Difference between revisions of "Team:Duesseldorf/Future Applications"

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<h1>Description</h1>
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<h1>Future Application</h1>
 
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In Germany, every fourth death is caused by cancer. The malignant tumors are a threat to every organ in the body, however most are found in men’s prostate or mammary gland in women. The most deaths are caused by cancer located in breast and lungs. <sup>[1]</sup>
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“The whole is more than the sum of its parts.” The very same principle is valid for OPTOPTOSIS. Besides our idea to induce apoptosis with the help of optogenetics, we expanded our construct into a whole concept. We did not only build two “kill- switches”, we also thought about what would come next. This means we developed a strategy how to <a href="#Viral_Vectors">get our construct in cancer cells</a> and found various solutions how to <a href="#Light">get the light to the target tissue</a>.
 
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<h2 id="Viral_Vectors">Viral Vectors </h1>
 
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Every treatment in use has various side effects, which can affect the body more than the actual disease, weakening the sick person even more. A new cancer therapy without side effects is needed and can be realized using optogenetics due to its high accuracy. <sup>[2]</sup>
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Viral vectors are modified viruses that are used in medical or biological research to insert specific genes into a test-organism. The concept of viral vectors is based on the ability of viruses to inject their genome into a cell while being specific to the membrane proteins of the particular target cell.
 
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From the beginning, the goal of Optoptosis was to fight cancer and to ameliorate commonly known and used cancer therapies. Decreasing the patients’ suffering and improving their quality of living was our driving incentive.
 
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Treatments with state of the art cancer therapies are painful for the patients and they not only have to suffer from the disease, but also from the side effects of the therapy which may last up to a lifetime.
 
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The number of mortal cancer cases worldwide sums up to 8.2 million deaths per year. Resulting in one dead american citizen per minute.
 
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Current <a href="https://2016.igem.org/Team:Duesseldorf/Therapies"> cancer therapies</a> fail in stopping the mortality rate. <br>
 
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<img src="https://static.igem.org/mediawiki/2016/b/bd/T--duesseldorf--Cancer_Stats.jpg">
 
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Reference: <a href="http://www.cdc.gov/cancer/international/images/worldwide-survivor-stackedchart.jpg">http://www.cdc.gov/cancer/international/images/worldwide-survivor-stackedchart.jpg</a>
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The virus replication is inhibited due to the deletion of some of its genes, so the virus needs a "helper virus" to complete their viral life cycle. These viruses are part of new approaches in cancer treatment, but this technique still is in the developmental stage due to side effects.
 
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Our innovation has the potential to decrease the suffering through specifically targeting the lost function of self-induced cell death (apoptosis) in cancer cells. The process of apoptosis can be learned here.
 
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Optoptosis uses two optogenetic proteins, namely LOV2 and Phytochrome B to combine the precision of light with the accuracy of viral vectors to induce apoptosis specifically in cancer cells. The red light switch controls expression through PhyB-VP16, while the blue light switch controls the localization of apoptotic proteins to their target site with the help of LOV2.
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Gene therapy uses a lot of different viral vectors depending on the application. Commonly used viral vectors are Adenoviruses, AAV's (Adeno-associated viruses), Herpes simplex or Lentiviruses.  
 
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<h2>Mechanism of an optogenetic system for induction of apoptosis in cancer cell lines</h2>
 
 
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The optogenetic induction of apoptosis in cell cultures (HeLa and CHO) serves as a model for the future application in situ. The application of optogenetic switches enables us to induct extremely precise and highly regulated elimination of malignant cells. Thereby, this system will represent an improvement in comparison to conventional, less target-specific methods. The sequential utilization of two optogenetic switches, namely a Phytochrome-based expression system and a LOV2-based switch needed for the localization of apoptotic proteins to the outer mitochondrial membrane allows the attainment of a very high level of spatiotemporal specificity for the activation of apoptosis.  
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AAVs belong to the group of so called satellite viruses, which depend on the help of other non-related viruses (Adenoviruses in this case) to be infectious. AAV that enter a cell cause less to no damage to the organism and therefore are ideal for gene therapy, as they can transport genes to certain tissues without triggering any disease in the host organism. <sup>[1]</sup>
 
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2. Spielerei mit den Lichtschaltern ON/OFF
 
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<h2>Mechanism of the Phytochrome-based expression system</h2>
 
