Abstract #1445: Molecular and clinical characterization of hepatocellular carcinoma with progenitor cell markers

Abstract

Background: Recent reports support the role of cancer stem cells in the molecular pathogenesis of hepatocellular carcinoma (HCC), and suggest that progenitor cell markers categorize a subgroup of tumors with poorer prognosis. Objectives: (1) To explore the molecular alterations of a subgroup of human HCC with progenitor cell markers, and (2) to determine the clinical outcome of these tumors. Methods: A total of 326 human HCC samples were analyzed in two sets (n=77 HCV-related HCCs, and n=249 HCCs from patients with multiple etiologies). Progenitor cell markers (EpCAM, CK-19, c-KIT and CD133) were assessed by immunostaining, and correlated with annotated data from copy number changes (Affymetrix 500K Sty-array), gene expression (Affymetrix U133 Plus 2.0 and Taqman Probes) and signaling pathway activation (WNT-ßcatenin, EGFR, RAS and IGF-Akt-mTOR signaling). Dysregulated gene sets and specific signatures associated with progenitor cell markers were obtained using GSEA and SAMR packages, respectively. Correlations between CK19+ and EpCAM+ samples with clinico-pathological features and patient outcome were evaluated using Kaplan-Meier curves and Cox Proportional Hazard Test. Results: EpCAM and CK19 staining were present in 14/77 (18.1%) and 9/77 (11.9%) HCCs, respectively, whereas c-KIT was positive in no-tumoral cells in 15% of cases and CD133 was negative in all samples. CK19 and EpCAM staining were highly correlated (P=0.001), and significantly clustered in the proliferation subclass of the molecular classification of HCC (Chiang et al. Cancer Res 2008, P=0.01). EpCAM and CK19 were associated with p-AKT staining (P=0.01). GSEA revealed a significant dysregulation of cell cycle genes and PI3K signaling in CK19-positive samples. These samples were associated with higher AFP levels (P<0.01) and macrovascular invasion (P=0.04), whereas EpCAM-positive samples were enriched in multinodular tumors (38% vs 12%, P=0.03). The CK19 gene signature was present in 27% of the samples in the validation set, and was enriched in the proliferation class (P<0.0001). Regarding outcome correlation, CK19+ (HR: 4.1, p=0.004), satellites (HR: 2.3, p=0.0001) and multinodular HCCs (HR: 1.8, p=0.011) were independently associated with recurrence in the multivariate analysis of the validation set. Conclusion: There is a subgroup of HCC patients (15%) characterized by molecular features of progenitor cells. These tumors belong to the proliferation subgroup of the current molecular classification of HCC, are associated with macrovascular invasion and multinodularity and have a worse clinical outcome.

Citation Information: In: Proc Am Assoc Cancer Res; 2009 Apr 18-22; Denver, CO. Philadelphia (PA): AACR; 2009. Abstract nr 1445.