C3a-C3aR signaling promotes breast cancer lung metastasis via modulating carcinoma associated fibroblasts
Mounting evidence suggests that complement components promote tumor progression via modulating immune suppression, angiogenesis, or tumor cell proliferation. However, the role of C3a-C3aR signaling in regulating lung metastasis of breast cancer remains unknown.
We performed various ex-vivo and in-vivo assays. Genetic and pharmacological C3aR blockade models were applied to investigate the role of C3a-C3aR in metastasis of breast cancer.
C3a-C3aR signaling in CAFs facilitates the metastasis of breast cancer. Mechanically, C3a-C3aR signaling augments pro-metastatic cytokine secretion and extracellular matrix components expression of CAFs via the activation of PI3K-AKT signaling. Genetic or pharmacological blockade of C3aR signaling effectively inhibited lung metastasis of breast cancer in mouse models.
C3a-C3aR signaling in CAFs facilitates the metastasis of breast cancer. Targeting C3aR signaling is a potential anti-metastasis strategy for breast cancer therapy.
KeywordsC3a C3a receptor Complement Cancer-associated fibroblast Metastasis Breast cancer
Compelment 3 receptor antagonist
Carcinoma associated fibroblast
Hepatocyte growth factor
Transforming growth factor
The complement system is an important part of innate immunity, which consists of a series of serine proteases encoded by the same ancestral gene as the coagulation protein . In recent years, the role of the complement system has shifted from a blood- based antimicrobial infection to a wide range of immune regulation and tissue homeostasis regulation [2, 3, 4]. In addition to participating in innate immunity, many complement proteins facilitate cross-talk between the immune cells and tumor cells in the tumor microenvironment (TME) [5, 6, 7]. Complement C3 is a central component in complement activation [1, 8], activation of C3 results in the generation of C3a, which is a prominent tumor-promoting factor in TME [9, 10]. Numerous studies have shown that myeloid cells (including monocytes, macrophages, DCs) and T cells express C3aR [7, 11]. In addition, activated astrocytes, endothelial cells, epithelial cells , smooth muscle cells , renal tubular epithelial cells  are also regulated by the C3a-C3aR axis. Previously, we and others demonstrated that C3aR signaling promotes tumor growth by promoting immune inhibition [6, 10, 14]. However, the role of C3a-C3aR signaling in breast cancer metastasis remains to be explored. Published studies suggested that C3a-C3aR signaling contributes to the formation of pulmonary fibrosis  and renal fibrosis , characterized by activation of fibroblasts, which reveal the potential of C3a-C3aR axis in promoting metastasis via regulating fibroblasts in TME.
A growing body of evidence suggests that tumor metastasis is not only dependent on tumor cells themselves, but is also regulated by the tumor microenvironment (TME) . Carcinoma associated fibroblasts (CAFs) are the largest populations of tumor cells which accumulate in TME [18, 19] (e.g. breast cancer , hepatocellular carcinoma ) and promote cancer metastasis through multiple pathways [22, 23]. Manipulating the function of CAFs is a promising strategy to treat cancer . However, whether and how C3a-C3aR signaling is involved in the regulation of CAFs remain largely unknown.
In the current study, we demonstrated that C3a promotes tumor cell metastasis by modulating CAFs. C3a binds to its cognate receptor C3aR to activate PI3K/AKT signaling, which resulted in CAFs activation. Moreover, in human invasive breast cancers, C3 expression is positively correlated with expression of CAFs activation markers and functional effectors. Genetic or pharmacological blockade of C3aR signaling effectively inhibits lung metastasis of breast cancer. Our data demonstrated that targeting C3aR might be an effective strategy in tumor metastasis control.
Material and methods
Cell lines and cell cultures
The mouse breast cancer cell lines 4 T1 and EO771 used in this study were obtained from the American Tissue Culture Collection (ATCC) and CH3 BioSystems respectively. Cells were routinely cultured in the recommended high-glucose DMEM medium (Hyclone) supplemented with 10% fetal bovine serum (Hyclone), L-glutamine (2 mM), penicillin (100 mg/mL), and streptomycin (100 mg/L). Primary CAFs were isolated from 4 T1 breast tumor tissues of BalB/c mice or C3a receptor-deficient (C3aR−/−) mice by FACS. All cultures were incubated at 37 °C in a humidified atmosphere of 5% CO2.