 
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The first optogenetic switch functions via Phytochrome B (PhyB) derived from Arabidopsis thaliana. PhyB’s natural chromophore is Phytochromobilin. Phytochromobilin is not found in mammalian cells but it is possible to use Phycocyanobilin extracted from Cyanobacteria instead (Q2) . Phycocyanobilin is ligated to the photosensory domain  at the N-Terminus of PhyB which is, upon photoexcitation, responsible for conformational change. The activation through conformation change is responsible for binding to PIF6 (phytochrome interacting factor6).  In response to red light (λ = 660nm) Phytochrome transits into its PhyBfr-conformation. In this state PhyB can interact with PIF6 through binding. <sup>[3]</sup>  
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Adenoviruses themselves are icosahedral double-strand DNA viruses, which cause harmless infections of the respiratory system in humans and are often used as vectors in gene therapy. <sup>[2]</sup>
 
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[GRAFIK ARABIDOPSIS THALIANA] [sTRUKTURMODELL VON PHYCOCHROMOBILIN PHYCICYANOBILIN]
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Herpes simplex viruses derivatives or hybrids with suitable viruses are other viral-based delivery systems for gene therapy. The natural property of a long term infection without symptoms suits these viruses perfect for a stable transcription of a specific gene-product. For example, for a therapy a HSV-1/AAV hybrid can be  advantageous with the specificity of the AAV and the replication as well as the capacity of the HSV-1 making this hybrid perfect for the transduction of large DNA-fragments.  <sup>[3]</sup> <sup>[4]</sup> <sup>[5]</sup> <sup>[6]</sup> <sup>[7]</sup>
 
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Q2:
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Phycocyanobilin, Phytochromobilin ( “The natural PhyB chromophore Phytochromobilin is not found in mammalian cells, but it can be substituted for PCB that is conveniently extracted from the cyanobacterium Spirulina and when added to the culture medium is autoligated to PhyB (9).” -”A red/far-red light-responsive bi-stable toggle switch to control gene expression in mammalian cells “, Konrad Müller et. al p. 5: Funktionsweisen, woher kommt das (pflanzen, Tiere), wie wird das den Zellen zugeführt
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Retroviruses can also be utilized as a viral-based vector system. MLV (Moloney leukemia virus) and HIV-1(human immunodeficiency virus) are used in gene therapy. This retroviral approach is a longterm expression system due to the genome integration of the inserted into the  host genome.  <sup>[8]</sup> Lentiviruses have been already used as vectors in clinical trials and can potentially be a powerful tool in gene therapy. <sup>[9][10][11]</sup>
 
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The N-terminus of PIF6  is fused to tetR (tetracyclin Repressor), which constitutively binds the operator tetO upstream of a minimal promoter (Pmin). On the other hand, PhyB is fused to the transcription factor VP16. When the red light switch is activated, VP16 is recruited to the promoter region, so that the vicinity of VP16 to the promoter region allows initiation of transcription. Far-red light (λ = 740nm) is applied to the system in order to deactivate the switch. Under far-red light PhyB reverts back to its PhyBr-state and interaction with PIF6 is terminated (see fig. 1). <sup>[4]</sup>
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Our constructs could be inserted into the targeted cells with AAV's, adenoviruses or even with a HSV-1/AAV like hybrid vector system. Once infected these cells would be able to express the blue light switch and the red light switch. It would be necessary that two viruses infect the same cell to ensure interaction due to the size of our constructs in kb. A double infection would only be necessary if AAV’s or Adenoviruses alone are used for transduction, this can be avoided if a e.g. AAV/HSV-1 Hybrid is used.
 
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<img src="https://static.igem.org/mediawiki/2016/0/0d/T--duesseldorf--03.png">
 
