Profiling the immune response in patients with breast cancer by phage-displayed cDNA libraries

Display on the surface of filamentous phages has been shown to be well suit ed for the enrichment of serum antibody-binding ligands. Here, we have take n the advantage of this technology to analyze the humoral immune response i n patients with cancer. The cDNA repertoires from breast cancer cell lines T47D and MCF-7 were fused to the 3'-end of the filamentous phage M13 gene V I in all three reading frames. When the libraries were biopanned on rabbit polyclonal IgG against the human Bcl-x(L) protein, positive clones were sel ected, thus confirming the utility of the libraries. Using serum antibodies from patients with breast cancer, we specifically selected IgG-binding pha ge-encoded cDNA products. Sequence analysis of the selected clones identifi ed important antigens including p53, centromere-f, int-2, pentraxin I, inte grin beta5, cathepsin L2 and S3 ribosomal protein. The selected phage-displ ayed cDNA products were recognized by a significant number of breast cancer sera as compared to sera from normal individuals. Although the human pentr axin I mRNA was reported to be exclusively localized in the nervous system, we found it also expressed by breast cancer cell fines. Four out of 30 pat ients with breast cancer (13 %) showed reactivity with the recombinant pent raxin expressed in Escherichia coli, while no reactivity was found in norma l sera. The obtained results demonstrate that phage display could be a valu able method for the identification of antigens recognized by the humoral im mune system in patients with cancer.