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Modulation of PD-L1 by Astragalus polysaccharide attenuates the induction of melanoma stem cell properties and overcomes immune evasion

BMC Cancer volume 24, Article number: 1034 (2024) Cite this article

Abstract

Background

Melanoma is a highly aggressive form of skin cancer. The existence of cancer stem cells (CSCs) and tumor immune evasion are two major causes of melanoma progression, but no effective treatment has been found at present. Astragalus polysaccharide (APS) is a principal active component derived from Astragalus membranaceus, showing anti-tumor effects in various tumors including melanoma. However, the underlying mechanism is still unclear.

Methods

The regulation of APS on self-renewal ability and CSC markers expression in melanoma stem cells (MSCs) was measured by tumor sphere formation and tumorigenicity assays, RT-qPCR, and western blot. Flow cytometry was conducted to evaluate the activation of immune system by APS in melanoma mice. Further, the mechanism was explored based on PD-L1 overexpression and knock-down B16 cells.

Results

APS attenuated the tumor sphere formation of MSCs in vitro as well as the tumorigenicity in vivo. It also decreased the expression of CD133, BMI1 and CD47. Based on the PD-L1 overexpression and knock-down B16 cells, it was confirmed that APS inhibited the induction of MSCs by down-regulating PD-L1 expression. Meanwhile, APS increased the infiltration of CD4+ and CD8+T cells in tumor tissues because of its inhibitory effect on PD-L1.

Conclusions

APS inhibited MSC induction and overcame tumor immune evasion through reducing PD-L1 expression. This study provided compelling evidence that APS could be a prospective therapeutic agent for treating melanoma.

Peer Review reports

Background

Melanoma is a highly aggressive form of skin cancer, with increasing mortality rates over time [1, 2]. Despite the utilization of multiple therapies such as chemotherapy, targeted therapy, and immunotherapy, many melanoma patients suffer poor prognosis due to rapid progression and frequent relapse [3, 4].

Cancer stem cells (CSCs) are present in various tumors and possess properties like self-renewal, limitless replication, and drug resistance [3]. CSC markers, such as CD133, BMI1 and CD47, are associated with these properties [5,6,7,8]. In melanoma, melanoma stem cells (MSCs) have been shown to play a significant role in tumorigenesis, progression and metastasis [9,10,11]. Additionally, MSCs are easier to evade from surveillance of the immune system than typical melanoma cells [12]. A notable feature of tumor immune evasion is the scarcity of tumor infiltrated CD8+T cells, which is accompanied by an inferior capacity of cytokine secretion, including IFN-γ and TNF-α [13, 14]. Thus, strategies targeting MSC induction and immune evasion could be regarded as promising approaches to manage melanoma progression.

Programmed cell death ligand 1 (PD-L1), a member of B7 family, is expressed on the surface of tumor cells [15]. By binding to its receptor PD-1, PD-L1 induces dysfunction of cytotoxic T lymphocytes, contributing to tumor immune evasion [16]. Interestingly, there is a positive correlation between CSC properties and PD-L1 expression. In breast cancer, PD-L1 is overexpressed on CSC-like cells [17], and the knockdown of PD-L1 inhibits tumor sphere formation [18]. The overexpression of PD-L1 has been shown to promote CSCs self-renewal and upregulate CSC markers expression across various cancers, including colorectal and gastric cancer [19, 20]. So, PD-L1 might be a crucial target to inhibit CSC formation and tumor immune evasion. However, the relationship between CSC properties and PD-L1 expression in melanoma remains poorly understood and warrants further investigation.

Astragalus polysaccharide (APS), extracted from the plant Astragalus membranaceus, possesses multiple pharmacological effects, including immunoregulation, anti-inflammatory and anti-tumor effects [21]. Our previous study demonstrated that APS decreased PD-L1 expression in cisplatin-resistant melanoma cells and increased their drug sensitivity [22]. However, the precise mechanism through which APS exerts its anti-tumor effects in melanoma remain unclear.

