Leveraging B cell specificities for tumor glycans to elicit potent anti-tumor immunity

总结 肿瘤相关碳水化合物抗原（TACA）是表达于肿瘤细胞表面的异常糖基化产物。 癌细胞，但在大多数正常细胞上不存在。它们的表达通常与转移有关， 预后和总生存率降低。Tn抗原（N-乙酰半乳糖胺O-连接至丝氨酸或苏氨酸）是 一种常见于癌症粘蛋白的TACA我们已经研究了B细胞对Tn-和其他细胞因子应答的调节。 使用小鼠模型的携带TACA的粘蛋白。我们的进展表明，TACA的特异性，包括Tn， 在小鼠的先天B（B1）细胞群中高度富集。我们还发现，B细胞内源性PD-1 表达有效地抑制肿瘤保护性TACA特异性抗体（Ab）应答， 是在PD-1抑制背景下观察到的增加的应答所必需的。最后，我们确定了 一种在体内具有显著和广泛的抗肿瘤活性的Tn特异性IgM单克隆抗体。我们理解 调节Ab对Tn和其它TACA应答的机制非常有限。同样，我们对 这些抗体有效杀死癌细胞的机制是不完整的。这些知识上的关键差距 为了利用TACA反应性B细胞及其产生的抗体的保护能力，必须填充。 这一提议的中心假设是，对TACA具有天然特异性的B细胞在以下方面起关键作用： 对癌症的有效抗肿瘤免疫反应。我们的主要目标是：1）确定机制 CD 4 + T细胞支持TACA特异性抗体应答的方式，以及PD-1抑制改变TACA特异性抗体应答的程度。 Tn特异性B细胞应答的多样性（目的1），2）确定Tn特异性IgM 促进肿瘤细胞杀伤和适应性抗肿瘤免疫应答（目的2），和3）检查 人Tn特异性B细胞库，并鉴定具有肿瘤杀伤作用的广泛反应性Tn特异性Ab 潜力（目标3）。这些研究的结果有望揭示以下新的机会：1） 利用对癌症表达的聚糖具有特异性的B细胞的抗肿瘤潜力，以及2）利用 广泛反应性TACA Ab，因为它们能够促进高度特异性适应性和动态免疫应答 靶向TACA相关肽。

SUMMARY Tumor associated carbohydrate antigens (TACAs) are aberrant glycosylation products that are expressed on cancer cells but absent on most normal cells. Their expression is typically associated with metastasis, poor prognosis, and reduced overall survival. Tn antigen (N-acetylgalactosamine O-linked to a serine or threonine) is a TACA often found on cancer mucins. We have investigated the regulation of B cell responses to Tn- and other TACA-bearing mucins using a mouse model. Our progress has shown that specificities for TACAs, including Tn, are highly enriched in the innate B (B1) cell population in mice. We have also found that B cell-intrinsic PD-1 expression potently suppresses tumor-protective TACA-specific antibody (Ab) responses and that CD4+ cells are required for the increased responses that are observed in the context of PD-1 inhibition. Finally, we identified a Tn-specific IgM monoclonal Ab that has significant and broad anti-tumor activity in vivo. Our understanding of the mechanisms regulating Ab responses to Tn and other TACAs is very limited. Similarly, our understanding of the mechanisms by which these Abs effectively kill cancer cells is incomplete. These critical gaps in knowledge must be filled in order to harness the protective capacity of TACA-reactive B cells and the Abs that they produce. The central hypothesis of this proposal is that B cells with natural specificities for TACAs play a critical role in the effective anti-tumor immune response to cancers. Our key objectives are to: 1) Determine the mechanisms by which CD4+ T cells support TACA-specific Ab responses and the extent to which PD-1 inhibition alters the diversity of the Tn-specific B cell response (Aim 1), 2) Identify the mechanisms by which Tn-specific IgM promotes both tumor cell killing and adaptive anti-tumor immune responses (Aim 2), and 3) Examine the repertoire of Tn-specific B cells in humans and identify broadly reactive Tn-specific Abs with tumor-killing potential (Aim 3). The findings emanating from these studies are expected to reveal novel opportunities to 1) harness the anti-tumor potential of B cells with specificities for cancer-expressed glycans and 2) leverage broadly-reactive TACA Abs for their ability to promote highly specific adaptive and dynamic immune responses targeting TACA-associated peptides.