Tumor-associated antigen arrays for the serological diagnosis of cancer

Abstract

The recognition that human tumors stimulate the production of autoantibodies against autologous cellular proteins called tumor-associated antigens (TAAs) has opened the door to the possibility that autoantibodies could be exploited as serological tools for the early diagnosis and management of cancer. Cancer-associated autoantibodies are often driven by intracellular proteins that are mutated, modified, or aberrantly expressed in tumor cells and hence are regarded as immunological reporters that could help uncover molecular events underlying tumorigenesis. Emerging evidence suggests that each type of cancer might trigger unique autoantibody signatures that reflect the nature of the malignant process in the affected organ. The advent of novel genomic, proteomic, and high throughput approaches has accelerated interest in the serum autoantibody repertoire in human cancers for the discovery of candidate TAAs. The use of individual anti-TAA autoantibodies as diagnostic or prognostic tools has been tempered by their low frequency and heterogeneity in most human cancers. However, TAA arrays comprising several antigens significantly increase this frequency and hold great promise for the early detection of cancer, monitoring cancer progression, guiding individualized therapeutic interventions, and identification of novel therapeutic targets. Our recent studies suggest that the implementation of TAA arrays in screening programs for the diagnosis of prostate cancer and other cancers should be preceded by the optimization of their sensitivity and specificity through the careful selection of the most favorable combinations of TAAs.

Fig. 1. The path to the identification of LEDGF/p75 as a candidate TAA in prostate cancer

A, autoantibodies with a nuclear fluorescence staining pattern resembling that of the known autoantigen LEDGF/p75 (also called DFS70) were initially detected in prostate cancer sera by screening the sera in Hep-2 slides and LnCaP prostate cancer cells growing on coverslips via immunofluorescence microscopy. B, the presence of these autoantibodies in prostate cancer sera (p) and some positive matched control sera (c) was detected by immunoblotting of LnCaP cell lysates using reference anti-LEDGF/p75 sera as positive controls. C, the frequency of these autoantibodies in prostate cancer was determined in an ELISA system using purified recombinant LEDGF/p75 by testing against sera from prostate cancer patients and age- and gender-matched controls. Significantly high frequencies were obtained in the prostate cancer group. D, validation of LEDGF/p75 as a protein associated with prostate cancer was first achieved by analyzing its expression in a panel of prostate cancer cell lines by immunoblotting. High expression was observed in most tumor and transformed cell lines. The lowest expression was in the primary normal cell line PrEC. E, the availability of the human prostate cancer Histo-Array^™ facilitated immunohistochemical analysis of LEDGF/p75 in tumor tissue. F, LEDGF/p75 was found to be highly expressed in the majority of prostate tumor tissue specimens but not in normal prostate tissue. For details see Ref. .