Cyclophosphamide Enhances the Antitumor Efficacy of Adoptively Transferred Immune Cells through the Induction of Cytokine Expression, B-Cell and T-Cell Homeostatic Proliferation, and Specific Tumor Infiltration

Abstract

Purpose: Immunotherapy is a promising antitumor strategy, which can be successfully combined with current anticancer treatments, as suggested by recent studies showing the paradoxical chemotherapy-induced enhancement of the immune response. The purpose of the present work is to dissect the biological events induced by chemotherapy that cooperate with immunotherapy in the success of the combined treatment against cancer. In particular, we focused on the following: (a) cyclophosphamide-induced modulation of several cytokines, (b) homeostatic proliferation of adoptively transferred lymphocytes, and (c) homing of transferred lymphocytes to secondary lymphoid organs and tumor mass. Experimental Design: Here, we used the adoptive transfer of tumor-immune cells after cyclophosphamide treatment of tumor-bearing mice as a model to elucidate the mechanisms by which cyclophosphamide can render the immune lymphocytes competent to induce tumor rejection. Results: The transfer of antitumor immunity was found to be dependent on CD4 + Tcells and on the cooperation of adoptively transferred cells with the host immune system. Of note, tumorimmune lymphocytes migrated specifically to the tumor only in mice pretreated with cyclophosphamide. Cyclophosphamide treatment also promoted homeostatic proliferation/activation of transferred B and T lymphocytes. Optimal therapeutic responses to the transfer of immune cells were associated with the cyclophosphamide-mediated induction of a ''cytokine storm'' [including granulocyte macrophage colony-stimulating factor, interleukin (IL)-1h, IL-7, IL-15, IL-2, IL-21, and IFN-g], occurring during the ''rebound phase''after drug-induced lymphodepletion. Conclusions: The ensemble of these data provides a new rationale for combining immunotherapy and chemotherapy to induce an effective antitumor response in cancer patients.

Low-dose cyclophosphamide depletes circulating naïve and activated regulatory T cells in malignant pleural mesothelioma patients synergistically treated with dendritic cell-based immunotherapy

“…39 And lastly, a cytokine storm and thereafter homeostatic proliferation, could be caused by the lympho-depletion due to the mCTX treatment. 42 This would be in concordance with the increased proportion of proliferating naïve Tregs, CD4 T cells and CD8 T cells. No change was observed in the proportions of B cells, NK cells, γδ T cells and monocytes.…”

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

“…40 Subsequent studies showed that the lymphodepleting effects induced by CTX are transient and that, soon after drug discontinuation, a homeostatic rebound overshoot of the lymphocytic pool occurs. 41,42 This implies that after drug administration, a reduction of both humoral and cellular responses may occur, but with different timing and kinetics. It has been proposed that the homeostatic replenishment of B and T lymphocyte compartments is sustained by a drug-induced 'cytokine storm' during which several hematopoietic and homeostatic factors, danger signals, pattern recognition receptors, inflammatory mediators and growth factors are expressed, thus boosting peripheral expansion.…”

“…It has been proposed that the homeostatic replenishment of B and T lymphocyte compartments is sustained by a drug-induced 'cytokine storm' during which several hematopoietic and homeostatic factors, danger signals, pattern recognition receptors, inflammatory mediators and growth factors are expressed, thus boosting peripheral expansion. 41,43 One might speculate that these mediators cooperate in sensing and amplifying drug-induced myelo-and lymphotoxicity, thus stimulating a DNA damage response that, in turn, promotes immune activation. Interestingly, genotoxic stress activates the expression of IFN-a and IFN-l genes, leading to the ultimate stimulation of immune responses resembling those evoked during viral infections.…”

“…42,53,54 Several mechanisms have been proposed to explain this effect: (i) drug-induced bystander proliferation of memory CD4 and CD8 T-cells; 55 (ii) drug-induced stimulation of CD8 T-cells proliferation and IFN-g production; 41 (iii) differentiation of adoptively transferred antigen-specific CD4 T-cells into activated polyfunctional T helper cells with potent antitumor activity; 56 (iv) specific homing of transferred T-cells to the lymphoid organs and tumor mass soon after drug discontinuation. 41,57 Accordingly, the therapeutic efficacy of combined CTX and adoptive transfer of tumor-specific spleen cells was shown to critically require donor CD4 T-cells. 42 Combined treatment with anti-4-1BB and CTX produced synergistic CD8-mediated anticancer effects in the B16 melanoma mouse model.…”

“…As an example, paclitaxel augments Th1 cellular immunity in patients with advanced non-small cell lung cancer by increasing the levels of circulating IFN-g-secreting CD8 Off-target effects of chemotherapy L Bracci et al T-cells and IL-2-secreting CD4 T-cells. 61 Moreover, CTX induces Th1-polarizing cytokines (IL-2 and IFN-g) and decreases Th2 cytokines (IL-4 and IL-10) both in tumorbearing mice 41 and rats. 62 Notably, in tumor-bearing mice CTX increased the frequencies of splenic Th1 and Th17 cells, which displayed a faster recovery from drug-induced lymphodepletion, with respect to Treg cells.…”