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Therapeutic miRNA Delivery Suppresses Tumorigenesis in a Murine Liver Cancer Model
Janaiah Kota,1 Raghu R. Chivukula,2 Kathryn A. O’Donnell,3,4 Erik A. Wentzel,2 Chrystal
LMontgomery,1Hun-Way Hwang,2 Tsung-Cheng Chang,2 Perumal Vivekanandan,5 Michael
Torbenson,5 K. Reed Clark,1,7Jerry R. Mendell,1,7,8,* and Joshua T. Mendell2,4,6,*
1Center for Gene Therapy, The Research Institute at Nationwide Children’s Hospital, Columbus, OH
43205, USA
2The McKusick-Nathans Institute of Genetic Medicine
3The High Throughput Biology Center
4Department of Molecular Biology and Genetics
5Department of Pathology
6Department of Pediatrics
Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
7Department of Pediatrics
8Department of Neurology
The Ohio State University, Columbus, OH 43210, USA
Cell 137, 1005–1017, 2009
Cell 137, 1005–1017, 2009
microRNA-Regulators of our genome
www.microrna.ic.cz/obr/image003.png
miRNA and Cancer
All examined tumor types
Abnormal miRNA expression patterns
• miRNA profiles Tumor classification
Prognosis
Response to therapy
• Functional Studies Potent pro- and anti- tumorigenic activity of
specific miRNA both in-vitro and in-vivo.
miRNA based Cancer Therapeutics
Two Approaches
Inhibition of oncogenic miRNA
Replacement of tumor suppressor miRNA
Progress In The Field
• Anti-sense mediated inhibition of oncogenic miRNAs (Love et al.,2008; Stenvang et al.,2008).
• Global miRNA repression enhances cellular transformation and tumorigenesis in both in vitro and in vivo models (Kumar et al., 2007)
• Myc activation in B cell lymphoma leads to widespread miRNA repression. (Mendel & Chang et.al)
• Enforced expression of these specific miRNAs dramatically suppresses lymphomagenesis.
• Re-expression of even a single miRNA could provide significant anti-cancer therapeutics.
• Viral delivery of let-7 miRNA ( Tumour Suppressor ) suppressed tumor growth in a mouse model of adenocarcenoma (Esquela-Kerscher et al., 2008; Kumar et al., 2008) .
• let-7 directly targets KRAS,( an Oncogene) the initiating oncogene in this tumor model.
• Thus, the utility of miRNA therapeutics in situations where they do not target the initiating oncogene remains to be studied.
HYPOTHESIS
• miRNAs can be directly used as general anticancer therapeutics even when they do not target the initiating oncogene.
• REASONING: The most therapeutically useful miRNAs would be expressed at low levels in tumors but would be highly expressed in
normal tissues.
Selection of Therapeutic miRNA
Along with mouse,miR-26a expressed at lower levels in human HCC.
Therapeutic Potential of miR-26a
• INITIAL TEST:- MSCV derived retroviral construct to enforce expression of miR-26a in HepG2 (Hepatocarcinoma Cell Lines) cells.
• Cell cycle profiles- PI staining and Flow Cytometry
Cell cycle profiles after Nocodazole treatment
miR26a expression induces G1 arrest in Human Liver Cancer Cells
miR-26a Directly Represses Expression of Cyclins D2 and E2
• Predicted targets of miR-26a examined by Targetscan algorithm.
Cyclin E1, cyclin E2, cyclin D2 and CDK6
Required in G1-S transition
Verification of direct regulation of transcripts by miR-26a
• Reporter plasmids with predicted binding sites cloned downstream of
luciferase ORF.
MYC is Not a Target of miR-26a
• Potent therapeutic role of miR-26a proved in vitro.
• Can systemic delivery of miR-26a be used as a therapeutic strategy for this tumor type in vivo?
• First confirmed that miR-26a does not regulate MYC itself.
• MYC not a predicted target of miR-26a by common algorithms –Targetscan, miRanda and PicTar.
• Western blotting confirms retroviral expression of miR-26a in HepG2 cells doesn’t affect MYC protein abundance.
AAV Vector System to express miR-26a and eGFP• CONSTRUCTS
VECTOR DELIVERY
• Single tail-vein injection.
• Liver tissue harvested after 3 weeks: >90% Transduction.
• Previous study-AAV mediated delivery of shRNA induced
acute liver toxicity probably due to inhibition of
miRNA pathway.
Suppression of Tumorigenesis by miR-26a
• Timeline:-
6/8 8/10
2/10 treated mice- aggressive tumor- lower transduction efficiency
Technical failure rather than resistance to miR-26a therapeutics.
EFFECT ON PROLIFERATION AND TUMOR-SPECIFIC APOPTOSIS
CELLULAR PROLIFERATION-
Ki67 staining
TUMOR-SPECIFIC APOPTOSIS-
TUNEL staining
Thank You