Therefore, this study aims to evaluate the anti-tumor efficacy of APS in melanoma and explore whether PD-L1 serves as a primary target for APS-mediated anti-tumor effects.

Methods

Cell culture and sphere formation

B16-F10 (hereinafter referred to as B16) and A375 cells were purchased from the Shanghai Institutes for Biological Sciences of the Chinese Academy of Sciences. Cells were cultured in Roswell Park Memorial Institute (RPMI) 1640 (Gibco, USA) containing 10% inactivated Fetal Bovine Serum (FBS) (Gemini, USA) with 5% CO2 at 37˚C. To induce tumor sphere formation, cells were seeded in ultra-low adsorption culture flasks with a cell concentration of 5000 cells/mL. Serum-free DMEM/F12 medium (Gibco, USA) was used for cell culture, containing 2% B27 supplement (Gibco, USA), 20 ng/mL EGF (PeproTech, USA) and 20 ng/mL FGF-basic (PeproTech, USA). APS (purity ≥ 98% UV) was obtained from Shanghai Yuan-ye Bio-Technology Co., Ltd. For cell experiments, cells were treated with APS for 7 days with a working concentration of 200 µg/mL, and optical microscope was used to photograph and count tumor spheres.

Animal experiments

Mice were purchased from Shanghai Ji-hui Experimental Animal Breeding Company and fed at the Animal Center of Yue-yang Hospital of Integrative Medicine (Shanghai, China). NOD/SCID mice (n = 6 per group) were given subcutaneous injections with B16 CSCs (1 × 105 and 1 × 104/each mouse) in their right axilla for assessing the tumorigenicity of CSCs in vivo. C57BL/6 mice (n = 5 per group) were subcutaneously injected with B16 cells (5 × 105/each mouse) which were transfected with PD-L1 overexpression lentivirus or negative control vectors. Mice were gavaged with APS (200 mg/kg) once daily, euthanized by cervical dislocation under anesthesia with 3% isofluranea (Yuyanbio, China) [23]. Tumor volume was measured and recorded every two days: Volume=(length×width2) /2.

Establishment of PD-L1 overexpressing and down-expressing cells

PD-L1 overexpression or knock-down lentivirus (GeneChem, China) were transduced into B16 cells, while empty lentiviral vectors were transduced as negative controls (OE-NC, sg-NC respectively). Protocols have been described previously [22]. In brief, B16 cells were cultured in 24-well plates and subjected to lentiviral infection for 72 h after adhesion. Stable transfected cells were screened using puromycin (Genechem, China) diluted at 2 µg/mL and then collected for subsequent experiments.

Western blot

Cells or tumor tissues (100 mg) were lysed using 1×RIPA lysis buffer (Beyotime, China) for protein extraction. After denaturation, protein was separated by 10% SDS-PAGE gels and transferred onto the 0.45 μm PVDF membrane. Next, these membranes were sealed in blocking reagent for 2 h and incubated at 4˚C overnight with primary antibodies: CD133 (ab19898, Abcam, UK), BMI1 (6964, CST, USA), CD47 (ab75388, Abcam, UK), PD-L1 (AF1019, R&D, USA), GAPDH (5174, CST, USA). The membranes were incubated with secondary antibodies next day and visualized by ECL substrate. Image J software version 1.4 was applied to analyze all results.

RT-qPCR

Relative mRNA expression of mCD133, mBMI1, mCD47, mPD-L1, mIFN-γ, mTNF-α, hCD133, hBMI1, hCD47 was quantified via RT-qPCR as previously reported [24]. And GAPDH was selected as an internal control. 2-ΔΔCt method was used for RNA quantification. The primers were listed in Table 1.

