TET1 methylation and mRNA expression in renal cell carcinoma: implications for tumor staging and prognosis

Abstract

Background: Renal cell carcinoma (RCC) is a prevalent cancer characterized by intricate molecular mechanisms that contribute to its advancement. Epigenetic alterations, particularly DNA methylation, play a critical role in cancer development. This research examines TET1 gene methylation's involvement in RCC development and its viability as a diagnostic marker.

Methods: We evaluated TET1 expression in 532 RCC tumor samples and 72 adjacent normal tissues using data from the TCGA database. A clinical case-control study involving 40 RCC patients and matched controls was conducted to evaluate TET1 methylation at nine CpG sites in the promoter region using pyrosequencing. The relationship between TET1 methylation, clinical indicators, and tumor markers was evaluated by combining clinical samples and cell experiments. The diagnostic efficacy of TET1 methylation and mRNA expression levels were assessed using ROC curve analysis.

Results: TET1 expression was notably reduced in RCC tumor tissues relative to adjacent normal tissues (P < 0.05) and was elevated in early stage (T1 and stage 1) tumors compared to advanced stages. RCC patients exhibited significantly higher methylation levels at all nine CpG sites and in the mean methylation level compared to controls (P < 0.001). Gender-specific analysis revealed lower TET1 methylation levels in males compared to females, with significant differences at CpG1-CpG8 sites (P < 0.05). TET1 methylation levels were positively correlated with tumor stage, tumor size, and serum markers, such as CA125, NSE and Ki67 (P < 0.05), and significantly negatively correlated with TET1 expression (r = - 0.665, P < 0.001). ROC curve analysis showed that the combination of TET1 average methylation and mRNA expression level (AUC = 0.876) had a high diagnostic efficacy. The levels of TET1 and p21 in RCC patients and 786-O cells were significantly reduced, and the level of Ki67 was significantly increased, suggesting that TET1 methylation may participate in the mechanism of malignant proliferation of RCC tumor cells by regulating p21 and Ki67.

Conclusions: This study underscores the importance of TET1 methylation in RCC progression and its promise as an early stage diagnostic biomarker, and may be involved in the mechanism of malignant proliferation of RCC cells. These findings offer fresh perspectives on RCC's epigenetic regulation and highlight TET1's potential in therapy and diagnosis.

Keywords: Biomarker; DNA methylation; Renal cell carcinoma; TET1; Tumor stage.

Fig. 1

Correlation analysis between TET1 and RCC in TCGA database. A TET1 expression was not different in bladder cancer patients. B TET1 expression was not different in prostate cancer patients. C TET1 expression was much lower in RCC than in controls. D Expression of TET1was significantly different in tumor T stages. E Expression of TET1 was significantly different in pathologic stages. F Distribution of TET1 expression in tumor grade. *P < 0.05, **P < 0.01, @Pathologic stage (T2 + T3 + T4 vs. T1), # Pathologic stage (II + III + IV vs. I)

Fig. 2

Locations and analysis of the nine CpGs in TET1gene. A Locations of the nine CpGs in TET1gene. B Representative sequencing analysis of nine methylation sites in Control and RCC groups

Fig. 3

Comparisons of TET1methylation among different groups. A Comparison between RCC and control groups. B Comparison between male and female groups. C Comparison between male RCC and control groups. D Comparison between female RCC and control groups. E Comparison between RCC male and female groups. F Comparison between control male and female groups. *P < 0.05, **P < 0.01, ***P < 0.001

Fig. 4

Correlation analysis between TET1methylation and clinical data. A Correlation analysis in all groups. B Correlation of TET1 methylation with T tumor stage. C Correlation of TET1 methylation with tumor size. D Correlation of TET1 methylation with CA125. E Correlation analysis between TET1 methylation and mRNA expression. F Correlation analysis between TET1 expression and T tumor stage. G Correlation analysis between TET1 expression and T tumor size. Pearson correlation or Spearman’s rank analysis were used to analyze data. After Bonferroni correction, the correlation between the average methylation level of TET1 and RCC tumor size, tumor stage, CA125 and mRNA remained significant (p adj < 0.05), while the correlation between mRNA and tumor size disappeared. *P < 0.05, **P < 0.01

Fig. 5

ROC curves of TET1 in RCC patients. A ROC curves of TET1 DNA methylation in RCC patients. B ROC curves of TET1 methylation and mRNA integration in RCC patients

Fig. 6

Analysis of TET1, p21 and Ki67 in pathological T staging of RCC. A Comparison of TET1, p21 and Ki67 transcriptomes in RCC and control groups. B Comparative analysis of TET1, p21 and Ki67 in 786-O and HK-2 cells. C Comparative analysis of TET1, p21 and Ki67 in renal cancer tissues. D Comparison of TET1, p21 and Ki67 counts in renal cancer tissues. E Comparison of TET1 methylation in RCC pathological T stage. F Paired analysis of TET1, p21 and Ki67. Results are presented as mean ± SEM. N = 20 or 3. *P < 0.05, **P < 0.01, ***P < 0.001

Fig. 7

Increased TET1 DNA methylation may regulate the p21 and Ki67 signaling pathways by reducing TET1 expression, thereby leading to abnormal proliferation of RCC tumor cells