1. Gene therapy involves introducing genetic material into patients' cells to treat disease. It has been used to treat head and neck cancers through corrective, cytoreductive, and immunomodulatory approaches. 2. Viral vectors such as adenoviruses and retroviruses are commonly used to deliver therapeutic genes to cancer cells, though they carry risks. Non-viral methods like electroporation are also used but less efficiently transduce cells. 3. Several gene therapy strategies for head and neck cancer have shown promise in clinical trials, such as Gendicine replacement of tumor suppressor p53 or use of oncolytic viruses to selectively replicate in cancer cells. However, challenges remain

1. Dr. SANJAY MAHARJAN
PG resident, ENT-HNS
MTH, Pokhara
“GENE THERAPY IN
HEAD AND NECK
CANCERS”

2. HISTORY:
• 1963 - Idea of gene therapy was introduced by Joshua
Lederberg
• 1980s - Gained momentum
• 1990 - First FDA-approved successful gene therapy treatment
of X- linked SCID
• 1999 - Death of Jesse Gelsinger in a gene-therapy experiment
• 2006 - Scientists at National Institutes of Health (Bethesda,
Maryland) successfully treated metastatic melanoma in
two patients

3. • 2011 - Medical community accepted that it can cure HIV as in
2008, Gero Hutter has cured a man from HIV using gene
therapy

4. INTRODUCTION:
• HNSCC:
 Malignant tumours of squamous cell origin arising from
mucosal surfaces of upper aerodigestive tract, salivary
glands, paranasal sinuses, and skin of head and neck
• Mainstay of treatment for HNSCC is surgery or radiotherapy,
+/- chemotherapy
• Results in 60% 5 year survival
• This figure has remained largely unchanged for 30 years

5. • Gene therapy is “the deliberate introduction of genetic
material into patient's cells in order to treat or prevent a
disease”
• Loco‐regional nature of HNSCC makes it accessible for both
intratumoral injection and tissue biopsy

6. GENETIC CHANGES IN CANCER
• Normal cell cycle is regulated
by numerous genes;
proto‐oncogenes and tumour
suppressor genes, held in
equilibrium
• Increased (proto‐) oncogene or
reduction in tumour suppressor
gene expression  aberrant
proliferation, hence “cancer”
• Hallmark changes of a
cancerous cell

7. • Cancer gene
therapy is based on
insertion of a gene
(transfection) into a
cell
• This new DNA is
then “transcribed”
to make mRNA
which encodes a
specific protein that
is made through
translation

8. TYPE OF GENE THERAPY
1. Corrective
2. Cytoreductive
3. Immunomodulatory

9. CORRECTIVE GENE THERAPY
• Attempts to block oncogenes or replace tumour suppressor
genes
• Tumour suppressor gene in HNSCC and most other forms of
cancer is p53
• Damage to genetic material within cell  protein encoded
by p53 gene stops cell cycle by binding to DNA
• If damage is not repairable  triggers cell death (apoptosis)
• Alteration to p53 results in continued propagation of
damaged cell line

10. • Gendicine from Schenzhen
SiBono GenTech, China.
• commercially available
gene therapy agent for
HNSCC based on p53
• 135 HNSCC pts (77% stage
III or IV) were
randomised to receive
radiotherapy alone or in
combination with
Gendicine
• Replacement of p53 results in reduced HNSCC growth and
increased radiochemo‐sensitivity
Gene +
Radiotherapy
93% response
rate
64%
complete
remission
Radiotherapy
alone
79% response
rate
19% complete
remission

11. • Effects of oncogene abnormalities can be overcome by
blocking the faulty gene
• May be by :
Inserting DNA into cell which binds & blocks oncogene
expression (e.g. Transfecting antisense cdna or
oligonucleotides)
Inhibiting oncogenes' DNA from making RNA (transcription)
and/or RNA from making protein (translation)
• No examples to date for HNSCC

12. CYTOREDUCTIVE GENE THERAPY
• Aims to directly or indirectly kill the cancerous cell
• Can be done by
Augmenting effects of other anti‐cancer therapies;
chemotherapy
Concentrating cytotoxic agents in cancerous cells
Interfering with tumor's blood supply or
Inducing apoptosis

13. •Augmentation of chemotherapy:
• By either a drug sensitisation or resistance approach
• Sensitisation approach:
Gene is transfected to convert a pro‐drug into its active
metabolite
Allows drug conversion and a high level of active drug
only in tumour bed
e.g. Herpes simplex virus thymidine kinase (TK) gene,
which converts gancyclovir into its cytotoxic triphosphate

14. • Resistance approach:
Drug resistant gene is added into normal cells sensitive to
chemotherapy, so that they can resist chemotherapy
Allows higher doses of chemotherapy to be used

15. •Concentrating radionucleotides:
Gene encoding membrane protein responsible for uptake of
iodide is sodium iodide symporter
This gene can be inserted into other cancer cells to cause
them to concentrate radioisotopes of iodine
Can be used for imaging and to administer concentrated
local dose of radiotherapy

16. •Anti‐angiogenic:
Targeting new blood vessel formation
By up regulating anti‐angiogenic or down regulating
pro‐angiogenic factors
•Pro‐apoptotic:
Normal cells are programmed to kill themselves and is under
numerous controls such as tumour necrosis factor (TNF)
These control mechanisms can be targeted
Yet to reach any clinical trials

