Rapid in vivo validation of candidate drivers derived from the PTEN-mutant prostate metastasis genome

Human genome analyses have revealed that increasing gene copy number alteration is a driving force of incurable prostate cancer (PC). Since most of the affected genes are hidden within large amplifications or deletions, there is a need for fast and faithful validation of drivers. However, classic genetic PC engineering in mouse makes this a daunting task because generation, breeding based combination of alterations and non-invasive monitoring of disease are too time consuming and costly. To address the unmet need, we recently developed RapidCaP mice, which endogenously recreate human PTEN-mutant metastatic PC based on Cre/Luciferase expressing viral infection, that is guided to PtenloxP/Trp53loxP prostate. Here we use a sensitized, non-metastatic Pten/ Trp53-mutant RapidCaP system for functional validation of human metastasis drivers in a much accelerated time frame of only 3-4 months. We used in vivo RNAi to target three candidate tumor suppressor genes FOXP1, RYBP and SHQ1, which reside in a frequent deletion on chromosome 3p and show that Shq1 cooperates with Pten and p53 to suppress metastasis. Our results thus demonstrate that the RapidCaP system forms a much needed platform for in vivo screening and validation of genes that drive endogenous lethal PC

P53 Mutations Change Phosphatidylinositol Acyl Chain Composition

Phosphatidylinositol phosphate (PIP) second messengers relay extracellular growth cues through the phosphorylation status of the inositol sugar, a signal transduction system that is deregulated in cancer. In stark contrast to PIP inositol head-group phosphorylation, changes in phosphatidylinositol (PI) lipid acyl chains in cancer have remained ill-defined. Here, we apply a mass-spectrometry-based method capable of unbiased high-throughput identification and quantification of cellular PI acyl chain composition. Using this approach, we find that PI lipid chains represent a cell-specific fingerprint and are unperturbed by serum-mediated signaling in contrast to the inositol head group. We find that mutation of Trp53 results in PIs containing reduced-length fatty acid moieties. Our results suggest that the anchoring tails of lipid second messengers form an additional layer of PIP signaling in cancer that operates independently of PTEN/PI3-kinase activity but is instead linked to p53