Higher LPA2 and LPA6 mRNA Levels in Hepatocellular Carcinoma Are Associated with Poorer Differentiation, Microvascular Invasion and Earlier Recurrence with Higher Serum Autotaxin Levels

PLoS One. 2016 Sep 1;11(9):e0161825. doi: 10.1371/journal.pone.0161825. eCollection 2016.

Abstract

Hepatocellular carcinoma (HCC) commonly develops in patients with liver fibrosis; in these patients, the blood levels of lysophosphatidic acid (LPA) and its generating enzyme autotaxin (ATX) increase with the liver fibrosis stage. We aimed to examine the potential relevance of ATX and LPA in HCC. Fifty-eight HCC patients who underwent surgical treatment were consecutively enrolled in the study. Among the LPA receptors in HCC, higher LPA2 mRNA levels correlated with poorer differentiation, and higher LPA6 mRNA levels correlated with microvascular invasion, which suggested a higher malignant potential of HCC with increased LPA2 and LPA6 expression. In patients with primary HCC, neither LPA2 nor LPA6 mRNA levels were associated with recurrence. However, when serum ATX levels were combined for analysis as a surrogate for plasma LPA levels, the cumulative intra-hepatic recurrence rate was higher in patients in whom both serum ATX levels and LPA2 or LPA6 mRNA levels were higher than the median. However, the mRNA level of phosphatidic acid-selective phospholipase A1ɑ, another LPA-generating enzyme, in HCC patients was not associated with pathological findings or recurrence, even in combination with the expression of LPA receptors. Higher LPA2 mRNA levels were associated with poorer differentiation, and higher LPA6 levels were associated with microvascular invasion in HCC; both became a risk factor for recurrence after surgical treatment when combined with increased serum ATX levels. ATX and LPA receptors merit consideration as therapeutic targets of HCC.

MeSH terms

  • Aged
  • Carcinoma, Hepatocellular / blood
  • Carcinoma, Hepatocellular / blood supply
  • Carcinoma, Hepatocellular / pathology*
  • Cell Differentiation*
  • Female
  • Humans
  • Liver Neoplasms / blood
  • Liver Neoplasms / blood supply
  • Liver Neoplasms / pathology*
  • Male
  • Middle Aged
  • Neovascularization, Pathologic*
  • Phosphoric Diester Hydrolases / blood*
  • RNA, Messenger / metabolism*
  • Receptors, Lysophosphatidic Acid / genetics*

Substances

  • RNA, Messenger
  • Receptors, Lysophosphatidic Acid
  • Phosphoric Diester Hydrolases
  • alkylglycerophosphoethanolamine phosphodiesterase

Grants and funding

This work was supported by JSPS KAKENHI Grant Number 15H05906 (Y.Y.) and CREST from JST/AMED. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.