High-Throughput Proteomics Using Stable Isotope Labelling With Amino Acids In Cell Culture (Silac) Reveals Potential Modulators Of Androgen-Independent Prostate Cancers

Prostate cancer is the most common malignancy and the second leading cause of cancer related deaths in men. One common treatment is androgen-deprivation therapy, which reduces symptoms in most patients. However, over time patients develop tumours that are androgen-independent and ultimately fatal. The mechanisms that cause this transition remain largely unknown, and as a result, there are no effective treatments against androgen-independent prostate cancer. As a model for androgen-independence, we used the LNCaP cell line which is naturally androgen-dependent grown in androgen depleted conditions for a 6 month period to generate the androgen-independent cell line LNCaP-SF. Preliminary experiments showed that the LNCaP-SF cell line had higher proliferation/viability rates in androgen-depleted conditions, and had increased expression of the androgen receptor protein, a key modulator in prostate cancer progression. Our next goal was to assess to differential global protein expression as well as differential expression of secreted proteins from each of the two cell lines. To identify differentially expressed proteins, we utilized Stable Isotope Labelling with Amino Acids in Cell Culture (SILAC) coupled to mass spectrometry. LNCaP cells were labelled in growth media containing light-Arg/Lys whereas LNCaP-SF was labelled in heavy Arg-Lys media. After proteomic analysis, we were able to quantify 3355 proteins with at least one peptide hit. From these proteins, using stringent criteria, 99 and 82 proteins were found to be up-regulated and down-regulated respectively, in LNCaP-SF cells compared to LNCaP cells. Using various bioinformatics tool, we found that genes involved in fatty acid degradation and ketogenesis as important pathways that with over-expressed in LNCaP-SF cells. We performed qPCR validation of genes involved in each of these pathways and found that LNCaP-SF cells generally had an increase in the expression of many these genes, compared to LNCaP cells. These preliminary results show that genes involved in fatty acid degradation and ketogenesis pathways could serve as potential biomarkers for androgen-independent prostate cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4870. doi:10.1158/1538-7445.AM2011-4870