The recent approval of a prostate cancer vaccine has renewed hope for anticancer immunotherapies. However, the immunosuppressive tumor microenvironment may limit the effectiveness of current immunotherapies. Antiangiogenic agents have the potential to modulate the tumor microenvironment and improve immunotherapy, but they often are used at high doses in the clinic to prune tumor vessels and paradoxically may compromise various therapies. Here, we demonstrate that targeting tumor vasculature with lower vascular-normalizing doses, but not high antivascular/antiangiogenic doses, of an anti-VEGF receptor 2 (VEGFR2) antibody results in a more homogeneous distribution of functional tumor vessels. Furthermore, lower doses are superior to the high doses in polarizing tumor-associated macrophages from an immune inhibitory M2-like phenotype toward an immune stimulatory M1-like phenotype and in facilitating CD4 ⁺ and CD8 ⁺ T-cell tumor infiltration. Based on this mechanism, scheduling lower-dose anti-VEGFR2 therapy with T-cell activation induced by a whole cancer cell vaccine therapy enhanced anticancer efficacy in a CD8 ⁺ T-cell–dependent manner in both immune-tolerant and immunogenic murine breast cancer models. These findings indicate that vascular-normalizing lower doses of anti-VEGFR2 antibody can reprogram the tumor microenvironment away from immunosuppression toward potentiation of cancer vaccine therapies. Given that the combinations of high doses of bevacizumab with chemotherapy have not improved overall survival of breast cancer patients, our study suggests a strategy to use antiangiogenic agents in breast cancer more effectively with active immunotherapy and potentially other anticancer therapies.

The chemokine CXCL12 and its receptor CXCR4 are expressed widely in human cancers, including ovarian cancer, in which they are associated with disease progression at the levels of tumor cell proliferation, invasion, and angiogenesis. Here, we used an immunocompetent mouse model of intraperitoneal papillary epithelial ovarian cancer to show that modulation of the CXCL12/CXCR4 axis in ovarian cancer has multimodal effects on tumor pathogenesis associated with induction of antitumor immunity. siRNA-mediated knockdown of CXCL12 in BR5-1 cells that constitutively express CXCL12 and CXCR4 reduced cell proliferation in vitro, and tumor growth in vivo. Similarly, treatment of BR5-1–derived tumors with AMD3100, a selective CXCR4 antagonist, resulted in increased tumor apoptosis and necrosis, reduction in intraperitoneal dissemination, and selective reduction of intratumoral FoxP3⁺ regulatory T cells (Treg). Compared with controls, CXCR4 blockade greatly increased T-cell–mediated antitumor immune responses, conferring a significant survival advantage to AMD3100-treated mice. In addition, the selective effect of CXCR4 antagonism on intratumoral Tregs was associated with both higher CXCR4 expression and increased chemotactic responses to CXCL12, a finding that was also confirmed in a melanoma model. Together, our findings reinforce the concept of a critical role for the CXCL12/CXCR4 axis in ovarian cancer pathogenesis, and they offer a definitive preclinical validation of CXCR4 as a therapeutic target in this disease. Cancer Res; 71(16); 5522–34. ©2011 AACR.