Table 1 The primer sequences
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Flow cytometry

Tumor tissues were digested into single cells in RPMI 1640 supplemented with 1 mg/mL collagenase type IV, 0.02 mg/mL DNase I, and 1 mg/mL neutral protease (Worthington Biochemical, USA). Fixable Viability Stain 660 (564405, BD Biosciences, USA) was applied to distinguish live/dead cells after removing red cells. Then cells were incubated in antibodies: PE-cy7-conjugated anti-CD45 (25-0451-82, eBioscience, USA), APC-cy7-conjugated anti-CD3 (560590, BD Bioscience, USA), FITC-conjugated anti-CD4 (340133, BD Biosciences, USA), PerCP-cy™5.5-conjugated anti-CD8 (3341049, BD Biosciences, USA). BD FACSVerse™ Flow cytometer was used for sample loading and Flowjo version 10 was used to analyze the flow cytometry data.

Immunofluorescence

Tumor tissues were paraffin-embedded and sectioned. After deparaffinization and dehydration, tissue sections were subjected to antigenic repair at 95–99˚C for 30 min and then sealed in 2% BSA (Beyotime, China). Then, tissue sections were incubated with PD-L1 primary antibody at 4˚C overnight, and incubated with fluorescent secondary antibody for 1 h in dark. The cell nucleus was counterstained with DAPI (Solarbio, China) diluted at 2 µg/ml, followed by visualization and image capture using microscopy.

Statistical analysis

GraphPad Prism was used to conduct data analysis. All results were expressed as mean ± SEM and analyzed by unpaired t-test for two groups comparison. And ANOVA with Tukey’s test was conducted for multiple group comparison. P < 0.05 was considered statistical significance.

Results

APS suppresses the induction of MSC properties in vitro

In order to obtain MSCs, B16 and A375 cells were cultured in serum-free medium. As shown in Fig. 1A-F, the formation of tumor sphere could be seen after 7 days of culturing, representing the basic manifestation of CSCs. Obviously, APS decreased the number and volume of spheres. Moreover, compared with those parent cells, increased mRNA and protein expressions of CSC markers including CD133, BMI1, and CD47 were shown in B16 and A375 CSCs, indicating the possession of CSC properties, whereas APS notably inhibited the expression of these CSC markers in B16 and A375 CSCs (Fig. 1G-J). The above results indicated that APS significantly inhibited CSC formation in B16 and A375 cells.

Fig. 1
figure 1

Effects of APS on tumor sphere formation and CSC markers expression of MSCs. A, D Representative pictures of B16 and A375 cells inducing for tumor spheres treated with or without APS. Scale bar: 200 μm. B, E The number of tumor spheres was calculated and presented as a frequency of CSCs. C, F The average diameter of tumor spheres was quantified. G-J The mRNA (G-H) and protein (I-J) expressions of CD133, BMI1 and CD47 were measured by RT-qPCR and western blot. Data are shown as means ± SEM; n = 3; *P < 0.05, **P < 0.01, ***P < 0.001

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APS attenuates the tumorigenic effect of MSCs in vivo

To investigate whether the inhibitory effect of APS on MSCs in vivo was similar to the results in vitro, two concentrations of B16 CSCs were subcutaneously injected to establish melanoma models respectively (1 × 105 and 1 × 104/each mouse). As we expected, smaller tumor size and slower tumor growth rate were presented in the APS group rather than the Model group (Fig. 2A-D). Further experiments revealed that tumor tissues from the APS group showed lower expression of CD133, BMI1 and CD47 in both mRNA and protein levels (Fig. 2E-F). Based on these results, we speculated that APS reduced the oncogenicity of MSCs.

