Serum miR-210 as a novel biomarker for molecular diagnosis of clear cell renal cell carcinoma
Introduction
Renal cell carcinoma (RCC) is the third most common urological cancer and it has a high mortality. Clear cell or conventional renal cell carcinoma (cRCC) is the most frequent subtype of RCC and accounts for approximately 75–80% of these tumors (Cohen and McGovern, 2005). Recent advances in diagnostic techniques have increased the early detection of cRCC and decreased the mortality rate. However, nearly 30–40% of patients will still metastasize after extended radical resections (Lam et al., 2005). There has been no serum marker for diagnosis and follow-up. Thus, we need new biomarkers to improve diagnosis and to monitor cRCC after resection.
MicroRNAs (miRNAs) are 18–25 nucleotide noncoding RNA molecules that are involved in tumorigenesis and the development of various cancers (Garzon et al., 2009, Inui et al., 2010). Several studies have focused on miRNAs' significance in RCC (Bartels and Tsongalis, 2009, Huang et al., 2009b, Juan et al., 2009). These papers have revealed that miRNAs may be potential diagnostic or prognostic tools for cancer (Esquela-Kerscher and Slack, 2006). More recently, Mitchell et al. (2008) clearly reported that circulating miRNAs existed in serum/plasma, and were originated from cancer tissue. They also showed the miRNAs can serve as potential biomarkers for detection of prostate cancer.
The majority of cRCCs exhibit VHL mutations which lead to enhanced hypoxia-inducible factor (HIF) action (Cohen and McGovern, 2005). Interestingly, miR-210 is directly regulated by HIF-1a in a variety of tumor types (Camps et al., 2008, Ho et al., 2010). Therefore, the levels of miR-210 would increase in tumor and serum samples of cRCC patients. We hypothesized that the circulating miR-210 in serum samples may have the potential capacity for the diagnosis of cRCC.
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Tissue samples and serum samples
Tissue samples were obtained from 32 patients with a cRCC. Under the supervision of an experienced pathologist, tumor tissue and adjacent non-tumoral renal parenchyma were collected. All tissue samples were immediately put in liquid nitrogen and stored at − 80 °C until RNA extraction.
68 serum samples (3.5 ml) were collected before surgery and processed within 5 h. The blood tube was centrifuged at 1200 ×g for 10 min at 4 °C followed by careful separation of serum. Another centrifugation was performed
Results
A total of 132 participants including 32 cRCC patients for paired tumoral and normal tissue, 68 cRCC patient for serum samples, and 42 healthy for control serum samples were included into this study. The characteristics of the study population are summarized in Table 1. No significant differences of age or gender were found between cRCCs and normal controls (p = 0.798, ANOVA; p = 0.886, x2 test). The mean Ct values (95% confidence interval) of 5s rRNA were 16.99 ± 0.96 (15.8–16.2), 16.16 ± 0.1
Discussion
Tumor-derived miRNAs was firstly described in plasma by Mitchell et al. (2008). They found that circulating miRNAs have the potential to be new biomarkers in patients with prostate cancers. They also showed the high stability of plasma miRNAs after prolonged incubation at room temperature and/or multiple freezing–thawing processes. These findings stimulate the search for circulating miRNAs in the detection of patients with a cancer.
MiR-210 is one of the most studied miRNAs in cancer. MiR-210
Conflict of interest
The authors declare that there are no conflicts of interest.
Acknowledgment
This research was supported by la Ligue Nationale contre le Cancer du Comité de la Loire, France. We thank Pr. J Tostain for his scientific advice during this work.
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An Zhao and Guorong Li are co-first authors.