This space represents the ideas, views, opinions, projects and data of researchers within the Aptamer Stream of the Freshman Research Initiative, a program developed at the University of Texas at Austin. These are projects we currently have in the pipeline.
- We're not exclusive...we are SELECTIVE!
RNA Aptamer Selection against FGF8b: diagnostic tool for neuronal differentiation
It is estimated
that over one million people will be diagnosed with cancer and over half a
million men and women will die of cancer of all sites this year. Particularly,
it is estimated that over 13,000 people will die of brain and nervous system
cancers this year (Howlader et al. 2012). Fibroblast growth factor 8b (FGF8b)
is an oncogene responsible in the formation of tumors. In the specific case of
neuronal differentiation, FGF8b signaling is largely involved in posterior
neural formation when studied in Xenopus.
It is found that “FGF8 is necessary for proper gastrulation and formation of
mesoderm” as well (Fletcher et al. 2006).
It has also been
observed that the loss of FGF8b reduces areas of the hindbrain and spinal cord
during development (Fletcher et al. 2006). Fgf8b activates the “Ras-extracellular
signal-regulated kinase (ERK) pathway,” which induces cerebellar development (Sato
et al. 2004). Besides neuronal sites, overexpression of FGF8b was found in the biopsies
of esophagus and prostate cancers (Lui et al. 2010, Zhong et al. 2011). “Upregulation
of the FGF8b signaling system seen in many cancers may contribute to the
proliferation of the malignant cells in vivo” (Viklund et al. 2006). Therefore,
an overexpression of FGF8b can lead to uncontrolled cell growth, leading to
tumors. An aptamer to be used as a diagnostic tool to detect the action of
neuronal differentiation could be used to quickly identify where and when
overexpression of this oncogene begins.
single-stranded RNA or DNA oligonucleic acid molecules which are selected for
different targets. Aptamer uses have expanded greatly since the discovery of
aptamers in 1990 (Tuerk and Gold 1990, Ellington and Szostak 1990). The
applications of aptamers include therapeutics, systems biology, diagnostics,
target validation, and drug delivery (Proske et al. 2005).Due to their three-dimension folded shape,
aptamers offer high selectivity and sensitivity. They have a high affinity for
a larger range of molecules: toxins, prions, and ion targets (Tombelli et al.
2004). Advantages of aptamers over monoclonal antibodies are that they can
differentiate between closely related targets, include chemically produced
oligonucleotide libraries, and have durable structure (Stoltenburg et al.
2007). The selection of this aptamer was applied through the SELEX (systematic
evolution of ligands by exponential enrichment) process, which, starting from
large libraries of oligonucleotides, allows the isolation of the high affinity
nucleic acids by the process of in vitro selection and amplification through
polymerase chain reaction (Proske et al. 2005).
Specific Aim 1: Selection of RNA
aptamers against FGF8b
FGF8b is an oncogene responsible in
the formation of tumors. When FGF8b is overexpressed, tumors are formed. Once a
particular sample of either early stage to late stage cancer cells has been
taken in vitro, an aptamer for FGF8b could
be introduced inside the cells. Where there is a proliferation of aptamer
binding (tagged with a fluorescent), a cancerous cell may be present. This will
enable surgeons to be able to remove cells in sites where these samples were
taken from (with continuous FGF8b aptamer binding) and prevent the spread of cancerous
cells. Figure 1 is a pictorial representation of how cells with aptamer binding
may be identified.
The figure above is a very simplified
idea of how an aptamer for FGF8b will help to identify cancerous neuron cells. Tagged
with a fluorescent, the aptamers will bind to the FGF8b oncogene. A large
amount of aptamer binding will indicate an overexpression of the oncogene, and
thus the cells can be isolated and therapy can start for the patient.
2.Ellington A, Szostak J. In vitro selection of
RNA molecules that bind specific ligands, Nature 1990; 346 (6287): 818-822.
3.Tombelli S, Minunni M, Mascini M. Analytical
applications of aptamers, Biosens Bioelectron 2004; 20 (12): 2424-2434.
Available from: http://www.ncbi.nlm.nih.gov/pubmed/15854817. Accessed2012 September 3.
4.Proske D, Blank M, Buhmann R, Resch A.
Aptamers—basic research, drug development, and clinical applications, Applied
Microbiology and Biotechnology 2005; 69 (4): 367-374. Available from:
http://www.springerlink.com/content/p77317t5u801gj31/. Accessed2012 September 1.
5.Lui VW, Yau DM, Cheung CS, Wong SC, Chan AK,
Zhou Q, Wong EY, Lau CP, Lam EK, Hui EP, Hong B, Hui CW, Chan AS, Ng PK, Ng YK,
Lo KW, Tsang CM, Tsui SK, Tsao SW, Chan AT. FGF8b oncogene mediates
proliferation and invasion of Epstein-Barr virus-associated nasopharyngeal
carcinoma cells: implication for viral-mediated FGF8b upregulation, Oncogene
2011 Mar 31;30(13):1518-30.
6.Fletcher R, Baker J, Harland R. FGF8 spliceforms
mediate early mesoderm and posterior
neural tissue formation in Xenopus, Development 133,
7.Sato T, Joyner AL, Nakamura H. How does Fgf
signaling from the isthmic organizer induce midbrain and cerebellum
development?, Dev Growth Differ. 2004 Dec;46(6):487-94.
8.Howlader N, Noone AM, Krapcho M, Neyman N,
Aminou R, Altekruse SF, Kosary CL, Ruhl J, Tatalovich Z, Cho H, Mariotto A,
Eisner MP, Lewis DR, Chen HS, Feuer EJ, Cronin KA (eds). SEER Cancer
Statistics Review, 1975-2009 (Vintage 2009 Populations), National Cancer
9.Zhong C, Saribekyan G, Liao C, Cohen M, Roy-Burman
P. Cooperation between FGF8b Overexpression and PTEN Deficiency in Prostate
Tumorigenesis. Cancer Res February 15, 2006 66; 2188.
10.Viklund L, Vorontsova N, Henttinen T, Salmivirta
M. Syndecan-1 regulates FGF8b responses in S115 mammary carcinoma cells. Growth
Factors. 2006 Jun;24(2):151-7.