Ling Meng

Disease biomarkers play critical roles in the management of various pathological conditions of diseases. This involves diagnosing diseases, predicting disease progression and monitoring the efficacy of treatment modalities. While efforts to identify specific disease biomarkers using a variety of technologies has increased the number of biomarkers or augmented information about them, the effective use of disease-specific biomarkers is still scarce. Here, we report that a high expression of protein tyrosine kinase 7 (PTK7), a transmembrane receptor protein tyrosine kinase-like molecule, was discovered in a series of leukemia cell lines using whole cell aptamer selection. With the implementation of a two-step strategy (aptamer selection and biomarker discovery), combined with mass spectrometry, PTK7 was ultimately identified as a potential biomarker for T-cell acute lymphoblastic leukemia (T-ALL). Specifically, the aptamers for T-ALL cells were selected using the cell-SELEX process, without any prior knowledge of the cell biomarker population, conjugated with magnetic beads and then used to capture and purify their binding targets on the leukemia cell surface. This demonstrates that a panel of molecular aptamers can be easily generated for a specific type of diseased cells. It further demonstrates that this two-step strategy, that is, first selecting cancer cell-specific aptamers and then identifying their binding target proteins, has major clinical implications in that the technique promises to substantially improve the overall effectiveness of biomarker discovery. Specifically, our strategy will enable efficient discovery of new malignancy-related biomarkers, facilitate the development of diagnostic tools and therapeutic approaches to cancer, and markedly improve our understanding of cancer biology.

Liver cancer is the third most deadly cancers in the world. Unfortunately, there is no effective treatment. One of the major problems is that most cancers are diagnosed in the later stage, when surgical resection is not feasible. Thus, accurate early diagnosis would significantly improve the clinical outcome of liver cancer. Currently, there are no effective molecular probes to recognize biomarkers that are specific for liver cancer. The objective of our current study is to identify liver cancer cell-specific molecular probes that could be used for liver cancer recognition and diagnosis. We applied a newly developed cell-SELEX (Systematic Evolution of Ligands by EXponential enrichment) method for the generation of molecular probes for specific recognition of liver cancer cells. The cell-SELEX uses whole live cells as targets to select aptamers (designed DNA/RNA) for cell recognition. In generating aptamers for liver cancer recognition, two liver cell lines were used: a liver cancer cell line BNL 1ME A.7R.1 (MEAR) and a noncancer cell line, BNL CL.2 (BNL). Both cell lines were originally derived from Balb/cJ mice. Through multiple rounds of selection using BNL as a control, we have identified a panel of aptamers that specifically recognize the cancer cell line MEAR with Kd in the nanomolar range. We have also demonstrated that some of the selective aptamers could specifically bind liver cancer cells in a mouse model. There are two major new results (compared with our reported cell-SELEX methodology) in addition to the generation of aptamers specifically for liver cancer. The first one is that our current study demonstrates that cell-based aptamer selection can select specific aptamers for multiple cell lines, even for two cell lines with minor differences (MEAR cell is derived from BNL by chemical inducement); and the second result is that cell-SELEX can be used for adhesive cells and thus open the door for solid tumor selection and investigation. The newly generated cancer-specific aptamers hold great promise as molecular probes for cancer early diagnosis and basic mechanism studies.

