PCAT-1 Expression is Associated With The Prognosis in Prostate Cancer.


 Purpose: In the study, we aimed to estimate the prognostic significance of PCAT-1 in patients with prostate cancer (PCa).Methods: The expression of PCAT-1 in paired PCa tissues and normal controls was examined via quantitative real-time polymerase chain reaction (qRT-PCR). The influence of PCAT-1 level on clinical features was assessed using Chi-square test. The survival curves were plotted to estimate the prognosis of patients. And the Cox analysis was carried out to find promising predictive factors for patients.Results: The expression level of PCAT-1 in PCa tissues was significantly elevated compared with the adjacent normal control (P<0.0001). The increased expression of PCAT-1 was affected by high Gleason score (P=0.017), positive serum PSA (P=0.011) and advanced TNM stage (P=0.003). The Kaplan-Meier survival curves showed that the overall survival rate of patients with high PCAT-1 expression was significantly lower than those with low PCAT-1 expression (P<0.001). Both univariate analysis (P=0.000, HR=10.623, 95%CI=5.798-19.464) and multivariate Cox regression analysis (P=0.000, HR=10.996, 95%CI=5.896-20.507) revealed that PCAT-1 could act as a prognostic biomarker for PCa patients.Conclusion: Taken together, overexpression of PCAT-1 is involved in PCa progression and could be a potential prognostic biomarker for PCa patients.

regulation, embryonic development and cancer development [16][17][18]. In addition, previous studies have demonstrated that approximately 15000 kinds of lncRNAs are found to be abnormally expressed in organism tissues. Prostate cancer-associated ncRNA transcripts 1 (PCAT-1) is a lncRNA that was originally identi ed in prostate cancer.
In the present study, we aimed to compare the expression levels of lncRNA PCAT-1 in PCa tissues and paired normal controls and to identify its role in the prognosis of PCa patients.

Materials And Methods
Patients and specimens Our retrospective study recruited 129 patients as objects, who were pathologically diagnosed with PCa in Zhongnan Hospital of Wuhan University, age range of 25 to 75 years. The tissue samples were immediately prepared and stored in liquid nitrogen after surgical resection. Patients received no chemoor radio-therapy before surgery. The information of patients is updated every 3 months for a 5-year follow-up. The study was carried out with the admission of Ethics Committee in Zhongnan Hospital of Wuhan University. And the informed consent was provided by each participant.
Quantitative real-time polymerase chain reaction (qRT-PCR) Total RNA was isolated from tissue samples using the Trizol Reagent (Invitrogen) according to the manufacture's instructions. The RNA was reverse transcribed into the rst strand of cDNA with a Reverse Transcription Kit (Takara). Then quantitative real-time PCR was conducted using the ABI PRISM 7000 Fluorescent Quantitative PCR system (Applied Biosystems, Foster City, USA). The expression of PCAT-1 was determined using the 2 −∆∆Ct method and normalized to the internal control GAPDH.

Statistical analysis
All data were analyzed by Sigmaplot 12.5 (Systat Software Inc, CA, USA) and SPSS 18.0 (International Business Machines Corporation, USA) software. The t-test was conducted to compare the expression difference of PCAT-1 in PCa tissues and paired normal controls. The χ 2 test was used to describe the associations between PCAT-1 levels and patients' clinical characteristics. Kaplan-Meier method was adopted to evaluate the overall survival rate of patients. The prognostic biomarkers for PCa patients were identi ed using Cox regression analysis. P values less than 0.05 were considered as statistical signi cant.

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The expression of PCAT-1 in PCa tissues and corresponding normal controls was determined using qRT-PCR. As shown in Fig. 1, the level of PCAT-1 in PCa tissues was 2.91 ± 0.70 (mean ± SD), while that in normal controls was 1.72 ± 0.57. The PCAT-1 expression was signi cantly increased in PCa tissues compared with normal controls (P < 0.0001).
The association between PCAT-1 expression and clinical parameters of PCa patients To explore the effects of clinical parameters on PCAT-1 expression, the Chi-square test was performed. Patient were divided into two groups based on the median value of PCAT-1 levels: the high expression group (n = 65) and the low expression group (n = 64). According to the results of χ 2 test, PCAT-1 upregulation was associated with high Gleason score (P = 0.017), positive serum PSA (P = 0.011) and advanced TNM stage (P = 0.003) ( Table 1). On the other hand, PCAT-1 expression shared no close relationship with age (P = 0.250), NED rate (P = 0.093), urine retention (P = 0.179) and hematuria (P = 0.135). The correlation between PCAT-1 expression and prognosis of patients The Kaplan-Meier curves and Cox regression analysis were conducted to evaluate the prognostic value of PCAT-1 in PCa. During the 5-year follow-up, 56 of 65 (86.15%) patients with high PCAT-1 expression died, while only 14 (21.88%) cases with low PCAT-1 expression died. As shown in Fig. 2, the overall survival rate of patients with high PCAT-1 expression was signi cantly lower than those with low PCAT-1 expression (P < 0.001). Furthermore, univariate Cox regression analysis revealed that urine retention (P = 0.015, HR = 1.790, 95%CI = 1.119-2.866), Gleason score (P = 0.000), serum PSA (P = 0.036), TNM stage (P = 0.026) and PCAT-1 expression (P = 0.000) were related with the prognosis of PCa patients (Table 2)

