Microarrays of tumor cell derived proteins uncover a distinct pattern of prostate cancer serum immunoreactivity

Abstract

The broad characterization of the immune responses elicited by tumors has valuable applications in diagnostics and basic research. We present here the use of microarrays of tumor-derived proteins to profile the antibody repertoire in the sera of prostate cancer patients and controls. Two-dimensional liquid chromatography was used to separate proteins from the prostate cancer cell line LNCaP into 1760 fractions. These fractions were spotted in microarrays on coated microscope slides, and the microarrays were incubated individually with serum samples from 25 men with prostate cancer and 25 male controls. The amount of immunoglobulin bound to each fraction by each serum sample was quantified. Statistical analysis revealed that 38 of the fractions had significantly higher levels of immunoglobulin binding in the prostate cancer samples compared to the controls. Two fractions showed higher binding in the control samples. The significantly higher immunoglobulin reactivity from the prostate cancer samples may reflect a strong immune response to the tumors in the prostate cancer patients. We used multivariate analysis to classify the samples as either prostate cancer or control. In a cross-validation study, recursive partitioning classified the samples with 84% accuracy. A decision tree with two levels of partitioning classified the samples with 98% accuracy. Additional studies will allow further characterization of tumor antigens in prostate cancer and their significance for diagnosis. These results suggest that microarrays of fractionated proteins could be a powerful tool for tumor antigen discovery and cancer diagnosis.

Humoral Response Profiling Reveals Pathways to Prostate Cancer Progression

“…cellular processes emphasizes the importance of using a screening platform containing proteins extracted from tumor, itself reflecting a physiologically realistic swath of the prostate cancer proteome. Such correlations to tumor function would be difficult to recapitulate using proteins fractionated from cell lines (35,36) or using phage array platforms (15,37). In addition, the multidimensional protein fractionation-coupled microarray retains post-translational modifications that are most indicative of the cellular phenotype and in most cases better reflects the reality of humoral response to cancer antigens.…”

Humoral Immunity Directed against Tumor-Associated Antigens As Potential Biomarkers for the Early Diagnosis of Cancer

“…The recombinant protein arrays use clones from cDNA expression libraries or peptide phage display libraries; [20][21][22] the native protein arrays use proteins derived from tumor tissue or cell lines. 23,24 Recent studies on prostate, 20 lung, 21 ovarian, 25 and breast cancer 26 have used the phage display technology. This approach involves the construction of a T7 cDNA phage display library from tumor tissue or a cell line.…”

“…Fractionated proteins from a tumor cell lysate can be used to spot the array. 23,24 In the study by Qiu et al, protein lysates from the A549 human lung adenocarcinoma cell line were separated into 1840 fractions that were spotted in duplicate, along with various controls, on nitrocellulosecoated slides. Sera from lung cancer patients and healthy controls were each hybridized to an individual microarray.…”

Serologic Autoantibodies as Diagnostic Cancer Biomarkers—A Review

“…The protein array methods are advantageous in that they require only minute amounts of patient sera (46) while enabling the simultaneous screening of large numbers of antigens in a single test (47)(48)(49)(50)(51)(52). In this methodology, purified or recombinant as well as synthetic proteins are used.…”