The identification of tumor related cell membrane protein targets is important in understanding tumor progression, the development of new diagnostic tools, and potentially for identifying new therapeutic targets. Here we present a novel strategy for identifying proteins that are altered in their expression levels in a diseased cell using cell specific aptamers. Using an intact viable B-cell Burkitt's lymphoma cell line (Ramos cells) as the target, we have selected aptamers that recognize cell membrane proteins with high affinity. Among the selected aptamers that showed different recognition patterns with different cell lines of leukemia, the aptamer TD05 showed binding with Ramos cells. By chemically modifying TD05 to covalently cross-link with its target on Ramos cells to capture and to enrich the target receptors using streptavidin coated magnetic beads followed by mass spectrometry, we were able to identify membrane bound immunoglobin heavy mu chain as the target for TD05 aptamer. Immunoglobin heavy mu chain is a major component of the B-cell antigen receptor, which is expressed in Burkitt's lymphoma cells. This study demonstrates that this two step strategy, the development of high quality aptamer probes and then the identification of their target proteins, can be used to discover new disease related potential markers and thus enhance tumor diagnosis and therapy. The aptamer based strategy will enable effective molecular elucidation of disease related biomarkers and other interesting molecules. The identification of tumor related cell membrane protein targets is important in understanding tumor progression, the development of new diagnostic tools, and potentially for identifying new therapeutic targets. Here we present a novel strategy for identifying proteins that are altered in their expression levels in a diseased cell using cell specific aptamers. Using an intact viable B-cell Burkitt's lymphoma cell line (Ramos cells) as the target, we have selected aptamers that recognize cell membrane proteins with high affinity. Among the selected aptamers that showed different recognition patterns with different cell lines of leukemia, the aptamer TD05 showed binding with Ramos cells. By chemically modifying TD05 to covalently cross-link with its target on Ramos cells to capture and to enrich the target receptors using streptavidin coated magnetic beads followed by mass spectrometry, we were able to identify membrane bound immunoglobin heavy mu chain as the target for TD05 aptamer. Immunoglobin heavy mu chain is a major component of the B-cell antigen receptor, which is expressed in Burkitt's lymphoma cells. This study demonstrates that this two step strategy, the development of high quality aptamer probes and then the identification of their target proteins, can be used to discover new disease related potential markers and thus enhance tumor diagnosis and therapy. The aptamer based strategy will enable effective molecular elucidation of disease related biomarkers and other interesting molecules. Membrane proteins play crucial roles in all living organisms. These include cell signaling, cell-cell interactions, ion/solute transport that facilitates the exchange of membrane impermeable molecules between the outer environment to the cells, and communication between cells through signal transduction. Recently, much interest has been focused on identification of membrane proteins that play an essential role in disease progression and in transforming healthy cells into diseased cells (1Dalton W.S. Friend S.H. Cancer biomarkers: an invitation to the table.Science. 2006; 312: 1165-1168Crossref PubMed Scopus (179) Google Scholar). The origin of these protein transformations can be due to genetic alternations and/or post-translational modifications of the vital membrane proteins on the cells (2Lin D. Tabb D.L. Yates III, J.R. Large scale protein identification using mass spectrometry.Biochim. Biophys. Acta. 2003; 1646: 1-10Crossref PubMed Scopus (190) Google Scholar). These alterations of membrane proteins are significant in cancer progression (3Pupa S.M. Tagliabue E. Menard S. Anichini A. HER-2: a biomarker at the crossroads of breast cancer immunotherapy and molecular medicine.J. Cell. Physiol. 