Six- to 8-week-old female Wild-type BalB/c mice were purchased from the Chinese Academy of Medical Sciences (Beijing, China). C3aR−/− mice with a BalB/c background were kindly provided by Dr. Zhou Hong (Department of Immunology, Nanjing Medical University). The mice were kept under specific pathogen-free conditions at the Animal Center of Third Military Medical University. Six- to 8-week-old female nude mice were purchased from the Animal Institute of the Academy of Medical Science (Beijing, China). The MMTV-PyMT mice were kindly provided by Dr. Liu Xiaolong (Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences). For sacrificing the mice, they were kept in a chamber with isoflurane (concentration: 3–4%) for 2–3 min. After the induction of anesthesia, mice were immediately sacrificed by cervical dislocation. The animal studies have been conducted in accordance with the guidelines of the Institutional Animal Care and Use Committee (IACUC) of the Third Military Medical University .
The orthotopic transplanted tumorigenicity
The 4 T1 cells were routinely cultured with DMEM containing 10% fetal bovine serum until they reached 70–80% confluency. Thereafter, 6 to 8-week-old female C3aR−/− (Balb/c background) or Balb/c mice were orthotopically injected with 1 × 105 4 T1 cells in 100 μl phosphate-buffered saline per mice in the third mammary fat pad at day 0. Tumor sizes were monitored two or three times per week from day 7,and tumor volume was calculated as follows: V = (length × width2) × 0.5 . The mice were anesthetized and sacrificed 28 days after tumor inoculation. Primary tumors were dissected from the body and weighed, and tumor weight and volume were analyzed. There were six to eight mice in each group.
Lung metastasis assays
For the orthotopic model of spontaneous metastasis, 4 T1 cells were inoculated into the third mammary fat pad of WT or C3aR−/− mice on day 0, and tumor sizes were monitored three times a week. The mice were anesthetized and sacrificed on day 28 post tumor injection. Indian ink was injected into the lungs of sacrificed mice with a syringe through the trachea until the lungs were completely filled with ink. The lungs were then removed immediately and immersed in Fekete’s solution for several minutes to show the pulmonary nodules; white dots on the black lungs were observed and counted for tumor metastasis. The MMTV-PyMT mice were sacrificed at 16 weeks of age, and tumor nodules in the lungs were counted after India ink injection as indicated above.
For the co-implantation assay, a total of 5 × 104 4 T1 cells alone or mixed with 2.5 × 105 sorted CAFs from either WT or C3aR−/− mice were co-injected into the third mammary fat pad of 6 week old female Balb/c nude mice. Tumor sizes were measured twice or three times a week and tumor volumes were calculated 28 days later, mice were anaesthetized and sacrificed. Filling the lungs with ink so that metastatic nodules were visible, the number of metastases was compared among three groups, each of which used 5–7 mice.
C3aR antagonism treatment
A selective antagonist of C3aR (C3aRA, SB290157, Cayman) was used for C3aR blockade. 4 T1 tumor-bearing mice were randomly assigned to control or experimental groups on day 1 post tumor inoculation and were intraperitoneally injected with C3aRA (10 mg/kg body weight) or PBS twice weekly, the mice were euthanized and sacrificed 28 days after tumor injection and the lung nodules were calculated and analyzed.
The MMTV-PyMT mice were treated with C3aRA(10 mg/Kg bodyweight) in 200 ul or PBS as early as 4-weeks of age, and they were sacrificed at 16 weeks of age. Lung metastases were identified and compared between the C3aRA treatment and control groups.
Protein was extracted from the cells or tumor tissues with RIPA buffer, dissolved with SDS–polyacrylamide gels and transferred to PVDF membranes (Millipore, 0.45 μm). The membranes were then blocked with 5% BSA at 37 °C for 1 h and incubated with primary antibodies at 4 °C overnight. Primary antibodies against a-SMA (clone: E184, Abcam,1:1000 diluted), p-AKT-Ser473 (clone: D9E, CST, 1:1000 diluted), AKT (CST, 1:1000), GAPDH (Beyotime, AF0006, 1:1000 diluted), Vimentin (Beyotime, AF0318, 1:1000 diluted), and E-Cadherin (Beyotime, AF0138,1:1000 diluted),α-Tubulin Rabbit Polyclonal Antibody (Beyotime, AF0001, 1:1000 diluted), were used. After washing with 0.1% TBST several times, the membranes were incubated with goat anti-rabbit secondary antibodies (Beyotime, 1:5000) or goat anti-mouse secondary antibodies (Beyotime, 1:5000) for 1 h at room temperature. The protein expression levels were visualized by the enhanced chemo-luminescence assay (ECL, Beyotime). Images were captured by using FluorChem HD2 system.
