Identification of signaling pathways and specifically miRNAs altered in familial and sporadic forms of medullary thyroid tumors

  1. Maliszewska, Agnieszka
Supervised by:
  1. Mercedes Robledo Batanero Director

Defence university: Universidad Autónoma de Madrid

Fecha de defensa: 26 October 2012

  1. Javier Benítez Ortiz Chair
  2. Beatriz Martínez Delgado Secretary
  3. Gema Moreno Bueno Committee member
  4. José Manuel Cameselle Teijeiro Committee member
  5. José Ángel Díaz Pérez Committee member

Type: Thesis


Medullary thyroid carcinoma (MTC) accounts for around 2¿5% of all thyroid malignancies. From these, around 25% are inherited forms attributable to germline RET mutations, and 75% are sporadic MTCs, with or without somatic mutation in the same RET proto-oncogene. Although the genotype-phenotype correlation related to specific germline RET mutations is well established, the knowledge of pathways specifically associated with each mutation, as well as to non-RET related sporadic MTC still remain largely unknown. Gene expression and microRNA patterns have provided a robust tool to identify molecular events related to specific tumor types and to different clinical features that could help to identify novel targets for therapy. Based on gene expression and microRNA profiling from an outstanding series of tumors, it was possible to identify differences between sporadic and familial MTCs. Specifically, PROM1 (also called CD133), LOXL2, GFRA1 and DKK4 over-expression were related to RETM918T, while GAL was associated with RET634 mutation. Pathway enrichment analysis pointed to Wnt, Notch, NF¿B, JAK/Stat and MAPkinase signaling as related to MTCM918T group. The immunohistochemical assessment of ESM1, GFRA1 and CD133 only revealed a marginal association of the M918T group with CD133 protein over-expression. The lack of validation at protein level could be due to other underlying mechanism, such as posttranscriptional modifications conducted by microRNAs. Based on the in vitro functional studies, we observed that PROM1 or CD133 is significantly expressed in MZ-CRC-1 cell lines harboring M918T RET mutation comparing to TT cell line model with RET634. On the other hand, silencing CD133 by siRNA induced apoptosis in MZ-CRC-1. CD133 confers resistance to death by apoptosis, but does not imply a selective advantage on proliferation. To our knowledge this is the first time that PROM1 or CD133 overexpression is reported among primary tumors. This finding could lead to the identification of novel therapeutic targets. The miRNome analysis revealed a downregulation of miR-30a, and miR-138 associated with MTCM918T group, and miR-124 with MTCC634X. These results were validated in independent series of frozen and FFPE series. Furthermore, mRNA-miRNA integration data on the same frozen MTC sample series pointed to inversely correlated miR-30a and PROM1 among MTCM918T group. In summary, this study has allowed us to identify genes and microRNAs that could be used as markers related to specific genetic conditions in MTCs, and that could be taken into account as future therapeutic targets.