Prognostic significance of tumor-infiltrating B cells and plasma cells in human cancer

There is abundant evidence that tumor-infiltrating CD8+ T cells contribute positively to anti-tumor immunity; however, the role of tumor-infiltrating B cells (TIL-B) and plasma cells (PC) remains controversial, leading to differing opinions about whether immunotherapies should be designed to enhance or inhibit these cells. Through a comprehensive PubMed search, we reviewed publications with cohorts of 50 or more cases in which the prognostic value of TIL-B/PC was assessed by immunohistochemistry and/or gene expression analysis. Sixty-nine studies representing 19 cancers met our review criteria. The large majority of studies assessed TIL-B by immunohistochemical detection of CD20. Of these, 50.0% reported a positive prognostic effect for CD20+ TIL-B, whereas the remainder found a neutral (40.7%) or negative (9.3%) effect. These differences in prognostic effect were not attributable to cancer type, other clinicopathological factors, or differing technical approaches. The prognostic significance of TIL-B/PC was generally concordant with that of CD3+ and/or CD8+ T cells, and the prognostic effect of T cells was generally stronger when TIL-B and/or PC were also present. Additionally, 21 studies inferred the presence of TIL-B/PC from gene expression data, and a large majority reported a positive prognostic effect. While more studies are required involving additional cancer types and independent patient cohorts, the weight of evidence supports a positive role for TIL-B and PC in anti-tumor immunity, suggesting that enhancement of these responses should be considered in the design of cancer immunotherapies.

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