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P53-dependent cell-killing by selective repression of thymidine kinase and reduced prodrug activation
Dong Xu1, Deitmar Falke, R L Juliano
1Department of Pharmacology, School of Medicine, University of North Carolina, Chapel Hill, NC 27599, USA.
Abstract:
Selective killing of tumor cells is an important goal for cancer therapeutics. The tumor suppressor transcription factor p53 is absent or mutated in more than 50% of human tumors. Thus, determining approaches that use p53 status to regulate therapy may be an important strategy for attaining cancer selectivity. We have shown previously that a designed transcriptional repressor, K2-5F, strongly and selectively reduces the expression of its target gene MDR1. In this study, we exploited p53 status and the strong repressor activity of K2-5F to establish a system for preferential killing of p53-negative cells. In this system, the expression of K2-5F is induced by p53 in normal cells, and the K2-5F repressor then inhibits the expression of herpes simplex virus thymidine kinase (HSV-TK) driven by an MDR1 minipromoter. In p53-deficient cells, little K2-5F is expressed, and thus HSV-TK is expressed, allowing the cells to be killed by ganciclovir (GCV). K2-5F induced by exogenous p53 dramatically reduced the expression of HSV-TK in human embryonic kidney 293 cells, and it subsequently increased cell survival in response to GCV. To further evaluate this approach in a uniform genetic background, we developed Saos-2 cells stably expressing physiological levels of p53 and paired them with wild-type p53-negative Saos-2 cells. Stable expression of moderate levels of p53 in Saos-2 cells was able to induce the expression of K2-5F and reduce HSV-TK expression and resulted in a modest but distinct protection from GCV toxicity. Thus, this system may be suitable for further development as an approach to selective cancer therapy.
Insights
This study developed a novel cancer therapy strategy that selectively targets p53-deficient tumor cells. The system utilizes a p53-inducible repressor to control gene expression, offering a promising approach for cancer treatment.
Area of Science:
- Oncology
- Molecular Biology
- Gene Therapy
Background:
- Selective cancer cell killing is crucial for effective therapeutics.
- The tumor suppressor p53 is mutated or absent in over 50% of human cancers.
- Exploiting p53 status can lead to targeted cancer therapies.
Purpose of the Study:
- To develop a system for preferential killing of p53-negative cancer cells.
- To leverage the p53 tumor suppressor pathway for therapeutic selectivity.
- To utilize a designed transcriptional repressor (K2-5F) for targeted gene regulation.
Main Methods:
- A system was designed where p53 induces K2-5F expression in normal cells.
- K2-5F represses herpes simplex virus thymidine kinase (HSV-TK) expression driven by an MDR1 minipromoter.
- p53-deficient cells express HSV-TK, enabling killing by ganciclovir (GCV).
- Experiments were conducted in human embryonic kidney 293 cells and Saos-2 cell lines with varying p53 expression.
Main Results:
- Exogenous p53 induction of K2-5F significantly reduced HSV-TK expression in HEK 293 cells.
- This reduction in HSV-TK led to increased cell survival in response to GCV.
- Stable p53 expression in Saos-2 cells induced K2-5F, reduced HSV-TK, and provided protection from GCV toxicity.
Conclusions:
- The developed system demonstrates potential for selective cancer therapy by targeting p53-deficient cells.
- This p53-dependent gene regulation strategy offers a promising avenue for future therapeutic development.
- The findings support the suitability of this approach for further investigation in cancer treatment.