 
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The PDZ-mCherry-BaxS184E construct, which expression is regulated by the PhyB-based switch, represents a component of the second optogenetic switch that is based on LOV2. The protein BaxS184E lays in a fusion with the fluorescent protein mCherry and the Jα-binding PDZ-domain (see fig. 2). We use the hBax mutant BaxS184E, because it is not as deadly as the natural human BaxS184E protein. The BaxS184E mutant binds less effectively to the mitochondrial membrane and shows a decreased apoptotic potential in comparison to the non-mutated version. We plan to use this as an additional safety measure, so that the sole expression of BaxS184E does not cause apoptosis, but only if it is  bound to the mitochondrial membrane with the help of the blue light switch construct.
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Non-viral approaches in gene therapy are also being developed, making use of the Crispr-cas9 editing system. Single gen-knockout or even knock-in can be used with this system making it suitable for gene therapy. The human immune system can be an obstacle in this therapy approach. <sup>[12]</sup>
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[The PDZ-mCherry-BaxS184E construct, which expression is regulated by the PhyB-based switch, represents a component of the second optogenetic switch that is based on LOV2. The human protein BaxS184E lays in a fusion with the fluorescent protein mCherry and the Jα-binding PDZ-domain. In our construct we used the weaker BaxS184E mutant BaxS184E. BaxS184E is not as deadly as the natural human BaxS184E because it is binding less effectively to the mitochondrial membrane and shows a decreased apoptotic potential. We planed to use this as an additional safety measure to prevent the BaxS184E from causing apoptosis by sole expression. Apoptosis only occurs when BaxS184E, triggered by our blue-light-switch construct is bound to the mitochondrial membrane.]  
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We plan to use this as an additional safety measure, because the sole expression of BaxS148E does not cause apoptosis. Only when the blue light switch turns on the BaxS184E is bound to the mitochondrial membrane and the apoptosis is triggered.
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Quelle BaxS184e: https://www.ncbi.nlm.nih.gov/pubmed/20976235
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<img src="https://static.igem.org/mediawiki/2016/5/55/T--duesseldorf--04.png">
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Another non-viral approach would be the use of so called minicircle DNA a vector system used for the transfection of mammal cells. All prokaryotic sequences have been removed from the plasmid leading to a great size-reduction of the vector and therefore significantly increasing the transfection efficiency and expression rate compared to usual plasmids. <sup>[13]</sup>
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  <hr style="border:solid #0C9476 1px;margin:auto; margin-top:10px;margin-bottom:10px;">
  
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<h2>Expression of fusion proteins utilizing a constitutive promoter</h2>
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<h2 id="Light">The Light Into Tissue Struggle</h2>
 
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Another construct needed for the LOV2-based optogenetic switch is expressed constitutively in the cells. For this purpose, expression of this construct is brought under control of the pSV40 viral promoter.
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To treat tumors effectively it is necessary for light to reach the effected organ with sufficient intensity. For PhytochromeB best results were achieved when it was exposed to over 60 nmol*cm-2. The optical density of live tissue is highly dependent on the length of the electromagnetic waves. For the needed wavelength of 473 nm the blue light only reaches about 1 mm into tissue. For a 660 nm however the absorption coefficient is lower, so red light can reach a depth of 1 cm. <sup>[14]</sup>
 
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The fusion protein consists of the mitochondrial anchor TOM5 (translocase of the outer membrane 5), the fluorescent protein GFP (green fluorescent protein) and the optogenetic protein LOV2 (light-oxygen- voltage-sensing 2) derived from Avena sativa (see fig. 3). The C-terminus of LOV2 contains the so called Jα-helix (see fig. 3), which allows binding with PDZ (see fig. 2).
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To overcome the hurdle of high absorption coefficient we developed different approaches. UCNPs stands for Upconversion Nanoparticles, artificial molecules with the feature of changing the wavelength of light. When exposed to near infrared (NIR) light with a length of 980 nm, UCNPs emit light of another length: 475 nm for example. <sup>[15]</sup>
 
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<img src="https://static.igem.org/mediawiki/2016/3/38/T--duesseldorf--18.png">
 
