Abstract
There is considerable evidence for an association between prostate cancer development and inflammation, which results in autoantibody generation against tumor proteins. This immune system-driven amplification of the autoantibody response to intracellular antigens can serve as a sensitive tool to detect low abundance serum proteomic tumor markers for prostate cancer as well as provide insight into biological processes perturbed during cancer development. Here we examine serum humoral responses in a cohort of 34 patients with either benign prostatic hyperplasia or clinically localized prostate cancer (PCa). The experimental strategy couples multidimensional liquid-phase protein fractionation of localized and metastatic prostate cancer tissue lysates to protein microarrays and subsequent mass spectrometry. A supervised learning analysis of the humoral response arrays generated a parsimonious predictor having 78% sensitivity and 75% specificity in distinguishing PCa from benign prostatic hyperplasia in a cohort of American males with elevated prostate-specific antigen. Enrichment analysis of the PCa-specific humoral signature revealed large scale immune reprogramming mediated by STAT transcription factors and the generation of autoantibodies to enzymes involved in nitrogen metabolism. Meta-analysis of independent prostate cancer gene expression data validated the presence of STAT-induced immunomodulation. Concomitant validation of elevated levels of the nitrogen metabolism pathway was obtained by direct measurement of metabolic levels of glutamate and aspartate in prostate cancer tissues. Thus, in addition to functioning as markers in prostate cancer detection, humoral response profiles can serve as powerful tools revealing pathway dysregulation that might otherwise be suppressed by the complexity of the cancer proteome.
Highlights
There is considerable evidence for an association between prostate cancer development and inflammation, which results in autoantibody generation against tumor proteins
This requirement motivates our strategy of coupling comprehensive two-dimensional liquid-phase fractionation of the prostate cancer proteome to protein microarray analysis of patient sera and mass spectrometry for the identification of proteins contributing to a discriminating multiplex humoral response to prostate cancer antigens
By coupling multidimensional protein fractionation with protein microarrays this proof-of-principle study demonstrates the power of immune system-driven autoantibody response in detection of prostate cancer
Summary
There is considerable evidence for an association between prostate cancer development and inflammation, which results in autoantibody generation against tumor proteins. This is supported by studies from humoral response trials where among the large numbers of patients tested only a subset of patients with a specific tumor type develop a response to a specific antigen This heterogeneity in humoral response generation necessitates the use of a multiplex panel of protein targets as autoantibody biomarkers to detect tumors with broad coverage for a large number of people. This requirement motivates our strategy of coupling comprehensive two-dimensional liquid-phase fractionation of the prostate cancer proteome to protein microarray analysis of patient sera and mass spectrometry for the identification of proteins contributing to a discriminating multiplex humoral response to prostate cancer antigens (see Fig. 1). In this work we used the humoral response signature for prostate cancer detection and for extensive analysis of pathways dysregulated in prostate cancer development and progression
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