2005; 205: 10-18Crossref PubMed Scopus (30) Google Scholar). Furthermore, because of their accessibility, plasma membrane proteins are of considerable interest for diagnostic and therapeutic purposes (4Wu C. Yates III, J.R. The application of mass spectrometry to membrane proteomics.Nat. Biotech. 2003; 21: 262-267Crossref PubMed Scopus (510) Google Scholar). There are several approaches, such as genetic and proteomics methodologies for the identification of membrane proteins (5Bledi Y. Inberg A. Linial M. PROCEED: a proteomic method for analysing plasma membrane proteins in living mammalian cells.Briefing Funct. Genomics Proteomics. 2003; 2: 254-265Crossref PubMed Scopus (27) Google Scholar, 6Oh P. Li Y. Yu J. Durr E. Krasinska K.M. Carver L.A. Testa J.E. Schnitzer J.E. Subtractive proteomic mapping of the endothelial surface in lung and solid tumors for tissue-specific therapy.Nature. 2004; 429: 629-635Crossref PubMed Scopus (443) Google Scholar). These methods are mainly designed to identify differences in protein expression patterns of cancer cell samples compared with healthy ones. Proteomics approaches, in particular, have emerged as an established tool. These include the analysis of complex protein samples using two-dimensional gel electrophoresis (7Shin B.K. Wang H. Yim A.M. Naour F.L. Brichory F. Jang J.H. Zhao R. Puravas E. Tra J. Michael C.W. Misek D.E. Hanash S.M. Global profiling of the cell surface proteome of cancer cells uncovers an abundance of proteins with chaperone function.J. Biol. Chem. 2003; 278: 7607-7616Abstract Full Text Full Text PDF PubMed Scopus (473) Google Scholar) and shotgun methods that employ different membrane solubilization strategies, such as isotope-coded affinity tagging (8Gygi S.P. Rist B. Scott A.G. Turecek F. Gelb M.H. Aebersold R. Quantitative analysis of complex protein mixtures using isotope-coded affinity tags.Nat. Biotechnol. 1999; 17: 994-999Crossref PubMed Scopus (4362) Google Scholar), multidimensional protein identification technology (9Washburn M.P. Wolters D. Yates III, J.R. Large-scale analysis of the yeast proteome by multidimensional protein identification technology.Nat. Biotechnol. 2001; 19: 242-247Crossref PubMed Scopus (4099) Google Scholar), and surface enhanced laser desorption ionization combined with time of flight mass analysis of complex biological mixtures (10Roboz J. Mass spectrometry in diagonistic oncoproteomics.Cancer Invest. 2005; 23: 465-478Crossref PubMed Scopus (21) Google Scholar). While these approaches are effective in identifying a large number of proteins in their expression patterns, identifying specific protein markers strongly correlated to disease remains a big challenge. In this regard, there is a growing interest in using monoclonal antibodies to target cell surface proteins that are significantly expressed on diseased cells or tissues. In particular, magnetic bead conjugated monoclonal antibodies have been used to isolate membrane proteins and plasma proteins using whole cellular lysates (11Lawson E.L. Clifton J.G. Huang F. Li X. Hixson D.C. Josic D. Use of magnetic beads with immobilized monoclonal antibodies for isolation of highly pure plasma membranes.Electrophoresis,. 2006; 27: 2747-2758Crossref PubMed Scopus (75) Google Scholar, 12Chang P.S. Absood A. Linderman J.J. Omann G.M. Magnetic bead isolation and quantification of membrane-associated guanine nucleotide binding proteins.Anal. Biochem. 2004; 325: 175-184Crossref PubMed Scopus (19) Google Scholar, 13Shangguan D. Li Y. Tang Z. Cao Z. Chen H. Mallikratchy P. Sefah K. Yang C.-J. Tan W. Aptamers evolved from live cells as effective molecular probes for cancer study.Proc. Natl. Acad. Sci. U. S. A. 2006; 103: 11838-11843Crossref PubMed Scopus (1226) Google Scholar). However, the major problem with antibodies is the difficulty in generating cell specific antibodies for the identification of the expression levels among different types of cells. We have recently developed an effective method to generate molecular aptamers based molecular probes for the specific recognition of cancer cells (14Tang Z. Shangguan D. Wang K. Shi H. Sefah K. Mallikaratchy P. Li Y. Tan W. Selection of aptamers for molecular recognition and characterization of cancer cells.Anal. Chem. 2007; 79: 4900-4907Crossref PubMed Scopus (403) Google Scholar). Using this method, referred to as Cell Based Systematic Evolution of Ligands by EXponential Enrichment (SELEX) 