GENE THERPAY PPT

1. Presented by
N.Narmatha
GENE THERAPY

2. CONTENTS
• Introduction
• History
• Gene therapy
• Genes
• Function of genes
• General principles of gene therapy
• Mode of transmission – vectors - types
• Types of gene therapy
• Techniques of gene therapy for oral cancer
• Clinical application in dentistry

3. INTRODUCTION:
• Gene therapy is an experimental technique that uses genes to treat
or prevent disease
• Consists of introducing specific genetic material into target cells
to compensate for abnormal genes or to make a beneficial protein
• Replace a faulty gene to introduce a new gene - cure or to
favourably modify the clinical course of the condition.

4. • Transferred genes – used for reparative or
pharmacological process
Genes are altered
Encoded proteins
Unable to carry out their normal function
Genetic disorders result

6. • 1995- potential impact of gene therapy on dentistry has been
described
• On the basis of initial studies of gene transfer applications to
salivary glands, keratinocytes and cancer cells
Gene therapy in seven areas relevant to dental practice are
• Bone repair
• Salivary glands
• Autoimmune disease
• Pain
• DNA vaccinations
• Keratinocytes
• Cancer

7. GENE THERAPY:
• It is a technique to deliver small DNA or RNA sequences to
cells or tissues to correct a genetic defect or treat a disease.
• Early 1980’s – genetic replacement therapy
GENES:
• Genes are the smallest functional units of the genetic system
specific sequences of bases that encode instructions to make
proteins
• linear sequence of DNA that codes for particular protein.

8. FUNCTON OF GENES:
• Determine the structure of proteins
• Controlling where, when and in what quantity each protein is made.

9. GENERAL PRINCIPLES OF GENE THERAPY:
Introduction of exogenous genes into somatic cells – form organs
with desired therapeutic effect
• DNA fragment cleaved using restriction
endonucleases
• Vector preparation – vector isolated,purified and
cleaved to allow insertion of DNA fragment
• DNA fragment joined to the cleaved ends of vector
• DNA chimera

10. Vector constructs- basis of recombinant DNA techniques
Second step
entry of modified vector to the target human cells
Releasing DNA sequence
becomes integrated within the chromosome.
As the gene is “switched on” in its correct location, the cells with the
new genetic design start forming the required therapeutic proteins

11. MODE OF TRANSMISSION:
VECTOR:
• Carrier called VECTOR is used to introduce therapeutic
gene into patient’s target cells.
• Most common vector – VIRUS that has been genetically
altered to carry normal human DNA
Types of vectors
Viral Non viral Physical

13. VIRAL VECTORS
Adenovirus
Retrovirus
Adenovirus –associated virus
Lentivirus
Vaccinia virus
Herpes simplex virus
NON VIRAL VECTORS:
Lipid complex
Liposomes
Peptide/protein
Polymers
PHYSICAL VECTORS
Electroporation
Microinjection
Gene gun
Ballistic particles

15. TYPES OF GENE THERAPY:
GERM LINE
THERAPY
SOMATIC
THERAPY
Gene insertion Into germ cells Into body cells
Modification Inherited by
offspring
Restricted to
individual
Safety Not ethically
safe
Ethically
sound and safe
TYPES OF GENE THERAPY

16. TECHNIQUES OF GENE THERAPY FOR ORAL CANCER
• Gene addition therapy
• Gene excision therapy
• Antisense RNA therapy
• Suicide gene therapy
• Gene therapy by oncolytic virus
• Immunotherapy

17. Gene addition therapy
• Regulates tumor growth
• Addition of tumor suppressor gene P53
• Induce apoptosis

18. Gene exicision therapy
• Inhibits tumor growth
• Removes defective oncogene
• Egr-1 (early growth response factor)
• Inhibits cell division

19. ANTISENSE RNA THERAPY
• Gene expression inhibited by RNA
• Prevents activity of oncogenes –myc, ras and fos
• Inhibits virus- HPV 1, HTLV, HSV -1

