Abstract
Multiple, complex molecular events characterize cancer development and progression. Deciphering the molecular networks that distinguish organ-confined disease from metastatic disease may lead to the identification of biomarkers of cancer invasion and disease aggressiveness. Although alterations in gene expression have been extensively quantified during neoplastic progression, complementary analyses of proteomic changes have been limited. Here we interrogate the proteomic alterations in a cohort of 15 prostate-derived tissues that included five each from adjacent benign prostate, clinically localized prostate cancer, and metastatic disease from distant sites. The experimental strategy couples isobaric tags for relative and absolute quantitation with multidimensional liquid phase peptide fractionation followed by tandem mass spectrometry. Over 1000 proteins were quantified across the specimens and delineated into clinically localized and metastatic prostate cancer-specific signatures. Included in these class-specific profiles were both proteins that were known to be dysregulated during prostate cancer progression and new ones defined by this study. Enrichment analysis of the prostate cancer-specific proteomic signature, to gain insight into the functional consequences of these alterations, revealed involvement of miR-128-a/b regulation during prostate cancer progression. This finding was validated using real time PCR analysis for microRNA transcript levels in an independent set of 15 clinical specimens. miR-128 levels were elevated in benign prostate epithelial cell lines compared with invasive prostate cancer cells. Knockdown of miR-128 induced invasion in benign prostate epithelial cells, whereas its overexpression attenuated invasion in prostate cancer cells. Taken together, our profiles of the proteomic alterations of prostate cancer progression revealed miR-128 as a potentially important negative regulator of prostate cancer cell invasion.
Highlights
Multiple, complex molecular events characterize cancer development and progression
In an effort to profile the proteome in the stages of prostate cancer progression, we used a combination of iTRAQ labeling and twodimensional liquid chromatography coupled with mass spectrometry to interrogate the relative levels of proteins across 15 prostate-related biospecimens
Assessment of miR-128 Expression in Prostate-derived Tissues and Cell Lines—miR-128 concepts were enriched in our Oncomine Concept Map (OCM) analysis by eight high confidence proteins, namely Golgi membrane protein 1 (GOLM1), TROVE domain family member 2 (TROVE2), PHB, solute carrier family 25 (SLC25A3), myristoylated alanine-rich protein kinase C substrate, heteronuclear ribonucleoprotein (HNRPF), TMSB10, and a member of RAS oncogene family (RAP1B), all of which were elevated in localized prostate cancer and further were predicted to be targets of the microRNA by picTAR
Summary
Like other cancers, develops in the background of diverse genetic and environmental factors [9]. With the advent of global profiling strategies, a systematic analysis of molecular alterations involved in prostate cancer is possible. A number of groups have used gene expression microarrays to profile prostate cancer tissues [15,16,17,18,19,20,21,22,23] as well as other tumors (24 –27) at the transcriptome level, but much less work has been done at the protein level. Multiple technologies have been used to identify proteomic alterations in the serum of prostate cancer patients including protein microarray and SELDI [13, 30]. We used a similar approach to quantify global changes associated with the prostate cancer proteome in the stages of progression from organ-confined to metastatic disease. We extended our analysis beyond delineation of tumor-specific proteomic signatures to nominate and confirm the miR-128 pathway as a critical intermediary in tumor invasion
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