Antigen Specificity and Clinical Significance of IgG and IgA Autoantibodies Produced in situ by Tumor-Infiltrating B Cells in Breast Cancer

Abstract

An important role for tumor infiltrating B lymphocytes (TIL-B) in the immune response to cancer is emerging; however, very little is known about the antigen specificity of antibodies produced in situ. The presence of IgA antibodies in the tumor microenvironment has been noted although their biological functions and clinical significance are unknown. This study used a 91-antigen microarray to examine the IgG and IgA autoantibody repertoires in breast cancer (BC). Tumor and adjacent breast tissue supernatants and plasma from BC patients together with normal breast tissue supernatants and plasma from healthy controls (patients undergoing mammary reduction and healthy blood donors) were analyzed to investigate relationships between autoantibodies and the clinical, histological and immunological features of tumors. Our data show that >84% of the BC samples tested contain autoantibodies to one or more antigens on the array, with ANKRD30BL, COPS4, and CTAG1B being most frequently reactive. Ex vivo TIL-B responses were uncoupled from systemic humoral responses in the majority of cases. A comparison of autoantibody frequencies in supernatants and plasma from patients and controls identified eight antigens that elicit BC-associated autoantibody responses. The overall prevalence of IgG and IgA autoantibodies was similar and while IgG and IgA responses were not linked they did correlate with distinct clinical, pathological and immunological features. Higher levels of ex vivo IgG responses to BC-associated antigens were associated with shorter recurrence-free survival (RFS), HER2 overexpression and lower tumor-infiltrating CD8+ T cell counts. Higher IgA levels were associated with estrogen and progesterone receptor-negative cancers but were not significantly associated with RFS. Furthermore, ex vivo IgA but not IgG autoantibodies reactive to BC-associated antigens were linked with germinal center and early memory B cell maturation and the presence of tertiary lymphoid structures suggesting that these TIL-B are activated in the tumor microenvironment. Overall, our results extend the current understanding of the antigen specificity, the biological and the clinical significance of IgG and IgA autoantibodies produced by BC TIL-B in situ.

Tumor-infiltrating B cells signal functional humoral immune responses in breast cancer

“…TIL-B are functional, reflected by their production of autoantibodies specific for TAA, with a previous demonstration that BC TIL-B expand oligoclonally (74). Our recent analysis of paired primary tissue supernatant and plasma samples detected autoantibodies in > 84% of our BC cohort to 1 or more antigens on a 91-TAA microarray (39). The 3 most frequently recognized proteins were ankyrin repeat domain 30B like (ANKRD-30BL), COP9 signalosome subunit 4 (COPS4), and CTAG1B (also known as NY-ESO-1).…”

“…The 3 most frequently recognized proteins were ankyrin repeat domain 30B like (ANKRD-30BL), COP9 signalosome subunit 4 (COPS4), and CTAG1B (also known as NY-ESO-1). This work also found that higher IgG but not IgA responses to BC-associated antigens were associated with shorter recurrence-free survival and lower CD8 + TIL, suggesting that Ig isotypes may provide different biological functions in the tumor microenvironment (39). In the present study, global Ig production -and specifically IgG1 levels -increase in the tumor tissue supernatant as TIL levels graduate from low to intermediate to high, but this was also associated with a bump in IgA in the TIL int group.…”

“…TIL-B have been shown to mount tumor-specific autoantibody responses directed against tumor-associated antigens (TAA). Our recent work revealed that > 84% of the BC patients examined produce autoantibodies to 1 or more of the antigens present on a 91-TAA microarray (39). We further identified 8 antigens that elicit BC-associated autoantibody responses (39).…”

“…Our recent work revealed that > 84% of the BC patients examined produce autoantibodies to 1 or more of the antigens present on a 91-TAA microarray (39). We further identified 8 antigens that elicit BC-associated autoantibody responses (39). In esophago-gastric adenocarcinoma, 48% of plasma samples were positive for 1 or more TAA (40).…”

Single cell genomic characterization reveals the cellular reprogramming of the gastric tumor microenvironment

“…Plasma cells in tumor tissue expressed IgGs rather than IgAs that were detected in paired normal tissue. IgGs have been associated with a pro-cancer role by influencing myeloid cell Fc-receptors (48).…”