Introduction from Summer 2008
A new discovery in the field of gene therapeutics resonates throughout the world
of clinical medicine. Gene therapy regimens are currently under investigation as possible
treatments of cancer9, 8, HIV/AIDS8, 10, cardiovascular diseases4, infectious diseases2, and
neurodegenerative disorders1. Clinical progress however has been slowed due to
problems regarding the vehicles of gene transduction into the patient’s genome. Today,
three major transgene vectors are used in gene therapy studies: retroviral vectors,
adenoviral vectors, and non-viral vectors
(fig 1)8. Of the three, adenoviral vectors
pose the most promise from a
pharmacological standpoint because of their
efficiency of gene transduction, ability to
transduce genes regardless of mitotic cell
status, tissue specificity, and potential
duration of transgene expression6, 7, 8, 9.
However, adenoviral vectors are
problematic pharmacological agents due to
the degree in which they elicit an innate
immune response in their host3, 5, 7, 8. A
robust innate immune response poses 2
major problems for gene therapy: 1) Strong
cytokine activation can result in patient
tissue damage and in extreme cases lead to
a “cytokine storm3, 7.” 2) A robust innate
immune response leads to instability in
transgene expression 3, 7.
Fig 1. Depicts the vectors used in gene therapy clinical
trials in 2003.
Summer 2009
Thomas CE. 2003. Nature Reviews Genetics 4:346-358.
Recent literature suggests that a
transient suppression of the innate
immune signaling cascade is possible through the inhibition of histone deacetylation.
Histone acetylation status is putatively associated with a more open chromatin structure,
resulting in more frequent binding of transcriptional regulators. While previously
believed to be global transcriptional repressors, the effect of histone deacetylase
inhibitors on transcription levels varies depending on the HDAC inhibitor, operon, celltype and dose. While many potential gene targets have been identified, the mechanism
by which HDACis mediate an anti-inflammatory response remains largely unknown.
Recently, the HDAC inhibitor SAHA (suberoylanilide hydroxamic acid) was shown to
mediate in vivo cytokine storm responses and inflammatory conditions such as
rheumatoid arthritis.
Methods
We propose to use high density spotted DNA microarrays to study the effect of
pretreatment with SAHA on the transcriptional profiles of macrophages challenged with
adenovirus in vitro. After gene expression data has been collected we plan to use various
cytokine assays and quantitative RT-PCR to elucidate the mechanisms by which SAHA
mediates its anti-inflammatory response.
Expected Results
Serotype 5 Ad is composed of dsDNA inside a viral capsid. Its replication stage
lacks an RNA intermediate. Therefore I hypothesize that differentially regulated genes
upon HDACi treatment will include signal transducer in the CAR, TLR9 and IPS-1
signaling pathways, and cytokines and chemokines involved in the acute inflammatory
response (Fig 2).
Figure 2: Depicts genes involved in the signaling cascades and cytokine response
upon adenoviral infection.
References
1. Baekelandt V., DeStrooper B., Nuttin B., Debyser Z. 2000. Gene therapeutic strategies
for neurodegenerative diseases. Current Opinion in Molecular Therapeutics
2:540-554.
2. Bunnell B & Morgan RA. 1998. Gene therapy for infectious deceases. Clinical
Microbiology Reviews 11:42-56.
3. Decker T., Muller Mathias., Stockinger Silvia. 2005. The yin and yang of type I
interferon activity in bacterial infection. Nature Reviews Immunology 5:675-687.
4. Isner, J.M. Myocardial gene therapy. 2002. Nature 415, 234-239.
5. Marshall E. 1999. Clinical Trials- Gene therapy death prompts review of adenovirus
vector. Science 286:2244-2245.
6. McCaffrey AP., Fawcett., Nakai H., McCaffrey L., Ehrhardt A., Pham T., Pandy K.,
Xu H., Feuss S., Storm T., Kay MA. 2008. The host response to adenovirus,
helper-dependent adenovirus, and adeno-associated virus in mouse liver.
Molecular Therapy 16(5):931-941.
7. Nusionzon I & Horvath CM. 2006. Positive and negative regulation of the innate
antiviral response and beta interferon gene expression by deacetylation. Molecular
and Cellular Biology 26(8):3106-3113.
8. Thomas CE., Ehrhardt A., Kay MA. 2003. Progress and problems with the use of viral
vectors for gene therapy. Nature Reviews Genetics 4:346-358.
9. Tseng JF & Mulligan RC. 2002. Gene therapy for pancreatic cancer. Surgical
Oncology Clinics of North America 11(3):537-569.
10. Wolkowicz R., Nolan GP. 2005. Gene therapy progress and prospects: Novel gene
therapy approaches for AIDS. Gene Therapy 12: 467-476.
Works Consulted
Nusinzon I., Horvath CM. 2005. Unexpected roles for deacetylation in interferon- and
cytokine – induced transcription. Journal of Interferon and Cytokine Research
25:745-748.
Akira Shizuo. 2003. Toll-like Receptor Signaling. The Journal of Biological Chemistry
278(40):38015-38108.