1The abbreviations used are: SELEX, Systematic Evolution of Ligands by EXponential Enrichment; IGHM, immunoglobin heavy mu; PEG, polyethylene glycol; 5-dUI, 5-iodo-deoxyuridine; IgM, immunoglobin M. ,we have generated DNA aptamers that can identify the differences in relative levels of membrane protein expression patterns of a given set of cells in a complex biological mixture (14Tang Z. Shangguan D. Wang K. Shi H. Sefah K. Mallikaratchy P. Li Y. Tan W. Selection of aptamers for molecular recognition and characterization of cancer cells.Anal. Chem. 2007; 79: 4900-4907Crossref PubMed Scopus (403) Google Scholar). These probes can then be used to identify the up-regulated membrane proteins in a given set of cells. We think that these profiling studies (13Shangguan D. Li Y. Tang Z. Cao Z. Chen H. Mallikratchy P. Sefah K. Yang C.-J. Tan W. Aptamers evolved from live cells as effective molecular probes for cancer study.Proc. Natl. Acad. Sci. U. S. A. 2006; 103: 11838-11843Crossref PubMed Scopus (1226) Google Scholar, 14Tang Z. Shangguan D. Wang K. Shi H. Sefah K. Mallikaratchy P. Li Y. Tan W. Selection of aptamers for molecular recognition and characterization of cancer cells.Anal. Chem. 2007; 79: 4900-4907Crossref PubMed Scopus (403) Google Scholar) would possibly assist in finding disease markers specific for one group of cell type. For example, in our previous studies, we have demonstrated that aptamer probes selected against a T-cell leukemia line, CCRF-CEM, can be used to identify T-cell leukemia in patient samples as well as CEM cells spiked into human bone marrow aspirates, suggesting the applicability of the cell specific aptamers in real samples. In addition, we have demonstrated that each aptamer has its own binding patterns when recognizing molecular signatures on cells, further suggesting that there is a correlation between aptamer mediated cell recognition and different protein expression patterns in diseased cells. In our recent studies with B-cell leukemia, we have identified an aptamer TD05 that recognizes Ramos cells, a Burkitt's lymphoma cell line. We reason that observed binding ability of this aptamer with Ramos cells can be used to identify a membrane protein related to Ramos cells. Through the work in this paper, we have found that TD05 binds selectively to membrane bound immunoglobin heavy mu chain (IGHM), which is the heavy chain portion of the IgM protein. IgM is a major component of B-cell receptor complex expressed in Burkitt's lymphoma that has been widely studied as a potential marker for Burkitt's lymphomas (15Thomas M.D. Srivastava B. Allman D. Regulation of peripheral B-cell maturation.Cell. Immunol. 2006; 239: 92-102Crossref PubMed Scopus (88) Google Scholar, 16Cambier J. C Campbell K.S. Membrane immunoglobin and its accomplices: new lessons from an old receptor.FASEB J. 1992; 6: 3207-3215Crossref PubMed Scopus (72) Google Scholar). Also, some studies emphasize its active role in Burkitt's lymphoma cell proliferation and survival (17Trujillo M.A. Jiang S.-W. Tarara J.E. Eberhardt N.L. Clustering of the B-cell receptor is not required for the apoptotic response.DNA Cell Biol. 2003; 22: 513-523Crossref PubMed Scopus (6) Google Scholar, 18Joseph L.F. Ezhevsky S. Scott D.W. Lymphoma models for B-cell activation and tolerance: anti-immunoglobin M treatment induces growth arrest by preventing complex which phosphorylates retinoblastoma gene product in G 11.Cell Growth & Differ. 1995; 6: 51-57PubMed Google Scholar, 19Carey G.B. Donjerkovic D. Mueller C.M. Liu S. Hinshow W. Scott D.W. B-cell receptor and for and 1995; Scholar, of the of monoclonal antibodies with surface IgM on J. 1999; 79: PubMed Scopus Google Scholar). the binding studies with different cell the identification of using the aptamer TD05 in a step the aptamer chemically with a for binding of the aptamer with cells. the target protein by magnetic using a the protein identified by followed by a the of the target protein using an and the selected aptamer. the used in this our this is the on the of aptamers in identifying Burkitt's lymphoma membrane proteins by the covalently of aptamer to its target using a whole of aptamers Burkitt's lymphoma cells has been selected by using SELEX, among which the aptamer TD05 showed significant and specific binding with Ramos cells. The aptamer TD05 with DNA were