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Experimental evolution of an oncolytic vesicular stomatitis virus with increased selectivity for p53-deficient cells

Significance statement

The field of oncolytic virotherapy is strongly dominated by genetic engineering strategies aiming at enhancing the tumor selectivity of certain viruses. However, this requires detailed knowledge of the molecular pathways determining viral tropism and pathogenesis. Directed evolution offers an alternative approach which exploits the power of artificial selection without prejudice towards the underlying mechanisms involved. Basic research in the field of experimental evolution has established that viral adaptation to a specific cell type often comes at the cost of reduced fitness in other cell types, thus suggesting that evolution of increased tumor selectivity is generally achievable. Here, we applied this concept by evolving a model oncolytic virus in cells deficient for the tumor suppressor gene p53, a hallmark of cancer. We show that the evolved virus exhibits greater potency and tumor selectivity in p53-deficient cancer cell lines and in a murine model.

 

Experimental Evolution of an Oncolytic Vesicular Stomatitis Virus with Increased Selectivity for p53-Deficient Cellfeat Experimental Evolution of an Oncolytic Vesicular Stomatitis Virus with Increased Selectivity for p53-Deficient Cell

 

 

 

 

 

 

 

 

 

 

Journal Reference

Garijo R1, Hernández-Alonso P2, Rivas C3, Diallo JS4, Sanjuán R5.

PLoS One. 2014 ;9(7):e102365.

1Instituto Cavanilles de Biodiversidad y Biologia Evolutiva, Universidad de Valencia, Valencia, Spain; Center for Innovative Cancer Research, Ottawa Hospital Research Institute, Ottawa, ON, Canada.and

2Instituto Cavanilles de Biodiversidad y Biologia Evolutiva, Universidad de Valencia, Valencia, Spain.and

3Departamento de Biología Molecular y Celular, Centro Nacional de Biotecnología, Madrid, Spain; Centro de Investigación en Medicina Molecular (CIMUS) and Instituto de Investigaciones Sanitarias (IDIS), Universidade de Santiago de Compostela, Santiago de Compostela, Spain.and

4Center for Innovative Cancer Research, Ottawa Hospital Research Institute, Ottawa, ON, Canada.and

5Instituto Cavanilles de Biodiversidad y Biologia Evolutiva, Universidad de Valencia, Valencia, Spain; Department of Genetics, Universidad de Valencia, Valencia, Spain.

 

Abstract

 Experimental evolution has been used for various biotechnological applications including protein and microbial cell engineering, but less commonly in the field of oncolytic virotherapy. Here, we sought to adapt a rapidly evolving RNA virus to cells deficient for the tumor suppressor gene p53, a hallmark of cancer cells. To achieve this goal, we established four independent evolution lines of the vesicular stomatitis virus (VSV) in p53-knockout mouse embryonic fibroblasts (p53-/- MEFs) under conditions favoring the action of natural selection. We found that some evolved viruses showed increased fitness and cytotoxicity in p53-/- cells but not in isogenic p53+/+ cells, indicating gene-specific adaptation. However, full-length sequencing revealed no obvious or previously described genetic changes associated with oncolytic activity. Half-maximal effective dose (EC50) assays in mouse p53-positive colon cancer (CT26) and p53-deficient breast cancer (4T1) cells indicated that the evolved viruses were more effective against 4T1 cells than the parental virus or a reference oncolytic vesicular stomatitis virus (MΔ51), but showed no increased efficacy against CT26 cells. In vivo assays using 4T1 syngeneic tumor models showed that one of the evolved lines significantly delayed tumor growth compared to mice treated with the parental virus or untreated controls, and was able to induce transient tumor suppression. Our results show that RNA viruses can be specifically adapted typical cancer features such as p53 inactivation, and illustrate the usefulness of experimental evolution for oncolytic virotherapy.

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