Expression profile of oncomiRs and tumor-suppressor miRs in urothelial carcinoma of the bladder

Apostolos Zaravinos1, George I. Lambrou2, Jelena Radojicic3, Dimitrios Volanis1,4, Ioannis Boulalas1,4, Dimitris Delakas4, Demetrios A. Spandidos1

1, Laboratory of Virology, Medical School, University of Crete, 71110 Heraklion, Crete, Greece.2, 1st Department of Pediatrics, Choremeio Research Laboratory, University of Athens, 11527 Athens, Greece.

3, Department of Surgical Pathology, Medical Faculty, University of Crete, 71110 Heraklion, Crete, Greece.4, Department of Urology, Asklipieio General Hospital, 16673 Voula, Athens, Greece.

INTRODUCTIONUrinary bladder cancer is the most common malignancy of the urinary tract, responsible for significant mortality and morbidity worldwide. MicroRNAs (miRNA) are a group of endogenous, small, noncoding RNA molecules of ~22 nucleotides. The interaction of miRNAs and target genes is intricately regulated, in that one miRNA may modulate multiple target genes whereas one target gene may be regulated by various miRNAs. MiRNAs negatively affect the expression level of their target genes through two distinctive mechanisms, depending on the degree of their complementarity to target sequences. In the first mechanism, a perfect or near-perfect match between miRNAs and their binding sequences within the 3’ untranslated regions (UTR) of their target mRNAs induces the RNA-mediated interference pathway. The RNA-induced silencing complex then recognizes the miRNA-mRNA interaction and cleaves the mRNA through an endonuclease activity. In the second mechanism, miRNAs control gene expression at the translational level through imperfect target matching. MiRNAs influence tumorigenesis through their regulation of specific proto-oncogenes and tumor suppressor genes.

DISCUSSION / CONCLUSIONS

Alteration in microRNA expression appear important for carcinogenesis. Their profile may be used to identify key tumourigenic pathways or clinical outcome. Overall, we present the expression profile of a group of 11 microRNAs in urinary bladder cancer. Our results suggest that different microRNAs (miR-10b, miR19a, miR19b, miR-122a, miR-145_1, miR-221, miR-222, miR-378-1 and miR-296-5p) are deregulated in urinary bladder cancer through down-regulation. MiR-21, miR-205_1 and miR-210 exhibited equall expression levels between BC and normal adjacent to the tumour tissue. A synergistic involvement of these genes in the development of bladder cancer is implied, through significant correlations detected among them.

RESULTSFigure 1. The majority of the microRNAs exhibited down-regulation in BC vs. normal tissue [miR-10b (p=0.0007), miR-19a (p=0.012), miR-19b (p=0.0361), miR-126_1 (p=0.0021), miR-145_1 (p<0.0001), miR-221 (p<0.0001), miR-296-5p (p<0.0001), miR-378-1 (p<0.0001)]. MiR-21, miR-205_1 and miR-210 expression levels did not present significant difference between BC and normal tissue. Group pairs were statistically compared using the Mann-Whitney U test. The bars indicate the mean with 95%CI values.

Seventy-seven primary BCs, along with 77 matched tumor-associated normal samples were investigated for the expression of 12 micro-RNAs using qPCR. Relationships between the expression of miR-10b, miR19a, miR19b, miR-21, miR-122a, miR-145_1, miR-205_1, miR-210, miR-221, miR-222, miR-378-1 and miR-296-5p and the pathologic features of the tumors were also examined.

MATERIALS AND METHODS

Table 1. Significant correlations among all of the studied microRNAs were scored both in BC and control tissue.

Our goal was explore the expression profile of oncomiRs and tumor-suppressor miRs, and to define their possible correlations in urothelial carcinoma of the bladder (BC).

AIM OF STUDY

Figure 1.

Figure 2. We noticed a great range in the x-fold expression values of all micro-RNAs. The log2 transformed median x-fold expression (range) was as follows: miR-10b, 0.45 (0-12.58); miR-19a, 0.56 (0-25.63); miR-19b, 0.50 (0-18.90); miR-21, 0.96 (0-52.95); miR-126_1, 0.36 (0-42.62); miR-145_1, 0.04 (0-56.36); miR-205_1, 1.07 (0.01-36.42); miR-210, 1.09 (0-44.43); miR-221, 0.32 (0-33.51); miR-296-5p, 0.08 (0-75.24); miR-378-1, 0.17 (0-3.66).

Figure 2.