Association of MiR-126 with Soluble Mesothelin-Related Peptides, a Marker for Malignant Mesothelioma

BACKGROUND: Improved detection methods for diagnosis of malignant pleural mesothelioma (MPM) are essential for early and reliable detection as well as treatment. Since recent data point to abnormal levels of microRNAs (miRNAs) in tumors, we hypothesized that a profile of deregulated miRNAs may be a marker of MPM and that the levels of specific miRNAs may be used for monitoring its progress. METHODS AND RESULTS: miRNAs isolated from fresh-frozen biopsies of MPM patients were tested for the expression of 88 types of miRNA involved in cancerogenesis. Most of the tested miRNAs were downregulated in the malignant tissues compared with the normal tissues. Of eight significantly downregulated, three miRNAs were assayed in cancerous tissue and adjacent non-cancerous tissue sample pairs collected from 27 formalin-fixed, paraffin-embedded MPM tissues by quantitative RT-PCR. Among the miRNAs tested, only miR-126 significantly remained downregulated in the malignant tissues. Furthermore, the performance of the selected miR-126 as biomarker was evaluated in serum samples of asbestos-exposed subjects and MPM patients and compared with controls. MiR-126 was not affected by asbestos exposure, whereas it was found strongly associated with VEGF serum levels. Levels of miR-126 in serum, and its levels in patients' serum in association with a specific marker of MPM, SMRPs, correlate with subjects at high risk to develop MPM. CONCLUSIONS AND SIGNIFICANCE: We propose miR-126, in association with SMRPs, as a marker for early detection of MPM. The identification of tumor biomarkers used alone or, in particular, in combination could greatly facilitate the surveillance procedure for cohorts of subjects exposed to asbestos

Box plot of miR-335, miR-126 and miR-32 expression levels according to tumor staging.

<p>Distribution of miR-335, miR-126 and miR-32 expression levels (ΔC_T) in S1, MPMs staged S-Ia, S-Ib, S-II without lymph nodes and metastases involvement and S2, MPMs staged S-III, S-IV with lymph nodes and metastases involvement. *S1 <i>vs.</i> S2, <i>p</i><0.05.</p

Demographic and pathological characteristics of MPM patients.

<p>EP, epithelioid; SA, sarcomatoid; BI, Biphasic; S-I (any T1a, any T1b); S-II (any T2); S-III (any T3, any N); S-IV (any T4, any N, any M).</p

Hierarchical cluster analysis of miRNAs.

<p>miRNA expression of 10 MPM tissues is shown with respect to the pooled miRNAs from 5 normal tissues. MiRNAs were considered differentially expressed if their levels were increased or decreased by more than 2-fold. Relative normalized expression for each miRNA is represented by color intensity (green, downregulation; yellow, no change in expression; red, increased expression; black, miRNA not detected).</p

Demographic and pathological characteristics of individual subjects.

<p>EP, epithelioid; SA, sarcomatoid; S-Ia (any T1a); S-Ib (any T1b); S-II (any T2); S-III (any T3, any N); S-IV (any T4, any N, any M).</p