 
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TOM5 is a mitochondrial protein that is responsible for recognizing and initially importing of all proteins directed to the mitochondria. Moreover, it is involved in transfer of precursors from the Tom70p and Tom20p receptors to the Tom40p pore, which are supposedly responsible for porin import into the mitochondria <sup>[6]</sup> <sup>[7]</sup>.
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Near infrared light travels further into tissue than blue light. Using this effect UCNPs found use in photodynamic therapies, to kill deep tumors using the better penetration of NIR light. Gang Han kills tumors in a greater depth than 1 cm with the aid of the artificial molecules. <sup>[16]</sup>
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Zitat aus (richtig zitieren)
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Component of the TOM (translocase of outer membrane) complex; responsible for recognition and initial import of all mitochondrially directed proteins; involved in transfer of precursors from the Tom70p and Tom20p receptors to the Tom40p pore 1 2
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For our project, we used a double mutant of LOV2 derived from Avena sativa phototrophin 1 fused with a peptide epitope on the Jα-helix called AsLOV2pep (Tulip supplementary Fig. 2a and Supplementary Note 1). The peptide epitope consists of the following sequence –SSADTWV–COOH. <sup<[8]</sup> AsLOV2pep is a double mutant. The original sequence of Jalpha is blub, the mutant sequence is blab.
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No bigger than 70 nm the UCNPs could either be injected in the blood, which poses the questions of how to get them out, or be attached to proteins. To fix UCNPs on proteins streptavidin is installed on the surface, which interacts with a StrepTag that is be synthesized on proteins.<sup>[17]</sup>
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Abbildung Figure 2 aus sup8
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<img src="https://static.igem.org/mediawiki/2016/0/0f/T--duesseldorf--sup8img2Schrift.png">
 
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<h2>The LOV2-based optogenetic switch allows localization of apoptotic proteins to the outer mitochondrial membrane</h2>
 
 
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Once both components of the LOV2-switch have been synthesized and brought automatically  to their target site they are ready to interact. In order to absorb light, the LOV2 protein needs the chromophore FMN which is produced from the cells themselves and binds to the α/β-scaffold of LOV2. The inactivated state of LOV2 is called D450 and converts to the activated State S390 after blue-light induction <sup<[9]</sup>
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To expose tumors which depth NIR cannot reach, the use of optical fibers becomes inevitable. The fibers direct light of any color to their tip exploiting the effect of total reflection. Being less invasive than common surgeries in cancer treatment due to a thickness of a few µm is the immense advantage. Also, the minuscule diameter allows immense precision for the illumination.
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<img src="https://static.igem.org/mediawiki/2016/a/a0/T--duesseldorf--01.png">
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https://static.igem.org/mediawiki/2016/a/a0/T--duesseldorf--01.png
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Our AsLOV2pep is flanked with α-helices on the N- and C-terminals. Upon photoexcitation with blue light (λ = 472nm) the C-terminal Jα-helix from the AsLOV2-core and unfolds slightly (TULIP, Fig. 1b). It forms weak interactions with the α/β-scaffold of LOV2 <sup<[10]</sup>.
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mögliche antworten hier?:
 
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Chem Biol. 2012 Apr 20;19(4):507-17. doi: 10.1016/j.chembiol.2012.02.006. Designing photoswitchable peptides using the AsLOV2 domain.Lungu OI1, Hallett RA, Choi EJ, Aiken MJ, Hahn KM, Kuhlman B.
 
 
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The exposure of the Jα-helix allows the interaction with a binding partner. The additional mutation of an epitope tag enables the Jα-helix to bind to ePDZ. ePDZ originally stems from mice, while LOV2 is derived from plants.  using the associated peptide elongation for stronger binding (erst möglich zu binden, dadurch, dass pep an As LOV2 hängt kann ePDZ binden) [tulip]. It is now able to attach the ePDZ-domain of the other fusion protein, which contains BaxS184E. LOV2 is bound to the OMM (outer mitochondrial membrane) due to its mitochondrial anchor TOM5. Therefore, binding between Jα and ePDZ causes recruitation of BaxS184E to the OMM (fig. 4).
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Fibers are already used in mice to test the change of behavior when brain cells are exposed to light. This application, aiming to heal mental conditions like Parkinson’s Disease and Dementia is proof for the applicability of fibers in optogenetics and surgeries.
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Lovpep mutante mit ePDZb1 variante+ graphen aus paper (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4766841/ )
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hier?: "> Huang, J., Koide, A., Makabe, K. & Koide, S. Design of protein function
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leaps by directed domain interface evolution. Proc. Natl. Acad. Sci. USA 105,
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6578–6583 (2008).
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<h5> References</h5>
 
