Low level of 5-Hydroxymethylcytosine predicts poor prognosis in non-small cell lung cancer

The loss of 5-hydroxymethylcytosine (5-hmC) has previously been demonstrated to be implicated in the initiation and progression of various tumors. However, its role in non-small cell lung cancer (NSCLC) remains unknown. The present study aimed to determine the level of 5-hmC in NSCLC and their adjacent normal lung tissues by immunohistochemistry and dot-blot analysis; then the relationship between 5-hmC level and the clinicopathological features of NSCLC and the prognostic significance of 5-hmC level in NSCLC patients were analyzed. By employing the dot-blot analysis, a significant reduction of 5-hmC level in NSCLC tissues compared with the adjacent normal tissues was detected, which were further verified by the immunohistochemistry results on tissue microarrays. Further analyses demonstrated that 65.38% (136/208) presented with low 5-hmC level, and low 5-hmC level was significantly associated with lymph node metastasis (P<0.001), histological type (P<0.001) and large tumor size (P=0.031). Notably, the 5-year overall survival rate of patients with low 5-hmC levels were significantly lower than patients with high 5-hmC levels (P<0.001). In addition, it was demonstrated that 5-hmC level was identified as independent prognostic factor in patients' overall survival. In conclusion, downregulation of 5-hmC may serve as a useful biomarker for NSCLC prognosis evaluation.