17. IMMUNOMODULATORY GENE THERAPY:
Modification of immune response to cancer
 By introducing gene into cancer cells which produces
foreign protein on cell's surface
 This tumour specific antigen allows cell to be seen and
destroyed by immune system
Cytokines or immune regulatory proteins can be introduced
Cytokine gene transfer can be performed in vivo or ex vivo

19. MONITORING OF GENE THERAPY:
1. Indirectly through cross‐sectional imaging
2. Excised and examined by immuno-histochemical methods
3. Molecular imaging to monitor gene therapy
• By introducing a “reporter gene”
• Based upon the premise that cells with transfected gene
concentrate or activate a marker

20. GENE DELIVERY (VECTORS):
• Main limiting factor to gene therapy is accuracy and efficacy
of delivery of gene by gene delivery vector
• Route of delivery almost always direct tumour injection
• Ideal vector:
Highly specific (targeting only tumour cells)
Highly efficient (all targeted cells become transfected)
Safe
• Unfortunately, so far this ideal does not exist

21. • Characterized as
1. Viral vectors
2. Non‐viral vectors
•Non‐viral vectors:
Physically forcing DNA into cell by direct injection in tumor

22. • Methods:
Electroportation  electric current increases cell
permeability

23. Bio‐ballistics (gene gun)  gold particles coated with DNA
“shot” into superficial tissue; ultrasound increases
permeability of cell membrane

24. High pressure hydrodynamics
• Uses hyrdrodynamic pressure to penetrate cell membrane
• Rapid, high volume DNA solution injection  increased
permeability of capillary endothelium; forms pores in plasma
membrane

25. Also possible with chemical carriers such as liposomes
carrying cationic lipids and polymers
Further enhanced by anionic ph sensitive peptides
• Advantage:
• Less immunogenic and hence may be given repeatedly
• Can carry more DNA
• Cheaper to produce
• Disadvantage:
• Low transfection rates

26. •Viral vectors:
Viruses rely on transcriptional apparatus of eukaryotic cell
for replication
Pathogenic elements of viral genome are removed
Replaced by exogenous genes with or without added
specificity for infection of cancer cells
Virus itself can also exert an anti‐cancer effect— “oncolytic
viruses”

27. • Types of viral vector:
According to whether their genome integrates into host cell
DNA (retroviruses and lentiviruses)
Or persists in cell nucleus as episomes (adenovirus,
adeno‐associated viruses (aavs, herpes virus))
According to virtue of their ability to replicate (oncolytic) or
replication deficient
• Most commonly used vectors in research

28. •Retroviruses:
Mainly used as ex vivo
Target cells are removed from pt 
genetically modified  reimplanted
Have a natural tendency to transduce
dividing cells
Risks:
Retroviral infection
May disrupt host genome
(insertional mutagenesis)

30. •Lentiviruses:
Members of retrovirus
Ability to infect non‐dividing cells

31. •Adenoviruses:
Strongly immunogenic
Can be either replication defective or
replication competent
• Replication defective:
Can be produced in large amounts in producer
cell lines
Ability to infect non‐dividing cells
Not inserted into host genome (minimal risk of
insertional mutagenesis)

33. •Herpes simplex viruses:
• Non‐replicating herpes simplex virus (HSV‐1):
Has ability to persist after initial infection in a latent state in
neuronal cells for lifespan of cell
Have large cloning capacity - allows for simultaneous
delivery of several genes
No benefit in HNSCC therapy so far

34. •Replicating viral vectors:
• Destruction of cell  new genetic material is also destroyed
• In order to be successful the effect of gene therapy must be
able to spread to surrounding cells
• Can be done by replication competent vectors
• Require limited initial transduction of target cells

35. • Replication competent Adeno virus:
Most commonly studied oncolytic
viral vectors
One such is ONYX‐015
Has gene responsible for binding
to and inactivating p53 removed
cell
Resulting in a virus unable to
replicate in normal cells but
capable of replicating in p53
negative cells

36. • Phase II trials of 40 patients with recurrent HNSCC
No viral replication or toxic effects in normal tissue
Tumour regression in 10%
Tumour growth stabilisation in 62%
Disease progression in 29%
• In earlier stage HNSCC in conjunction with cisplatin and
5‐fluorouracil (5‐fu)  response rate of 63% versus expected
35% was observed

37. • Replicating herpes simplex viruses:
• With deletion of genes from HSV which control virulence
(e.g. ICP6 and/or ICP34.5) virus depends on dividing host cells
to replicate  results in cancer cell selectivity
• Oncovex:
Oncolytic HSV with both these deletions and added GM‐CSF

38. •Other replicating viral vectors
•Newcastle virus:
Replicates in cells with defects in interferon signalling
pathways
Oncolytic strain termed P701, administered intravenously,
has undergone phase I trials in 79 patients
 22% of patients tumours stopped growing

39. •Vaccinia virus:
By deleting thymidine kinase (TK) gene they can only
replicate at certain phases of cell cycle and in cancer cells
Ability to carry large quantities of DNA, therefore multiple
genes
Long history of their safety in clinical use