Elsevier

Clinical Immunology

Volume 129, Issue 2, November 2008, Pages 219-229
Clinical Immunology

Differential impairment of regulatory T cells rather than effector T cells by paclitaxel-based chemotherapy

https://doi.org/10.1016/j.clim.2008.07.013Get rights and content

Abstract

Characterized as a mitotic inhibitor, paclitaxel has gained importance as a promising agent for the treatment of advanced non-small cell lung cancer (NSCLC). However, whether paclitaxel has immune modulatory effects remains unclear. In this study, we analyzed 55 peripheral blood samples from NSCLC patients who underwent paclitaxel-based chemotherapy. We found that among the lymphocyte subsets, paclitaxel selectively decreased the size of the regulatory T cell (Treg) population rather than other subsets including effector T cells (Teff). Apoptosis by upregulating the expression of the cell death receptor Fas (CD95) contributed to the reduced cell number of Treg. Importantly, the inhibitory function of Treg was significantly impaired, while the production of Th1 cytokines IFN-γ and IL-2 and the expression of the activation marker CD44 among CD4+ and CD8+ T cells were augmented after paclitaxel treatment. These results strongly demonstrated that paclitaxel-based chemotherapy played important roles in modulating immune responses.

Introduction

The antineoplastic agent paclitaxel (Taxol) belongs to the family of taxanes [1], and is effective and widely used against a broad range of cancers [2]. Paclitaxel exhibits its tumoricidal activity chiefly by disturbing microtubule dynamics and inducing apoptosis in a Fas/Fas ligand-dependent manner [3], [4]. In several murine models, administrated alone or in combination with doxorubicin and/or cyclophosphamide, paclitaxel could enhance the antitumor response of cancer vaccines or other tumor immunotherapies [5], [6], [7].

Regulatory T cells (Treg), a subpopulation comprising 3%–5% of CD4+ T cells has been identified both in murine models [8], [9] and in humans [10], [11], [12]. The nuclear transcription factor fork-head box P3 (Foxp3), which is crucial to the development and regulatory functions of Treg [13], serves as its unique marker. Treg is capable of mediating peripheral tolerance to self-antigens [14], which is a pivotal mechanism of defense against autoimmunity [9], [15]. Since tumors are of intrinsic (self) origin, Treg also inhibits antitumor immunity by suppressing tumor-specific effector T cell, and functions through cell–cell contact [12] and/or production of cytokines such as IL-10 or TGF-β [16], [17]. Thus, the presence of Treg could inhibit effective tumor eradication by the immune system. In a number of human malignancies, circulating and tumor-infiltrating Treg had been shown to be elevated [18], [19], [20], [21], [22], [23], [24].

For these reasons, the depletion or suppression of Treg could augment tumor antigen-specific immunity [25], [26], [27] or even lead to tumor regression [28], [29]. Recently, the use of denileukin diftitox, a humanized monoclonal anti-CD25 antibody, to deplete Treg has been reported in clinical trials [30], [31]. Such strategies, however, carry the limitation of losing activated CD25-expressing effector T cells. On the other hand, some reports have shown that the chemotherapeutic agents cyclophosphamide and fludarabine could down-regulate the number and functions of Treg in several animal models [32], [33], [34], [35] and cancer patients [36], [37]. And the use of cyclophosphamide, has been shown to synergize with cancer immunotherapy including cancer vaccines [6], [38], [39], [40] and adoptive cell transfer therapy [41], [42], contrary to conventional belief that chemotherapy is primarily immunosuppressive and goes against active immunity induction. Since paclitaxel-based chemotherapy is also a first-line treatment in numerous cancer types, knowledge of whether it brings about similar immunomodulatory effects carries significant therapeutic implications. However, reports on how paclitaxel affects the immune system remain scarce, and its effect on Treg has not yet been investigated.

Therefore, in the present study, we aim to investigate the immunoregulatory effect of paclitaxel. We analyzed 55 peripheral blood samples of NSCLC patients undergoing paclitaxel-based chemotherapy. Through stepwise analysis of alterations in lymphocyte profiles, we observed, for the first time, a selective reduction of Treg by paclitaxel-based chemotherapy. To account for such preferential reduction, we compared apoptotic change of Treg with Teff after paclitaxel-based chemotherapy, and the possible pathway behind apoptosis induction. On further analysis, we discovered that the suppressive function of Treg was also impaired by paclitaxel, which may be associated with reduced Foxp3 expression. This may offer explanations for our observed enhancement in Th1 cytokine production and CD44 expression of Teff following paclitaxel-based chemotherapy. This report presents immunomodulatory mechanisms by which paclitaxel suppresses cancer, in addition to its direct inhibition of tumor cell division, and the potential benefits of combining paclitaxel with immunotherapies in the treatment of cancer.

