Module 3 - Research Proposal

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Steph Leger

20.109: W/F - Yellow

overview

topic: medullary thyroid carcinoma (MTC)

relevant background:

  • MTC is a form of thyroid carcinoma which originates from the parafollicular cells (C cells), which produce the hormone calcitonin.
  • MTC accounts for roughly 8% of all thyroid cancers.
  • Hereditary medullary thyroid cancer is inherited as an autosomal dominant trait however 75% MTC cases are sporadic
  • MTC poses a difficult challenge for treatment. This carcinoma is non-responsive to both chemotherapy and radiotherapy. While thyroidectomy stands as a possible treatment route, MTC is not always removed by this method and the surgery has no effect on parts of the cancer that have metastasized.
  • Research has looked to the genetic components of MTC to determine if specific gene targeting can be used to cure MTC. Research is just beginning to emerge concerning the genes that can be targeted to most effectively reduce MTC phenotypes. Currently, clinical trials of several new tyrosine kinase inhibitors are being studied; however, there are a few other genetic pathways that could potentially be targeted to provide therapeutics for MTC.
  • The RET (REarranged during Transfection) oncogene has been found to play a role in the development of MTC. The RET gene is responsible for the production of a transmembrane receptor with a tyrosine kinase (RTK) domain. Mutations to the RET gene (particularly M918T) have found success in reducing occurrences of MTC. However, it has been found that roughly 50% of MTC cases do not carry RET mutations.


project proposal

problem:

  • although the RET oncogene has been associated with occurrence of MTC, the RET mutations are not found in all MTC cases, particularly those that are sporadic

overall goal:

  • design an effective targeting strategy for siRNA knockdown in MTC expression

project design:

  • develop siRNA that seeks to restore the activity of candidate tumor suppressor gene CDKN2C (known as P18)
  • (1) test the siRNA to see if it is effective in reducing occurrence of MTC
  • (2) conduct a microarray assay to see if P18 induction is associated with any of the other genes of interest in MTC (particularly RET)

discussion of proposals

  • for proposal 1, an assay will need to be conducted that will indicate whether MTC has developed in the cell or not
  • for proposal 2, a list of genes that are expected to influence MTC needs to be compiled and compared to P18 in order to see if similar pathways are involved

current project proposal

  • use siRNA to target the induction of P18
  • measure levels of calcitonin, with high levels being indicative of MTC development
  • look to see if siRNA could provide a feasible method of therapy for MTC
  • since P18 has been found in both sporadic and familial MTC cases, this approach looks at providing more broad based therapy for MTC

moving ahead

  • need to consider what cell lines to utilize
  • develop an assay/find a means of measuring calcitonin levels
  • determine sequencing needed to target P18 with siRNA


related research of interest

Cerrato, Aniello, Valentina De Falco, Massimo Santoro. Molecular genetics of medullary thyroid carcinoma: the quest for novel therapeutic targets. JME-09-0024v2

  • This study offers a review of the numerous research endeavors that have explored the genetic components that influence MTC development. In addition to observing the behavior of the primary RET oncogene, the study also considered how other genes and pathways can be linked to MTC formation. The study found that the RB/TP53, RAS/BRAF, and mTOR pathways all potentially influence expression of the disease. This study aimed at providing information that would lead to increased efficacy in RET-targeted therapies. Particularly, this study suggested the argument that knockdown of multiple genes/gene components may be necessary to achieve therapeutics for MTC.


Pinchot, Scott N, Rebecca S Sippel, Herbert Che. Multi-targeted approach in the treatment of thyroid cancer. Therapeutics and Clinical Risk Management 2008:4(5) 935–947

  • This study was again a review that looked at the different targeting routes that can be used for MTC therapeutics. Along with RET, the study also found that mutations to epidilial growth factor (EGFR) and B-type RAS kinase (BRAF) are associated with the MTC phenotype. The presence of MTC appears to be controlled by many factors that intertwine and interact to deliver the diseased phenotype. The review raised the question concerning the extent of targeting that would be required to effectively reduce MTC occurrence. Specifically, the knockdown of one genetic component (RET for example) may not be enough to restrict MTC development. The study suggested that a multi-targeting approach should be used in the treatment of MTC.


Veelen, Wendy van, Rob Klompmaker, Martijn Gloerich, Carola J.R. van Gasteren, Eric Kalkhoven, Ruud Berger, Cornelis J.M. Lips, Rene H. Medema, Jo W.M. H€oppener and Dennis S. Acton. P18 is a tumor suppressor gene involved in human medullary thyroid carcinoma and pheochromocytoma development. Int. J. Cancer: 124, 339–345 (2009)

  • Research conducted by this team found that the P18 gene acts as a tumor suppressor in cases of MTC. These findings are particularly interesting because they offer an alternative to RET targeting. Although RET as been shown to be a genetic factor of MTC, RET mutations are not found in every MTC case. Most RET mutations are concentrated to the familial cases of the disorder which only make up 1.5% of all MTC cases. The discovery of an additional gene functioning in MTC offers the potential for therapeutics that are more widely applicable for MTC cases. This study suggests that P18 targeting may be a solution to the issue of developing MTC therapies that are not overly specific and only beneficial to a few individuals.
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