The green fluorescent protein - revolutionising cancer imaging and surgery.
GFP – what is it?
How does it work?
The gene that codes for GFP was cloned in 1994 and can now be found in laboratories all over the world, where it is used in countless plants and animals.
Using biomolecular techniques, the gene for GFP can be inserted into another gene before the stop codon, so that the encoded protein will be synthesised with the GFP attached. This protein will glow when illuminated by ultra-violet light and can now be traced within an organism. As GFP is a relatively small protein, it attaches easily to other proteins without hindering their original function, and can follow them into neurons without obstructing the fused proteins’ passage. Unlike other bioluminescent molecules, which require modifications before they fluoresce, GFP is intrinsically fluorescent (Zimmer, 2011).
Applications in cancer imaging and surgery
Cos-1 cells (cell line from African green monkey kidney)
expressing the different colour fluorescent proteins.
Nuclei are counterstained in blue.
One of the more advanced applications of GFP is as a method of labelling tumours for surgical navigation, which requires very precise identification and differentiation between malignant and benign tissue (Hoffman, 2002 & Teicher, 2010). Scientists have recently developed technology to insert and activate the GFP in the malignant tissue within an organism using an adenovirus that expresses the protein. This technique was trialled in two mouse-models manifesting widespread occurrence of cancer, which in humans would usually present as very challenging cases when using current imaging methods. However in both models only the metastatic tissue fluoresced, meaning that the GFP was specifically localised only in areas of malignancy. These promising results suggest that adenoviral-GFP labelling of tumours could provide greater precision in cancer treatment through fluorescence-guided surgical navigation (Teicher, 2010).
Click here for more information on cancer imaging using GFP.
Neuron expressing the molecule Arch,
here fused to green fluorescent protein.
However, the imaging of cancers and tumours is only one of the many possible applications of GFP. Other uses currently include utilising GFP to analyse brain circuitry, measure neural membrane potential and track the activity of certain receptors on cell membranes (Baker et. al, 2008). These applications continue to grow in scope and every month, over 100 papers are published reporting yet another novel method of using GFP (Zimmer, 2010).
Overall the green fluorescent protein gene is highly versatile: its simple but elegant application may eventually prove indispensable to all fields utilising molecular techniques and it also has the potential to revolutionise current methods used in these fields.
For more information on the green fluorescent protein's structure and applications, follow these links:
Baker et al 2008, ‘Genetically encoded fluorescent sensors of membrane potential’, Brain Cell Biology, vol. 36, no. 4, pp 53-67.
Boyden, E 2008, ‘Optogenetics’, Nature Neuroscience, vol. 8, pp 163 – 168.
Hoffman, RM 2002, ‘In vivo imaging of metastatic cancer with fluorescent proteins’, Cell Death and Differentiation, vol. 9, no. 8, pp786-789.
Kiefer, F 2010, Mammalian cell signalling laboratory, Max Planck Insitute for Molecular Biomedicine, viewed 1st April 2011, <http://www.mpi-muenster.mpg.de/en/research/teams/groups/rgkiefer/index.html>
Teicher, BA 2010, Tumour models in cancer research, 2nd edn, Springer, New York.
Yorkshire Cancer Research, 2010, Luminous cells from jellyfish could diagnose cancers deep within human body, Science Daily, viewed 18 March 2010, <http://www.sciencedaily.com/releases/2010/11/101103083906.htm>
Zimmer, M 2010, Green fluorescent protein: a molecular microscope, viewed 1st April 2012, <http://www.photobiology.info/Zimmer.html>
Zimmer, M 2011, The history of green fluorescent protein, viewed 17 March 2010,