PMCCPMCCPMCC

Search tips
Search criteria 

Advanced

 
Logo of onclettLink to Publisher's site
 
Oncol Lett. 2017 April; 13(4): 2323–2329.
Published online 2017 February 13. doi:  10.3892/ol.2017.5731
PMCID: PMC5403228

Immunological effects of vaccines combined with granulocyte colony-stimulating factor on a murine WEHI-3 leukemia model

Abstract

Granulocyte colony-stimulating factor (G-CSF) mobilizes regulatory T cells (Tregs) from bone marrow into the peripheral blood, by reducing the expression of stromal cell-derived factor-1α (SDF-1α). However, G-CSF has rarely been studied in acute myeloid leukemia (AML) immunotherapy. The present study performed a Transwell migration assay in vitro to determine the contribution of SDF-1α to the migration of leukemia cells, and the effects of G-CSF were evaluated. The effects of G-CSF on SDF-1α and Tregs in the AML microenvironment were examined, by employing a WEHI-3-grafted BALB/c mouse AML model (AML-M4). It is evident that G-CSF reversed immunosuppression of the AML microenvironment by reducing SDF-1α in bone marrow and elevating Tregs in the peripheral blood in in vivo studies. Furthermore, AML mice treated with vaccines combined with G-CSF achieved a longer survival time than those treated with vaccines without G-CSF, showing the efficiency of the regimen. The present study demonstrates the effects of G-CSF on the mobilization of leukemia cells and Tregs into the peripheral blood. In addition, immunotherapy with G-CSF priming represents a promising therapeutic strategy of targeting the immunosuppression.

Keywords: vaccines, granulocyte colony-stimulating factor, acute myeloid leukemia, regulatory T cells, stromal cell-derived factor-1α

Introduction

Acute myeloid leukemia (AML) is the predominant type of acute leukemia in adults (1). In AML patients who achieve complete remission following induction chemotherapy, a significant percentage of patients relapse within the first three years (2). Granulocyte colony-stimulating factor (G-SCF) priming, combined with chemotherapy, has been reported to be an effective and well-tolerated regimen in refractory or relapsed AML patients who are not eligible for intensive chemotherapy (36). In addition, immunotherapy is an active modality (7) and has had various levels of successes (8). However, there are few detailed studies about whether G-CSF makes a difference on immunotherapy in AML.

Cluster of differentiation (CD)4+/CD25+/forkhead box protein P3 (Foxp3+) regulatory T cells (Tregs) are a subpopulation of T cells with a suppressive activity on immune responses (9). Tregs that exist in the AML microenvironment (10), and other cancer bearing individuals, (1114) are mediators of immune suppression. It is known that inhibiting Treg function in cancer patients is an essential procedure to achieve successful immunotherapy in clinical practice (15,16). As previously reported, chemokine stromal cell-derived factor-1α (SDF-1α), also termed chemokine CXC motif ligand 12, which is expressed in bone marrow, is involved in inducing Treg chemotaxis and adhesion, as well as inducing hematopoietic stem cells (HSCs) (17,18). Activation of SDF-1α signals increases recruitment of Tregs to the tumor microenvironment (17,19), and it is a potential mechanism of tumor resistance to chemotherapy and immunotherapy (20). G-CSF, which was initially used to increase the production of neutrophils in patients with chemotherapy-induced neutropenia and transit HSCs from bone marrow to the peripheral blood for transplantation (21), mobilizes Tregs from bone marrow into the peripheral blood through reducing marrow-derived SDF-1α expression (17).

Based on these studies, the present study examined the immunological effect of G-CSF on the tumor vaccines. An established syngeneic leukemia mouse model using the murine AML WEHI-3 cell line (22,23) was used to determine whether the function of the vaccine was improved in vivo following administration of G-CSF.

Materials and methods

Cells and reagents

The human monocytic leukemia U937 cell line and murine AML WEHI-3 cell line were maintained in the laboratory of the Department of Clinical Hematology, Second Affiliated Hospital, Medical School of Xi'an Jiatong University (Xi'an, China) and were grown in RPMI-1640 medium supplemented with 10% fetal bovine serum (HyClone; GE Healthcare Life Sciences, Logan, UT, USA) and 1% penicillin-streptomycin (100 U/ml penicillin and 100 mg/ml streptomycin). Antibodies for flow cytometry (FCM; fluorescein isothiocyanate (FITC) anti-mouse CD4 [dilution, 1:100; cat. no. 11-0042], allophycocyanin (APC) anti-mouse CD25 [dilution, 1:100; cat. no. 17-0251], phycoerythrin (PE) anti-mouse/rat Foxp3 [dilution, 1:40; cat. no. 12-5773]) were purchased from eBioscience, Inc. (cat. co. 88-8111; San Diego, CA, USA). The mouse SDF-1α ELISA kits were bought from R&D Systems, Inc. (cat. no. MCX120; Minneapolis, MN, USA). The recombinant human granulocyte colony-stimulating factor (rhG-CSF) was provided by GeneScience Pharmaceuticals Co., Ltd. (Changchun, China).