Blockade of immune‐checkpoint programmed cell death protein 1 (PD‐1) or programmed cell death ligand 1 can enhance effector T‐cell responses. However, the lack of response in many patients to checkpoint‐inhibitor therapies emphasizes the need for combination immunotherapies to pursue maximal antitumor efficacy. We have previously demonstrated that antagonism of C‐X‐C chemokine receptor type 4 (CXCR4) by plerixafor (AMD3100) can decrease regulatory T (T _reg )‐cell intratumoral infiltration. Therefore, a combination of these 2 therapies might increase antitumor effects. Here, we evaluated the antitumor efficacy of AMD3100 and anti‐PD‐1 (αPD‐1) antibody alone or in combination in an immunocompetent syngeneic mouse model of ovarian cancer. We found that AMD3100, a highly specific CXCR4 antagonist, directly down‐regulated the expression of both C‐X‐C motif chemokine 12 (CXCL12) and CXCR4 in vitro and in vivo in tumor cells. AMD3100 and αPD‐1 significantly inhibited tumor growth and prolonged the survival of tumor‐bearing mice when given as monotherapy. Combination of these 2 agents significantly enhanced antitumor effects compared with single‐agent administration. Benefits of tumor control and animal survival were associated with immunomodulation mediated by these 2 agents, which were characterized by increased effector T‐cell infiltration, increased effector T‐cell function, and increased memory T cells in tumor microenvironment. Intratumoral T _reg cells were decreased, and conversion of T _reg cells into T helper cells was increased by AMD3100 treatment. Intratumoral myeloid‐derived suppressor cells were decreased by the combined treatment, which was associated with decreased IL‐10 and IL‐6 in the ascites. Also, the combination therapy decreased suppressive leukocytes and facilitated M2‐to‐M1 macrophage polarization in the tumor. These results suggest that AMD3100 could be used to target the CXCR4‐CXCL12 axis to inhibit tumor growth and prevent multifaceted immunosuppression alone or in combination with αPD‐1 in ovarian cancer, which could be clinically relevant to patients with this disease.—Zeng, Y., Li, B., Liang, Y., Reeves, P. M., Qu, X., Ran, C., Liu, Q., Callahan, M. V., Sluder, A. E., Gelfand, J. A., Chen, H., Poznansky, M. C. Dual blockade of CXCL12‐CXCR4 and PD‐1‐PD‐L1 pathways prolongs survival of ovarian tumor‐bearing mice by prevention of immunosuppression in the tumor microenvironment. FASEB J. 33, 6596–6608 (2019). www.fasebj.org

Pancreatic β‐cell replacement by islet transplantation for the treatment of Type 1 Diabetes (T1D) is currently limited by donor tissue scarcity and the requirement for lifelong immunosuppression. The advent of in vitro differentiation protocols for generating functional β‐like cells from human pluripotent stem cells, so‐called SC‐β cells, could eliminate these obstacles. To avoid the need for immunosuppression, alginate‐microencapsulation is widely investigated as a safe path to β‐cell replacement. Nonetheless, inflammatory foreign body responses leading to pericapsular fibrotic overgrowth often causes microencapsulated islet‐cell death and graft failure. Here, we used a novel approach to evade the pericapsular fibrotic response to alginate‐microencapsulated SC‐β cells; an immunomodulatory chemokine, CXCL12, was incorporated into clinical grade sodium alginate to microencapsulate SC‐β cells. CXCL12 enhanced glucose‐stimulated insulin secretion of SC‐β cells and induced expression of genes associated with β‐cell function in vitro. SC‐β cells co‐encapsulated with CXCL12 showed enhanced insulin secretion in diabetic mice and accelerated the normalization of hyperglycemia. SC‐β cells co‐encapsulated with CXCL12 evaded the pericapsular fibrotic response, resulting in long‐term functional competence and glycemic correction (>150 days) without systemic immunosuppression in immunocompetent C57BL/6 mice. These findings lay the groundwork for further preclinical translation of this approach into large animal models of T1D.

There are currently no proven or approved treatments for coronavirus disease 2019 (COVID‐19). Early anecdotal reports and limited in vitro data led to the significant uptake of hydroxychloroquine (HCQ), and to lesser extent chloroquine (CQ), for many patients with this disease. As an increasing number of patients with COVID‐19 are treated with these agents and more evidence accumulates, there continues to be no high‐quality clinical data showing a clear benefit of these agents for this disease. Moreover, these agents have the potential to cause harm, including a broad range of adverse events including serious cardiac side effects when combined with other agents. In addition, the known and potent immunomodulatory effects of these agents which support their use in the treatment of auto‐immune conditions, and provided a component in the original rationale for their use in patients with COVID‐19, may, in fact, undermine their utility in the context of the treatment of this respiratory viral infection. Specifically, the impact of HCQ on cytokine production and suppression of antigen presentation may have immunologic consequences that hamper innate and adaptive antiviral immune responses for patients with COVID‐19. Similarly, the reported in vitro inhibition of viral proliferation is largely derived from the blockade of viral fusion that initiates infection rather than the direct inhibition of viral replication as seen with nucleoside/tide analogs in other viral infections. Given these facts and the growing uncertainty about these agents for the treatment of COVID‐19, it is clear that at the very least thoughtful planning and data collection from randomized clinical trials are needed to understand what if any role these agents may have in this disease. In this article, we review the datasets that support or detract from the use of these agents for the treatment of COVID‐19 and render a data informed opinion that they should only be used with caution and in the context of carefully thought out clinical trials, or on a case‐by‐case basis after rigorous consideration of the risks and benefits of this therapeutic approach.