Fig. 2
figure 2

Impact of APS on the tumorigenesis of MSCs in NOD/SCID mice. B16 CSCs were subcutaneously injected into NOD/SCID mice at a concentration of 1 × 105 and 1 × 104 cells/per mouse respectively (n = 6). Images of tumors were shown in A and C. B, D Tumor growth curves of NOD/SCID mice (n = 6). E-F The mRNA (E) and protein (F) expression of CD133, BMI1 and CD47 in tumor tissues from Model and APS groups (n = 3). Data are shown as means ± SEM; *P < 0.05, **P < 0.01, ***P < 0.001

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PD-L1 overexpression is beneficial to the induction of MSCs

Multiple researches have mentioned the prominently expression of PD-L1 in CSCs across various tumors [20,21,22,23,24,25]. In order to figure out whether PD-L1 affects the stemness of MSCs, we first detected the expression of PD-L1 in B16 cells and B16 CSCs. The results showed that both mRNA and protein expressions of PD-L1 were notably increased in B16 CSCs (Fig. 3A and B). Then, we constructed overexpressing-PD-L1 (OE-PD-L1) B16 cells through lentivirus transfection (Fig. 3C). We found that these cells possessed enhanced ability to form tumor spheres (Fig. 3D-E). Meanwhile, compared with the group transduced with empty lentiviral vectors (OE-NC), PD-L1 overexpression resulted in an increased expression of CD133, BMI1 and CD47 in B16 cells (Fig. 3F). The aforementioned findings provided evidence that PD-L1 promoted B16 cells to obtain MSC properties.

Fig. 3
figure 3

The positive relationship between PD-L1 expression and MSC properties. A-B The mRNA (A) and protein (B) expression of PD-L1 detected by RT-qPCR and western blot. C The protein expression of PD-L1 was examined after PD-L1 overexpression lentivirus were transduced into B16 cells. D Representative pictures of tumor spheres formed in negative control (OE-NC) and overexpression PD-L1 (OE-PD-L1) B16 CSCs. Scale bar: 200 μm. E The number of tumor spheres was calculated and presented as a frequency of OE-NC B16 CSCs. F The protein expression of CD133, BMI1 and CD47 in B16 cells with PD-L1 overexpression or not. Data are shown as means ± SEM; n = 3; *P < 0.05, **P < 0.01

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APS suppresses PD-L1 expression in MSCs

Based on the previous results, we investigated the impact of APS on PD-L1 expression. As shown in Fig. 4A and B, APS remarkably downregulated the expression of PD-L1 in B16 CSCs. Moreover, APS was able to reduce the expression of PD-L1 in B16 CSCs with PD-L1 overexpression (Fig. 4C). Furthermore, we observed PD-L1 expression in tumor tissues of melanoma mice. And a decreased expression of PD-L1 could be seen in tumor tissues from the APS group compared to the Model group (Fig. 4D and E). The above results indicated that APS had a suppressive effect on PD-L1 expression.

Fig. 4
figure 4

The regulatory effect of APS on PD-L1 expression. A-B The mRNA (A) and protein (B) expressions of PD-L1 in MSCs were measured by RT-qPCR and western blot (n = 3). C The mRNA expression of PD-L1 in PD-L1 overexpression cells with or without APS administration (n = 3). D The mRNA expression of PD-L1 in tumor tissues of mice from Model and APS groups (n = 6). E Representative images of IF staining to present PD-L1 expression in tumor tissues. Scale bar: 50 μm. Data are shown as means ± SEM; *P < 0.05, **P < 0.01, ***P < 0.001

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APS attenuates MSC formation and tumor progression by suppressing PD-L1 expression

To figure out the role of PD-L1 in APS impacting MSC formation, sphere formation assay was conducted first. And the results showed that PD-L1 overexpression promoted MSC formation, while APS reduced the number of tumor spheres in OE-PD-L1 B16 CSCs (Fig. 5A-B). Moreover, the mRNA and protein expressions of CD133, BMI1 and CD47 were reduced by APS in OE-PD-L1 B16 CSCs (Fig. 5C and D). Next, we constructed B16 cells with PD-L1 knock-down (sg-PD-L1 B16 cells), which resulted in less MSC formation, but the intervention of APS on sg-PD-L1 B16 cells didn’t show further inhibition of MSC formation (Fig. 5E-F). Compared with the sg-NC group, lower expression of CD133, BMI1 and CD47 in mRNA and protein level could be seen in sg-PD-L1 group, while no significant difference presented between sg-PD-L1 and sg-PD-L1 + APS group (Fig. 5G-I). In melanoma mice, those who were transplanted with OE-PD-L1 B16 cells presented a higher rate of tumor growth, while APS slowed down the tumor growth rate (Fig. 5J). In addition, the expression of CD133, BMI1 and CD47 were elevated in tumor tissues from the OE-PD-L1 group compared to the OE-NC group as well as the OE-PD-L1 + APS group (Fig. 5K and L). So, it could be speculated that APS attenuated MSC formation in vitro and inhibited tumor growth in vivo through suppressing PD-L1 expression in melanoma cells.