<p>
 
<p>
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Here BaxS184E forms pores in the OMM allowing the release of cytochrome c, triggering apoptosis (fig. 5). So BaxS184E is only capable of fulfilling its function, when its expression has firstly been activated by the phyB-based switch and secondly, when it has been recruited to the mitochondria by activation of the LOV2-based switch. An autonomous localization of BaxS184E to the mitochondria does not occur, because a mutant form (Bax S184E) (Grund? oben) is used, which ability to localize to the OMM is lost. Thus BaxS184E will only be found at its target site after activation of the blue light regulated switch. The fluorescent proteins GFP and mCherry serve as markers. verweis apoptose
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<sup>[1]</sup>= Madigan et al., Brock Mikrobiologie (Pearson, 13th edition), p. 371 <br>
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<sup>[2]</sup>= Madigan et al., Brock Mikrobiologie (Pearson, 13th edition), p. 931<br>
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<sup>[3]</sup>= Saydam et al.2015, construction and packaging of herpes simplex virus/adeno-associated virus (HSV/AAV) Hybrid amplicon vector <a href=”https://www.ncbi.nlm.nih.gov/pubmed/22383640”> https://www.ncbi.nlm.nih.gov/pubmed/22383640</a> <br>
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<sup>[4]</sup>= Andreas Jacobs et al. 1999,HSV-1-Based Vectors for Gene Therapy of Neurological Diseases and Brain Tumors: Part II. Vector Systems and Applications <a href=”https://www.ncbi.nlm.nih.gov/pubmed/25431072”>https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1508111/</a> <br>
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<sup>[5]</sup>= Marconi et al.2015, Herpes simplex virus type 1(HSV-1)-derived recombinant vectors for gene transfer and gene therapy <a href=”https://www.ncbi.nlm.nih.gov/pubmed/25431072”>https://www.ncbi.nlm.nih.gov/pubmed/25431072</a> <br>
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<sup>[6]</sup>= Published online 2013 Apr 23,<a href=”https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3908892/figure/F1/”>https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3908892/figure/F1/ </a> <br>
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<sup>[7]</sup>=  Michele Simonato et al.2013 Apr 23,Progress in gene therapy for neurological disorders <a href=”https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3908892/”>https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3908892/</a><br>
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<sup>[8]</sup>= José Eduardo Vargas, Leonardo Chicaybam et al. 2016 Oct 12, Retroviral vectors and transposons for stable gene therapy: advances,  current challenges and perspectives <a href=”http://translational-medicine.biomedcentral.com/articles/10.1186/s12967-016-1047-x”>http://translational-medicine.biomedcentral.com/articles/10.1186/s12967-016-1047-x </a> <br>
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<sup>[9]</sup>=Seassa M. et al. 2016 Jul 30, Lentiviral haemopoietic stem-cell gene therapy in early-onset metachromatic leukodystrophy: an ad-hoc analysis for a non-randomised, open-label, phase 1/2 trial <a href=”https://www.ncbi.nlm.nih.gov/pubmed/27289174”> https://www.ncbi.nlm.nih.gov/pubmed/27289174 </a><br>
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<sup>[10]</sup>=Nasirinezhad et al. 2015 Jan 7 , Viral vectors encoding endmorphins and serine histogranin attenuate pain symptoms after spinal cord injury in rats <a href=” https://www.ncbi.nlm.nih.gov/pubmed/25563474#”> https://www.ncbi.nlm.nih.gov/pubmed/25563474#</a> <br>
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<sup>[11]</sup>=Mautino, Morgan. 2002 Jan 16, Gene therapy of HIV-1 infection using lentiviral vectors expressing anti-HIV-1 genes <a href=” https://www.ncbi.nlm.nih.gov/pubmed/11839215 “>  https://www.ncbi.nlm.nih.gov/pubmed/11839215</a> <br>
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<sup>[12]</sup>=Fogleman et al. 2016 Aug 20, Crispr/cas9 and mitochondrial gene replacement therapy: promising techniques and ethical considerrations<a href=”https://www.ncbi.nlm.nih.gov/pubmed/27725916”> https://www.ncbi.nlm.nih.gov/pubmed/27725916 </a><br>
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<sup>[13]</sup>=Kobelt, D., Schleef, M., Schmeer, M. et al., Performance of High Quality Minicircle DNA for In Vitro and In Vivo Gene Transfer, Mol Biotechnol (2013)  
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<sup>[14]</sup>= Scott Prahl, Optical Absorption of Hemoglobin, Oregon Medical Laser Center, http://omlc.org/spectra/hemoglobin/ retrieved 2016-10-15 <br>
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<sup>[15]</sup>= Steven L Jacques (2013) Optical properties of biological tissues: a review, Institute of Physics and Engineering in Medicine, http://omlc.org/news/dec14/Jacques_PMB2013/Jacques_PMB2013.pdf <br>
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<sup>[16]</sup>= Jim Fessenden (2014) Tuning light to kill deep cancer tumors, http://www.umassmed.edu/news/news-archives/2014/10/tuning-light-to-kill-deep-cancer-tumors/ retrieved 2016-10-15<br>
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<sup>[17]</sup>= Tan, He, Han, Zhou, Optogenetic Immunomodulation: Shedding Light on Antitumor Immunity, Cell Press, TIBTEC 1434
 
