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Updated: Jul 2, 2026
DNA Vector-based RNA Interference to Study Gene Function in Cancer
Published on: June 4, 2012
Gene silencing with siRNA targeting E6/E7 as a therapeutic intervention in a mouse model of cervical cancer
Amy L Jonson1, Lisa M Rogers, Sundaram Ramakrishnan
1University of Minnesota Medical School, Department of Obstetrics, Gynecology and Women's Health, 420 Delaware Street S.E., MMC 395, Minneapolis, MN 55455-0374, USA.
Objective:
Selective silencing of HPV oncogenes using short interfering RNA (siRNA) blocks E6/E7 expression and restores normal p53 and Rb function. Our objective was to determine if siRNA targeting E6/E7 would inhibit the growth of established tumors in a mouse model of cervical cancer.
Methods:
In vitro studies were performed using unique siRNA sequences to confirm their ability to target and reduce E6/E7 mRNA and restore functioning p53. Next, siRNA targeting lamin was injected daily for three days into tumors established from HPV 16 positive CaSki human cervical cancer cells. Immunohistochemistry and branched DNA gene quantification were used to determine distribution and duration of activity of these siRNA. For our therapeutic studies tumors were directly injected with siRNA targeting E6/E7, non-targeting control siRNA, or saline. In preliminary experiments injections were daily or every three days for a total of three doses. A second therapeutic experiment utilized every three day dosing for 35 days. Tumor volume, growth curves and E7 mRNA levels were assessed.
Results:
The two most active siRNA sequences resulted in a 67% and 71% reduction in E6/E7 mRNA. Fluorescent lamin siRNA was visualized up to 120 h after the initial tumor injection and was evenly distributed throughout the tumors. IHC showed lamin expression to be inhibited by 68% and 75% when compared to controls at 54 and 120 h respectively. In our preliminary therapeutic intervention experiments there was no significant difference in tumor growth between the treatment groups when mice were treated with three daily injections (p=0.41). However, when treated every third day for three injections final tumor volume was less in animals injected with siRNA sequences A (78% reduction; p<0.0001) and G (60% reduction; p=0.005) compared to saline injection. Tumors showed a corresponding decrease in E6/E7 mRNA. Extended treatment with siRNA completely or nearly eradicated tumors in 70% of the animals.
Conclusion:
Therapeutic siRNA targeting E6/E7 significantly inhibits tumor growth in this mouse model of cervical cancer. Further investigation is needed to determine optimal dosing and route of delivery.
Insights
Short interfering RNA (siRNA) targeting E6/E7 oncogenes effectively inhibited cervical cancer growth in a mouse model. This novel therapeutic approach demonstrated significant tumor reduction and near eradication in many subjects.
Area of Science:
- Oncology
- Molecular Biology
- Virology
Background:
- Human papillomavirus (HPV) oncogenes E6 and E7 drive cervical cancer development.
- Selective silencing of these oncogenes via short interfering RNA (siRNA) can restore tumor suppressor functions (p53 and Rb).
Purpose of the Study:
- To evaluate the efficacy of siRNA targeting HPV E6/E7 oncogenes in inhibiting established cervical cancer tumor growth in a preclinical mouse model.
Main Methods:
- In vitro validation of siRNA sequences for E6/E7 mRNA targeting and p53 restoration.
- Direct intratumoral injection of siRNA targeting E6/E7 or control sequences in a mouse model of HPV16-positive cervical cancer (CaSki cells).
- Assessment of tumor volume, growth kinetics, and E6/E7 mRNA levels following various dosing regimens.
Main Results:
- Selected siRNA sequences achieved significant reduction (67-71%) in E6/E7 mRNA levels.
- Intratumoral siRNA distribution and duration of activity were confirmed.
- Therapeutic siRNA administration every three days for 35 days led to significant tumor growth inhibition (78% and 60% reduction with sequences A and G, respectively) and near-complete tumor eradication in 70% of animals.
Conclusions:
- Therapeutic siRNA targeting HPV E6/E7 oncogenes demonstrates significant potential for inhibiting cervical cancer progression.
- Further research is warranted to optimize siRNA dosing schedules and delivery methods for clinical translation.
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