Circulating methylated THBS1 DNAs as a novel marker for predicting peritoneal dissemination in gastric cancer

Abstract

Objectives: Thrombospondin 1 (THBS1) is known to play a key role in tumor metastasis, and aberrant DNA methylation is one of the mechanisms regulating THBS1. The present study investigated whether methylated THBS1 in circulating cell-free DNA from preoperative peritoneal lavage fluid (PPLF) and peripheral blood could be used as a potential biomarker for predicting peritoneal dissemination in gastric cancer (GC) patients.

Methods: The status of THBS1 methylation was detected by quantitative methylation-specific PCR (MSP) in tumor tissues, paired PPLF, and serum from 92 GC patients. The correlation between methylated THBS1 levels and peritoneal dissemination of GC was studied, and its diagnostic value for predicting peritoneal dissemination was clarified by the receiver operating characteristic (ROC) curve.

Results: Aberrant THBS1 methylation in tumor tissues was significantly higher than that in paracancerous normal tissues (p < 0.0001). No THBS1 methylation was found in 40 healthy controls, and partial methylation was detected in 3 of 48 patients with chronic non-atrophic gastritis. The frequency of THBS1 methylation in pairing PPLF and serum from 92 GC patients was 52.2% (48/92) and 58.7% (54/92), respectively. The results of methylated THBS1 in pairing PPLF and serum were similar to those of tumor tissues. Aberrant THBS1 methylation in tumor tissues and pairing PPLF or serum was closely related to peritoneal dissemination, tumor progression, and poor prognosis (all p < 0.0001).

Conclusion: Circulating methylated THBS1 DNAs in PPLF/serum may predict peritoneal dissemination, a potential poor prognostic factor for GC patients.

Keywords: THBS1 gene; gastric carcinoma; methylation; peritoneal dissemination; prognosis.

FIGURE 1

Comparison of THBS1 methylation in GC tissues, paired preoperative peritoneal lavage fluid (PPLF), and serum samples (T: tumor tissues; P: preoperative peritoneal lavage fluid (PPLF); and S: serum). The figure only showed % methylation of tumor tissue in GC, and Ⅰ‐Ⅳ represent the clinical staging

FIGURE 2

Correlation analysis of THBS1 methylation results between GC tissues and paired PPLF or paired serum (A: correlation of THBS1 methylation results between GC tissues and paired PPLF (γ = 0.9673, p < 0.0001); B: correlation of THBS1 methylation results between GC tissues and paired serum (γ = 0.9521, p < 0.0001))

FIGURE 3

Diagnostic value of THBS1 methylation in GC tissues, PPLF, and serum for the peritoneal dissemination of GC and its effect on patient prognosis (A–C): The diagnostic value of THBS1 methylation in GC tissues, paired PPLF, and serum for peritoneal dissemination of GC was determined by ROC curves, of which the Aζ value of the ROC curve was 0.8234 for GC tissues, 0.8331 for PPLF, and 0.8053 for serum compared with positive PPLF cytology. (D–F): THBS1 methylation in GC tissues, PPLF, and serum correlated with patient prognosis. Cumulative DFS curves were plotted against THBS1 methylation level in GC tissues (D), PPLF (E), and serum (F). In D, E, and F, Kaplan‐Meier analysis was used, and all parameters were p < 0.0001