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Updated: May 19, 2026
Genome-wide RNAi Screening to Identify Host Factors That Modulate Oncolytic Virus Therapy
Published on: April 3, 2018
Oncolytic virus-mediated tumor radiosensitization in mice through DNA-PKcs-specific shRNA
Takashi Kon1, Xiuwu Zhang, Qian Huang
1Departments of Radiation Oncology, Duke University Medical Center, Durham, NC, USA.
Abstract:
One of the key issues in cancer radiotherapy research is to sensitize tumor cells to the cell killing effects of ionizing radiation while leaving normal tissues intact. One potential approach to achieve this is through tumor-specific targeting of DNA repair genes. In this study, we engineered a replication-deficient adenovirus encoding a mini shRNA gene targeted to the DNA-PKcs gene, which is involved in double strand break DNA repair, and evaluated its anti-tumor efficacy in combination with radiotherapy. Our shRNA-encoding adenovirus showed significant efficacy in down-regulating the levels of the DNA-PKcs protein that was accompanied by increased radiation sensitivity in the human HCT116 colon cancer cells. However, when delivered intratumorally to xenograft human tumors, minimal anti-tumor effects of the virus were seen either alone or in combination with radiation therapy, suggesting an inefficiency of the non-replicative adenovirus in delivering shRNA genes to the tumor mass. When a conditionally replicative adenovirus targeted to telomerase-positive tumor cells was used in conjunction with the DNA-PKcs-targeted shRNA-encoding non-replicative adenovirus, the efficiency of tumor-specific anti-DNA-PKcs shRNA gene expression was enhanced significantly. Most importantly, this enhanced shRNA expression led to significant anti-tumor efficacy of concurrently delivered radiation therapy. Our results suggest our shRNA-based DNA-PKcs- targeting approach in combination with tumor-targeting replicative adenovirus is a promising method to sensitize solid tumors to radiation therapy.
Insights
Targeting DNA repair genes like DNA-PKcs with shRNA-encoding adenoviruses can sensitize cancer cells to radiation. Combining a tumor-targeting replicative adenovirus with this approach enhances efficacy against solid tumors.
Area of Science:
- Oncology
- Molecular Biology
- Gene Therapy
Background:
- Cancer radiotherapy aims to enhance tumor cell killing while sparing normal tissues.
- Targeting DNA repair pathways, specifically DNA-PKcs, offers a strategy to sensitize tumors to radiation.
- Adenovirus-mediated gene delivery is a tool for cancer therapy.
Purpose of the Study:
- To engineer and evaluate an adenovirus encoding shRNA against DNA-PKcs for cancer radiotherapy.
- To assess the combination therapy's efficacy in sensitizing tumors to ionizing radiation.
- To improve tumor-specific gene delivery using a dual-adenovirus system.
Main Methods:
- Engineered a replication-deficient adenovirus carrying a mini shRNA targeting the DNA-PKcs gene.
- Tested the adenovirus's efficacy in down-regulating DNA-PKcs and increasing radiation sensitivity in HCT116 colon cancer cells.
- Utilized a conditionally replicative adenovirus targeting telomerase-positive cells in combination with the shRNA-encoding adenovirus for enhanced tumor delivery.
Main Results:
- The shRNA-encoding adenovirus successfully reduced DNA-PKcs protein levels and increased radiation sensitivity in cancer cells.
- Intratumoral delivery of the non-replicative adenovirus showed limited anti-tumor effects.
- Combining the non-replicative shRNA adenovirus with a tumor-targeting replicative adenovirus significantly enhanced shRNA expression and anti-tumor efficacy with radiation therapy.
Conclusions:
- shRNA-mediated targeting of DNA-PKcs is a viable strategy to sensitize solid tumors to radiotherapy.
- A dual-adenovirus system, combining a tumor-targeting replicative vector with a gene-silencing vector, improves therapeutic efficiency.
- This combined approach holds promise for enhancing the effectiveness of cancer radiation therapy.