Transwell migration assay

For migration studies, U937 and WEHI-3 cells (5×106 cells/ml) suspended in RPMI-1640 medium were placed in the upper chambers of Transwell plates (pore size, 5 µm; Costar; Corning Incorporated, Corning, NY, USA) with 100 ng/ml SDF-1α added to 600 µl RPMI-1640 in the lower chambers. Following incubation for 4 h at 37°C in a humidified CO2 incubator, non-migrated U937 cells that remained on the upper chamber of the insert were removed by placing the insert into a sterile 24-well plate, and cells migrating across the membrane were photographed with a digital camera (x100 magnification; Olympus Corporation, Tokyo, Japan). U937 cells that migrated to the lower chambers were collected in a 1.5 ml centrifuge tube, centrifuged at 100 × g for 5 min at room temperature, re-suspended in 100 µl PBS and counted on a hemocytometer in an inverted microscope (x100 magnification; Nikon Corporation, Tokyo, Japan). The migrated U937 cells were spread on polylysine-coated slides (Wuhan Boster Biological Technology, Ltd., Wuhan, China), fixed in methyl alcohol for 5 min and stained with 4′,6-diamidino-2-phenylindole. Stained cells were visualized in five randomly selected microscopic fields (x100 magnification) and photographed with a mercury fluorescence lamp (Nikon Corporation). WEHI-3 cells that had not migrated and remained in the upper chamber were removed by wiping with a cotton swab, and the cells that had migrated were fixed in methyl alcohol for 30 min and stained with 0.1% crystal violet. The number of WEHI-3 cells on the lower surface of the filter membrane was determined using a light microscope (x100 magnification; Olympus Corporation) and ImageJ software (version 1.47; National Institutes of Health, Bethesda, MD, USA). All experiments were conducted in triplicate.

Leukemia mouse model

All animal experiments were reviewed and approved by the Ethics Committee of the Medical College, Xi'an Jiaotong University (Xi'an, China). Male BALB/c wild-type mice (6 to 8 weeks old) were purchased from the Laboratory Animal Center, Medical College of Xi'an Jiaotong University and maintained under specific pathogen-free conditions, with a 12/12 h light/dark cycle at 21±2°C and ad libitum access to food and water, and were handled according to standard protocols for the use of laboratory animals under specific pathogen-free conditions. In total, 40 mice were randomly divided into four groups (n = 10 per group). For the syngeneic leukemia-implanted mouse acute myelomonocytic leukemia model (AML-M4), BALB/c mice were injected intravenously through their tail vein with WEHI-3 cells (1×106 cells/animal) in 500 µl of PBS (22,23).

Tumor vaccines

WEHI-3 cells (1×106 cells/ml) were inactivated in mitomycin-C and mixed with recombinant mouse interleukin-2 (rmIL-2) (400 U/ml), recombinant mouse granulocyte-macrophage colony-stimulating factor (rmGM-CSF) (1 µg/ml) and incomplete Freund's adjuvant (24). The vaccines were administered on days 15, 18, 22 and 25 following injection with WEHI-3 cells.

Mobilization of mice

G-CSF (1 µg/10 g weight) was administered to two groups of mice subcutaneously from day 26–30, following injection of WEHI-3 cells. At 6 h after the last injection, five mice in each group were randomly sacrificed by cervical dislocation, and peripheral blood, spleens, and femurs were collected as described in a previous study (25). The remaining five mice in each group were raised for observation of survival time until day 50.

ELISA

SDF-1α levels in the bone marrow supernatant were determined by using commercially available mouse CXCL12/SDF-1 alpha ELISA kits (cat. no. MCX120 R&D Systems, Inc.) following the manufacturer's protocol. The bone marrow supernatant and peripheral serum samples were added to the anti-SDF-1α pre-coated wells (with the exception of the control samples), followed by the addition of horseradish peroxidase-labeled detection antibody (cat. no. 892403; R&D Systems, Inc.). The plates were incubated for 1 h at room temperature and subsequently washed five times with the wash buffer, then detected with 50 µl substrates A and B. Reactions were stopped with stop solution, and absorbance at 450 nm was measured on a microplate reader (BioTek Instruments, Inc., Winooski, VA, USA).

