GENETHERAPY-Deepwater：基因疗法-深水.ppt

GENE THERAPY By Sam Lai and Meng Lee Gene Therapy nIntroduction : What is it? nGene Therapy : A Closer Look nHow much did you learn?! nCase Study : SCID nModel for Gene Therapy Medical Framework nDiscussion / Q&A What is it? nGene therapy, which was first conceived in the mid-1970s, aims to insert working copies of genes into cells containing dysfunctional ones ntreat, cure, or ultimately prevent disease by changing the expression of a persons genes ncurrent gene therapy is primarily experimental, with most human clinical trials only in the research stages nMost often in context of treating lethal and disabling diseases, potential also for disease prevention Human Genome Project nA genome is all the DNA in an organism, including its genes. Genes carry information for making all the proteins required by all organisms nVariations in structure of persons genes collectively helps define us as individuals nRationale for GT is based on knowledge of the human genetic code nBegan formally in 1990, set as a 13 year project. HGP GOALS nIdentify aproximately 30,000 genes nDetermine 3 billion chemical base pairs that make up human DNA nStore information in databases nImprove tools for data analysis nAddress ethical, legal and social issues that might arise from this HGP cont nAchieve these goals, researchers look at genetic makeup of other organisms nThis project is important because the governments dedication to the transfer of technology to the private sector Which Cells Targeted? nsomatic gene therapy the recipients genome is changed, but the change is not passed along to the next generation ngermline gene therapy, the sex cells are changed with the goal of passing these changes to their offspring. But, this is not being actively investigated, at least not humans, although a lot of discussion is being conducted about its value and desirability. Somatic Stem Cells nSomatic stem cells are remarkable cells in the body nThese different stem cell types are targets for gene therapy nGenetically treated stem cells, when reintroduced into the patients body are expected to naturally travel through the blood stream to the bone marrow. Germline Gene Therapy nGene therapy in germline cells has the potential to affect not only the individual, but also their children as well. nAny genetic changes in the reproductive cells or changes made to the embryo before the stage of differentiation, would affect all future offspring of that person. This makes an vital distinction, affecting major ethcial issues Delivery of Genes nNeed an efficient method to deliver the gene to live cells. nDone via vectors (gene carriers), delivering therapeutic genes to cells - common vector is viruses nAlternative delivery methods seen with use of lipids and proteins Use of Viruses nViruses evolved a way of delivering their genes to human cells in pathogenic matter. nTake advantage of this, manipulate genome to remove disease genes and insert therapeutic genes Risks with GT trials nViruses can usually infect more than one type of cell. nWhen DNA is injected directly into a tumor, there is a slight chance that this DNA could unintentionally be introduced into reproductive cells. nOther concerns include the possibility that transferred genes could be “overexpressed“ Add a new chromosome? nExperimentation seen with introduction of 47th chromosome nExist along 46th chromosome, large vector capable carrying genetic code, that hopefully the immune system would not attack Understanding? nScientists know little about function of the thousands of genes. Attempting therapy without this knowledge would address few genes of a particular disease ni.e. Sickle Cell Anemia Sickle Cell Anemia nCaused by error in gene that informs our body on how to make hemoglobin nPrevalent in African Americans nHowever deadly the error is, this increased the survival rate for those who also had malaria in the region Hurdles nMost genetic disorders involve more than one gene, only few genetic diseases involve merely one nThis multigene disorders also involve the environment, such as diet, exercise, smoking, etc. Everything has a price nHigh costs associated with developing this technology, and regulations that needed to be implied on it with experimentations are great hurdles for experimenters in this field. First Human Gene Therapy attempt nBegan in 1990, using ex vivo strategy, where patient cells were cultivated in laboratory and incubated with vectors ntransplanted back into the patient nAttempted to treat 2 genetic disorders, including children with immune defiency as well as people with high levels of serum cholesterol First Human GT cont nPractical approaches, delivering genes based on so-called in vivo GT where viruses are