Fig. 5
figure 5

The impact of APS on MSC formation depended on its downregulation of PD-L1. A Representative picture of tumor spheres formed in OE-NC and OE-PD-L1 B16 CSCs treated with or without APS (n = 3). Scale bar: 200 μm. B The number of tumor spheres was presented as a frequency of OE-NC CSCs. C-D The mRNA (C) and protein (D) expressions of CD133, BMI1 and CD47 in OE-NC, OE-PD-L1 and OE-PD-L1 + APS groups (n = 3). E Representative picture of tumor spheres formed in sg-NC and sg-PD-L1 B16 CSCs treated with or without APS (n = 3). Scale bar: 200 μm. F The number of tumor spheres was presented as a frequency of sg-NC CSCs. G-I The mRNA (G) and protein (H-I) expressions of CD133, BMI1 and CD47 in sg-NC, sg-PD-L1 and sg-PD-L1 + APS groups (n = 3). J C57BL/6 mice were subcutaneously injected with OE-NC B16 cells, or OE-PD-L1 B16 cells with or without APS administration. Tumor images and growth curves were shown (n = 5). K-L The mRNA (K) and protein (L) expressions of CD133, BMI1 and CD47 in tumor tissues (n = 3). Data are shown as means ± SEM; *P < 0.05, **P < 0.01, ***P < 0.001

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APS activates T lymphocytes via reducing PD-L1 expression

High expression of PD-L1 in tumor cells has been confirmed to impair cytotoxic T lymphocytes recruitment, leading to tumor immune evasion. In this study, we investigated the variation of CD4+ and CD8+T cells in melanoma mice. The results showed that APS increased the frequency of CD4+ and CD8+T cells in both tumor tissues and spleen in melanoma mice (Fig. 6A-B). And with APS administration, the expression of IFN-γ and TNF-α was also increased (Fig. 6C-D). Next, OE-PD-L1 B16 cells were used to evaluate the crucial role of PD-L1 in APS alleviating tumor immune evasion. As shown in Fig. 6E-F, in melanoma tissues, the percentage of CD4+ and CD8+T cells was lower in the OE-PD-L1 group compared to the OE-NC group. However, it was notably increased in the OE-PD-L1 + APS group. The results indicated that the anti-tumoral immune responses of T lymphocytes were promoted by APS through inhibiting PD-L1 expression.

Fig. 6
figure 6

Effects of APS on T lymphocytes infiltration. A-B The percentage of CD4+ and CD8+T cells in tumor tissues (A) and spleen (B) of mice in Model and APS groups. C-D The mRNA expression of IFN-γ (C) and TNF-α (D) in tumor tissues. E-F The percentage of CD4+ (E) and CD8+T (F) cells in tumor tissues in OE-NC, OE-PD-L1 and OE-PD-L1 + APS groups. Data are shown as means ± SEM; n = 3; *P < 0.05, **P < 0.01, ***P < 0.001

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Discussion

CSCs exist as a small subset within human malignancies, arising either from the transformation of normal adult stem cells or the reprogramming of differentiated cancer cells [26]. The existence of CSCs leads to the incomplete eradication of tumor cells, facilitating tumor recurrence and metastasis. Therefore, eliminating CSCs is an essential and promising strategy in cancer therapy [27, 28]. In this study, we investigated the effects of APS, a principal active component derived from Astragalus membranaceus, on CSCs in melanoma. we demonstrated that APS reduced the tumor sphere formation in vitro and inhibited the tumorigenesis of MSCs in vivo. Furthermore, APS administration resulted in the decreased expression of CSC markers including CD133, BMI1 and CD47. These findings illustrated that APS could attenuate the induction of MSC properties.