For in vitro stimulation of fibroblasts assay, sorted fibroblasts were seeded in 24-well plates in DMEM containing 10% FBS and 100 units/ml penicillin/streptomycin until 80% confluency. After washing with PBS, the cells were cultured in fresh serum-free media or stimulated with different doses of recombinant mouse C3a (rmC3a) (R&D). Supernatants were collected 48 h later, and filter sterilized using a 0.22 μm filter. The TGFβ1-ELISA kit (Dakewe, 1,217,102) was used for TGF-β1 detection. All experiments were performed according to the manufacturer’s instructions.
Quantitative PCR and RNA sequencing
The RNA extraction of C3aR+/+ or C3aR−/− CAFs were performed as previously described in . In brief, 500 ng of RNA was reverse-transcribed using the PrimeScript™ RT Master Mix kit (Takakra). Real-time PCR was conducted with SYBR Premix Ex Taq™ II (Takara) to quantify the relative expression of mRNA. All primer sequences for real-time qPCR are shown in (Additional file 1: Table S1). Relative changes were quantified using the 2 − ΔΔCT method .
For RNA sequencing, after RNA collection from four WT tumors and four C3aR−/− tumor tissues, sequencing libraries were generated using NEBNext® UltraTM RNA Library Prep Kit for Illumina® (NEB, USA). The library preparations were sequenced on an Illumina Hiseq platform and was performed by Novogene (Beijing, China). The DESeq2 R package was used for differential expression analysis of two groups. The clusterProfiler R package was used to conduct Gene Ontology (GO) enrichment analysis on differentially expressed genes to correct gene length deviation. The significance of the differential gene expression was as setting the p value threshold at 0.05.
Analysis of the 2012 Cancer genome atlas (TCGA) data set
The mRNA profiles for tumor samples of 526 invasive breast cancer patients were downloaded in February 2019 from the cBioPortal for cancer genomics (www.cbioportal.com) [27, 28, 29]. Spearman’s correlation analyses were conducted to determine the correlation between C3 expression and expression of CAF markers and functional cytokine transcript levels. P-values < 0.05 were considered statistically significant.
Transwell and wound-healing assays
Transwell assays were performed in 24-well inserts (Falcon 8.0-μm pore size, Corning) for migration or invasion assays. 4 T1 or EO771 cells were serum starved overnight. Then, 2 × 104 tumor cells were plated in transwell inserts or matrigel-coated inserts as previously described , followed by co-culturing with 1 × 105 CAFs isolated from WT mice or C3aR−/− mice for 24 h. Cells in the upper part of the transwells were removed with a cotton swab, and the migrated cells were fixed in 4% paraformaldehyde and stained with 0.5% crystal violet. The membrane was observed under the microscope and photographed to calculate the total number of cells. Each experiment was repeated at least three times independently.
For the wound-healing assay, 2 × 105/wells of 4 T1 were seeded in six-well plates. A pipette tip was used to draw a gap on the plates. The sorted WT CAFs or C3aR−/− CAFs were plated in the upper inserts. The migration of 4 T1 to the blank area was observed under the microscope and imaged at a specific time point.
Flow cytometry assays and CAFs isolation
The mammary tumors were dissected from the mice at the indicated time points. The tissues were cut into pieces and digested with collagen IV (1 mg/ml, sigma) and Dispase II (1 mg/ml, Sigma) and they were shaking for 1 h at 37 °C. The tissue/media mixture was strained using a 70 μm cell strainer for single cell suspension preparation. The cells were added anti-mouse CD16/CD32 (Clone 93, Biolegend) and incubated on ice for 10 min. Thereafter they were labeled with anti-mouse PDGFRα (Clone APA5, Biolegend) and anti-mouse F4/80 antibodies (Clone BM8, Biolegend) at a 1:100 dilution for 30 min on ice. Cells were fixed and permeabilized using Fixation/permeabilization concentrate (Ebioscience) and labeled with anti-Ki67 (Clone SolA15, Ebioscience). The FACS data were acquired using a CantoII flowcytometer (BD) and analyzed with FlowJo software. The living PDGFRα+F4/80− CAFs were sorted using Aria II cell sorter (BD Bioscience).
