Identification of PEG10 as a progression related biomarker for hepatocellular carcinoma

Widespread DNA copy number alterations are well recognized in hepatocellular carcinoma (HCC), although the affected genes expression remained largely undefined. In this study, we performed genome-wide analysis on HCC to examine the relationship between gene copy number and corresponding transcriptional changes. To ensure analysis on a homogenous population of tumor cells, integrative analysis of array-based CGH and expression profilings was performed on 20 HCC cell lines using a 19,200-element cDNA microarray platform. Further validation studies were carried out on a large series of primary HCC tumors and paired adjacent non-malignant liver to ascertain finding. Correlative analyses highlighted 31 candidate genes that manifested both copy gains and gene up-regulations (R2>0.5; p<0.05). Of interest was over-expressed paternally expressed 10 (PEG10) resided within the chromosome region 7q21 that has been implicated in the progression of HCC. Quantitative PCR and qRT-PCR studies verified concurrent genomic gains and over-expression of PEG10 in HCC cell lines and primary tumors (34/40 cases; 85%). In addition, qRT-PCR demonstrated a significant progressive trend of increasing PEG10 expressions from the putative pre-malignant adjacent livers to early resectable HCC tumors, and to late inoperable HCCs (p=0.007). In summary, the present study demonstrated the usefulness of integrated genomic and expression profilings in identifying candidate genes within regions of genomic alteration. Our results also suggested that PEG10 may be a potential biomarker in the progressive development of HCC, and that genomic gain represents one of the major mechanisms in the induction of PEG10 over-expressions.