Immunoglobulin repertoire of B lymphocytes infiltrating breast medullary carcinoma

Tumor specific peptides recognized by T lymphocytes infiltrating solid tumors, as well as the corresponding T cell receptor (TcR) repertoire usage, have been extensively investigated. By contrast, tumor infiltrating B cells and their immunoglobulin (Ig) repertoire have been studied only in a limited number of tumors. The objective of the present study was to determine, whether DNA sequence analysis of the expressed immunoglobulin variable regions of B cells that infiltrate breast cancer, could be used to reveal a potential specific tumor binding capacity of the antibodies. To answer this question, about 200 expressed Ig heavy (VH) and light chain variable gene (VL) regions were cloned, sequenced and comparatively analysed from a typical medullary beast carcinoma (MBC), where the massive B and plasma cell infiltration correlates with favourable prognosis despite of its high grade. The tumor infiltrating B cell Ig heavy and light chain sequences could be classified into clusters, families and subgroups, based on the identity level to germline, showing a pattern of oligoclonality. Some overrepresented clusters could be determined. In the course of a detailed analysis and search in Blastn database, a number of VH and VL sequences showed more than 99% homology to DNA sequences of Ig VH region, with proved tumor antigen binding capacity. Our data suggest, that potential tumor binder Ig VH and VL sequences might be selected using a detailed immunoglobulin variable region analysis. This new approach might have a benefit for further antibody engineering, as difficulties in search for tumor binders by phage library selection might be reduced and the time for selection shortened.