20. SUICIDE GENE THERAPY
Genes introduced
stimulates generation of products toxic to tumour cells
Enable prodrug to active cytotoxic drug

21. IMMUNE THERAPY
• Increases patient immune response
• Increases efficacy of NK cells,T cells and cytokines
TYPES:
• Therapeutic cancer vaccines
• Monoclonal antibodies
• Checkpoint inhibitors
• Cytokines
Administration of IL -2
activates T cells & NK cells activates TNF

22. GENE THERAPY BY ONCOLYTIC VIRUS:
• Viruses are genetically modified
• Replicates and lyses tumor cells
• Virus – HSV ,cheifly adenovirus
Adeno ONYX-015
Adeno ONYX15 + 5 –fluoracil
Increase in cytokines- IL – 6 ,TNF
Tumor regression

23. CLINICAL APPLICATION:
Accomplished in either of the two ways
Invivo exvivo
Invivo gene transfer:
Foreign gene introduced into patient by viral or non viral methods
Ex vivo gene transfer:
Foreign gene transduced into the cells of a tissue biopsy
Results in genetically modified cells
Transplanted back into patient

26. CLINICALAPPLICATION IN DENTISTRY

27. GENE THERAPY FOR PAIN MANAGEMENT
Management of chronic pain by sparing the use of drugs
• modified adenovirus,
• adeno associated virus (AAV)
• lipid encapsulated plasmids
coding for Interleukin-10 (therapeutic protein)
sub arachnoid space to transduce the pia mater cells
production and secretion of anti-nociceptive proteins
in or near spinal dorsal horns

28. Modified herpes virus
intradermal injection to the skin
nerves of Dorsal Root Ganglia (DRG)
• rationale for using herpes virus - infects nerves, ability to travel to
the DRG via nerve endings in the skin
• codes for inhibitory neurotransmitter, an anti-inflammatory
peptide or
• decreases the synthesis of an endogenous nociceptive molecule
alleviation of pain

29. CARCINOMAS
• Response rate is higher in combination of gene therapy with
other conventional treatment modalities.
• Carcinogenesis occurs by either
• overexpression of oncogenes such as Ras, Myc, Bcl‐2, ErbB2
• underexpression
• mutation of tumour suppressor genes such as p53, p16, p21,
Rb genes

30. Injection into the localized tumor mass precludes unwanted side
effects on the body and premature degradation of the gene before it
reaches the target cells

32. CORRECTIVE GENE THERAPY (GENE REPLACEMENT
THERAPY)
• correction of underlying genetic defect - control unrestricted
multiplication of tumour cells.
• over-expressed oncogenes are blocked or silenced by inclusion of
DNA into the cell - disrupting transcription and translation.
• With gene therapy
correct copy of p53 gene
introduced into the tumor cells
apoptosis.

33. In 2003 - the first gene therapy drug Gendicine, a recombinant
human adenovirus p53 - formulated for the treatment of SCCHN
and other cancerous lesions.

34. CYTOREDUCTIVE GENE THERAPY
• Aims at destruction of tumour cells
• Insertion of suicide genes - tumour cells - encode for enzymes –
convert chemotherapeutic drugs into their toxic form
• Limit angiogenesis
• apoptosis in tumour cells
• Selectively multiply in tumour cells and kill them-
• size of the tumour after its surgical removal and prevent
metastasis
In 2005 - first genetically engineered oncolytic virus, H101
Adenovirus, - approved for treatment of SCC

35. MODIFICATION OF IMMUNE SYSTEM:
Injecting genetically modified hematopoietic stem cells & T cells
boost up host’s immune system
Identify and kill tumor cells.
Insertion of a gene in tumor cells
Upregulate their antigen markers
Susceptible to destruction by the body’s own immune system.

