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Updated: Aug 7, 2026
DNA Vector-based RNA Interference to Study Gene Function in Cancer
Published on: June 4, 2012
A new inducible RNAi xenograft model for assessing the staged tumor response to mTOR silencing
Ning Ke1, Demin Zhou, Jon E Chatterton
1Immusol, Inc., 10790 Roselle Street, San Diego, CA 92121, USA.
Abstract:
Human xenograft tumor models are widely used for efficacy evaluation of potential cancer targets. siRNA is usually stably introduced into tumor cells prior to transplantation. However, silencing of the cancer therapeutic target usually results in reduced cell growth/survival in vitro and/or failure to establish tumors in vivo, thus hindering tumor response-based efficacy evaluation. The present study explored a new tumor response model based on regulated RNAi, which is more relevant from a clinical standpoint. As a proof of principle, an inducible lentiviral RNAi vector was used to silence the known cancer therapeutic target mTOR upon induction with Doxycycline (DOX). The responses to DOX-induced mTOR silencing were tested both in vitro and in vivo for prostate cancer PC3 models. Significant reduction in cancer cell survival was observed due to cell cycle arrest and apoptosis when mTOR silencing was induced in vitro. mTOR silencing also caused tumor regression for the early-staged PC3 tumors (100% tumor regressed and 45% became tumor-free). The advanced-staged tumors also demonstrated significant responses (100% regressed). Therefore, our results demonstrate the powerful utility of this new inducible xenograft tumor model for efficacy evaluation of cancer targets, and it provides a direct in vivo efficacy validation of mTOR as a cancer therapeutic target.
Insights
This study introduces a novel inducible xenograft model for cancer target evaluation. This regulated RNA interference approach effectively validates mTOR as a therapeutic target in prostate cancer models.
Area of Science:
- Oncology
- Molecular Biology
- Cancer Research
Background:
- Human xenograft models are standard for evaluating cancer therapeutic targets.
- Current methods using stable RNA interference (RNAi) often hinder efficacy assessment due to reduced tumor growth.
- A clinically relevant model for evaluating therapeutic responses is needed.
Purpose of the Study:
- To develop and validate a new tumor response model using regulated RNA interference.
- To assess the efficacy of silencing the mechanistic target of rapamycin (mTOR) in prostate cancer models.
- To demonstrate the utility of inducible xenograft models for cancer target validation.
Main Methods:
- Utilized an inducible lentiviral RNAi vector for doxycycline (DOX)-regulated silencing of mTOR.
- Tested the in vitro and in vivo responses in prostate cancer PC3 models.
- Evaluated cancer cell survival, cell cycle, apoptosis, and tumor regression.
Main Results:
- In vitro mTOR silencing induced cell cycle arrest and apoptosis, reducing cancer cell survival.
- In vivo, DOX-induced mTOR silencing led to significant regression of both early- and advanced-stage PC3 tumors.
- 45% of early-stage tumors achieved complete remission (tumor-free) after mTOR silencing.
Conclusions:
- The developed inducible xenograft model is a powerful tool for evaluating cancer targets.
- Regulated RNAi provides a clinically relevant approach for in vivo efficacy studies.
- This study provides direct in vivo validation of mTOR as a viable cancer therapeutic target.
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