H19 DMR methylation correlates to the progression of esophageal squamous cell carcinoma through IGF2 imprinting pathway

Abstract

Background: H19 gene has been proved to be essential for human tumor growth which contains CpG rich regions. Imprinted gene expression in many cancers is usually associated with the function of methylation. We performed this study to better understand wether H19 DMR methylation correlates to the progression of esophageal squamous cell carcinoma through IGF2 imprinting pathway.

Methods: LOI of IGF2 was detected in 276 samples, which were determined as heterozygote with ApaI polymorphism in exon 9 of IGF2 by PCR-RFLP and RT-PCR-RFLP. Methylation status of H19 DMR in informative samples was analyzed by bisulfite sequencing PCR. IGF2 expression was examined by real-time PCR and IHC.

Results: 208 ESCC patients were informative for ApaI polymorphism. 92 tumor and 30 normal tissues showed IGF2 LOI. Methylation status of H19 CBS6 was higher in patients with IGF2 LOI compared to patients with IGF2 MOI (p < 0.05). IGF2 expression in patients with IGF2 LOI was higher than patients with IGF2 MOI (p < 0.05) which was correlated with lymph node involvement, neoplastic grade and metastasis (p < 0.05).

Conclusions: Our results suggested that H19 CBS6 hypermethylation is related to the LOI of IGF2 which usually leads to an overexpression of IGF2, playing important roles in the occurrence, development as well as metastasis of ESCC. Therefore, H19 CBS6 methylation potentially represents a novel clinically relevant epigenetic marker to identify individuals at increased risk for the occurrence, progression and prognosis of ESCC.