FCM

Single cell suspensions of spleen cells and leukocytes in the peripheral blood were directly stained with FITC-conjugated anti-mouse CD4 (dilution, 1:100) and APC-conjugated anti-mouse CD25 (dilution, 1:100) for 30 min on ice. The cells were washed with cold flow cytometry staining buffer (eBioscience, Inc.) and then resuspended in 1 ml of fixation/permeabilization working solution (eBioscience, Inc.) at 4°C in the dark overnight. The cells were washed twice with 1X permeabilization buffer (eBioscience, Inc.) and incubated for 30 min in 1X permeabilization buffer containing PE-conjugated anti-mouse Foxp3 (dilution, 1:40) antibody. Lymphocytes were gated by plotting forward vs. side scatter, followed by gating on CD4+ T cells, and these cells were then analyzed for the expression of CD25 and FoxP3.

Results

G-CSF decreases U937 and WEHI-3 cell migration induced by the SDF-1α chemokine in vitro

As demonstrated in the Transwell migration assay, SDF-1α increased migration of U937 and WEHI-3 cells to the lower chambers over 4 h culture (Figs. 1A and B; 2Ab and Bb), consistent with previous studies (26). U937 and WEHI-3 cells were cultured with G-CSF for 18 h and SDF-1α was added to the lower chambers. It is evident that the migration was significantly decreased (P<0.05) in the two cells following treatment with G-CSF, compared with the control group (Figs. 1A and B; 2Ac and Bc).

Figure 1.
The effect of SDF-1α on (A) U937 and (B) WEHI-3 cell migration with or without G-CSF. G-CSF decreases U937 and WEHI-3 cell migration in response to the SDF-1α chemokine. *P<0.05 vs. blank group; #P<0.05 vs. control group. ...
Figure 2.
G-CSF inhibits cell migration with SDF-1α exposure in U937 and WEHI-3 cells. Representative panels show migrated (A) U937 and (B) WEHI-3 cells in the lower chambers. The images in (A) were obtained by photographing the migrated U937 cells, which ...

G-CSF leads to in vivo reduction of SDF-1α in bone marrow in AML and vaccination groups

A schematic diagram of the in vivo study was exhibited in Fig. 3. ELISA results demonstrated that the concentrations of SDF-1α in the bone marrow supernatant had significantly decreased (P<0.05) following the administration of G-SCF in AML mice and vaccination groups (Fig. 4).

Figure 3.
Schematic diagram of the in vivo study. Mice in groups 1, 2, 3 and 4 were all injected with WEHI-3 cells on day 0. Groups 3 and 4 were then treated with vaccines. Groups 2 and 4 were primed with G-CSF. G-CSF, granulocyte colony-stimulating factor; FCM, ...
Figure 4.
Effect of G-CSF on the concentration of SDF-1α in mouse bone marrow. G-CSF reduced SDF-1α in the bone marrow in acute myeloid leukemia and vaccination groups. *P<0.05, #P<0.05. W, WEHI-3; W+G, WEHI-3 + G-CSF; W + V, WEHI-3 ...

G-CSF increases Tregs in the peripheral blood and spleen of AML and vaccination groups

FCM was performed to investigate the percentage of CD4+/CD25+/FoxP3+ Tregs. Results revealed that the level of Tregs was elevated in the peripheral blood (Fig. 5) and spleen (Fig. 6), following administration of G-CSF in AML mice. In addition, the same phenomenon was observed in the vaccination combined with G-CSF group (Figs. 5 and and66).

Figure 5.
G-CSF increases the frequency of regulatory T cells in the peripheral blood of acute myeloid leukemia and vaccination groups. (A) The ratio of CD4+CD25+ cells to CD4+ T cells in each group analyzed by FCM. *P<0.05, #P<0.05. (B) The ratio ...
Figure 6.
G-CSF increases the frequency of regulatory T cells in the spleen of acute myeloid leukemia and vaccination groups. (A) The ratio of CD4+CD25+ cells to CD4+ T cells in each group analyzed by FCM. *P<0.05, #P<0.05. (B) The ratio of CD25 ...

