Promoter Methylation of DNA Repair Genes Predicts Disease-free Survival of Gastric Adenocarcinoma after Adjuvant Radiotherapy

Low RPMB indicates better disease-free survival of adjuvant radiotherapy after radical surgery in thymoma

BACKGROUND

The current use of adjuvant radiotherapy in thymoma (THYM) following radical surgery is primarily based on clinical factors and is a subject of ongoing debate.

METHODS

We developed a new biomarker, promotor methylation burden of Deoxyribonucleic acid repair genes (RPMB), to identify patients who may benefit from adjuvant radiotherapy after complete resection in THYM. RPMB quantitatively measures the promoter methylation level of Deoxyribonucleic acid (DNA) repair genes.

RESULTS

The methylation profile of 124 patients and corresponding clinical data were retrieved from The Cancer Genome Atlas (TCGA) database. The methylation level of DNA repair genes (DRGs) was found to be significantly hypomethylated juxtaposed to other genes across the whole human genome (all P < 0.001). THYM patients with higher RPMB tended to be female (P = 1.114×10-12) and have a more advanced Masaoka stage (P = 0.034). Kaplan-Meier analysis showed that high RPMB could significantly predict a poor disease-free survival (DFS) in THYM patients who received adjuvant radiotherapy after complete resection (HR = 5.750, 95% CI: 1.213-27.251, P = 0.013). Furthermore, Cox regression analysis indicated that RPMB was the only prognostic factor significantly associated with DFS after adjuvant radiotherapy (P = 0.028).

CONCLUSIONS

Low RPMB may be a potential indicator to identify suitable patients who can benefit from adjuvant radiotherapy in THYM, sparing others from treatment toxicity.

Prediction of disease-free survival of N1/2 non-small cell lung cancer after adjuvant chemotherapy by the biomarker RPMB

No molecular biomarkers have been proven applicable in clinical practice to identify patients who can benefit from adjuvant chemotherapy in non-small cell lung cancer (NSCLC). In this study, we established a biomarker, RPMB, short for promotor methylation burden of DNA repair genes (DRGs), to identify the subgroup of patients who might benefit from adjuvant chemotherapy in NSCLC. Methylation profiles of 828 NSCLC primary tumors and their clinical information were downloaded from The Cancer Genome Atlas (TCGA) database. The RPMB for each patient after radical resection was calculated and its correlation with the prognosis of NSCLC was extensively investigated. DRGs of NSCLC were much more hypomethylated than the other genes (all p＜0.001). RPMB was defined as the ratio of methylated DRGs to the total number of all the DRGs. Patients with higher RPMB values tended to be nonsmokers, had adenocarcinoma, were female and had peripheral tumors. Subgroup analysis of forest plot among different clinical factors showed that high RPMB was significantly correlated to better disease-free survival (DFS) in pathologic N-positive patients after adjuvant chemotherapy (HR = 0.404, n = 62, p = 0.034). Notably, more superior DFS was exhibited in high RPMB NSCLCs with N1 nodal stage compared with those with low RPMB values (HR = 0.348, n = 47, p = 0.043). High RPMB might be used as a potential predictor to identify suitable N-positive NSCLC patients who can benefit from adjuvant chemotherapy after radical surgery.

DNA Methylation: An Important Biomarker and Therapeutic Target for Gastric Cancer

Gastric cancer (GC) is a very common malignancy with a poor prognosis, and its occurrence and development are closely related to epigenetic modifications. Methylation of DNA before or during gastric cancer is an interesting research topic. This article reviews the studies on DNA methylation related to the cause, diagnosis, treatment, and prognosis of gastric cancer and aims to find cancer biomarkers to solve major human health problems.