from pure used for all the aptamer were using using an DNA were to the of with the of the aptamer. were used to of the DNA using The on a with a The for aptamer probes were further by followed by gel a aptamer through a with with the beads were into a The beads were with and for or at to the The and the beads were by gel electrophoresis with T-cell line, human Ramos B-cell line, human Burkitt's B-cell line, human Burkitt's human T-cell B-cell line, human large cell leukemia, and and were from the of the cells were in with and were and with and in with and used for by yeast and DNA into to The of of with by TD05 with aptamer were with for at in the binding with the cells were then and by the in the of TD05 using a by DNA used as a and were at with of using a of of aptamers to cells in binding The cells and the aptamers were at for to the with the aptamer in The aptamers were with in the with bound aptamer were in the in a a the the cell to the The with of from a laser at for The cells were in a mixture DNA and using a with protein were from the membrane by at for at membrane in and with at The membrane proteins were from cell by at for at cell with of magnetic beads at for probes were and with by for at were used to proteins and to the of the as and with magnetic beads were at for with and The on to and a of and for were using to the the gel to and by in the in and by and a at the of heavy chain used to further the protein were using a of with CEM cells at for and the were then with of heavy mu chain for at of the and by Cell The used to which Ramos cells using a to one (14Tang Z. Shangguan D. Wang K. Shi H. Sefah K. Mallikaratchy P. Li Y. Tan W. Selection of aptamers for molecular recognition and characterization of cancer cells.Anal. Chem. 2007; 79: 4900-4907Crossref PubMed Scopus (403) Google Scholar). in this the of the among a significant number of selected TD05 recognizes target Ramos cells and (14Tang Z. Shangguan D. Wang K. Shi H. Sefah K. Mallikaratchy P. Li Y. Tan W. Selection of aptamers for molecular recognition and characterization of cancer cells.Anal. Chem. 2007; 79: 4900-4907Crossref PubMed Scopus (403) Google Scholar). We by cell surface proteins with to that TD05 binds with a cell surface protein. the treatment with the TD05 not recognize Ramos cells suggesting that the target a or membrane protein (14Tang Z. Shangguan D. Wang K. Shi H. Sefah K. Mallikaratchy P. Li Y. Tan W. Selection of aptamers for molecular recognition and characterization of cancer cells.Anal. Chem. 2007; 79: 4900-4907Crossref PubMed Scopus (403) Google Scholar). We have designed a and method for the identification of a target protein by a step binding of the aptamer with the target magnetic bead and magnetic and analysis to identify target proteins, and analysis of the target protein. of TD05 with facilitates its with the target protein on the cell the target protein with the aptamer would be from the cell to high the of the nucleotide in the TD05 has a compared with we that the would not the aptamer binding with Ramos cells. However, when the TD05 aptamer with 5-dUI, Ramos cells not is that can be by modifications of the characterization of a Sci. 1999; PubMed Scopus Google Scholar, D. J. and of Cell. Proteomics. 2003; 2: Full Text Full Text PDF PubMed Scopus Google Scholar) because the mainly on of the aptamer that a specific binding in protein binding as in the aptamer with in of the and This aptamer suggesting the not its affinity TD05 binds to Ramos cells with to that of the TD05 Large through a at the of the aptamer. of the the of complex from the streptavidin coated magnetic the TD05 for binding with target cells through a with aptamer. The that the aptamers with each other because the in a in This that the binding ability of the TD05 We have studies to the of on TD05 using a cell T-cell cells not the to and time were to effective of aptamer from the magnetic beads using the complex its we the TD05 using at the The TD05 bound to Ramos cells were with of a laser to of the aptamer with the cell surface protein. of TD05 with its target protein to the of the and to by In to the were further by using a mixture of DNA and in the cell by plasma proteins, proteins were to magnetic using an The membrane in membrane solubilization a mixture of and the which in proteins with the the mixture