Abstract 4632: A new mouse model for rapid identification of key factors driving prostate cancer progression and invasiveness

Abstract

Abstract Prostate Cancer is amongst the most frequently diagnosed malignancies and the second leading cause of cancer-related death in men worldwide accompanied by an increasing incidence. Until now its heterogeneity has been a major challenge in the establishment of good in vivo models for fast validation of potential driver genes. Classic in vivo models are costly, time-consuming and often target the majority of the prostate epithelium. We successfully introduced a novel prostate cancer mouse model based on CRISPR/Cas9 technology, ensuring multiplexed gene editing. In this model, specific in vivo gene editing was obtained in murine prostate epithelium cells of a transgenic mouse strain, harboring the CRISPR associated protein 9 (Cas9) endonuclease. Prostate epithelium cells were transduced by an Adeno-associated virus (AAV), carrying multiple single guide RNAs (sgRNA). Genetically different viral constructs were designed, each expressing different sgRNA combinations against Pten, representing the main driver in prostate cancer, tumor suppressor Trp53 and either one of the AP1 transcription factor subunits Junb or Fos, or tumor suppressor Smad4. Since viral transduction occurs in only a few cells, edited cell clones can clonally expand and undergo a natural selection process. Furthermore, the simultaneous gene knockouts reflect the human scenario of tumor heterogeneity. Mouse prostates were isolated and analyzed three to nine months post-injection to obtain insight on whether or not a gene appears crucial for tumor development in a specific tissue and wherein different gene combinations correlate with tumor severity. Histological analysis revealed increased proliferation, increased AKT activation, as well as invasiveness in samples with multiple gene knockouts compared to controls with single Pten knockout. Furthermore, loss of SMAD4 accelerated cancer progression when compared to the loss of the AP-1 transcription factor. Surprisingly, knockout of Trp53 was rarely observed in prostate samples while it occurred frequently in other tumor types in the same model system. This indicates that knockout of Trp53 may not be required for prostate cancer initiation. Overall, we established an in vivo model system of simultaneous, multiplexed gene editing in the prostate epithelium to address the biological cross-talk between various, altered pathways in prostate cancer initiation and progression. Citation Format: Maria Riedel, Latifa Bakiri, Martin F. Berthelsen, Michael Borre, Mikkel H. Vendelbo, Erwin F. Wagner, Martin K. Thomsen. A new mouse model for rapid identification of key factors driving prostate cancer progression and invasiveness [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4632.