Value of 5-Hydroxymethylcytosine in HBV-Carrying High-Risk Hepatocellular Carcinoma Population: An Evaluation Based on Differential Analysis.

Objective: To clarify the application value of 5-hydroxymethylcytosine (5hmC) in evaluating the progression of chronic hepatitis B (CHB) to hepatocellular carcinoma (HCC) based on difference analysis.

Methods: A total of 180 patients were enrolled. Among them, 84 patients with chronic hepatitis B virus (HBV) infection while no progression to hepatocellular carcinoma (HCC) were included in the control group (CG), and 96 patients with HCC developed from HBV infection were included in the research group (RG). Two-thirds of the samples were used in the training set and 1/3 samples in the validation set to detect the level of 5hmC in both groups based on the modified nano-hmC-Seal technique. The expression levels of 5hmC-related genes TET2 and TET3 were quantified by qPCR, and the correlation between TET3 and 5hmC was analyzed by Pearson's correlation coefficients. Receiver operating characteristic (ROC) curves were drawn to evaluate the application value of the TET3-based 5hmC prediction model in the early diagnosis of HCC.

Results: (i) The expression of 5hmC in RG was lower than that in CG, no matter in the training set or the validation set. (ii) 5hmC was significantly enriched in the region between the transcription initiation site and the transcription end site but was depleted in the flanking region. (iii) 5hmC-related genes TET2 and TET3 were significantly downregulated in HCC patients, whether in the training set or the validation set. (iv) In both the training and validation sets, TET3 showed a positive association with 5hmC. (v) ROC analysis results showed that the 5hmC prediction model could be used to predict the progression of CHB to HCC (training set: AUC = 0.81, 0.729-0.893; validation set: AUC = 0.84, 0.739-0.936).

Conclusions: TET3 expression based on 5hmC sequencing is a landmark molecule for evaluating the progression of HCC in CHB patients, which is worthy of further study and promotion.