with streptavidin coated magnetic beads to aptamer that at the Use of streptavidin coated magnetic beads for the specific of the TD05 with the covalently bound target protein. The of the complex the the TD05 with we the of the by the on the beads compared with cell using a of the in protein from cell lysates is the of and other proteins with the aptamer. the of the complex to with proteins, which in a gel from to were to the of proteins the magnetic to the of the protein target and the such not the protein to from the aptamer of target proteins and or of protein due to the affinity between and we an between the aptamer and the in proteins are using to gel of the between the aptamer and has in the of the complex from the beads the of the the high of to recognize the complex using a the the the by have a significant of This be because the by from cell a highly complex However, were based on molecular and the of membrane of these potential targets of TD05 based on found to be of development and of large and protein. these we to be the because protein to be expressed in its molecular to the molecular of the protein the molecular of the is a membrane and the protein that were identified are in all types of cells. The have further the the to that is the target for we the binding of with Ramos and the number of T-cell leukemia cell leukemia cells, and a Burkitt's lymphoma cell line that surface IgM cell and a cell line that not surface IgM cells) and cells Burkitt's lymphoma cells, these cells not the of Burkitt's For this these cells not or membrane C. H. M. R. and in the of lymphoma cell J. 1999; PubMed Scopus (30) Google Scholar). we the of TD05 aptamer and with surface IgM TD05 and showed binding with the cell line, suggesting that be the target protein. TD05 aptamer and with cells, and TD05 aptamer and not to cells. these that the is the target for TD05 aptamer. we TD05 and to IGHM, we a between the two in We the of TD05 binding with Ramos cells the of TD05 not However, the between TD05 with Ramos cells as in suggesting probes to target with different In addition, we found that TD05 binds to a membrane protein based on our study (14Tang Z. Shangguan D. Wang K. Shi H. Sefah K. Mallikaratchy P. Li Y. Tan W. Selection of aptamers for molecular recognition and characterization of cancer cells.Anal. Chem. 2007; 79: 4900-4907Crossref PubMed Scopus (403) Google Scholar) of the aptamer binding treatment of and K. this we observed that TD05 binding with Ramos cells not by of has been that the in of membrane proteins using can be with the a observed (5Bledi Y. Inberg A. Linial M. PROCEED: a proteomic method for analysing plasma membrane proteins in living mammalian cells.Briefing Funct. Genomics Proteomics. 2003; 2: 254-265Crossref PubMed Scopus (27) Google Scholar). We patterns be observed with the with Ramos cells with The not its ability to recognize Ramos cells with further that TD05 and to the and recognize Ramos cells with TD05 and analysis of binding of with cells for and have that there is on binding with the aptamer or the Large We have a strategy for identifying expressed proteins by aptamer probes selected against target tumor cells. This method the of molecular probes specific cells and the cell specific aptamers for effective identification of target previous work established that aptamer binding signatures to each cell be as expression patterns of protein Also, has been demonstrated that each aptamer has its own when recognizing target proteins in complex biological (13Shangguan D. Li Y. Tang Z. Cao Z. Chen H. Mallikratchy P. Sefah K. Yang C.-J. Tan W. Aptamers evolved from live cells as effective molecular probes for cancer study.Proc. Natl. Acad. Sci. U. S. A. 2006; 103: 11838-11843Crossref PubMed Scopus (1226) Google Scholar, 14Tang Z. Shangguan D. Wang K. Shi H. Sefah K. Mallikaratchy P. Li Y. Tan W. Selection of aptamers for molecular recognition and characterization of cancer cells.Anal. Chem. 2007; 79: 4900-4907Crossref PubMed Scopus (403) Google Scholar, P.S. R. L.A. R. of new for 1999; PubMed Scopus Google Scholar). Furthermore, we have that is to recognize up-regulated proteins that have a role in transforming cells into diseased cells (14Tang Z. Shangguan D. Wang K. Shi H. Sefah K. Mallikaratchy P. Li Y. Tan W. Selection of aptamers for molecular recognition and