) had lower PCDH18 expression than EpCAM-negative cell lines (PLC/PRL/5, HLE, HLF, and SK-Hep-1), and PCDH18 knockdown in HCC2 cells slightly enhanced cell proliferation. CONCLUSIONS:Our data suggest that PCDH18 is functionally suppressed in a subset of EpCAM-positive HCCs through somatic mutations, and may play a role in the development of EpCAM-positive HCCs.