Nucleic acid–triggered tumoral immunity propagates pH‐selective therapeutic antibodies through tumor‐driven epitope spreading

Abstract

Important roles of humoral tumor immunity are often pointed out; however, precise profiles of dominant antigens and developmental mechanisms remain elusive. We systematically investigated the humoral antigens of dominant intratumor immunoglobulin clones found in human cancers. We found that approximately half of the corresponding antigens were restricted to strongly and densely negatively charged polymers, resulting in simultaneous reactivities of the antibodies to both densely sulfated glycosaminoglycans (dsGAGs) and nucleic acids (NAs). These anti‐dsGAG/NA antibodies matured and expanded via intratumoral immunological driving force of innate immunity via NAs. These human cancer–derived antibodies exhibited acidic pH–selective affinity across both antigens and showed specific reactivity to diverse spectrums of human tumor cells. The antibody‐drug conjugate exerted therapeutic effects against multiple cancers in vivo by targeting cell surface dsGAG antigens. This study reveals that intratumoral immunological reactions propagate tumor‐oriented immunoglobulin clones and demonstrates a new therapeutic modality for the universal treatment of human malignancies.

Immune repertoire profiling for disease pathobiology

“…There are three major approaches to obtain repertoire sequencing data. One is repertoire sequencing using bulk tissue samples, wherein the purified total RNA is subjected to multiplex PCR using multiplex primers designed for all possible V and C segments of the immune receptor genes 8,10–12 . By performing NGS on the amplicons, more than 10 5 –10 6 heavy/light and alpha/beta chain sequences for B and T cells, respectively, can theoretically be obtained for each sample.…”

“…The advantage of bulk sequencing is that substantially deeper repertoire information can be obtained as compared to single‐cell sequencing; however, the repertoire sequences of heavy/light chains of BCR/Ig and alpha/beta chains of TCR are obtained separately, and it is generally not possible to reconstruct heavy/light and alpha/beta chain combinations from the data. In previous studies, only top‐ranked dominant BCR clones in each examined tissue could successfully be reconstructed as Ig molecules 8–10 . On the other hand, by single‐cell repertoire sequencing, the proper combinations of heavy/light and alpha/beta chains of BCR/Ig and TCR can be defined at single‐cell resolution.…”

“…Identification of the corresponding antigen for a given BCR/Ig clone is important for understanding the function of specific B cell immunity and clarifying the molecular background of the disease pathology (Figure 1). Once the dominant Ig clones in diseased tissues and/or disease‐related Ig clones are identified by repertoire sequencing, it is feasible to identify their corresponding antigens by biochemical experiments 8–10,37 . Identified Ig clone sequences of heavy and light chains can be constructed directly in expression plasmids.…”

“…Clarifying the cellular and stromal components by which the antigens are expressed is key to deepening our understanding of the mechanisms of the diseases. Second, RNA in situ hybridization targeting specific CDR3 sequences of interest can be used to investigate the distribution of specific B/plasma cell clones in human histopathological specimens 10 . This experiment can help obtain the spatial information of disease‐related B/plasma cells in relation to the histological features of the diseases.…”

“…Immune repertoire sequencing has been applied to many scientific fields recently and paved the way to understand varieties of disease pathobiology. Selected representative recent achievements of this methodology are summarized in Table 3 and introduced below 8–10,13,37,39–48 …”