MicroRNA Profiles in Familial and Sporadic Medullary Thyroid Carcinoma: Preliminary Relationships with RET Status and Outcome

Abstract

Background: MicroRNAs (miRNAs) are involved in the pathogenesis of human cancers, including medullary thyroid carcinoma (MTC). The aim of this study was to test the hypothesis that different miRNA profiles are related to RET status and prognosis in patients with hereditary MTC (hMTC) and sporadic MTC (sMTC). Methods: We analyzed the expression of nine miRNAs (miR-21, miR-127, miR-154, miR-224, miR-323, miR-370, miR-9*, miR-183, and miR-375) by quantitative real-time-polymerase chain reaction in 34 cases of sMTC, 6 cases of hMTC, and 2 cases of C-cell hyperplasia (CCH). We also analyzed the immunohistochemical expression of PDCD4, an miR-21 gene target. sMTC (n = 34) was genotyped for somatic RET and RAS mutations. Disease status was defined on the basis of the concentration of serum calcitonin at the latest follow-up and other parameters as indicated in the results. Results: MTC and CCH were both characterized by a significant overexpression of the whole set of miRNAs (the increase being 4.2-fold for miR-21, 6.7-fold for miR-127, 8.8-fold for miR-154, 6.6-fold for miR-224, 5.8-fold for miR-323, 6.1-fold for miR-370, 13-fold for miR-9*, 6.7-fold for miR-183, and 10.1 for miR-375, p < 0.0001). PDCD4 expression was significantly downregulated in MTC samples, consistent with miR-21 upregulation. Significantly lower miR-127 levels were observed in sMTC carrying somatic RET mutations in comparison to sMTC carrying a wild-type RET. In sMTC and familial MTC, the miR-224 upregulation correlated with the absence of node metastases, lower stages at diagnosis, and with biochemical cure during follow-up. Conclusions: miRNAs are significantly dysregulated in MTC, and this dysregulation is probably an early event in C-cell carcinogenesis. miR-224 upregulation could represent a prognostic biomarker associated with a better outcome in MTC patients.

RAS proto-oncogene in medullary thyroid carcinoma

“…Overall, RAS mutations were present in 69.2% (18/26) of the RET WT cases and in only 2.5% of the RET-positive sporadic MTC (P!0.0001), suggesting that activation of the protooncogenes RAS and RET represents alternative genetic events in sporadic MTC tumorigenesis. These results were confirmed by other groups , Schulten et al 2011, Boichard et al 2012, Mian et al 2012, Tamburrino et al 2012, Ciampi et al 2013, Nikiforova et al 2013, Lyra et al 2014, Simbolo et al 2014, Pennelli et al 2015. We found no other mutations in the entire coding region of the genes HRAS, KRAS and RET in the RET and RAS WT sporadic MTC (M M Moura, B M Cavaco and V Leite, unpublished observations).…”

“…In a large series of 64 MTC (56 sporadic and eight familial), Pennelli et al (2015) demonstrated significant PDCD4 nuclear downregulation together with miR-21 upregulation, thus confirming their previous results obtained in a small series of MTC (Mian et al 2012), and showed also that miR-21/PDCD4 expression correlates with clinicopathological findings and prognosis. Although these authors were unable to detect any significant correlation between the miR-21/PDCD4 pathway and somatic RET or RAS mutation status, they found that the six RAS-positive cases in their series of MTC sporadic tumors had higher nuclear PDCD4 expression levels than the RET-positive/RAS-negative or RET/RAS WT patients.…”

“…In a series of 19 MTC, a signature of three miRNA (miR-183, miR-375, and miR-9*) enabled to distinguish familial from sporadic cases (Abraham et al 2011). Mian et al (2012) analyzed the expression of nine miRNA (miR-21, miR-127, miR-154, miR-224, miR-323, miR-370, miR-9*, miR-183, and miR-375) in 34 sporadic MTC and correlated this expression with RET status. From the whole set of nine miRNA, only miR-127 was significantly associated with RET status, with sporadic MTC carrying somatic RET mutations showing a lower upregulation of this miRNA than those with a WT RET.…”

“…Since not all series analyzed all RAS isoforms, we present in Table 3 the overall prevalence of Part of the series (nZ34) was previously reported in another publication (Mian et al 2012). RAS mutations in the studies where all RAS isoforms were screened.…”

“…Boichard et al (2012) screened the somatic mutational status of RAS genes in a series of 50 MTC, including 30 sporadic cases, and three mutations were detected in exon 4 both of HRAS (nZ1, codon 117) and KRAS (nZ2, codon 146). Mian et al (2012) reported a p.Met72Ile mutation in exon 3 of the HRAS gene in a case with sporadic MTC.…”