Surface Functionalization of Orthopedic Titanium Implants with Bone Sialoprotein.

Orthopedic implant failure due to aseptic loosening and mechanical instability remains a major problem in total joint replacement. Improving osseointegration at the bone-implant interface may reduce micromotion and loosening. Bone sialoprotein (BSP) has been shown to enhance bone formation when coated onto titanium femoral implants and in rat calvarial defect models. However, the most appropriate method of BSP coating, the necessary level of BSP coating, and the effect of BSP coating on cell behavior remain largely unknown. In this study, BSP was covalently coupled to titanium surfaces via an aminosilane linker (APTES), and its properties were compared to BSP applied to titanium via physisorption and untreated titanium. Cell functions were examined using primary human osteoblasts (hOBs) and L929 mouse fibroblasts. Gene expression of specific bone turnover markers at the RNA level was detected at different intervals. Cell adhesion to titanium surfaces treated with BSP via physisorption was not significantly different from that of untreated titanium at any time point, whereas BSP application via covalent coupling caused reduced cell adhesion during the first few hours in culture. Cell migration was increased on titanium disks that were treated with higher concentrations of BSP solution, independent of the coating method. During the early phases of hOB proliferation, a suppressive effect of BSP was observed independent of its concentration, particularly when BSP was applied to the titanium surface via physisorption. Although alkaline phosphatase activity was reduced in the BSP-coated titanium groups after 4 days in culture, increased calcium deposition was observed after 21 days. In particular, the gene expression level of RUNX2 was upregulated by BSP. The increase in calcium deposition and the stimulation of cell differentiation induced by BSP highlight its potential as a surface modifier that could enhance the osseointegration of orthopedic implants. Both physisorption and covalent coupling of BSP are similarly effective, feasible methods, although a higher BSP concentration is recommended.

Systematic comparative protein expression profiling of clear cell renal cell carcinoma: a pilot study based on the separation of tissue specimens by two-dimensional gel electrophoresis.

Proteome-based technologies represent powerful tools for the analysis of protein expression profiles, including the identification of potential cancer candidate biomarkers. Thus, here we provide a comprehensive protein expression map for clear cell renal cell carcinoma established by systematic comparative two-dimensional gel electrophoresis-based protein expression profiling of 16 paired tissue systems comprising clear cell renal cell carcinoma lesions and corresponding tumor-adjacent renal epithelium using overlapping narrow pH gradients. This approach led to the mapping of 348 distinct spots corresponding to 248 different protein identities. By implementing restriction criteria concerning their detection frequency and overall regulation mode, 28 up- and 56 down-regulated single target spots were considered as potential candidate biomarkers. Based on their gene ontology information, these differentially expressed proteins were classified into distinct functional groups and according to their cellular distribution. Moreover, three representative members of this group, namely calbindin, gelsolin, and heart fatty acid-binding protein, were selected, and their expression pattern was analyzed by immunohistochemistry using tissue microarrays. Thus, this pilot study provides a significant update of the current renal cell carcinoma map and defines a number of differentially expressed proteins, but both their potential as candidate biomarkers and clinical relevance has to be further explored in tissues and for body fluids like serum and urine.

Ubiquitin COOH-terminal hydrolase 1: a biomarker of renal cell carcinoma associated with enhanced tumor cell proliferation and migration.

