Search

Background: The role of B cells and antibodies in anticancer immune responses may correlate with improved prognosis in several types of cancer. Indeed, tumor-reactive antibodies are detected in the blood of cancer patients, tumor-infiltrating B cells have been shown to produce tumor-reactive antibodies, and tumor-reactive antibodies can cause tumor regression in several mouse models. Taken together, these observations support further identification, isolation and characterization of antitumor antibodies from patients demonstrating effective anticancer responses and defining the cognate targets and mechanisms whereby they contribute to tumor control. Methods: We identified cohorts of patients with nonprogressing metastatic cancer who had received checkpoint immunotherapy and isolated their circulating plasmablasts. Antibody heavy and light chain paired sequences were obtained from individual cells using Atreca's Immune Repertoire Capture (IRCTM) technology. The expressed antibodies were then analyzed for their ability to bind to tumor cells as well as tumor tissue and their ability to mediate antitumor activity was explored in syngeneic mouse tumor models. Results: Elevated plasmablast levels were observed in individuals with nonprogressing metastatic cancer, and analysis of plasmablast antibody sequences revealed clonal families of B cells that persisted over time with hallmarks of affinity maturation and class switching. We also identified antibody sequences with features common to more than one patient, consistent with convergent antibody selection. In particular, one antibody (AB-213) isolated from a NSCLC patient was found to demonstrate binding to unrelated human tumors as well as the mouse EMT6 tumor. When AB-213 was expressed with a mouse IgG2a constant region the chimeric antibody showed efficacy in vivo by reducing tumor volume and increasing survival in Balb/c mice harboring the syngeneic EMT6 model. Antitumor activity of the chimeric antibody was observed to be dose-dependent when administered as monotherapy or in combination with checkpoint inhibitors. We feel, based on these data, AB-213 could become a very important clinical therapeutic. Citation Format: Gilson Baia, Amy Manning-Bog, Alexander Scholz, Jeff DeFalco, Michael Harbell, Danhui Zhang, Felix Chu, Beatriz Millare, May Sumi, Patricia Zuno, Judevin Lugar Sapugay, Dongkyoon Kim, Yvonne Leung, Shuwei Jiang, Xiaobin Tang, Kevin Williamson, Xiaomu Chen, Sean Carroll, Christine Dowd, Ish Dhawan, Jonathan Benjamin, Gregg Espiritu Santo, Nicole Haaser, Ngan Nguyen, Eldar Giladi, David Minor, Yann Chong Tan, Jeremy B. Sokolove, Lawrence Steinman, Tito Serafini, Guy Cavet, Norman M. Greenberg, Jacob Glanville, Wayne Volkmuth, Daniel E. Emerling, William H. Robinson. Mining the cancer immuno-responsome: The identification of functional antitumor antibodies from patients receiving checkpoint inhibitors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3966.

Patient immune response to tumor can drive profound and durable clinical benefit, but the contribution of antibodies to this benefit is poorly understood. To further our understanding of the role of the humoral response, we compared antibody sequence repertoires of durable responder and non-responder melanoma patients before and during checkpoint inhibitor treatment. We collected pre- and on-treatment peripheral blood from 26 melanoma patients treated with pembrolizumab (9), ipilimumab (8) or nivolumab+ipilimumab (9). Of the 26 patients, 14 were durable responders (RECIST stable disease, partial response, or complete response for at least 6 months) and 12 were non-responders. We generated natively paired heavy and light chain antibody sequences from individual IgG plasmablasts (CD19+CD20-CD38+CD3-CD14-IgA-IgM-IgD-). Sequences were obtained from a total of 26,725 plasmablasts. These sequences were used to reconstruct lineages (sets of plasmablasts likely derived from a common progenitor B cell) where each lineage shares heavy and light V genes, CDR3 length and 80% sequence similarity in CDR3s. Durable responders exhibited an increase in somatic hypermutation (SHM) after initiation of treatment. In contrast, no significant change in SHM was observed in non-responders. Higher SHM was also observed in on-treatment repertoires of responders compared with those of non-responders suggesting that T cell checkpoint inhibitors promote activation of humoral immunity in clinical responders. Furthermore, persistent antibody lineages (observed both before and during treatment) showed higher SHM than lineages observed at only a single time point. Comparison of lineages between patients identified antibodies with high sequence similarity suggesting these antibodies may have arisen from convergent selection, i.e., different patients raising antibodies against shared or similar epitopes. These putative convergent antibodies were enriched in IgG2. IgG2 usage was also higher overall in durable responders than non-responders, even in samples taken prior to treatment. The higher levels of IgG2 observed in responders and in the potentially convergent sets of antibodies suggest that IgG2 antibodies may play a role in effective anti-tumor responses. In conclusion, our analysis of plasmablast repertoires from melanoma patients suggests that treatment with checkpoint inhibitors promotes SHM in durable responders, and that responder plasmablasts are enriched in IgG2. Moreover, patients make potentially convergent antibodies that are also enriched for the IgG2 subclass. Our observations demonstrate that the humoral immune response is remodeled in patients with anti-tumor responses and support a role for the humoral arm of the immune response in driving clinical benefit in patients treated with checkpoint inhibitors. Citation Format: Ngan Nguyen, Alusha Mamchak, Mariano Severgnini, Kevin S. Williamson, Xinqi Wu, Elliott F. Drabek, Michael Manos, Xiaomu Chen, Xiaobin Tang, Zoe Amiri, Chantia Carroll, Yvonne Leung, Dongkyoon Kim, Wayne Volkmuth, Norman Greenberg, Daniel Emerling, William H. Robinson, Guy Cavet, F. Stephen Hodi. Increased somatic hypermutation in the immunoglobulin sequences of melanoma patients who have durable response to checkpoint inhibitor therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 615.