Sorted CAFs were seeded in 24-well plates in DMEM containing 10% FBS and 100 units/ml penicillin/streptomycin. Subsequently, non-adherent cells were removed by extensive washing with PBS and adherent cells were treated as indicated for further analysis.
For the cell immunofluorescence assay sorted CAFs were seeded in a cell culture dish (NEST) and cultured overnight. The CAFs were fixed in 4% paraformaldehyde for 20 min and incubated with solution (including 1% BSA and 0.3% Triton X-100 in PBS) for permeabilization and blockade of unspecific binding at room temperature for 45 min. The primary antibody against mouse C3aR (14D4, Hycult biotech, 1:50 diluted) and rabbit anti-mouse α smooth muscle actin (E184, Abcam, 1:500 diluted) were incubated at 4 °C overnight. For tumor tissues, frozen sections of mammary tissue from WT/C3aR−/− mice were fixed with ice-cold 4% paraformaldehyde for 15 min at room temperature. After washing with PBS, the sections were blocked with 5% bovine serum albumin-containing PBS for 1 h at room temperature, followed by primary antibody incubation overnight at 4 °C. The following antibodies were used for tissue immunofluorescence staining: E-Cadherin mouse monoclonal antibodies (AF0138, Beyotime, 1:50 diluted) and Vimentin Mouse Monoclonal Antibodies (AF0318, Beyotime, 1:100 diluted). Alexa Fluor 488-labeled goat anti-rabbit IgG (1:200 dilution, Abcam), Alexa Fluor 488-labeled goat anti-Armenian hamster antibody (1:200 dilution, Abcam),or Alexa Fluor647-labeled goat anti-rabbit IgG (1:200 dilution, Abcam) were used as secondary antibodies. After counterstaining with DAPI (Beyotime), sections were imaged under an Olympus Fluorescence Microscope.
RNA-sequencing data has been deposited to NCBI (PRJNA600392).
Data were expressed as the means ± SEM after more than three repeated independent experiments and were analyzed using the GraphPad 7.0 software. Either two-tailed unpaired Students T-tests or other statistical methods indicated were used to evaluate the differences. P-values < 0.05 were considered statistically significant.
C3aR deficiency reduced metastasis of breast cancer to the lungs
Involvement of CAFs in C3aR mediated breast cancer lung metastasis
C3 expression is correlated with CAF activation and function makers in human breast cancer
C3aR signaling is involved in CAFs activation
The elevated expression of soluble factors in CAFs has been suggested to act as a possible regulator of adjacent cancer cell migration. To test this, we co-cultured 4 T1 cells or EO771 cells with CAFs isolated from C3aR+/+ or C3aR−/− tumor-bearing mice, respectively. Scratch assay and transwell migration/invasion assays confirmed that the co-culturing of C3aR−/− CAFs with 4 T1 cells rarely stimulated breast cancer epithelial cell migration and invasion, while co-culturing of C3aR+/+ CAFs significantly promoted EO771 cells migration and invasion (Fig. 4b-d). Moreover, recombinant mouse C3a did not only induce CAFs phenotype markers characterized by alpha smooth muscle actin (a-SMA) expression (Fig. 4e), but it also stimulated the expression and secretion of TGFβ, a crucial pro-metastasis cytokine effector of CAFs. Furthermore, the expression of genes associated with phenotype markers and functional cytokines of CAFs were upregulated under C3a stimulation (Fig. 4g). For the analysis of whether C3aR signaling on CAFs altered the ability of promoting metastasis in-vivo, we injected 4 T1 cells alone, with WT CAFs or with C3aR−/− CAFs orthotopically into the mammary fat pad of immunodeficient nude mice. Co-inoculation of 4 T1 cells with WT CAFs accelerated lung metastasis, compared with 4 T1 alone, while C3aR signaling deficiency in CAFs abrogated its metastasis-promoting effect (Fig. 4h and i). These results indicated that C3a acts directly on CAFs in a C3aR dependent manner.
