Optimization of Intracellular Transportation of Gene Therapeutic DNA in Small Cell Lung Cancer (Ph.d.)

Frederik Cramer

    Abstract

    Small cell lung cancer (SCLC) is a highly malignant disease characterized as being very aggressive and
    metastasizing at a rapid pace. The malevolent pace of SCLC cell migration results in almost three out of
    four SCLC patients having disseminated SCLC at the time of diagnosis. Unfortunately, there are
    currently no satisfactory treatments for SCLC and the prognosis is poor. New treatments are therefore
    in high demand and one such could potentially be gene therapy. However, curing a metastasizing
    disease such as SCLC by gene therapy requires a systemically applied delivery system. Such a delivery
    system has to be able to repeated systemic delivery of gene therapy to cancer cells in a both safe and
    efficient way. Non-viral delivery vectors fulfill many of these requirements except the latter. It is
    currently very difficult to systemically transport sufficient amounts of therapeutic DNA, by a non-viral
    delivery system, to the nuclei of the SCLC cells. As a result, the gene therapy expression obtained is too
    low to have any clinical relevance. We have at the Department of Radiation Biology developed a
    transcriptionally targeting suicide gene therapy system which is built on a double stranded DNA
    plasmid framework. One of the most significant barriers for efficient plasmid transport however, is the
    nuclear envelope that compartmentalizes the transcriptional machinery from the translational in a
    human cell. As only a small fraction of plasmids is able to breach the nuclear envelope and gain access
    to the transcriptional machinery many attempts have been made to improve nuclear translocation of
    therapeutic plasmids in order to gain a better gene therapy outcome.
    The aim of this PhD project was to investigate if the intracellular translocation of our gene therapeutic
    system could be optimized in SCLC cells and thereby improving the efficacy of the treatment.
    By implementing what is known as a DNA nuclear targeting sequence (DTS) strategy, we found that
    we could utilize the SCLC cells own transportation system thereby manipulating the cancer cells to
    bring our therapeutic plasmids from the cytoplasm and into the nucleus. We found that we could
    significantly increase the gene therapy efficacy in both in vitro and in vivo by exploiting the transcription
    factor nuclear factor kappa B system which is often seen to be hyperactive in many forms of cancer. As
    almost all SCLC tumors develop chemoresistance, which is one of the reasons for the terrible poor
    prognosis, we also investigated if we could identify cellular pathway systems that could be exploited for
    gene therapy nuclear transport in SCLC cells that have developed chemoresistance. We identified
    several such pathways that could, similar to NF B, be “hijacked” to improve our gene therapy
    suggesting that the evasive alterations undertaken by cancer cells upon chemotherapy exposure, just
    might be turned against themselves.
    The results obtained in this PhD, strongly suggest that systemically applied gene therapy for SCLC can
    be significantly increased by optimizing the intracellular transportation of therapeutic DNA.
    OriginalsprogEngelsk
    Antal sider121
    StatusUdgivet - 14 jun. 2013

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