36. Insertion of a gene encoding for cytokines.
concentration of cytokines in tumor cells
• Immunotherapy beneficial in treatment of SCC, melanoma,
lymphoma and some virus induced malignancies

37. BONE REGENERATION
At least four imperative elements are required for successful
bone regeneration
• osteoinduction,
• differentiation of osteoblasts
• osteoconduction and
• mechanical stimulation.
• Gene therapy enhances the first three conditions

38. Osteoinductive potential of Bone morphogenetic proteins (BMP-2,
4 and 7) - induce de novo bone formation
delivering the BMP-2 genes directly to the tissues
via an adenoviral vector
healing of mandibular osseous defects

39. • Non-osteogenic fibroblasts (from human gingiva and dental
pulp) and myoblasts, osteoblasts - express BMP-7 gene after
infected with an adenoviral vector – differentiate into bone
forming cells when placed in an osseous defect in vivo

40. • Growth arrest specific (gas) gene encodes the PDGF factor –
down regulation of PDGF activity – transient biological
activity
• Bioactive PDGF gene - inhibitory effects of growth arrest
gene - wound healing
• bone sialoprotein - involved in bone repair along with the
CBFA1 gene- involved in cell differentiation and gene
expression of bone sialoprotein

41. Salivary glands exhibit
• Self-containment due to a surrounding capsule - minimize
undesirable access of administered vectors and transgenes to
other tissues
• Highly efficient protein production
• Secrete proteins into bloodstream - potentially useful target
sites for gene transfer in a minimally invasive manner with
the help of intraductal cannulation.

42. IONIZED RADIATION
Damage to fluid secretory portion (acinar cells) of the salivary
gland
Hypofunctional salivation aquaporin 1 gene
• Aquaporin 1 (aq1) is a water channel protein that counter
balances this detriment by a constitutively activated water
channel.

43. • Human trial in 2012 - promising results for using aquaporin-1
cDNA for the management of radiation-related salivary
hypofunctions
• AQP1 gene therapy for the management of xerostomia patients

44. • Osteoprotegerin (OPG)+ receptor activator of nuclear factor
kappa-B ligand (RANKL) - inhibits osteoclastogenesis
jamming the process of bone resorption.
• Local RANKL gene - transferred to periodontal tissue -
accelerated orthodontic tooth movement
• (150% after 21 days) - reducing the time of treatment.

45. DNA VACCINATION
Immunization of salivary gland
plasmid DNA encoding P.gingivalis fimbrial gene
fimbrial protein in salivary gland tissue
specific salivary immunoglobulin A, or IgA, G, or IgG,
fimbrial protein in saliva
bind to pellicle components
inhibit the attachment of P. gingivalis to the developing
plaque.

46. • Prevent periodontal diseases and dental caries.
• plasmid pCIA-P encoding pac gene of S.mutans - induce
anticaries immune responses

47. TOOTH REPAIR AND REGENERATION
• Gene therapy presents an attractive concept of restoring the oral
tissues lost due to caries, periodontal diseases and trauma.
• Widen the scope for development of new teeth—the biological
implants for missing teeth.

49. Two basic approaches
In vivo gene therapy,
• Healing potential of tissues such as dentine pulp complex -
enhanced by genes - dentine formation - on the exposed dental
pulp
• Third dentition - induced to form teeth - turning on or
activating genes - code for proteins and signaling molecules
making up the basic structure of teeth

50. Ex vivo gene therapy -
• based on multipotent dental stem cells - potential to differentiate
into any tissues including dental tissues.
• sources - dental pulp, apical papilla, dental follicles, deciduous
teeth, and periodontal ligaments.

51. Stem cells - cultured, modified or transfected - re-implanted back
into the recipient.
stem cells engineered by the adenovirus to express the BMP-2 gene
regeneration of the periodontal attachment apparatus including
alveolar bone and cementum

52. CONCLUSIONS
Considering the exponential rise in reported cases of oral squamous
cell carcinoma and periodontal diseases, gene therapy is expected to
be a very useful tool for the management of oral diseases and
improving the prognosis and quality of life.

53. REFERENCES
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