PI3K-AKT signaling is involved in C3aR signaling-driven CAFs activation
Pharmacological inhibition of C3aR signaling inhibits breast cancer metastasis
Breast cancer related deaths are primarily attributed to metastasis . It is well known that CAFs form the major population of tumor stromal cells and serve as a main source of tumor extracellular matrix components [31, 36]. Crosstalk between cancer cells and CAFs is involved in the metastasis of breast cancer , yet the master regulators and their underlying mechanisms remain largely unknown. In this study, we demonstrated that C3a-C3aR signaling facilitates the metastasis of breast cancer via modulating CAFs function. Activation of PI3K/AKT signaling was involved in C3a-C3aR signaling which drive CAF activation. Moreover, previous studies demonstrated that PI3K-AKT signaling is involved in CAFs’ function [10, 30], and we and others have revealed that C3aR signaling could promote PI3K-AKT activation . Genetic or pharmacological blockade of C3aR signaling effectively inhibited lung metastasis in breast cancer mouse models. Our findings suggest C3aR signaling might be a promising anti-metastatic strategy in breast cancer therapy.
Previously, complement activation has been identified as an important element in infection [1, 38]. However, new insights regarding the mechanism of complement activation have revealed an additional complex level involved in biology and its impact on diseases. A series of complement components accumulated in TME determined tumor development by binding to their corresponding receptors. Our findings were in line with those from previous studies which demonstrated that C3a-C3aR signaling promotes tumor growth via the alteration of TME [6, 7, 9, 33, 39]. It was reported that B16 tumor growth in C3aR deficient mice was suppressed by relieving the neutrophil and CD4+ T cell responses . Additionally, C3aR blockade delayed tumor growth of orthotopic inoculated CMT and LLC in an immunocompetent model of lung cancer . Finally, intracellular activation of complement C3 contributed to tumor growth via the modulation of tumor associated macrophages [10, 40] . A recent study demonstrated that tumor-cell-derived C3 activates the C3a receptor of the choroid plexus epithelium to disrupt the blood-CSF barrier, which promotes leptomeningeal metastasis . However, whether and how C3a-C3aR signaling promotes the metastasis of breast cancer remains unknown.
In this study, we demonstrated that C3a-C3aR signaling promotes breast cancer metastasis via the modulation of CAFs. CAFs are the largest population of stromal cells within breast cancers and accumulating evidence suggest that CAFs play a critical role in cancer metastasis by releasing cytokines, chemokines, and extracellular matrix . Our findings suggest that C3a-C3aR signaling promotes the activation of CAFs as characterized by enhanced expression of activation markers, such as alpha-SMA. Consistent with our results, previous studies have revealed a key role of C3a-C3aR signaling in the promotion of fibrosis, a process orchestrated by activated fibroblast.
Accumulating evidence suggest that EMT induction is one of the most important mechanisms for cancer metastasis [22, 42], and the down-regulation of epithelial marker E-cadherin and the upregulation of mesenchymal marker vimentin are typical characteristics of EMT . Our data suggest that C3aR signaling activated CAFs augmenting metastasis by promoting EMT of tumor cells. EMT is one of the major mechanisms in tumor metastasis, and TGFβ has been approved as a critical promoter for transforming epithelial cells into mesenchymal cells . We assumed that C3aR signaling activated CAFs facilitated EMT of tumor cells via TGFβ, which was induced by recombinant mouse C3a in-vitro. Decreased secretion of pro-metastasis factors (such as TGF-β, platelet-derived growth factor [PDGF], hepatocyte growth factor [HGF]) involved in CAFs activity were observed in the C3aR deficiency CAFs in the 4 T1-bearing model. Moreover, increasing TGF-β and CAF markers were found in C3a-treated CAFs in vitro. Importantly, the effects of C3aR signaling on metastasis, independent from mechanisms operating in primary tumors, did not delay the growth of the primary tumor. This finding, which is in contrast with our previously reported findings, can be attributed to the difference in tumor type, as was previously reported for C5aR signaling in cancer .
Mechanically, we identified that PI3K/AKT signaling plays an essential role in C3a/C3aR signaling mediated the activation of CAFs. Our data suggest that recombinant C3a induced the phosphorylation of AKT and C3aR antibodies. Moreover, increasing TGF-β and CAF markers were found in C3a-treated CAFs in vitro. Additionally, C3a-stimulated elevation of TGFβ and migration capacity of 4 T1 cells can be blocked by C3aR antibodies and C3aR antagonists assist with the suppression of AKT-phosphorylation. Consistent with our data, previous reports showed that alterations in the PI3K/AKT pathway are involved in the activation of tumor stromal cells .