PD-L1 is prominently elevated in many types of tumors, including melanoma. The overexpression of PD-L1 has been linked to oncogenesis and disease progression [29]. It has been reported that high level of PD-L1 promotes CSC markers expression and plays an crucial role in maintaining the properties of CSCs, including self-renewal, epithelial-mesenchymal transition (EMT) and chemo-resistance [20]. In lung cancer cells, once PD-L1 is overexpressed, they can form clones with EMT and stem cell-like phenotypes [28]. On the contrary, suppressing PD-L1 expression markedly impairs the ability of drug-resistant CSCs to form tumor spheres [30]. According to present reports, multiple signaling pathways are involved in the modulation of cancer cell stemness mediated by PD-L1. For instance, the positive feedback loop composed by PD-L1/Frizzled6/β-catenin is reported to promote CSC expansion [31]. In colorectal cancer, PD-L1 interacts directly with HMGA1, activating PI3K/AKT and MEK/ERK pathways to foster CSC proliferation [19]. Similarly, PD-L1/PI3K/AKT pathway is also associated with the stemness score in breast cancer [32]. And the high expression of BRD4 in breast CSCs can induce IL-6 secretion, and promote CSC formation through activating PD‑L1/RelB/p65 pathway [18].

Consistent with the aforementioned findings, we observed higher PD-L1 expression in MSCs compared to B16 cells. Moreover, elevated PD-L1 levels contributed to increased expression of CD133, BMI1 and CD47, promoting self-renewal of B16 cells and accelerating tumor growth in melanoma mice. Conversely, reduced PD-L1 expression hindered CSC formation in B16 cells. These results supported the notion that targeting PD-L1 could be considered as a viable strategy to inhibit CSC formation and impede tumor progression.

APS has been shown to attenuate tumor progression, with PD-L1 identified as an important target for its anti-tumor effects. PD-L1 is known to be highly expressed on tumor cells. Through decreasing the expression of PD-L1 by APS, the improved tumor immunotherapy can be observed [33]. In drug-resistant tumor cells, characterized by elevated PD-L1 expression, APS has been reported to increase the drug sensitivity and reverse chemotherapy resistance [22,23,24,25,26,27,28,29,30,31,32,33,34]. Notably, these cells often present enhanced CSC characteristics [35]. In our study, APS effectively reduced PD-L1 expression in MSCs. Accordingly, the CSC properties were also attenuated, accompanied by a slower tumor growth rate. Furthermore, APS administration was conducted on B16 cell lines with PD-L1 over/down-expression. As we expected, APS diminished tumor sphere formation and reduced CSC markers expression in OE-PD-L1 B16 cells, but no significant difference was observed between sg-PD-L1 and sg-PD-L1 + APS group, both of which attenuating the CSC formation compared to sg-NC B16 cells. These findings confirmed the pivotal role of PD-L1 in APS attenuating the induction of MSC properties.

On the other hand, PD-L1 is a kind of immune checkpoint molecule. The binding of PD-L1/PD-1 impairs cytotoxicity and proliferation of T cells, facilitating immune evasion of tumor cells [36]. Suppression or blockage of PD-L1 has been shown to significantly enhance the cytotoxicity of T cells [37], hence promoting an anti-tumor immune response. As mentioned above, APS could downregulate PD-L1 expression in tumor cells, so we next observed its effect on T lymphocytes in melanoma mice. We found that APS increased the frequency of CD4+ and CD8+T cells in both tumor tissue and spleen of melanoma mice, accompanied by higher expression levels of IFN-γ and TNF-α. Furthermore, overexpression of PD-L1 reduced the tumor infiltration of CD4+ and CD8+T cells, while APS reversed this phenomenon.