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<h3>References:</h3>
 
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<p>
 
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<sup>[1]</sup>= Peter Kaatsch, Claudia Spix, Alexander Katalinic, Stefan Hentschel, Nadia Baras, Benjamin Barnes, Joachim Bertz, Stefan Dahm, Jörg Haberland, Klaus Kraywinkel, Antje Laudi, Ute Wolf: <a href=”http://www.krebsdaten.de/Krebs/DE/Content/Publikationen/Krebs_in_Deutschland/krebs_in_deutschland_node.html”>Krebs in Deutschland 2007/2008 – Häufigkeiten und Trends.</a> A publication from „Robert-Koch-Institut“ and „Gesellschaft der epidemiologischen Krebsregister in Deutschland e. V.“, 8. Edition, 2012, retrieved 3/15/2013
 
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<sup>[2]</sup>= Enger, Eldon; et al. Concepts in Biology' 2007 Ed.2007 Edition. McGraw-Hill. p. 173. ISBN 978-0-07-126042-8. Retrieved 23 November 2012.
 
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<sup>[3]</sup>= Khanna,R., Huq,E., Kikis,E.A., Al-Sady,B., Lanzatella,C. and Quail,P.H. (2004) A novel molecular recognition motif necessary for targeting photoactivated phytochrome signaling to specific basic helix-loop-helix transcription factors. Plant Cell, 16, 3033–3044.
 
  
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<br>
 
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<sup>[4]</sup>= Müller et al.(2013) A red/far-red light-responsive bi-stable toggle switch to control gene expression in mammalian cells, Nucleic Acids Research, 2013, Vol. 41, No. 7 e77 doi:10.1093/nar/gkt002
 
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<sup>[6]</sup>= Krimmer T., Rapaport D., Ryan Michael T., Meisinger C., Kenneth Kassenbrock C., Blachly-Dyson E., Forte M., Douglas Michael G.Neupert W., Nargang Frank E., Pfanner N. (2001 Jan. 22),  Biogenesis of Porin of the Outer Mitochondrial Membrane Involves an Import Pathway via Receptors and the General Import Pore of the Tom Complex, J Cell Biol., Vol. 152(2): 289–300. PMCID: PMC2199606
 
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<sup>[7]</sup>= <a href=”http://www.yeastgenome.org/locus/tom5/overview”>http://www.yeastgenome.org/locus/tom5/overview</a> [last access: 10/16/2016]
 
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<sup>[8]</sup> = Strickland D., Lin Y., Wagner E., Hope M., Zayner J., Antonious C., Sosnick T.R., Weiss E.L., Glotzer M. (2012), TULIPS: tunable, light-controlled interacting protein tags for cell biology, Nature Vol.9(4), doi:10.1038
 
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<br>
 
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<sup>[9]</sup> =Okajima K. (2016), Molecular mechanism of phototropin light signaling, J Plant Res 129(2):149-157. doi: 10.1007/s10265-016-0783-6
 
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<br>
 
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<sup>[10]</sup> = Halavaty AS, Moffat K (2007), N- and C-terminal flanking regions modulate light-induced signal transduction in the LOV2 domain of the blue light sensor phototrophin 1 from Avena Sativa. Biochemistry 46:14001-14009
 
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evtl noch Quellen:
 
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Levskaya,A., Weiner,O.D., Lim,W.A. and Voigt,C.A. (2009), Spatiotemporal control of cell signalling using a light-switchable protein interaction. Nature, 461, 997–1001.
 
  
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"> Strickland, D., Moffat, K. & Sosnick, T.R. Light-activated DNA binding in a
 
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designed allosteric protein. Proc. Natl. Acad. Sci. USA 105, 10709–10714
 
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(2008).
 