In summary, our study showed that C3aR signaling plays a unique role in promoting lung metastasis of breast cancer by modulating CAFs. C3aR deficiency inhibits pro-metastatic cytokines production by CAFs in a 4 T1 tumor model. Moreover, increased expression of TGF-β and CAF markers were found in C3a-treated CAFs in vitro. Mechanically, we identified that PI3K/AKT signaling plays an essential role in C3a-C3aR signaling mediated by CAFs activation. Our data demonstrated that targeting C3aR might be an effective strategy in tumor metastasis control in breast cancer.
We thank Zhou Hong (Department of Immunology, Nanjing Medical University) for kindly providing C3aR knockout mice; Liu Xiaolong (Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences) for kindly providing MMTV-PyMT mice.
CS, BG and BZ contributed the conception and design. CS, HL and XW contributed to the development of methodology. CS and HZ discussed the results and analyzed the data and wrote the manuscript conceived and designed the experiments. CS and FY contributed to the animal experiments. CS and JG contributed to statistical analysis. CH and LZ contributed to the FACs sorting. CS and HZ revised the manuscript. All of the authors were involved in the discussions.
This work was supported by the National Nature Science Foundation of China (No. 81472648 and No. 81620108023 to Bo Zhu, No. 31570866 to Bo Guo, No.31900627 to Haoran Zha).
Ethics approval and consent to participate
The animal studies have been conducted in accordance with the guidelines of the Institutional Animal Care and Use Committee (IACUC) of the Third Military Medical University .
Consent for publication
The authors declare that they have no competing interests.
- 7.Kwak JW, Laskowski J, Li HY, McSharry MV, Sippel TR, Bullock BL, Johnson AM, Poczobutt JM, Neuwelt AJ, Malkoski SP, et al. Complement activation via a C3a receptor pathway alters CD4(+) T lymphocytes and mediates lung Cancer progression. Cancer Res. 2018;78(1):143–56.PubMedCrossRefPubMedCentralGoogle Scholar
- 15.Gu H, Fisher AJ, Mickler EA, Duerson F 3rd, Cummings OW, Peters-Golden M, Twigg HL 3rd, Woodruff TM, Wilkes DS, Vittal R. Contribution of the anaphylatoxin receptors, C3aR and C5aR, to the pathogenesis of pulmonary fibrosis. FASEB J : official publication of the Federation of American Societies for Experimental Biology. 2016;30(6):2336–50.CrossRefGoogle Scholar
- 20.Dumont N, Liu B, DeFilippis RA, Chang H, Rabban JT, Karnezis AN, Tjoe JA, Marx J, Parvin B, Tlsty TD. Breast fibroblasts modulate early dissemination, tumorigenesis, and metastasis through alteration of extracellular matrix characteristics. Neoplasia. 2013;15(3):249–IN247.PubMedPubMedCentralCrossRefGoogle Scholar
- 23.Djurec M, Grana O, Lee A, Troule K, Espinet E, Cabras L, Navas C, Blasco MT, Martin-Diaz L, Burdiel M, et al. Saa3 is a key mediator of the protumorigenic properties of cancer-associated fibroblasts in pancreatic tumors. Proc Natl Acad Sci U S A. 2018;115(6):E1147–56.PubMedPubMedCentralCrossRefGoogle Scholar
- 28.Cancer Genome Atlas N: Comprehensive molecular portraits of human breast tumours. Nature. 2012;490(7418):61–70.Google Scholar
- 37.Santolla MF, Lappano R, Cirillo F, Rigiracciolo DC, Sebastiani A, Abonante S, Tassone P, Tagliaferri P, Di Martino MT, Maggiolini M, et al. miR-221 stimulates breast cancer cells and cancer-associated fibroblasts (CAFs) through selective interference with the A20/c-Rel/CTGF signaling. J Exp Clin Cancer Res. 2018;37(1):94.PubMedPubMedCentralCrossRefGoogle Scholar
- 41.Cirillo F, Lappano R, Bruno L, Rizzuti B, Grande F, Guzzi R, Briguori S, Miglietta AM, Nakajima M, Di Martino MT, et al. AHR and GPER mediate the stimulatory effects induced by 3-methylcholanthrene in breast cancer cells and cancer-associated fibroblasts (CAFs). J Exp Clin Cancer Res. 2019;38(1):335.PubMedPubMedCentralCrossRefGoogle Scholar
Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.