In vivo CRISPR inactivation of Fos promotes prostate cancer progression by altering the associated AP-1 subunit Jun

Abstract

Prostate cancer is a major global health concern with limited treatment options for advanced disease. Its heterogeneity challenges the identification of crucial driver genes implicated in disease progression. Activating protein-1 (AP-1) transcription factor is associated with cancer since the first identification of its subunits, the proto-oncogenes JUN and FOS. Whereas both JUN and FOS, have been implicated in prostate cancer, this study provides the first functional evidence that FOS acts as a tumor suppressor during prostate cancer progression and invasion. Data mining revealed decreased FOS expression in prostate cancer and a further downregulation in metastatic disease, consistent with FOS expression in cell lines derived from different prostate cancer stages. FOS deficiency in prostate cancer cell lines increases cell proliferation and induces oncogenic pathway alterations. Importantly, in vivo CRISPR/Cas9-mediated Fos and Pten double mutation in murine prostate epithelium results in increased proliferation and invasiveness compared to the abrogation of Pten alone. Interestingly, enhanced Jun expression is observed in the murine prostatic intraepithelial neoplasia lacking Fos. CRISPR/Cas9-mediated knockout of Jun combined with Fos and Pten deficiency diminishes the increased proliferation rate in vivo, but not the ability to form invasive disease. Overall, we demonstrate that loss of Fos promotes disease progression from clinical latent prostate cancer to advanced disease through accelerated proliferation and invasiveness, partly through Jun.

Targeting AP-1 transcription factors by CRISPR in the prostate

“…This method ensures simultaneous, multiplexed gene editing in adult mice and therefore bypassing timely breeding schemes. Another advantage of this method is the targeting of only few cells in the prostate epithelium, which allows tumor cells to clonally expand, similar to human cancer initiation [ 11 ].…”

“…First, we analyzed FOS expression at different stages of PCa from publicly available datasets. Our analyses revealed that FOS expression is decreased in advanced disease and further downregulated in metastatic PCa [ 11 ]. This indicated that FOS acts as a tumor suppressor gene in PCa progression.…”

“…In this setting, we altered Fos in the murine prostate in combination with Pten . Intriguingly, loss of Fos increased cell proliferation and lead to an invasive tumor, whereas inactivation of Pten led to lesions that remained indolent and classified as high grade PIN [ 11 ]. This showed that Fos is indeed a tumor suppressor gene in prostate cancer.…”

“…By introducing three sgRNAs in the AAV construct, we generated triple-deficient prostate lesions. While the loss of Jun in combination with Fos and Pten decreased cell proliferation, the lesions still progressed to an invasive cancer [ 11 ]. This shows that Jun regulates proliferation, but that Fos is a gate keeper for the development of invasive prostate cancer independently of Jun.…”

The CRISPR/Cas9 Minipig—A Transgenic Minipig to Produce Specific Mutations in Designated Tissues

“…The CRISPR/Cas9 system induces mutations at the sgRNA target site by deletions or insertions (Indel) of base pairs, which often disrupt the reading frame [ 16 ]. The CRISPR/Cas9 system has been applied to in vivo studies and is widely used in mouse studies [ 16 , 17 , 18 ]. The method has multiple advantages, especially by simultaneous multiplex gene alteration in somatic cells.…”