  
 
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Revision as of 07:22, 19 October 2016


Heinrich-Heine University
Universitätsstraße 1
40225 Düsseldorf
Design by Marvin van Aalst

Future Application

“The whole is more than the sum of its parts.” The very same principle is valid for OPTOPTOSIS. Besides our idea to induce apoptosis with the help of optogenetics, we expanded our construct into a whole concept. We did not only build two “kill- switches”, we also thought about what would come next. This means we developed a strategy how to get our construct in cancer cells and found various solutions how to get the light to the target tissue.

Viral Vectors

Viral vectors are modified viruses that are used in medical or biological research to insert specific genes into a test-organism. The concept of viral vectors is based on the ability of viruses to inject their genome into a cell while being specific to the membrane proteins of the particular target cell.

The virus replication is inhibited due to the deletion of some of its genes, so the virus needs a "helper virus" to complete their viral life cycle. These viruses are part of new approaches in cancer treatment, but this technique still is in the developmental stage due to side effects.

Gene therapy uses a lot of different viral vectors depending on the application. Commonly used viral vectors are Adenoviruses, AAV's (Adeno-associated viruses), Herpes simplex or Lentiviruses.

AAVs belong to the group of so called satellite viruses, which depend on the help of other non-related viruses (Adenoviruses in this case) to be infectious. AAV that enter a cell cause less to no damage to the organism and therefore are ideal for gene therapy, as they can transport genes to certain tissues without triggering any disease in the host organism. [1]

Adenoviruses themselves are icosahedral double-strand DNA viruses, which cause harmless infections of the respiratory system in humans and are often used as vectors in gene therapy. [2]

Herpes simplex viruses derivatives or hybrids with suitable viruses are other viral-based delivery systems for gene therapy. The natural property of a long term infection without symptoms suits these viruses perfect for a stable transcription of a specific gene-product. For example, for a therapy a HSV-1/AAV hybrid can be advantageous with the specificity of the AAV and the replication as well as the capacity of the HSV-1 making this hybrid perfect for the transduction of large DNA-fragments. [3] [4] [5] [6] [7]

Retroviruses can also be utilized as a viral-based vector system. MLV (Moloney leukemia virus) and HIV-1(human immunodeficiency virus) are used in gene therapy. This retroviral approach is a longterm expression system due to the genome integration of the inserted into the host genome. [8] Lentiviruses have been already used as vectors in clinical trials and can potentially be a powerful tool in gene therapy. [9][10][11]

Our constructs could be inserted into the targeted cells with AAV's, adenoviruses or even with a HSV-1/AAV like hybrid vector system. Once infected these cells would be able to express the blue light switch and the red light switch. It would be necessary that two viruses infect the same cell to ensure interaction due to the size of our constructs in kb. A double infection would only be necessary if AAV’s or Adenoviruses alone are used for transduction, this can be avoided if a e.g. AAV/HSV-1 Hybrid is used.

Non-viral approaches in gene therapy are also being developed, making use of the Crispr-cas9 editing system. Single gen-knockout or even knock-in can be used with this system making it suitable for gene therapy. The human immune system can be an obstacle in this therapy approach. [12]

Another non-viral approach would be the use of so called minicircle DNA a vector system used for the transfection of mammal cells. All prokaryotic sequences have been removed from the plasmid leading to a great size-reduction of the vector and therefore significantly increasing the transfection efficiency and expression rate compared to usual plasmids. [13]

The Light Into Tissue Struggle

To treat tumors effectively it is necessary for light to reach the effected organ with sufficient intensity. For PhytochromeB best results were achieved when it was exposed to over 60 nmol*cm-2. The optical density of live tissue is highly dependent on the length of the electromagnetic waves. For the needed wavelength of 473 nm the blue light only reaches about 1 mm into tissue. For a 660 nm however the absorption coefficient is lower, so red light can reach a depth of 1 cm. [14]

To overcome the hurdle of high absorption coefficient we developed different approaches. UCNPs stands for Upconversion Nanoparticles, artificial molecules with the feature of changing the wavelength of light. When exposed to near infrared (NIR) light with a length of 980 nm, UCNPs emit light of another length: 475 nm for example. [15]