Vaccination induces Treg reduction in the peripheral blood and spleen of AML mice

To determine whether the leukemia vaccines can affect the percentage of Tregs in vivo, one group of AML mice were injected with the vaccines subcutaneously for two weeks. Data revealed that the level of Tregs in the peripheral blood and spleen of the vaccination group was significantly lower (P<0.05) than the AML group without vaccination (Table I).

Table I.
Comparison of the level of regulatory T cells in the peripheral blood between acute myeloid leukemia mice and vaccinated mice.

Administration of G-CSF prolongs the survival time of vaccinated mice

To analyze the protective efficacy of G-CSF, the survival time of vaccinated mice with or without administration of G-CSF was assessed (Fig. 7). The vaccine-treated mice mobilized with G-CSF had a significantly (P<0.01) prolonged survival time (42 days) compared with the control mice that received vaccines without G-CSF (38 days) and AML mice (33 days).

Figure 7.
Kaplan-Meier curve representing the survival time of mice in different groups. Log-rank test showed a significant difference in the overall survival among the groups (P<0.001; n=5 for each group). The vaccine-treated mice mobilized with G-CSF ...

Discussion

Cancer cell-based vaccines combined with adjuvants are generally designed to induce an antigen to activate dendritic cells (DCs) (2730). DC-based immunotherapies utilize monocyte-derived conventional DCs to prime cytotoxic T lymphocyte (CTL)-mediated immune responses (2729,31). The administration of therapeutic vaccines can stimulate the host's own immune system to attack cancer cells (32,33). Leukemia immunotherapy has been studied for a number of years (24) and the present study demonstrates that the aforementioned vaccines can also promote cellular immunity and enhance the cytotoxicity of CTL. G-CSF is a strong mobilizing factor for mononuclear cells and DCs (34), and it may enhance DC differentiation and activation, and antitumor responses (3538). Furthermore, G-CSF correlates with tumor vaccines efficacy (31). However, to the best of our knowledge, no studies have assessed the impact of G-CSF on AML vaccines. Considering the advantage of cancer vaccines and the role of G-CSF in immunity, the present study examined the efficiency of leukemia vaccines combined with G-CSF in AML mice.

The bone marrow microenvironment (BMM) provides a protective niche that supports growth and survival of HSCs (39) and the primary site of minimal residual disease following chemotherapy (4042). The SDF-1α is pivotal for regulation of homing to and retention of hematopoietic cells in the bone marrow. It was reported that over 20 types of cancer respond to SDF-1α (43). In vitro studies demonstrated that adding SDF-1α increased the migration of leukemia cells compared with the control group, which is consistent with previous studies (26). By contrast, co-culture of AML cells with G-CSF decreased migration of tumor cells to SDF-1α, suggesting that G-CSF may destroy the interaction between SDF-1α and leukemia cells in BMM, thus driving more leukemia cells into the peripheral blood. In the present in vivo study, the peripheral blood smears of the AML mice demonstrated that with the administration of G-CSF, more leukemia cells migrated to the peripheral blood, which was in accordance with the findings of the in vitro study.

SDF-1α also induces Treg chemotaxis and adhesion to BMM (17). Tregs are recruited to evade immunosurveillance in the microenvironment of AML (10), suppress effector cells and antigen presenting cells (APCs) and induce immunosuppression against cancer cells through cytokines (4447). Previous studies have demonstrated that the in vivo administration of G-CSF could decrease the number of Tregs in the bone marrow and increase the number of Tregs in the peripheral blood (17,48). Following application of G-CSF in AML mice, an increase in the number of Tregs in the peripheral blood was also detected. The lower level of Tregs in the bone marrow may reduce the immunosuppression in the microenvironment, thus improving the function of the vaccine. One approach to overcome evasion of immunosurveillance and promote antitumor response is the depletion of Tregs in the peripheral blood. Previous studies have demonstrated that a number of therapies can reduce Tregs in vivo. For example, imatinib reduces Tregs frequency and immunosuppressive function in chronic myelogenous leukemia (CML) mice (49), the chaperone-rich cell lysate vaccine can resist Treg suppression (50), and lenalidomide reduces Tregs in tumor-bearing lymphoma mice (51). In the present study, AML mice were vaccinated, and it was detected that the tumor vaccines induced Treg reduction in the peripheral blood of AML mice. This suggests that the vaccines serve a direct role in overcoming tumor-induced immunosuppression. However, the vaccines combined with G-CSF did not decrease the percentage of Tregs in the peripheral blood compared with the control group, suggesting that other methods may be employed to target Tregs in the subsequent studies. Whether G-CSF priming combined with low-dose chemotherapy functions through SDF-1α/CXCR4 still requires further study. It can be speculated that G-CSF decreases the concentration of SDF-1α in bone marrow and motivates the migration of leukemia cells and Tregs into the peripheral blood, where tumor cells are killed by the chemotherapy drugs.

