PLOD2 induced under hypoxia is a novel prognostic factor for hepatocellular carcinoma after curative resection

Under hypoxia, tumour cells undergo genetic and adaptive changes that allow their survival. Previously, we reported that high expression of hypoxia-inducible factor (HIF)-1 was a significant predictive factor for recurrence in hepatocellular carcinoma (HCC). Hypoxia also stimulates expression of procollagen-lysine, 2-oxoglutarate 5-dioxygenase (PLOD) genes via the HIF-1 pathway.

The aim was to evaluate the relationship between hypoxia stress and expression of PLOD genes in HCC in vitro and to identify a new prognostic marker in HCC patients.

The PLOD2 expression was assessed under hypoxia in hepatoma cell lines and characterized in 139 HCC samples following hepatic resection using microarray experiments, quantitative RT-PCR and immunohistochemistry. Prognostic factors in HCC patients were assessed using univariate and multivariate analyses.

The PLOD2 expression was induced under the hypoxia in vitro. Disease-free survival in the high PLOD2 expression group of HCC patients was significantly shorter when compared with the low-expression group (P = 0.002). In a subset of HCCs, we found that the PLOD2 expression of microarray was correlated with data of quantitative RT-PCR and immunohistochemistry. Of clinicopathological factors, PLOD2 expression was significantly correlated with tumour size (P = 0.022) and macroscopic intrahepatic metastasis (P = 0.049). In univariate analysis, six prognostic factors (tumour multiplicity, macroscopic intrahepatic metastasis, histological grade, microscopic portal invasion, microscopic intrahepatic metastasis and PLOD2 expression) were significant for disease-free survival. PLOD2 expression was identified as a significant, independent factor of poor prognosis (P = 0.013).

PLOD2 is a potential novel prognostic factor for HCC patients following surgery.