Cyclophosphamide Induces Dynamic Alterations in the Host Microenvironments Resulting in a Flt3 Ligand-Dependent Expansion of Dendritic Cells

Abstract

Preconditioning a recipient host with lymphodepletion can markedly augment adoptive T cell therapy. However, the precise mechanisms involved are poorly understood. In a recent study, we observed a significant increase in the circulating levels of dendritic cells (DCs; CD11c+CD11b+) during the recovery from cyclophosphamide (CTX)-induced lymphodepletion. Herein, we demonstrate that the CTX-induced DC expansion was not altered by adjuvant chemotherapy or tumor burden but was augmented by coadministration of granulocyte-colony stimulating factor. Although the increase in the number of DCs was preceded by a systemic expansion of a population expressing the phenotype of myeloid-derived suppressor cells (Gr-1+CD11b+), depletion of these Gr-1+ cells had no effect on the noted expansion. Moreover, when Gr-1highCD11bhigh cells were sorted from CTX-treated mice and adoptively transferred into control or CTX-treated recipients, they did not differentiate into DCs. Post-CTX expansion of DCs was associated with proliferation of DCs in bone marrow (BM) during the lymphopenic phase and in the blood and spleen during the recovery phase. Furthermore, adoptive transfer of BM cells from CTX-treated mice produced equal numbers of DCs in the blood of either CTX-treated or untreated recipients. CTX induced a dynamic surge in the expression of growth factors and chemokines in BM, where CCR2 and Flt3 signaling pathways were critical for DC expansion. In sum, our data suggest that CTX induces proliferation of DCs in BM prior to their expansion in the periphery. Targeting DCs at these phases would significantly improve their contribution to the clinical application of lymphodepletion to adoptive immunotherapy

Immune-based mechanisms of cytotoxic chemotherapy: implications for the design of novel and rationale-based combined treatments against cancer

“…[80][81][82] Increased circulating MDSC frequencies were observed in breast cancer patients and in B16 melanoma-bearing mice injected with CTX plus doxorubicin. 83,84 Recently, low-dose CTX treatment of mice spontaneously developing melanomas led to an accumulation of inflammatory mediators, such as GM-CSF, IL-1b, IL-5, IL-10, IFN-g and TNF-a, in skin tumors and metastatic LNs, inducing accumulation and activation of MDSCs that abrogated CTX antitumor effects. 85 Other reports, however, show that CTX induces early myeloid effector cells that may inhibit tumor cell growth through nitric oxide (NO) release, 86 and that metronomic CTX plus gemcitabine mitigates Treg-and MDSC-mediated immunosuppression and elicits antitumor immunity in vivo.…”

Adoptive Transfer of Cytotoxic T Lymphocytes Targeting Two Different Antigens Limits Antigen Loss and Tumor Escape

“…In this respect, it has been shown that the in vivo activity of Pmel T cells can be boosted very effectively, beyond the effects of irradiation alone, by a combination of vaccination and IL-2 Wang et al, 2005). In addition, CPA has often been used as an adjunct to adoptive T-cell transfer due to its multiple, pleiotropic effects (Bracci et al, 2007;Salem et al, 2010;Zhao et al, 2010;Schiavoni et al, 2011), and we have previously reported that low-dose CPA leads to activation of antitumor lymphocytes in vivo (Kottke et al, 2009). Therefore, we investigated whether low-dose CPA could be used as a rescue strategy at the point of detectable tumor escape from combination T-cell therapy.…”

“…Once such populations have been established in vivo, it should be possible to derive further benefit from the cells even after recurrent tumors are detected. In this respect, cyclophosphamide (CPA) is often used as an adjunct to adoptive T-cell transfer because of its multiple, pleiotropic effects, including activation of endogenous antigen-presenting cells (Salem et al, 2010), depletion of regulatory T cells (Zhao et al, 2010), and induction of immunogenic tumor cell death (Schiavoni et al, 2011)-all of which can enhance the function of the adoptively transferred cells (Bracci et al, 2007). Therefore, we tested whether CPA could rescue therapy following tumor escape in situations where both populations of adoptively transferred T cells persisted in vivo and in which the combination T-cell therapy had preserved antigen expression in the escape tumors.…”

CX3CR1 reduces Ly6Chigh-monocyte motility within and release from the bone marrow after chemotherapy in mice

“…[3][4][5] The alkylating agent cyclophosphamide (CP) is a common chemotherapeutic drug known to adversely cause transient ablation of mature myeloid cell populations. [6][7][8] The recovery phase following CP treatment provides a model of clinical relevance in which to study the processes that control monocyte trafficking.…”