Decreased TCL6 expression is associated with poor prognosis in patients with clear cell renal cell carcinoma

Abstract

One-third of clear cell renal cell carcinoma (ccRCC) patients present with metastasis at the time of diagnosis. The prognosis of these patients is poor. To identify potential prognostic biomarkers and therapeutic targets for ccRCC, we re-evaluated published long non-coding RNA (lncRNA) expression profiling data from the Gene Expression Omnibus and ArrayExpress database. We found that five lncRNAs were differentially expressed in ccRCC and adjacent tissues. These lncRNAs were assessed in an independent cohort of 71 paired patient samples using real-time PCR. Differences in expression of three of the lncRNAs (ENSG00000177133, TCL6, and ENSG00000244020) were validated in this analysis. Kaplan-Meier analysis indicated that low expression of ENSG00000177133 and TCL6 was associated with a poor prognosis. Univariate and multivariate regression analyses demonstrated that TCL6 but not ENSG00000177133 expression was an independent predictor of ccRCC aggressiveness and had hazard ratios predictive of clinical outcome. TCL6 expression was negatively correlated with pTNM stage. Overexpression of TCL6 in 786-O and Caki-1 ccRCC cells decreased proliferation and increased apoptosis compared to controls. Our results indicate that lncRNA expression is altered in ccRCC and that decreased TCL6 expression may be an independent adverse prognostic factor in ccRCC patients.

Keywords: TCL6; clear cell renal cell carcinoma; lncRNA; microarray analysis; prognosis.

Figure 1. Schematic of the workflow

All analyses were performed with the GSE53757 and E-TABM-282 datasets.

Figure 2. Microarray analysis showing differential expression of lncRNAs between ccRCC and normal renal tissue in the GSE53757 dataset

The red and green colors indicate high and low expression, respectively. The GSE53757 dataset included 72 ccRCC and paired normal renal tissue samples.

Figure 3. Quantification of the expression of three candidate lncRNAs in ccRCC and paired adjacent tissue (n = 71; Non-parametric Mann-Whitney test)

Figure 4. Associations between lncRNAs and survival in 71 patients with ccRCC

Survival analysis indicates that patients with tumors that have high TCL6 or ENSG00000177133 expression have a more favorable prognosis compared to those with lower expression (Log-rank test).

Figure 5. Univariate (A) and multivariate analyses (B) of TCL6 in ccRCC patients

Univariate (C) and multivariate analyses (D) of ENSG00000177133. All bars correspond to 95% CIs.

Figure 6

(A) Quantitative RT-PCR confirming ectopic expression of TCL6 in ccRCC cell lines (786-0 and Caki-1) after TCL6 plasmid transfection (n = 3; P < 0.05; Non-parametric Mann-Whitney test). Error bars represent the SD. (B) TCL6 overexpression inhibits renal cell growth in vitro (n = 3; Non-parametric Mann-Whitney test). (C) Flow cytometry analysis of apoptosis after TCL6 overexpression in renal cells (n = 3). (D) Cell proliferation assays after TCL6 knockdown with siRNA (n = 3; Non-parametric Mann-Whitney test).