Targeted inhibition of myeloid-derived suppressor cells in the tumor microenvironment by low-dose doxorubicin to improve immune efficacy in murine neuroblastoma / 中华医学杂志(英文版)

BACKGROUND@#High agglomeration of myeloid-derived suppressor cells (MDSCs) in neuroblastoma (NB) impeded therapeutic effects. This study aimed to investigate the role and mechanism of targeted inhibition of MDSCs by low-dose doxorubicin (DOX) to enhance immune efficacy in NB.@*METHODS@#Bagg albino (BALB/c) mice were used as tumor-bearing mouse models by injecting Neuro-2a cells, and MDSCs were eliminated by DOX or dopamine (DA) administration. Tumor-bearing mice were randomly divided into 2.5 mg/kg DOX, 5.0 mg/kg DOX, 50.0 mg/kg DA, and control groups (n = 20). The optimal drug and its concentration for MDSC inhibition were selected according to tumor inhibition. NB antigen-specific cytotoxic T cells (CTLs) were prepared. Tumor-bearing mice were randomly divided into DOX, CTL, anti-ganglioside (GD2), DOX+CTL, DOX+anti-GD2, and control groups. Following low-dose DOX administration, immunotherapy was applied. The levels of human leukocyte antigen (HLA)-I, CD8, interleukin (IL)-2 and interferon (IFN)-γ in peripheral blood, CTLs, T-helper 1 (Thl)/Th2 cytokines, perforin, granzyme and tumor growth were compared among the groups. The Wilcoxon two-sample test and repeated-measures analysis of variance were used to analyze results.@*RESULTS@#The slowest tumor growth (F = 6.095, P = 0.018) and strongest MDSC inhibition (F = 14.632, P = 0.001) were observed in 2.5 mg/kg DOX group. Proliferation of T cells was increased (F = 448.721, P < 0.001) and then decreased (F = 2.047, P = 0.186). After low-dose DOX administration, HLA-I (F = 222.489), CD8 (F = 271.686), Thl/Th2 cytokines, CD4+ and CD8+ lymphocytes, granzyme (F = 2376.475) and perforin (F = 488.531) in tumor, IL-2 (F = 62.951) and IFN-γ (F = 240.709) in peripheral blood of each immunotherapy group were all higher compared with the control group (all of P values < 0.05). The most significant increases in the aforementioned indexes and the most notable tumor growth inhibition were observed in DOX+anti-GD2 and DOX+CTL groups.@*CONCLUSIONS@#Low-dose DOX can be used as a potent immunomodulatory agent that selectively impairs MDSC-induced immunosuppression, thereby fostering immune efficacy in NB.

Therapeutic effects of signal transducer and activator of transcription 3 siRNA on human breast cancer in xenograft mice / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Signal transducer and activator of transcription 3 (STAT3) is usually constitutively activated in a variety of malignancies. It directly contributes to tumorigenesis, invasion, and metastasis. The surgical treatment of breast cancer has made no breakthroughs in terms of treatment effect, in spite of its long history. Current biotherapies bring a note of optimism to breast cancer treatment. To explore the possibility of a siRNA targeted STAT3 blocking treatment for over-activated tumor cells, we evaluated the efficacy of a STAT3 siRNA on human breast cancer cells in vitro and in vivo.</p><p><b>METHODS</b>Three MCF-7 human breast cancer cell lines were tested: control MCF-7 cells, non-specific siRNA transfected MCF-7 cells and STAT3 siRNA transfected MCF-7 cells. Expression of STAT3 in MCF-7 cells was inhibited by RNA interference (RNAi). The STAT3 mRNA and protein levels were detected by semi-quantity RT-PCR and Western blotting. Cell proliferation and apoptosis were determined by MTT method and flow cytometry. The three groups of MCF-7 cells mentioned above were transplanted subcutanuously into nude mice and their tumorgenic ability observed. The STAT3 mRNA and protein levels of the samples from tumors in different groups were determined by semi-quantity RT-PCR and Western blotting and compared.</p><p><b>RESULTS</b>In STAT3 siRNA transfected MCF-7 cells, the expressions (STAT3/β-actin) of STAT3 mRNA (0.327 ± 0.020) and protein (0.153 ± 0.006) were significantly lower than that in control MCF-7 cells (mRNA 1.093 ± 0.018, protein 1.374 ± 0.022) and non-specific siRNA transfected MCF-7 cells (mRNA 1.035 ± 0.050, protein 1.320 ± 0.033) (P < 0.05). MTT showed that cell proliferation was significantly reduced and the cell growth inhibition ratio in the STAT3-siRNA group was (44.00 ± 5.10)%, significantly higher than that in non-specific siRNA transfected MCF-7 cells ((16.10 ± 1.05)%, P < 0.05). Flow cytometry results showed that more apoptosis was observed in the STAT3-siRNA group. The rate of apoptosis was (14.79 ± 0.22)%, much higher than in control MCF-7 cells (7.06 ± 0.71) and non-specific siRNA transfected MCF-7 cells (8.45 ± 0.43) (P < 0.05). The tumor growth in the STAT3 siRNA transfected MCF-7 cells was significantly slower than in the two control groups. On the 22th day after transplantation the tumor weight ((21.40 ± 10.57) mg) and volume ((41.15 ± 12.17) mm(3)) in the STAT3 siRNA transfected group were significantly lower than in control group (weight (88.60 ± 12.16) mg, volume (118.45 ± 24.68) mm(3)) and non-specific siRNA transfected group (weight (57.20 ± 21.86) mg, volume (101.36 ± 21.90) mm(3)) (P < 0.05). Both the STAT3 mRNA and protein levels in the tumors from the STAT3 siRNA transfected group were significantly lower than in the tumors from the two control groups.</p><p><b>CONCLUSIONS</b>STAT3 siRNA can effectively silence the STAT3 gene in vitro and in vivo, increase cell apoptosis rate and significantly decrease cell proliferation, which inhibits the growth of breast cancer cell in vitro. Tumor growth of xenograft mice is significantly inhibited. The results obtained in vivo are in consistency with those in vitro. STAT3 may be a novel therapeutic target for breast cancer and RNA interference has potential clinical application.</p>