Near infrared light travels further into tissue than blue light. Using this effect UCNPs found use in photodynamic therapies, to kill deep tumors using the better penetration of NIR light. Gang Han kills tumors in a greater depth than 1 cm with the aid of the artificial molecules. [16]

No bigger than 70 nm the UCNPs could either be injected in the blood, which poses the questions of how to get them out, or be attached to proteins. To fix UCNPs on proteins streptavidin is installed on the surface, which interacts with a StrepTag that is be synthesized on proteins.[17]

To expose tumors which depth NIR cannot reach, the use of optical fibers becomes inevitable. The fibers direct light of any color to their tip exploiting the effect of total reflection. Being less invasive than common surgeries in cancer treatment due to a thickness of a few µm is the immense advantage. Also, the minuscule diameter allows immense precision for the illumination.

Fibers are already used in mice to test the change of behavior when brain cells are exposed to light. This application, aiming to heal mental conditions like Parkinson’s Disease and Dementia is proof for the applicability of fibers in optogenetics and surgeries.

References

[1]= Madigan et al., Brock Mikrobiologie (Pearson, 13th edition), p. 371
[2]= Madigan et al., Brock Mikrobiologie (Pearson, 13th edition), p. 931
[3]= Saydam et al.2015, construction and packaging of herpes simplex virus/adeno-associated virus (HSV/AAV) Hybrid amplicon vector https://www.ncbi.nlm.nih.gov/pubmed/22383640
[4]= Andreas Jacobs et al. 1999,HSV-1-Based Vectors for Gene Therapy of Neurological Diseases and Brain Tumors: Part II. Vector Systems and Applications https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1508111/
[5]= Marconi et al.2015, Herpes simplex virus type 1(HSV-1)-derived recombinant vectors for gene transfer and gene therapy https://www.ncbi.nlm.nih.gov/pubmed/25431072
[6]= Published online 2013 Apr 23,https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3908892/figure/F1/
[7]= Michele Simonato et al.2013 Apr 23,Progress in gene therapy for neurological disorders https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3908892/
[8]= José Eduardo Vargas, Leonardo Chicaybam et al. 2016 Oct 12, Retroviral vectors and transposons for stable gene therapy: advances, current challenges and perspectives http://translational-medicine.biomedcentral.com/articles/10.1186/s12967-016-1047-x
[9]=Seassa M. et al. 2016 Jul 30, Lentiviral haemopoietic stem-cell gene therapy in early-onset metachromatic leukodystrophy: an ad-hoc analysis for a non-randomised, open-label, phase 1/2 trial https://www.ncbi.nlm.nih.gov/pubmed/27289174
[10]=Nasirinezhad et al. 2015 Jan 7 , Viral vectors encoding endmorphins and serine histogranin attenuate pain symptoms after spinal cord injury in rats https://www.ncbi.nlm.nih.gov/pubmed/25563474#
[11]=Mautino, Morgan. 2002 Jan 16, Gene therapy of HIV-1 infection using lentiviral vectors expressing anti-HIV-1 genes https://www.ncbi.nlm.nih.gov/pubmed/11839215
[12]=Fogleman et al. 2016 Aug 20, Crispr/cas9 and mitochondrial gene replacement therapy: promising techniques and ethical considerrations https://www.ncbi.nlm.nih.gov/pubmed/27725916
[13]=Kobelt, D., Schleef, M., Schmeer, M. et al., Performance of High Quality Minicircle DNA for In Vitro and In Vivo Gene Transfer, Mol Biotechnol (2013) [14]= Scott Prahl, Optical Absorption of Hemoglobin, Oregon Medical Laser Center, http://omlc.org/spectra/hemoglobin/ retrieved 2016-10-15
[15]= Steven L Jacques (2013) Optical properties of biological tissues: a review, Institute of Physics and Engineering in Medicine, http://omlc.org/news/dec14/Jacques_PMB2013/Jacques_PMB2013.pdf
[16]= Jim Fessenden (2014) Tuning light to kill deep cancer tumors, http://www.umassmed.edu/news/news-archives/2014/10/tuning-light-to-kill-deep-cancer-tumors/ retrieved 2016-10-15
[17]= Tan, He, Han, Zhou, Optogenetic Immunomodulation: Shedding Light on Antitumor Immunity, Cell Press, TIBTEC 1434