PURPOSE: Renal cell carcinoma (RCC) accounts for 2% to 3% of all malignancies. It represents one of the most radiation- and chemotherapy-resistant tumors and surgical resections are only effective in organ-defined disease. However, RCC is an immunogenic tumor with response rates to immunotherapies between 10% and 20% of the treated patients. Due to the currently inefficient therapies and the low 5-year survival rates of RCC patients, novel diagnostic, prognostic, and therapeutic markers are urgently needed for this disease. EXPERIMENTAL DESIGN: Proteome-based approaches were used to identify (a) differentially expressed proteins in RCC compared with normal kidney epithelium and (b) proteins that are able to induce an antibody response in RCC patients. Based on these experiments, a promising candidate was subsequently validated by reverse transcription-PCR, Western blot analyses, and immunohistochemistry. In addition, functional assays were done in generated transfectants. RESULTS: The ubiquitin COOH-terminal hydrolase L1 (UCHL1) was found to be differentially expressed in both RCC lesions and RCC cell lines and immunoreactive using patients' sera. UCHL1 expression was often down-regulated in primary RCC when compared with normal kidney epithelium but dependent on the RCC subtype, the von Hippel-Lindau phenotype, and the tumor grading. Moreover, the frequency and the level of UCHL1 expression were higher in metastases when compared with primary RCC lesions. Gain-of-function transfectants exhibited a significant higher proliferation and migration rate than UCHL1-negative RCC cells. CONCLUSIONS: UCHL1 expression seems to be associated with the metastatic phenotype of RCC and therefore might serve as potential biomarker for the diagnosis and prognosis of RCC patients.

Identification of fatty acid binding proteins as markers associated with the initiation and/or progression of renal cell carcinoma.

Renal cell carcinoma (RCC) representing the most common neoplasia of the kidney in Western countries is a histologic diverse disease with an often unpredictable course. The prognosis of RCC is worsened with the onset of metastasis, and the therapies currently available are of limited success for the treatment of metastatic RCC. Although gene expression analyses and other methods are promising tools clarifying and standardizing the pathological classification of RCC, novel innovative molecular markers for the diagnosis, prognosis, and for the monitoring of this disease during therapy as well as potential therapeutic targets are urgently needed. Using proteome-based strategies, a number of RCC-associated markers either over-expressed or down-regulated in tumor lesions in comparison to the normal epithelium have been identified which have been implicated in tumorigenesis, but never linked to the initiation and/or progression of RCC. These include members of the fatty acid binding protein family, which have the potential to serve as diagnostic or prognostic markers for the screening of RCC patients.

Identification of markers for the selection of patients undergoing renal cell carcinoma-specific immunotherapy.

Renal cell carcinoma (RCC) represents the most common malignant tumor in the kidney and is resistant to conventional therapies. The diagnosis of RCC is often delayed leading to progression and metastatic spread of the disease. Thus, validated markers for the early detection of the disease as well as selection of patients undergoing specific therapy is urgently needed. Using treatment with the monoclonal antibody (mAb) G250 as a model, proteome-based strategies were implemented for the identification of markers which may allow the discrimination between responders and nonresponders prior to application of G250-mediated immunotherapy. Flow cytometry revealed G250 surface expression in approximately 40% of RCC cell lines, but not in the normal kidney epithelium cell lines. G250 expression levels significantly varied thereby distinguishing between low, medium and high G250 expressing cell lines. Comparisons of two-dimensional gel electrophoresis expression profiles of untreated RCC cell lines versus RCC cell lines treated with a mAb directed against G250 and the characterization of differentially expressed proteins by mass spectrometry and/or Edman sequencing led to the identification of proteins such as chaperones, antigen processing components, transporters, metabolic enzymes, cytoskeletal proteins and unknown proteins. Moreover, some of these differentially expressed proteins matched with immunoreactive proteins previously identified by proteome analysis combined with immunoblotting using sera from healthy donors and RCC patients, a technique called PROTEOMEX. Immunohistochemical analysis of a panel of surgically removed RCC lesions and corresponding normal kidney epithelium confirmed the heterogeneous expression pattern found by proteome-based technologies. In conclusion, conventional proteome analysis as well as PROTEOMEX could be successfully employed for the identification of markers which may allow the selection of patients prior to specific immunotherapy.

Identification of metabolic enzymes in renal cell carcinoma utilizing PROTEOMEX analyses.