Molecular profiles of tumors and tumor-associated cells hold great promise as biomarkers of clinical outcomes. However, existing datasets are fragmented and difficult to analyze systematically. We present a pan-cancer resource and comprehensive meta-analysis of expression signatures from ~18,000 human tumors with overall survival outcomes across 39 malignancies. While a third of prognostic genes were cancer-specific, a FOXM1 regulatory network is a major predictor of adverse outcomes, while favorably prognostic genes largely reflect tumor-associated leukocytes. Using a novel computational approach, we enumerated leukocyte subsets in bulk tumor transcriptomes, revealing complex novel malignancy-specific associations between 22 distinct leukocytes and cancer survival. Tumor-associated neutrophil-like polymorphonuclear cell and plasmacytic cells emerged as significant but opposite predictors of survival for diverse solid tumors, including breast and lung adenocarcinomas. Our results introduce new analytical tools for delineating prognostic genes and leukocytes within and across cancers, and shed light on the impact of tumour heterogeneity on cancer outcomes, with applications for discovering novel biomarkers and therapeutic targets Citation Format: Andrew J. Gentles, Aaron M. Newman, Chih Long Liu, Scott V. Bratman, Weiguo Feng, Dongkyoon Kim, Viswam S. Nair, Xu Yue, Amanda Khuong, Chuong D. Hoang, Maximilian Diehn, Robert B. West, Sylvia K. Plevritis, Ash A. Alizadeh. The prognostic landscape of genes and infiltrating immune cells across human cancers. [abstract]. In: Proceedings of the AACR Special Conference on Translation of the Cancer Genome; Feb 7-9, 2015; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(22 Suppl 1):Abstract nr PR09.

Multiple myeloma is a plasma cell neoplasm characterized by frequent relapse following initial therapy, implying the presence of a therapy-resistant and tumor-initiating cell population. While tumor-initiating cells have been reported for human multiple myeloma, the data provide conflicting information regarding the surface immunophenotype of these cells. Here, we analyzed bone marrow myeloma and B-lineage cells of patients for fractionation, examined engraftment of myeloma cells in various mouse models, and finally investigated myeloma-initiating population by examining the repopulation of human myeloma cells in recipient mice. The clonality of repopulating cells was also determined by RT-PCR of immunoglobulin gene variable regions. First, the examination of immunophenotype of patients’ bone marrow cells allowed us to fractionate myeloma/plasma cell-enriching CD138+/CD38high plasmacytic cells and CD19+CD38low/− B lymphocytic cells in 82% (31/38) of human samples. Then, we transplanted patient bone marrow cells into RAG2−/−γc−/−, NOD/scid or NOD/scid/γc−/− mice with/without human fetal bone pieces and examined the engraftment of myeloma cells. While human bone-bearing mice engrafted myeloma/plasma cells of 10 out of 19 samples, none of 18 samples gave rise to the repopulation of clonal myeloma/plasma/B cells in human bone-free immunodeficient mice. Further analysis of fractionated cells demonstrated that CD38high/CD138+ cells led to production of clonal human antibodies (2/10 samples) and a repopulation of clonally-related CD19+CD38low or CD138+CD38+ B lineage cells (5/10 samples) in grafted human bone of recipient mice. However, CD19+CD38low/−CD138− cells did not engraft clonally-related cells in human bone-bearing mice (0/9 samples). The analysis of CD38high/CD138+ myeloma cells demonstrated that more than 70% of patients still have heterogeneous plasmacytic cells in the expressions of CD45, CD19 or CD27. Our results suggest that human bone marrow microenvironment may be required for the survival and the engraftment of primary myeloma cells into recipient mice and that CD38high/CD138+/− plasmacytic cells but not CD19+CD38low/− B cells enrich clonal myeloma cells engrafting into recipient mice which may be responsible for tumor-initiation of multiple myeloma. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4315.