Profilin 1 is a Potential Biomarker for Bladder Cancer Aggressiveness
Biotechnology Division, Biomedical Research Foundation, Academy of Athens, Greece. Molecular & Cellular Proteomics
(Impact Factor: 6.56).
12/2011; 11(4):M111.009449. DOI: 10.1074/mcp.M111.009449
Of the most important clinical needs for bladder cancer (BC) management is the identification of biomarkers for disease aggressiveness. Urine is a "gold mine" for biomarker discovery, nevertheless, with multiple proteins being in low amounts, urine proteomics becomes challenging. In the present study we applied a fractionation strategy of urinary proteins based on the use of immobilized metal affinity chromatography for the discovery of biomarkers for aggressive BC. Urine samples from patients with non invasive (two pools) and invasive (two pools) BC were subjected to immobilized metal affinity chromatography fractionation and eluted proteins analyzed by 1D-SDS-PAGE, band excision and liquid chromatography tandem MS. Among the identified proteins, multiple corresponded to proteins with affinity for metals and/or reported to be phosphorylated and included proteins with demonstrated association with BC such as MMP9, fibrinogen forms, and clusterin. In agreement to the immobilized metal affinity chromatography results, aminopeptidase N, profilin 1, and myeloblastin were further found to be differentially expressed in urine from patients with invasive compared with non invasive BC and benign controls, by Western blot or Elisa analysis, nevertheless exhibiting high interindividual variability. By tissue microarray analysis, profilin 1 was found to have a marked decrease of expression in the epithelial cells of the invasive (T2+) versus high risk non invasive (T1G3) tumors with occasional expression in stroma; importantly, this pattern strongly correlated with poor prognosis and increased mortality. The functional relevance of profilin 1 was investigated in the T24 BC cells where blockage of the protein by the use of antibodies resulted in decreased cell motility with concomitant decrease in actin polymerization. Collectively, our study involves the application of a fractionation method of urinary proteins and as one main result of this analysis reveals the association of profilin 1 with BC paving the way for its further investigation in BC stratification.
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- "Pfn1 has also been implicated in tumorigenesis as a tumor suppressor. Pfn1 has been shown to be downregulated in human pancreas, breast, liver, and bladder cancers    , and depletion of Pfn1 led to faster migration of the breast cancer cell line MDA-MB231 . More importantly, downregulated Pfn1 levels correlate with the metastasis of breast cancer . "
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ABSTRACT: Profilin1 (Pfn1) is a key mediator of actin polymerization and regulates cell migration. Low expression of Pfn1 is implicated in tumorigenesis of various cancers, including breast cancer. The regulatory mechanism behind Pfn1 levels has not yet been elucidated. In the present study, we find that Pfn1 is poly-ubiquitinated in human cell lines, and a portion of poly-ubiquitinated Pfn1 is regulated in a proteasome-dependent manner. C-terminus of Hsc70-interacting protein (CHIP), a co-chaperone E3 ligase, interacts with and ubiquitinates Pfn1, targeting it for proteasome-dependent degradation. Depletion of CHIP stabilizes Pfn1, suggesting that CHIP functions as a major E3 ligase for Pfn1. Stable expression of wild-type CHIP in the breast cancer cell line MDA-MB231 yielded downregulation of Pfn1 and enhanced cell migration. Pfn1 overexpression in MDA-MB231 cells expressing wild-type CHIP suppressed the enhanced cell migration. Taken together, our results demonstrate that CHIP regulates Pfn1 levels as an E3 ligase, and possibly plays a role in cell migration and metastasis of breast cancer.
Available from: Arun Kumar Trivedi
- "It interacts with other proteins such as vasodilatorstimulated phosphoprotein , Wiskott–Aldrich syndrome protein, Wiskott–Aldrich syndrome protein-associated verprolin homolog , Drebrin, Gephyrin , Diaphanous , and Daam1  involved in various biological functions . Recent studies have revealed that PFN-1 also acts a tumor suppressor in breast and other cancer types    . "
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ABSTRACT: Nuclear receptor coregulators play an important role in the transcriptional regulation of nuclear receptors. In the present study we aimed to identify Estrogen Receptor α (ERα) interacting proteins in Tamoxifen treated MCF7 cells. Using in-vitro GST-Pull down assay with ERα ligand binding domain (ERα-LBD) and mass spectrometry based proteomics approach we identified Profilin1 as a novel ERα interacting protein. Profilin1 contains I/LXX/L/H/I amino acid signature motif required for co-repressor interaction with ERα. We show that these two proteins physically interact with each other both in-vitro as well as in-vivo by GST-pull down and co-immunoprecipitation respectively. We further show that these two proteins also co-localize together in the nucleus. Previous studies have reported reduced expression of Profilin1 in breast cancer; and here we found that Tamoxifen increases Profilin1 expression in MCF7 cells. Our data demonstrates that over expression of Profilin1 inhibits ERα mediated transcriptional activation as well as its downstream target genes in ERα positive breast cancer cells MCF7. In addition, Profilin1 over expression in MCF7 cells leads to inhibition of cell proliferation which apparently is due to enhanced apoptosis. In nutshell, these data indicate that mass spectrometry based proteomics approach identifies a novel ERα interacting protein Profilin1 which serves as a putative co-repressor of ERα functions.
Available from: Partha Roy
- "Acquisition of a motile phenotype by tumor cells is typically associated with a disrupted actin cytoskeleton. Along this line, it was previously reported that Pfn1 expression is downregulated in a few different types of human cancer, including breast cancer [6,7]. We have found that lower Pfn1 expression correlates with increased metastatic propensity in human breast cancer, and furthermore, Pfn1 depletion in MDA-MB-231 cells (a metastatic BCC line) can actual enhance various dissemination-promoting activities (migration, extracellular matrix degradation and invasion, transendothelial migration) in vitro and vascular dissemination from tumor xenografts in vivo [8-10]. "
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ABSTRACT: Proteins belonging to the profilin family of actin-binding proteins are considered to be important control elements for actin polymerization and have been linked to a broad spectrum of cellular functions, including cell migration. An intriguing paper recently published in Cancer Cell unveils differential effects of profilin-1 and profilin-2, the two major isoforms of profilin, on actin cytoskeletal regulation, motility, and invasion of breast cancer cells, and further establishes a mechanism underlying profilin-2's suppressive effect on breast cancer cell migration. This viewpoint discusses the implications of these findings in the context of how profilins might regulate breast cancer cell motility.
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