directly given to patients nFirst model was dependent on a version of adenovirus to treat cystic fibrosis GT on Cancer Treatment nResearchers are working to improve the bodys natural ability to fight the disease or to make the cancer cells more sensitive to other kinds of treatment, such as chemotherapy nSubstitution of a “working“ copy of a gene for an inactive or defective gene. GT on Cancer cont nInjection of cancer cells with a gene that makes them more sensitive to treatment with an anticancer drug. nIntroduction of the multidrug resistance gene into stem cells. The MDR gene is used to make the stem cells more resistant to the side effects of the high doses of anticancer drugs. Hurdles Summary nThere are many obstacles that prevent researchers and scientist from developing successful gene therapy techniques. nThe issues being confronted are the same ones that are faced whenever a powerful new technology is developed. When All is Said nA proposed gene therapy trial, or protocol, must be approved by at least two review boards at the scientists institution. nAny studies involving humans must be reviewed with great care. CASE STUDY: SCID nSCID = Severe Combined Immunodeficiency What is SCID? nSCID patients can neither Construct cell-mediated immune response Make Antibodies nPatients do not die of SCID itself nMore Boys than Girls SCID Cases, Past & Present nNot discovered until early 1960s nOccur in 1 out of 1.000,000 n“Bubble Boy” David Vetter Spent 12 years in Texas Hospital Sterile Tent nUsually not discovered until too late Science Behind SCID (1) What Happens in SCID nLymphocyte T & B cells do not get developed Normal catabolism of purines deficient nBody lack messenger to identify foreign bodies nCannot initiate immune response Science Behind SCID (2) What Caused SCID? nADA (Adenosine Deaminase) enzyme deficiency Autosomal recessive inheritance of genes coding for ADA (25%) nCannot Make T cells Spontaneous Mutation of IL-7 Gene Science Behind SCID (3) Science Behind SCID (4) Possible Therapies nGem free tent (life long) nRegular injections of PEG-ADA nBone Marrow Transplant nGene Therapy GT Curing SCID (1) How mutated genes were discovered? nLate 1970s understood mechanism for immune system nMatch SCID to missing enzyme nBrute force / luck n1983 ADA cDNA identified & cloned GT Curing SCID (2) How mutations are corrected nRecombinant DNA technologies! nGene Splicing nInsertion of correct gene into retrovirus vector nSeparate & Multiply nInsert into patient GT Curing SCID (3) How to decide on delivery mechanism? nGoals: Must take up long-term residence in patient Must be expressed adequately nMethods: 1990 use patients own T cells (ADA) 1993 use blood stem cells (ADA) 1999 use blood stem cells (X-linked IL-7) GT Curing SCID (4) Gene Therapy Successes nSo far approximately 80% success rate nRestoration of normal cellular immunity in patients nBlood Stem Cells Method done on an increasing scale SCID Cure Analysis Why GT works in SCID? nDefect at a single gene locus nGenes identified & cloned nUndergo irradiation or immunosuppressive chemotherapy nTreatment of young children Discussion of Ethical, Legal & Social Issues nMany issues & concerns, little answers nReal life solutions come from idea brainstorms Today: Sample Medical System Framework Current Development nSigns of Development State Laws & Federal Bills which prohibits discrimination based on genetic information Special committee reviewing gene therapy (NIH + FDA) 3-5% of all funds for genetics studies must be used for investigation of such issues Targeted Issues nRegulation of Gene Therapy Assurance of Quality of Treatment Targeted Treatment nDisease Treatment vs. Enhancement nOnly Disease Treatment nFair & Readily Available Treatment Same Treatment for everyone At an affordable price nProtection of Genetic Information Assumptions nPossible to isolate and provide treatment only for disease alleles without committing enhancement nDevelopment in medical technologies will make medication cheaper in the long run nModel applies for a closed country only Model Philosophy nPossession of genetic information causes many problems nMust have a tightly regulated system in place (multi-level, multi-group) Proposal nCentral Gene Therapy Monitoring Administration Structure of Medical System n3 Levels, 5 Groups Government:CGTMAReview Committee Practitioners:DoctorsGene Therapeutics Patients:Patients Patient Treatment Process (1) n7 Steps nDisease Identification 1.1 Doctor Identifies Genetic Problem nApplication for Treatment 2.1 Doctor Submit Application nTreatment Approval 3.1 CGTMA Reviews Application Patient Treatment Process (2) nPreparation of Delivery Material 4.1 Gene Therapeutics cure the disease genes, deliver to patients stem cell nCo