In Vivo Quantitative Phosphoproteomic Profiling Identifies Novel Regulators of Castration Resistant Prostate Cancer Growth

explanatory Essay
1912 words
1912 words

LNCaP xenografts mimic many of the features of human prostate tumors making them a valuable model to study the mechanism of progression to CRPCa (12, 18). In order to obtain an overview of these mechanisms LNCaP xenografts were grown orthotopically in intact and castrated mice. The analysis of tumor growth show that castration resistant LNCaP tumors (CR-LNCaP) proliferate at a higher rate than androgen sensitive tumors (HS-LNCaP) at the time of harvest, 60 days after surgical orthotopic implantation (Figure 1A, B). This mimics the situation with human CRPCa, which proliferate at a higher rate than castration naïve localized tumors. Moreover, immunohistochemical analysis of orthotopically grown tumors show an increased number of Ki67 positive cells confirming an enhanced proliferative rate. Measurements of active caspase 3 by IHC show diminished activity in castration resistant tumors; indicating that both enhanced proliferation and diminished apoptosis contribute to the increased growth rate of tumors in castrated mice (Figure 1C and 1D). Next, we perform a comprehensive quantitative phosphoproteomic profiling using SILAC labeled LNCaP cells as internal, spiked-in controls in all samples analyzed (19) . In order to account for biological variation, 4 individual tumors were analyzed for each experimental group. In parallel, we also performed a genome-wide transcriptomic analysis (Figure 1E).

A total of 2782 phosphorylated peptides from a total of 1212 proteins were quantified in at least one of the samples. Sufficient data across biological replicates were obtained for 800 of those phosphopeptides. Statistical analysis identified differential expression for 98 peptides defined as fold changes of more than 50%, p<0.05 (Suppleme...

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In this essay, the author

  • Explains that lncap xenografts mimic human prostate tumors, which proliferate at a higher rate than castration nave localized crpca. they perform phosphoproteomic profiling using silac labeled cells as internal, spiked-in controls.
  • Analyzes the phosphorylation levels of 2782 peptides from a total of 1212 proteins in at least one of the samples.
  • Analyzes the phosphoproteomic data of the mapk, mtorc1 pathways, and pak2 and yap1 in cr-lncap tumors.
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