Lactate Dehydrogenase-5 (LDH-5) Expression in Human Gastric Cancer: Association with Hypoxia-Inducible Factor (HIF-1α) Pathway, Angiogenic Factors Production and Poor Prognosis

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Abstract
Lactate-dehydrogenase-5 (LDH-5) is an important isoenzyme converting pyruvate to lactate under hypoxic conditions and might play an important role in the development and progression of malignancies. However, the role of LDH-5 in gastric cancer is still unclear. In this study, we investigated the clinical significance of LDH-5 expression in gastric carcinoma. LDH-5 expression in 152 patients with different grade and stage gastric carcinoma was analyzed by immunohistochemistry. In addition, hypoxia-inducible factor 1α (HIF-1α) as a marker of tumor hypoxia, as well as vascular endothelial growth factor (VEGF) and cyclooxygenase-2 (COX-2) as angiogenesis parameters were also assessed in this study. Correlations between the expression of investigated proteins and various clinicopathological factors including survival were determined. There were 94 cases (61.8%) showing high LDH-5 expression, and 95 patients (62.5%) had high HIF-1α expression. Positive correlation was found between LDH-5 expression and HIF-1α, VEGF, and COX-2. The overexpression of LDH-5 was more prevalent in advanced tumors having positive vessel invasion. Patients with overexpression of LDH-5 showed far lower disease-free (63.5% vs 82.7%) and overall (56.3% vs 78.4%) survival rates compared with patients with low LDH-5 expression. HIF-1α expression was shown to have no significance on survival. In multivariate analysis, high LDH-5 expression kept its independence as a negative prognostic indicator. The results of the current study show that LDH-5 expression may be a useful prognostic factor for patients with gastric carcinoma.