Lactate Dehydrogenase A as a Potential New Biomarker for Thyroid Cancer

Abstract

Background: Several cancers show increased levels of lactate dehydrogenase A (LDHA), which are associated with cancer progression. However, it remains unclear whether LDHA levels are associated with papillary thyroid cancer (PTC) aggressiveness or with the presence of the PTC prognostic marker, the BRAFV600E mutation. This study aimed to evaluate the potential of LDHA as a PTC prognostic marker.

Methods: LDHA expression was examined in 83 PTC tissue specimens by immunohistochemistry. Human thyroid cell lines were genetically manipulated to overexpress BRAFV600E or were treated with a BRAF-specific short hairpin RNA (shBRAF), whose effects on LDHA expression were evaluated by Western blotting. Data from 465 PTC patients were obtained from The Cancer Genome Atlas (TCGA) database and analyzed to validate the in vitro results.

Results: LDHA was aberrantly overexpressed in PTC. Intense immunostaining for LDHA was observed in PTC specimens carrying mutated BRAF, whereas the intensity was less in wild-type BRAF samples. Overexpression of BRAFV600E resulted in LDHA upregulation, whereas treatment with shBRAF downregulated LDHA in human thyroid cell lines. Furthermore, LDHA mRNA expression was significantly elevated and associated with BRAFV600E expression in thyroid cancer tissues from TCGA database. Additionally, LDHA overexpression was found to be correlated with aggressive clinical features of PTC, such as lymph node metastases and advanced tumor stages.

Conclusion: LDHA overexpression is associated with the BRAFV600E mutation and an aggressive PTC behavior. Therefore, LDHA may serve as a biomarker and therapeutic target in PTC.

Keywords: BRAF; Biomarkers; Lactate dehydrogenase A; Prognosis; Thyroid cancer, papillary.

Fig. 1

Lactate dehydrogenase A (LDHA) expression in normal and tumor tissues analyzed by immunohistochemistry. (A) Normal thyroid tissue; (B) weakly, (C) intermediately, and (D) strongly stained papillary thyroid carcinoma tissues (×400).

Fig. 2

Protein expression in Nthy-ori 3-1 cells stably expressing the wild-type (WT) BRAF or BRAF with the V600E mutation. (A) Photomicrographs of BRAF^V600E- and WT BRAF-overexpressing cells. (B) BRAF, extracellular signal-regulated kinase (ERK), phosphorylated ERK (pERK), lactate dehydrogenase A (LDHA), and β-actin levels in BRAF^V600E- and WT BRAF-overexpressing cells. The blot is representative of three independent experiments.

Fig. 3

Lactate dehydrogenase A (LDHA) expression in human thyroid cell lines after BRAF-specific short hairpin RNA (shBRAF) treatment. (A) SNU-790 and (B) 8505c cells. Each blot is representative of three independent experiments.

Fig. 4

mRNA expression of glycolytic enzyme-encoding genes based on The Cancer Genome Atlas thyroid cancer database. (A) Glucose transporter 1 (GLUT1), (B) pyruvate kinase isoform M2 (PKM2), and (C) lactate dehydrogenase A (LDHA) expression levels in 465 papillary thyroid carcinoma and 55 normal thyroid tissues. Data are presented as the individual value, median, and interquartile range. RSEM, RNA-Seq by expectation-maximization.

Fig. 5

Lactate dehydrogenase A (LDHA) gene expression levels according to the BRAF^V600E mutational status or papillary thyroid cancer (PTC) subtype, based on The Cancer Genome Atlas (TCGA) thyroid cancer database. (A) LDHA mRNA expression levels in BRAF wild-type (WT) and V600E mutant PTC. (B) LDHA mRNA expression levels according to the subtype of PTC. Data are presented as the individual value, median, and interquartile range. RSEM, RNA-Seq by expectation-maximization. ^aClassic, classical/usual; ^bFV, follicular (≥99% follicular patterned); ^cTV, tall-cell (≥50% tall cell features); ^dOther, uncommon PTC variants.