Previous studies have reported that immunotherapy is effective for the treatment of AML (7,30). In the present study, it was observed that the survival time of the vaccination group was notably longer than the AML mice, demonstrating the direct antitumoral effect of the vaccines. Among all the groups, the one that was treated with tumor vaccines combined with G-CSF achieved the longest survival time, proving the efficiency of the regimen.

In conclusion, the present study suggests that combining tumor vaccines with G-CSF is a new, effective regimen for the treatment of AML. The results demonstrate that treating AML mice with G-CSF reverses immunosuppression in the tumor microenvironment. In addition, the tumor vaccines can delete Tregs in the peripheral blood, thus alleviating immune suppression further. Combining tumor vaccines with G-CSF regimen is shown to be a promising therapeutic strategy.

Acknowledgements

The present study was supported by Fundamental Research Funds for the Central Universities in China (grant no. 0602-08143041) and the National Natural Science Foundation of China (grant nos. 81270597; 81070441).

References

1. Martner A, Thorén FB, Aurelius J, Hellstrand K. Immunotherapeutic strategies for relapse control in acute myeloid leukemia. Blood Rev. 2013;27:209–216. doi: 10.1016/j.blre.2013.06.006. [PubMed] [Cross Ref]
2. Thol F, Schlenk RF, Heuser M, Ganser A. How I treat refractory and early relapsed acute myeloid leukemia. Blood. 2015;126:319–327. doi: 10.1182/blood-2014-10-551911. [PubMed] [Cross Ref]
3. Zhang WG, Wang FX, Chen YX, Cao XM, He AL, Liu J, Ma XR, Zhao WH, Liu SH, Wang JL. Combination chemotherapy with low-dose cytarabine, homoharringtonine, and granulocyte colony-stimulating factor priming in patients with relapsed or refractory acute myeloid leukemia. Am J Hematol. 2008;83:185–188. doi: 10.1002/ajh.20903. [PubMed] [Cross Ref]
4. Gu LF, Zhang WG, Wang FX, Cao XM, Chen YX, He AL, Liu J, Ma XR. Low dose of homoharringtonine and cytarabine combined with granulocyte colony-stimulating factor priming on the outcome of relapsed or refractory acute myeloid leukemia. J Cancer Res Clin Oncol. 2011;137:997–1003. doi: 10.1007/s00432-010-0947-z. [PubMed] [Cross Ref]
5. Becker PS, Medeiros BC, Stein AS, Othus M, Appelbaum FR, Forman SJ, Scott BL, Hendrie PC, Gardner KM, Pagel JM, et al. G-CSF priming, clofarabine, and high dose cytarabine (GCLAC) for upfront treatment of acute myeloid leukemia, advanced myelodysplastic syndrome or advanced myeloproliferative neoplasm. Am J Hematol. 2015;90:295–300. doi: 10.1002/ajh.23927. [PMC free article] [PubMed] [Cross Ref]
6. Liu L, Zhang Y, Jin Z, Zhang X, Zhao G, Si Y, Lin G, Ma A, Sun Y, Wang L, Wu D. Increasing the dose of aclarubicin in low-dose cytarabine and aclarubicin in combination with granulocyte colony-stimulating factor (CAG regimen) can safely and effectively treat relapsed or refractory acute myeloid leukemia. Int J Hematol. 2014;99:603–608. doi: 10.1007/s12185-014-1528-8. [PubMed] [Cross Ref]
7. Grosso DA, Hess RC, Weiss MA. Immunotherapy in acute myeloid leukemia. Cancer. 2015;121:2689–2704. doi: 10.1002/cncr.29378. [PubMed] [Cross Ref]
8. La-Beck NM, Jean GW, Huynh C, Alzghari SK, Lowe DB. Immune checkpoint inhibitors: New insights and current place in cancer therapy. Pharmacotherapy. 2015;35:963–976. doi: 10.1002/phar.1643. [PubMed] [Cross Ref]
