Methylation of RUNX3 and RASSF1A and the risk of Malignancy in small solitary pulmonary nodules

Background: This study aimed to evaluate the methylation of RUNX3 and RASSF1A gene promoter regions as a marker to distinguish between benign and malignant of small solitary pulmonary nodule (SPN) <= 10 mm in size. Materials and Methods: A total of 147 patients with pathologically confirmed SPNs were enrolled. DNA samples were extracted from biopsy tissues or serum. Methylation of RUNX3 and RASSF1A gene promoter regions was detected by the methylation-specific polymerase chain reaction. The expression of RUNX3 and RASSF1A in SPN tissues was detected by western blot. Results: Of the 147 patients, 89 had benign SPNs and 58 had malignant SPNs. The rate of serum RUNX3 and RASSF1A gene methylation in malignant SPNs was significantly higher than that in benign SPNs (65.5% vs. 12.3%, and 67.2% vs. 10.1%, respectively; P < 0.05). The expression of RUNX3 and RASSF1A in malignant SPN tissues was lower than that in benign SPN tissues. The hypermethylation status of RUNX3 or RASSF1A genes was not significantly associated with age, gender, and smoking. Conclusions: The methylation level of the RUNX3 and RASSF1A gene promoter regions is a promising marker for assessing SPNs.