An intriguing discovery from our team is the potential of APS to decrease the infiltration of CD8+T cells into the central nervous system in experimental autoimmune encephalomyelitis (EAE), as reported in a previous study [38], seemingly contradictory to the current findings. This discrepancy underscores the diverse therapeutic benefits of APS across different diseases, where underlying mechanisms can vary even when targeting the same cell types. One classic example is about macrophages. In lung cancer, APS promotes M1 polarization of macrophages [39], while in diabetic models, APS promotes M2 polarization of macrophages to enhance secretion of anti-inflammatory factors such as IL-4, IL-10, and Arg-1 [40]. Therefore, exploring the pharmacological mechanism of APS in diverse diseases is warranted, with potential implications for its clinical utility.

Conclusions

In conclusion, our study elucidates the therapeutic potential of APS in melanoma by targeting PD-L1 to inhibit CSC induction and enhance anti-tumor immunity (Fig. 7). Understanding APS’s mechanisms across diseases will facilitate its clinical translation and application in cancer therapy.

Fig. 7
figure 7

Mechanism of Astragalus polysaccharide attenuating MSC formation and overcoming immune evasion

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Data availability

The data of this study are available from the corresponding author upon reasonable request.

Abbreviations

APS:

Astragalus polysaccharide

CSCs:

Cancer stem cells

EMT:

Epithelial-mesenchymal transition

NC:

Negative control

MSCs:

Melanoma stem cells

OE-PD-L1:

Overexpression of PD-L1

PD-L1:

Programmed cell death ligand 1

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Funding

This study was supported by the National Natural Science Foundation of China (Grant No. 82304779), the Science and Technology Innovation Project of Shanghai University of Traditional Chinese Medicine (Grant No. YYKC-2021-01-154), the Scientific Research Project in YueYang Hospital of Integrative Medicine, Shanghai University of Traditional Chinese Medicine (Grant No. 2021yygm02) and The Planned Science Program of the Shanghai University of Traditional Chinese Medicine (Grant No. 2021LK089).

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Author notes

  1. Hua Yu and Guiqing Ding contributed equally to this work.

Authors and Affiliations

  1. Institute of Clinical Immunology, Yue-yang Hospital of Integrative Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, 200437, China

    Hua Yu, Guiqing Ding, Qianyi Gong, Jinyun Ma, Yan Zhao, Yuanhua Wang, Xi Qiao & Xiaodong Cheng

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  1. Hua Yu
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  2. Guiqing Ding
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  3. Qianyi Gong
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  7. Xi Qiao
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  8. Xiaodong Cheng
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Contributions

All authors contributed to the study conception and design. HY, GQD and XDC conceived and designed this study. HY, GQD and XQ performed the experiments. HY and YZ analyzed the data. JYM, QYG and YHW were involved in conceiving the project and provided several important suggestions for the research plan. HY and GQD wrote the manuscript. All authors have read and approved the final version of the manuscript.

Corresponding author

Correspondence to Xiaodong Cheng.

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Ethical approval and consent to participate

The present study was approved by the Ethics Committee of Yue-yang Hospital of Integrative Medicine from Shanghai University of Traditional Chinese Medicine (the Ethics Approval Number: YYLAC-2021-105-1).

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Not applicable.

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The authors declare no competing interests.

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Yu, H., Ding, G., Gong, Q. et al. Modulation of PD-L1 by Astragalus polysaccharide attenuates the induction of melanoma stem cell properties and overcomes immune evasion. BMC Cancer 24, 1034 (2024). https://doi.org/10.1186/s12885-024-12788-4

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  • DOI: https://doi.org/10.1186/s12885-024-12788-4

Keywords

BMC Cancer

ISSN: 1471-2407

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