PROTEOMEX, an approach which combines conventional proteome analysis with serological screening, is a powerful tool to separate proteins and identify immunogenic components in malignant diseases. By applying this approach, we characterized nine metabolic enzymes which were differentially expressed in renal cell carcinoma (RCC) cell lines and compared their expression profiles to that of normal kidney epithelium cells. Four of these proteins, superoxide dismutase (SODC), triosephosphatase isomerase (TPIS), thioredoxin (THIO) and ubiquitin carboxyl-terminal hydrolase (UBL1) were further analysed for both their constitutive and interferon (IFN)-gamma inducible protein expression pattern in cell lines or tissue specimens derived from RCC or normal kidney epithelium using Western blot analysis and immunohistochemistry, respectively. With the exception of the RCC cell line MZ1940RC, which completely lacks the expression of UBL1, a heterogeneous and variable expression pattern of the different metabolic enzymes was detected in RCC and normal renal epithelium. The highest differences in the expression levels were found for THIO in the RCC cell lines, which was 2-fold upregulated when compared to autologous normal kidney epithelium. Moreover, IFN-gamma treatment did not influence the constitutive expression of these metabolic enzymes. Thus, PROTEOMEX represents a valuable approach for the identification of metabolic enzymes which might be used as markers for the diagnosis of RCC.

Targeting of tumor associated antigens in renal cell carcinoma using proteome-based analysis and their clinical significance.

The suitability of proteome-based strategies for the targeting of tumor-associated markers along with further analysis regarding their clinical significance were investigated in human renal cell carcinoma (RCC). The immunogenic protein expression profile of normal kidney and RCC cell lines was studied by proteome analysis combined with immunoblotting using sera from healthy donors and RCC patients, also termed PROTEOMEX. Employing this approach, a series of proteins reactive with either RCC patient sera and/or reactive with control sera were identified by microanalysis of tryptic peptides. Some of these candidate antigens represent members of the cytoskeletal family, such as cytokeratins, in particular cytokeratin 8, cytoskeletal tropomyosin, F-actin capping protein, gamma-actin, stathmin, tubulin-alpha, tubulin-beta and vimentin. The expression pattern and clinical significance of three of these antigens, namely cytokeratin 8, stathmin and vimentin, were further analyzed in a large series of surgically removed RCC lesions of distinct subtypes. A heterogeneous expression pattern of cytokeratin 8, stathmin and vimentin was demonstrated in the different RCC subtypes. All epithelial cells of the autologous normal kidney showed a strong cytokeratin 8 staining pattern, whereas they totally lack vimentin expression. Stathmin was expressed in 10% of tubule cells. In conclusion, PROTEOMEX could be employed for the identification of tumor-associated antigens of the cytoskeleton which are differentially expressed in RCC of distinct subtypes as well as in normal renal epithelium.

Heat shock protein expression and anti-heat shock protein reactivity in renal cell carcinoma.

Heat shock proteins (HSP) are families of highly conserved proteins which are induced in cells and tissues upon exposure to extreme conditions causing acute or chronic stress. They exhibit distinct functions and have been implicated in the pathogenesis of a number of diseases, including cancer. A causal relationship between HSP expression and immunogenicity has been demonstrated in murine and human tumors and is also associated with the immune response. In order to investigate the correlation of HSP expression and their immunogenic potential in renal cell carcinoma (RCC), we here analyzed (i) the protein expression profile of various members of the HSP family in untreated and interferon (IFN)-gamma treated RCC cell lines as well as normal kidney epithelium, and (ii) the anti-heat shock protein reactivity in sera derived from RCC patients and healthy controls using proteomics-based techniques. A heterogeneous expression pattern of members of the HSP families was demonstrated in RCC cell lines and in cells representing normal renal epithelium. In some cases the expression rate is moderately altered by IFN-gamma treatment. In addition, a distinct anti-heat shock protein reactivity could be detected in autologous and allogeneic sera from RCC patients and healthy controls. These data suggest that HSP play a role in the immunogenicity of RCC and thus might be used for the design of immunization strategies to induce a potent antitumor response in this disease.