Discussion
PCa is one of the most important malignancies in the male reproductive system, and also a common malignant tumor in men. Its biological behavior is complicated and its pathological process is di cult to grasp. An increasing number of investigations have demonstrated that the occurrence and development of PCa is controlled and regulated by multiple indicators, such as daily habit, environmental factors and gene variation [19]. In recent years, the incidence rate of PCa has increased remarkably in China. To improve the treatment e cacy and the outcomes of patients, numerous studies are carried out to seek relative prognostic biomarkers for PCa. Mavridis et al. showed that miR-224 down-regulation was related with poor prognosis of PCa patients [20]. In the study of Zheng et al., they reported that SFRP1 could act as a prognostic marker for PCa patients [21]. However, the etiology and tumorigenesis of PCa has not been fully elucidated yet. Therefore, searching novel biomarkers is requested to understand the PCa pathogenesis and improve the patients' outcomes.
LncRNAs have increasingly been linked to many human diseases. The diversity and nucleotide length of lncRNAs allow them to possess a broad range of biological functions despite the lack of protein-coding potential. PCAT-1, a newly con rmed lncRNA, is mapped to human chromesome 8q24 desert and is signi cantly contributed to the development and progression of cancers [22,23]. It is reported by Zhao et al. that lncRNA PCAT-1 up-regulation could enhance the cell proliferation and migration in non-small cell lung cancer [24]. Prensner et al. found that PCAT-1 expression could generate a functional de ciency of homologous recombination in cancers through targeting BRCA2 [25]. The study carried out by Yan et al. demonstrated that the expression of lncRNA PCAT-1 was signi cantly elevated in hepatocellular carcinoma tissues compared with adjacent normal controls and this over-expression was related with poor prognosis of patients [26]. Furthermore, Prensner et al. claimed that lncRNA PCAT-1 could stimulate cell proliferation in PCa through regulation cMyc [16]. However, the clinical role fo lncRNA PCAT-1 in PCa patients was still unclear.
In the present study, the correlation between PCAT-1 expression and prognosis of PCa patients was evaluated. First, we determined and compared the expression of lncRNA PCAT-1 in PCa tissues and the corresponding normal controls using qRT-PCR and t-test. The results showed a signi cantly high expression of PCAT-1 in PCa tissues compared to adjacent normal controls, which was consistent with the previous studies. Chi-square test was carried out to explore the potential biomarkers in uencing PCAT-1 expression. Gleason score, serum PSA and TNM stage were nally proved to play important roles in the expression of PCAT-1. Based on these ndings, we concluded that PCAT-1 is closely related with the development and progression of PCa, and thus we hypothesized that PCAT-1 might be involved in the prognosis of PCa patients. The Kaplan-Meier curves revealed that patients with low PCAT-1 expression had a higher survival rate than those with high expression. Furthermore, the Cox regression analysis showed that PCAT-1 was a predictive candidate biomarker for the prognosis of PCa patients.
Clinically, our study con rmed the over-expression of lncRNA PCAT-1 in PCa tissues compared to normal controls. lncRNA PCTA-1 overexpression has been implicated in the poor prognosis of PCa. While the direct therapeutic targeting of lncRNAs has not been proven and how PCAT-1 affects the development and progression of PCa is still needed more investigations with larger sample size.

Conclusions
In conclusion, our study con rmed the over-expression of lncRNA PCAT-1 affected the cancer development and progression in PCa and lncRNA PCAT-1 might be a valuable prognosis biomarker for patients. Moreover, our study identi ed the prognostic role of lncRNA PCAT-1 for PCa patients for the rst time. The subjects had been informed the objective. Certainly, written consents were signed by every subject in this study.

Consent for publication
We obtaining permission from participants to publish their data.

Availability of data and materials
Data sharing is not applicable to this article as no datasets were generated or analysed during the current study.

Con ict of Interest
The authors declare that they have no con ict of interest.

Funding
The authors did not receive support from any organization for the submitted work.
Authors' contributions S.L. design of the work; S.L. the acquisition, analysis, X.R. interpretation of data; X.R. the creation of new software used in the work; T.L. have drafted the work or substantively revised it. All authors read and approved the nal manuscript.

Figure 1
The expression of PCAT-1 in PCa tissues and adjacent normal controls. The PCAT-1 level was signi cantly higher in PCs tissues than the paired normal controls (P<0.0001).