9. Halvorsen EC, Mahmoud SM, Bennewith KL. Emerging roles of regulatory T cells in tumour progression and metastasis. Cancer Metastasis Rev. 2014;33:1025–1041. doi: 10.1007/s10555-014-9529-x. [PubMed] [Cross Ref]
10. Ustun C, Miller JS, Munn DH, Weisdorf DJ, Blazar BR. Regulatory T cells in acute myelogenous leukemia: Is it time for immunomodulation? Blood. 2011;118:5084–5095. doi: 10.1182/blood-2011-07-365817. [PubMed] [Cross Ref]
11. Olkhanud PB, Baatar D, Bodogai M, Hakim F, Gress R, Anderson RL, Deng J, Xu M, Briest S, Biragyn A. Breast cancer lung metastasis requires expression of chemokine receptor CCR4 and T regulatory cells. Cancer Res. 2009;69:5996–6004. doi: 10.1158/0008-5472.CAN-08-4619. [PMC free article] [PubMed] [Cross Ref]
12. Ducloux D. Regulatory T cells and cancer: An undesired tolerance. Kidney Int. 2014;86:16–18. doi: 10.1038/ki.2014.46. [PubMed] [Cross Ref]
13. Joshi NS, Akama-Garren EH, Lu Y, Lee DY, Chang GP, Li A, DuPage M, Tammela T, Kerper NR, Farago AF, et al. Regulatory T cells in tumor-associated tertiary lymphoid structures suppress anti-tumor T cell responses. Immunity. 2015;43:579–590. doi: 10.1016/j.immuni.2015.08.006. [PMC free article] [PubMed] [Cross Ref]
14. Pastille E, Bardini K, Fleissner D, Adamczyk A, Frede A, Wadwa M, von Smolinski D, Kasper S, Sparwasser T, Gruber AD, et al. Transient ablation of regulatory T cells improves antitumor immunity in colitis-associated colon cancer. Cancer Res. 2014;74:4258–4269. doi: 10.1158/0008-5472.CAN-13-3065. [PubMed] [Cross Ref]
15. Colombo MP, Piconese S. Regulatory-T-cell inhibition versus depletion: The right choice in cancer immunotherapy. Nat Rev Cancer. 2007;7:880–887. doi: 10.1038/nrc2250. [PubMed] [Cross Ref]
16. Motz GT, Coukos G. Deciphering and reversing tumor immune suppression. Immunity. 2013;39:61–73. doi: 10.1016/j.immuni.2013.07.005. [PMC free article] [PubMed] [Cross Ref]
17. Zou L, Barnett B, Safah H, Larussa VF, Evdemon-Hogan M, Mottram P, Wei S, David O, Curiel TJ, Zou W. Bone marrow is a reservoir for CD4+CD25+ regulatory T cells that traffic through CXCL12/CXCR4 signals. Cancer Res. 2004;64:8451–8455. doi: 10.1158/0008-5472.CAN-04-1987. [PubMed] [Cross Ref]
18. Tabe Y, Konopleva M. Advances in understanding the leukaemia microenvironment. Br J Haematol. 2014;164:767–778. doi: 10.1111/bjh.12725. [PMC free article] [PubMed] [Cross Ref]
19. Shen X, Li N, Li H, Zhang T, Wang F, Li Q. Increased prevalence of regulatory T cells in the tumor microenvironment and its correlation with TNM stage of hepatocellular carcinoma. J Cancer Res Clin Oncol. 2010;136:1745–1754. doi: 10.1007/s00432-010-0833-8. [PubMed] [Cross Ref]
20. Duda DG, Kozin SV, Kirkpatrick ND, Xu L, Fukumura D, Jain RK. CXCL12 (SDF1alpha)-CXCR4/CXCR7 pathway inhibition: An emerging sensitizer for anticancer therapies? Clin Cancer Res. 2011;17:2074–2080. doi: 10.1158/1078-0432.CCR-10-2636. [PMC free article] [PubMed] [Cross Ref]
21. Bendall LJ, Bradstock KF. G-CSF: From granulopoietic stimulant to bone marrow stem cell mobilizing agent. Cytokine Growth Factor Rev. 2014;25:355–367. doi: 10.1016/j.cytogfr.2014.07.011. [PubMed] [Cross Ref]
22. Lin JP, Yang JS, Lu CC, Chiang JH, Wu CL, Lin JJ, Lin HL, Yang MD, Liu KC, Chiu TH, Chung JG. Rutin inhibits the proliferation of murine leukemia WEHI-3 cells in vivo and promotes immune response in vivo. Leuk Res. 2009;33:823–828. doi: 10.1016/j.leukres.2008.09.032. [PubMed] [Cross Ref]