characterization of cancer cells.Anal. Chem. 2007; 79: 4900-4907Crossref PubMed Scopus (403) Google Scholar). the of the in this with is to identify up-regulated protein in to or genetic the cells that to We have the for of DNA aptamers by different to their as molecular These modifications two important and This is one of the for DNA aptamers can be to binding of the complex through of the complex to in which important in and of proteins from a cell of the aptamer from the streptavidin through of a The for membrane proteins from the cell membrane is to of that the membrane in an However, of in of the receptor and/or of the receptor because the of these receptor molecules on the of the cell This to of the complex when the target protein or These protein alterations by in the of is one of the major in identification of membrane proteins using aptamers and can possibly be one of the when using these probes in identifying molecular We have this by modifying the aptamer with to of the with the target which the of the using have been for in affinity and other M. and to the 1999; PubMed Scopus Google Scholar, The and in Chem. PubMed Scopus Google Scholar). However, one of the major of such is that such affinity to the of the streptavidin coated solid Also, these in the complex or in for in to analysis (7Shin B.K. Wang H. Yim A.M. Naour F.L. Brichory F. Jang J.H. Zhao R. Puravas E. Tra J. Michael C.W. Misek D.E. Hanash S.M. Global profiling of the cell surface proteome of cancer cells uncovers an abundance of proteins with chaperone function.J. Biol. Chem. 2003; 278: 7607-7616Abstract Full Text Full Text PDF PubMed Scopus (473) Google Scholar). The aptamer with the group to the at the can be by treatment with used to gel This the aptamer with its protein to the beads with for gel Also, this can potential the is one of the major of B-cell receptor complex expressed in Burkitt's lymphoma cells. has been that expression on is related to Burkitt's lymphoma development of the of monoclonal antibodies with surface IgM on J. 1999; 79: PubMed Scopus Google Scholar). The of on the Ramos cells is correlated with our of this study for the binding of TD05 with Ramos cells correlated with expression patterns of these cells compared with other cell lines and in real bone marrow samples. Furthermore, is a receptor that has a role in development of Burkitt's and this protein is a marker for Burkitt's these the of this in identifying cell membrane receptors that have altered expression levels in tumor cells. In we have that cancer aptamers an effective in identifying target proteins that expression levels on a of diseased cells. The in of the DNA aptamer has binding and for the effective and identification of target receptors on cell membrane In addition, of the that the of aptamers using followed by identification of binding of each aptamer can be in marker proteins in a given cell type. In to such as a specific the of based protein is in its on finding cell surface membrane markers with of the molecular of the cell Also, to their and of DNA aptamers by this method is and from the ability of identification of disease markers that play roles in cancer progression, this method can be in and as molecular in recognition as well as studies of diseased cells. We and for their and with

Early diagnosis is the way to improve the rate of lung cancer survival, but is almost impossible today due to the lack of molecular probes that recognize lung cancer cells sensitively and selectively. We developed a new aptamer approach for the recognition of specific small-cell lung cancer (SCLC) cell-surface molecular markers. Our approach relies on cell-based systematic evolution of ligands by exponential enrichment (cell-SELEX) to evolve aptamers for whole live cells that express a variety of surface markers representing molecular differences among cancer cells. When applied to different lung cancer cells including those from patient samples, these aptamers bind to SCLC cells with high affinity and specificity in various assay formats. When conjugated with magnetic and fluorescent nanoparticles, the aptamer nanoconjugates could effectively extract SCLC cells from mixed cell media for isolation, enrichment, and sensitive detection. These studies demonstrate the potential of the aptamer approach for early lung cancer detection.