1. Fig. 2 Customizable physical characteristics of a nanoparticle
MicroRNAs as a novel treatment option for reproductive cancers Dr. Vincenzo Noto MSc in Reproduction & Development University of Bristol, Bristol, UK
1. Introduction
4. Study design and methods
Until few decades ago scientists considered non-protein coding RNAs as junk nucleotide sequences of no biological value. Now many papers have proven that these molecules seem to influence activities like apoptosis, gene expression, physiology, development and disease. MicroRNAs, discovered in 1993 in Caenorhabditis elegans, are small (21-23 nucleotides) single stranded non-coding RNAs that play a primary role in many cellular systems and tissues (Lee et al. 1993). Their discovery made the old postulate - DNA / mRNA / protein - obsolete since they act at post-transcriptional level modifying gene expression either repressing translation or degrading the mRNA (Fig. 1). MiRNAs play also an important role in carcinogenesis. In many tumours miRNAs are upregulated and by consequence considered like oncogenes while in others they are depleted indicating a role as tumour suppressors.
To test this hypothesis miR-449a profiling will be performed on blood samples and prostate biopsies taken from men (n=62) undergoing surgery for advanced T2-T3 PCa and the results compared to those of a group of healthy men age-matched (n=62). Mir-449a profiling will be used to better classify prostate cancers through an improved correlation with their histotype and to monitor prostate cancer treatment. In vivo experiments will be performed xenografting human PCa biopsies subcutaneously in immunodeficient mice and evaluating the tumoral response to systemically delivered mimic miR-449a encapsulated in new-generation nanoparticles. This original experimental protocol is also the occasion to test the nanoparticle vector Cyclosert™ for safe and reliable delivery of small molecules like miRNAs (Fig. 2).
Fig. 1 A simplified view of the miRNAs genesis . (a) Pri-miRNA, (b) Pre-miRNA , (c) Double stranded miRNA molecule after loop removal
Fig. 2 Customizable physical characteristics of a nanoparticle
2. Use of miR-449a in controlling human prostate cancer
5. Conclusions
Prostate cancer (PCa) is the 2nd cause of death in men after lung cancer and is a challenging disease because of its complexity in terms of histopathological findings and clinical aspects. Although many treatments have been used to eradicate tumours (radical surgery, radiotherapy, castration) aggressive prostate cancers, especially those with already present metastasis, often reappear within two years from the treatment and are hormone-insensitive, a condition not treatable with the available therapies. MiR-449a appears downregulated in PCa and has proven its effectiveness as anticancer tool in vitro in some human PCa cell lines (Noonan et al. 2010). Suggested mechanisms of action of miR-449a are:
Cell-cycle arrest
Apoptosis
Senescent-like cell phenotype
There is still little evidence in the literature regarding its use in in vivo animal models. In this grant proposal the possible use in vivo on an animal model (NOD-SCID mice) of a mimic miR-449a in replacement therapy is suggested.
MiRNAs represent a new and potentially powerful tool to work against tumoral cell growth and spreading (Bader et al. 2011). In vitro and in vivo animal studies have proven the potential application of miRNAs in oncology although further evidence of efficacy is required before clinical application. Further investigations on the possible use of miRNAs in prostate cancer identification and classification and also in establishing prognosis and recurrence risk are also needed. MiR-449a may be considered as a natural tumour suppressor (Noonan et al. 2009) and its replacement in prostate cancer should determine cell modifications that would allow tumour healing.
5. References
Bader AG, Brown D, Stoudemire J, and Lammers P. (2011) Developing therapeutic microRNAs for cancer. Gene Ther; Davis ME, Zuckerman JE, Choi CH, Seligson D, Tolcher A, Alabi CA, Yen Y, Heidel JD, and Ribas A. (2010) Evidence of RNAi in humans from systemically administered siRNA via targeted nanoparticles. Nature; Lee R, Feinbaum R, and Ambros V. (1993) The C. elegans heterochronic gene lin-4 encodes small RNAs with antisense complementarity to lin-14. Cell; Noonan E, Place R, Basak S, Pookot D, and Li L. (2010) miR-449a causes Rb-dependent cell cycle arrest and senescence in prostate cancer cells. Oncotarget; Noonan E, Place R, Pookot D, Basak S, Whitson J, Hirata H, Giardina C, and Dahiya R. (2009) miR-449a targets HDAC-1 and induces growth arrest in prostate cancer. Oncogene;
3. Main research hypothesis
Using miRNA replacement therapy is an effective and targeted way to control tumour growth. It is suggested that miR-449a may be used in PCa patients to control tumour growth and diffusion.
This hypothesis is based on:
MiR-449a regulates prostate cell proliferation
Its loss leads to the development of malignancy
Restoration of this miRNA will impose proliferative control of PCa cells reducing their growth
Nanoparticle delivery of mimic may solve the problems related to the traditional and often badly tolerated treatment options (side effects and systemic toxicity) (Davis et al. 2010)
6. Acknowledgments
I would like to express my gratitude to Dr. Kate Whittington, my supervisor and mentor, for helping and guiding me during the preparation of this dissertation.