Section snippets

Patients and normal donors

Between January 2006 and May 2007, having obtained informed consent from each individual, 5 ml heparinized peripheral blood samples were collected from 51 NSCLC patients (Table 1). The advanced stage patients were receiving paclitaxel-based chemotherapeutic regimen without adjuvant therapy at the time of the study. Peripheral blood mononuclear cells (PBMC) were obtained by the centrifugation of whole blood on a Ficoll/Hypaque gradient (Sinopharm Chemical Reagent, Shanghai, China) for 30 min at

CD4+CD25+Foxp3+ Treg was increased in NSCLC patients and positively correlated with advanced stage

It has been reported that CD4+CD25+Foxp3+ regulatory T cells were increased in tumor patients [18], [19], [20], [21], [22], [23], [24]. To investigate whether the size of the Treg population was altered in the circulation of the subjects in our study, PBMCs from 51 NSCLC patients with various tumor stages (Table 1) were isolated and CD4+CD25+Foxp3+ T cells were counted by flow cytometry via intracellular staining with Foxp3. Control was from 20 healthy adults. Result showed a significant

Discussion

In our analysis of 51 patients with NSCLC and 20 healthy controls, we observed a significantly increased percentage and number of Treg, which clearly correlated with advanced tumor stage, consistent with similar findings from other cancer types [19], [23], [24], [45], [46], [47]. Importantly, by determining changes in lymphocyte subset distribution, we have demonstrated, for the first time, paclitaxel-based chemotherapy induced a selective reduction in the size of the circulating Treg

Acknowledgments

This work was supported by grants from the National Natural Science Foundation of China (Grant Nos. 30571713 and 60537030); Chun-Tsung Scholar Program of Fudan University; and the Basic and Clinical Medicine Cross-Disciplinary Research Foundation of Shanghai Medical College of Fudan University (Grant Nos. 2005JL19 and 2007JL01).

We thank Xiujuan Zheng and Yi Lin at the Department of Immunology for excellent technical assistance, and Dr. Chong-xian Pan (Department of Hematology/Oncology, UC Davis

References (49)

  • R.K. Srivastava et al.

    Bcl-2 mediated drug resistance: inhibition of apoptosis by blocking nuclear factor of activated T lymphocytes (NFAT)-induced Fas ligand transcription

    J. Exp. Med.

    (1999)
  • B. Yu et al.

    Effective combination of chemotherapy and dendritic cell administration for the treatment of advanced-stage experimental breast cancer

    Clin. Cancer Res.

    (2003)
  • J.-P. Machiels et al.

    Cyclophosphamide, doxorubicin, and paclitaxel enhance the antitumor immune response of granulocyte/macrophage-colony stimulating factor-secreting whole-cell vaccines in HER-2/neu tolerized Mice

    Cancer Res.

    (2001)
  • Y. Eralp et al.

    Doxorubicin and paclitaxel enhance the antitumor efficacy of vaccines directed against HER 2/neu in a murine mammary carcinoma model

    Breast Cancer Res.

    (2004)
  • A.M. Thornton et al.

    CD4+CD25+ immunoregulatory T cells suppress polyclonal T cell activation in vitro by inhibiting interleukin 2 production

    J. Exp. Med.

    (1998)
  • T. Takahashi et al.

    Immunologic self-tolerance maintained by CD25+CD4+ regulatory T cells constitutively expressing cytotoxic T lymphocyte-associated antigen 4

    J. Exp. Med.

    (2000)
  • C. Baecher-Allan et al.

    CD4+CD25 high regulatory cells in human peripheral blood

    J. Immunol.

    (2001)
  • H. Jonuleit et al.

    Identification and functional characterization of human CD4+CD25+ T cells with regulatory properties isolated from peripheral blood

    J. Exp. Med.

    (2001)
  • J.D. Fontenot et al.

    Foxp3 programs the development and function of CD4+CD25+ regulatory T cells

    Nat. Immunol.

    (2003)
  • R.H. Schwartz

    Natural regulatory T cells and self-tolerance

    Nat. Immunol.

    (2005)
  • M.-L. Chen et al.

    Regulatory T cells suppress tumor-specific CD8 T cell cytotoxicity through TGF-β signals in vivo

    Proc. Natl. Acad. Sci. U. S. A.

    (2004)
  • T.J. Curiel

    Tregs and rethinking cancer immunotherapy

    J. Clin. Invest.

    (2007)
  • E.Y. Woo et al.

    Regulatory CD4+CD25+ T cells in tumors from patients with early-stage non-small cell lung cancer and late-stage ovarian cancer

    Cancer Res.

    (2001)
  • M.K.Y.Y.M.K.A.T. Tetsuro Sasada

    CD4+CD25+ regulatory T cells in patients with gastrointestinal malignancies

    Cancer

    (2003)
  • Cited by (182)

    • Targeting chromosomal instability and aneuploidy in cancer

      2024, Trends in Pharmacological Sciences
    View all citing articles on Scopus
    1

    These authors contributed equally to this manuscript and should be considered as co-first authors.

    2

    These authors are considered co-senior authors.

    View full text