23. Wen YF, Yang JS, Kuo SC, Hwang CS, Chung JG, Wu HC, Huang WW, Jhan JH, Lin CM, Chen HJ. Investigation of anti-leukemia molecular mechanism of ITR-284, a carboxamide analog, in leukemia cells and its effects in WEHI-3 leukemia mice. Biochem Pharmacol. 2010;79:389–398. doi: 10.1016/j.bcp.2009.09.011. [PubMed] [Cross Ref]
24. Zhang WG, Liu SH, Cao XM, Cheng YX, Ma XR, Yang Y, Wang YL. A phase-I clinical trial of active immunotherapy for acute leukemia using inactivated autologous leukemia cells mixed with IL-2, GM-CSF and IL-6. Leuk Res. 2005;29:3–9. doi: 10.1016/j.leukres.2004.04.015. [PubMed] [Cross Ref]
25. Radford KJ, Tullett KM, Lahoud MH. Dendritic cells and cancer immunotherapy. Curr Opin Immunol. 2014;27:26–32. doi: 10.1016/j.coi.2014.01.005. [PubMed] [Cross Ref]
26. Kirkwood JM, Butterfield LH, Tarhini AA, Zarour H, Kalinski P, Ferrone S. Immunotherapy of cancer in 2012. CA Cancer J Clin. 2012;62:309–335. doi: 10.3322/caac.20132. [PMC free article] [PubMed] [Cross Ref]
27. Ali OA, Emerich D, Dranoff G, Mooney DJ. In situ regulation of DC subsets and T cells mediates tumor regression in mice. Sci Transl Med. 2009;1:8ra19. doi: 10.1126/scitranslmed.3000359. [PMC free article] [PubMed] [Cross Ref]
28. Hansen M, Hjortø GM, Donia M, Met Ö, Larsen NB, Andersen MH, Straten P thor, Svane IM. Comparison of clinical grade type 1 polarized and standard matured dendritic cells for cancer immunotherapy. Vaccine. 2013;31:639–646. doi: 10.1016/j.vaccine.2012.11.053. [PubMed] [Cross Ref]
29. Steinman RM, Banchereau J. Taking dendritic cells into medicine. Nature. 2007;449:419–426. doi: 10.1038/nature06175. [PubMed] [Cross Ref]
30. Lichtenegger FS, Krupka C, Köhnke T, Subklewe M. Immunotherapy for acute myeloid leukemia. Semin Hematol. 2015;52:207–214. doi: 10.1053/j.seminhematol.2015.03.006. [PubMed] [Cross Ref]
31. Ali OA, Verbeke C, Johnson C, Sands RW, Lewin SA, White D, Doherty E, Dranoff G, Mooney DJ. Identification of immune factors regulating antitumor immunity using polymeric vaccines with multiple adjuvants. Cancer Res. 2014;74:1670–1681. doi: 10.1158/0008-5472.CAN-13-0777. [PMC free article] [PubMed] [Cross Ref]
32. Lichtenegger FS, Schnorfeil FM, Hiddemann W, Subklewe M. Current strategies in immunotherapy for acute myeloid leukemia. Immunotherapy. 2013;5:63–78. doi: 10.2217/imt.12.145. [PubMed] [Cross Ref]
33. Emens LA. Cancer vaccines: On the threshold of success. Exp Opin Emerging Drugs. 2008;13:295–308. doi: 10.1517/14728214.13.2.295. [PMC free article] [PubMed] [Cross Ref]
34. Arpinati M, Green CL, Heimfeld S, Heuser JE, Anasetti C. Granulocyte-colony stimulating factor mobilizes T helper 2-inducing dendritic cells. Blood. 2000;95:2484–2490. [PubMed]
35. Pulendran B, Banchereau J, Burkeholder S, Kraus E, Guinet E, Chalouni C, Caron D, Maliszewski C, Davoust J, Fay J, Palucka K. Flt3-ligand and granulocyte colony-stimulating factor mobilize distinct human dendritic cell subsets in vivo. J Immunol. 2000;165:566–572. doi: 10.4049/jimmunol.165.1.566. [PubMed] [Cross Ref]
36. Anderlini P. Effects and safety of granulocyte colony-stimulating factor in healthy volunteers. Curr Opin Hematol. 2009;16:35–40. doi: 10.1097/MOH.0b013e328319913c. [PMC free article] [PubMed] [Cross Ref]
37. Greter M, Helft J, Chow A, Hashimoto D, Mortha A, Agudo-Cantero J, Bogunovic M, Gautier EL, Miller J, Leboeuf M, et al. GM-CSF controls nonlymphoid tissue dendritic cell homeostasis but is dispensable for the differentiation of inflammatory dendritic cells. Immunity. 2012;36:1031–1046. doi: 10.1016/j.immuni.2012.03.027. [PMC free article] [PubMed] [Cross Ref]
38. Vuckovic S, Kim M, Khalil D, Turtle CJ, Crosbie GV, Williams N, Brown L, Williams K, Kelly C, Stravos P, et al. Granulocyte-colony stimulating factor increases CD123hi blood dendritic cells with altered CD62L and CCR7 expression. Blood. 2003;101:2314–2317. doi: 10.1182/blood-2002-03-0973. [PubMed] [Cross Ref]
39. Nwajei F, Konopleva M. The bone marrow microenvironment as niche retreats for hematopoietic and leukemic stem cells. Adv Hematol. 2013;2013:953982. doi: 10.1155/2013/953982. [PMC free article] [PubMed] [Cross Ref]
40. Meads MB, Hazlehurst LA, Dalton WS. The bone marrow microenvironment as a tumor sanctuary and contributor to drug resistance. Clin Cancer Res. 2008;14:2519–2526. doi: 10.1158/1078-0432.CCR-07-2223. [PubMed] [Cross Ref]
41. Konopleva M, Andreeff M. Targeting the leukemia microenvironment. Curr Drug Targets. 2007;8:685–701. doi: 10.2174/138945007780830827. [PubMed] [Cross Ref]
42. Burger JA, Bürkle A. The CXCR4 chemokine receptor in acute and chronic leukaemia: A marrow homing receptor and potential therapeutic target. Br J Haematol. 2007;137:288–296. doi: 10.1111/j.1365-2141.2007.06590.x. [PubMed] [Cross Ref]
43. Balkwill F. The significance of cancer cell expression of the chemokine receptor CXCR4. Semin Cancer Biol. 2004;14:171–179. doi: 10.1016/j.semcancer.2003.10.003. [PubMed] [Cross Ref]
44. Maloy KJ, Powrie F. Regulatory T cells in the control of immune pathology. Nat Immunol. 2001;2:816–822. doi: 10.1038/ni0901-816. [PubMed] [Cross Ref]
45. O'Garra A, Vieira P. Regulatory T cells and mechanisms of immune system control. Nat Med. 2004;10:801–805. doi: 10.1038/nm0804-801. [PubMed] [Cross Ref]
46. Shalev I, Schmelzle M, Robson SC, Levy G. Making sense of regulatory T cell suppressive function. Semin Immunol. 2011;23:282–292. doi: 10.1016/j.smim.2011.04.003. [PMC free article] [PubMed] [Cross Ref]
47. Coleman CA, Muller-Trutwin MC, Apetrei C, Pandrea I. T regulatory cells: Aid or hindrance in the clearance of disease? J Cell Mol Med. 2007;11:1291–1325. doi: 10.1111/j.1582-4934.2007.00087.x. [PMC free article] [PubMed] [Cross Ref]
48. Jun HX, Jun CY, Yu ZX. In vivo induction of T-cell hyporesponsiveness and alteration of immunological cells of bone marrow grafts using granulocyte colony-stimulating factor. Haematologica. 2004;89:1517–1524. [PubMed]
49. Larmonier N, Janikashvili N, LaCasse CJ, Larmonier CB, Cantrell J, Situ E, Lundeen T, Bonnotte B, Katsanis E. Imatinib mesylate inhibits CD4+ CD25+ regulatory T cell activity and enhances active immunotherapy against BCR-ABL- tumors. J Immunol. 2008;181:6955–6963. doi: 10.4049/jimmunol.181.10.6955. [PMC free article] [PubMed] [Cross Ref]
50. Larmonier N, Fraszczak J, Lakomy D, Bonnotte B, Katsanis E. Killer dendritic cells and their potential for cancer immunotherapy. Cancer Immunol Immunother. 2009;59:1–11. doi: 10.1007/s00262-009-0736-1. [PubMed] [Cross Ref]
51. Sakamaki I, Kwak LW, Cha SC, Yi Q, Lerman B, Chen J, Surapaneni S, Bateman S, Qin H. Lenalidomide enhances the protective effect of a therapeutic vaccine and reverses immune suppression in mice bearing established lymphomas. Leukemia. 2014;28:329–337. doi: 10.1038/leu.2013.177. [PMC free article] [PubMed] [Cross Ref]

Articles from Oncology Letters are provided here courtesy of Spandidos Publications