Targeting ERK-MYD88 interaction leads to ERK dysregulation and immunogenic cancer cell death.

The quest for targeted therapies is critical in the battle against cancer. The RAS/MAP kinase pathway is frequently implicated in neoplasia, with ERK playing a crucial role as the most distal kinase in the RAS signaling cascade. Our previous research demonstrated that the interaction between ERK and MYD88, an adaptor protein in innate immunity, is crucial for RAS-dependent transformation and cancer cell survival. In this study, we examine the biological consequences of disrupting the ERK-MYD88 interaction through the ERK D-recruitment site (DRS), while preserving ERK's kinase activity. Our results indicate that EI-52, a small-molecule benzimidazole targeting ERK-MYD88 interaction induces an HRI-mediated integrated stress response (ISR), resulting in immunogenic apoptosis specific to cancer cells. Additionally, EI-52 exhibits anti-tumor efficacy in patient-derived tumors and induces an anti-tumor T cell response in mice in vivo. These findings suggest that inhibiting the ERK-MYD88 interaction may be a promising therapeutic approach in cancer treatment.

The hexosamine pathway and coat complex II promote malignant adaptation to nutrient scarcity.

The glucose-requiring hexosamine biosynthetic pathway (HBP), which produces UDP-N-acetylglucosamine for glycosylation reactions, promotes lung adenocarcinoma (LUAD) progression. However, lung tumor cells often reside in low-nutrient microenvironments, and whether the HBP is involved in the adaptation of LUAD to nutrient stress is unknown. Here, we show that the HBP and the coat complex II (COPII) play a key role in cell survival during glucose shortage. HBP up-regulation withstood low glucose-induced production of proteins bearing truncated N-glycans, in the endoplasmic reticulum. This function for the HBP, alongside COPII up-regulation, rescued cell surface expression of a subset of glycoproteins. Those included the epidermal growth factor receptor (EGFR), allowing an EGFR-dependent cell survival under low glucose in anchorage-independent growth. Accordingly, high expression of the HBP rate-limiting enzyme GFAT1 was associated with wild-type EGFR activation in LUAD patient samples. Notably, HBP and COPII up-regulation distinguished LUAD from the lung squamous-cell carcinoma subtype, thus uncovering adaptive mechanisms of LUAD to their harsh microenvironment.

Caspase-8 deficiency induces a switch from TLR3 induced apoptosis to lysosomal cell death in neuroblastoma.

In cancer cells only, TLR3 acquires death receptor properties by efficiently triggering the extrinsic pathway of apoptosis with Caspase-8 as apical protease. Here, we demonstrate that in the absence of Caspase-8, activation of TLR3 can trigger a form of programmed cell death, which is distinct from classical apoptosis. When TLR3 was activated in the Caspase-8 negative neuroblastoma cell line SH-SY5Y, cell death was accompanied by lysosomal permeabilization. Despite caspases being activated, lysosomal permeabilization as well as cell death were not affected by blocking caspase-activity, positioning lysosomal membrane permeabilization (LMP) upstream of caspase activation. Taken together, our data suggest that LMP with its deadly consequences represents a "default" death mechanism in cancer cells, when Caspase-8 is absent and apoptosis cannot be induced.

A Gender-Dependent Molecular Switch of Inflammation via MyD88/Estrogen Receptor-Alpha Interaction.

INTRODUCTION: Most Toll-like receptors and IL-1/IL-18 receptors activate a signaling cascade via the adaptor molecule MyD88, resulting in NF-κB activation and inflammatory cytokine and chemokine production. Females are less susceptible than males to inflammatory conditions, presumably due to protection by estrogen. The exact mechanism underlying this protection is unknown. METHODS: MCF7 cells expressing wild-type or mutated LXXLL motif were used to determine MyD88/estrogen receptor (ER)-a interaction by immunoprecipitation and cell activation by ELISA and luciferase reporter assay. IL-1b and/or E2 were used to activate MCF7 cells expressing normal or knocked down levels of PRMT1. Finally, in situ proximity ligation assay with anti-MyD88 and anti-methylated ER-a (methER-a) antibodies was used to evaluate MyD88/methylated ER-a interaction in THP1 cells and histological sections. RESULTS: We show that MyD88 interacts with a methylated, cytoplasmic form of estrogen receptor-alpha (methER-α). This interaction is required for NF-κB transcriptional activity and pro-inflammatory cytokine production, and is dissociated by estrogen. Importantly, we show a strong gender segregation in gametogenic reproductive organs, with MyD88/methER-α interactions found in testicular tissues and in ovarian tissues from menopausal women, but not in ovaries from women age 49 and less - suggesting a role for estrogen in disrupting this complex in situ. DISCUSSION: Collectively, our results indicate that the formation of MyD88/methER-α complexes during inflammatory signaling and their disruption by estrogen may represent a mechanism that contributes to gender bias in inflammatory responses.

Cisplatin unleashes Toll-like receptor 3-mediated apoptosis through the downregulation of c-FLIP in malignant mesothelioma.

Toll-like receptor 3 (TLR3) is an immune receptor that behaves like a death receptor in tumor cells, thereby providing an original target for cancer therapy. The therapeutic potential of TLR3 targeting in malignant mesothelioma, an aggressive and incurable neoplasia of the pleura and peritoneum, has so far not been addressed. We investigated TLR3 expression and sensitivity of human mesothelioma cell lines to the synthetic dsRNA Poly(I:C), alone or in combination with cisplatin, the gold standard chemotherapy in mesothelioma. Activation of TLR3 by Poly(I:C) induced apoptosis of 4/8 TLR3-positive cell lines but not of TLR3-negative cell lines. The combined cisplatin/Poly(I:C) treatment enhanced apoptosis of 3/4 Poly(I:C)-sensitive cell lines and overcame resistance to Poly(I:C) or cisplatin alone in 2/4 cell lines. Efficacy of the combined treatment relied on cisplatin-induced downregulation of c-FLIP, the main regulator of the extrinsic apoptotic pathway, leading to an enhanced caspase-8-mediated pathway. Of note, 6/6 primary cell samples isolated from patients with peritoneal mesothelioma expressed TLR3. Patient-derived cells were sensitive to Poly(I:C) alone while the combined cisplatin/Poly(I:C) treatment induced dramatic cell death. Our findings demonstrate that TLR3 targeting in combination with cisplatin presents an innovative therapeutic strategy in mesothelioma.

Toll-like receptor 3 downregulation is an escape mechanism from apoptosis during hepatocarcinogenesis.

BACKGROUND & AIMS: Low levels of toll-like receptor 3 (TLR3) in patients with hepatocellular carcinoma (HCC) are associated with poor prognosis, primarily owing to the loss of inflammatory signaling and subsequent lack of immune cell recruitment to the liver. Herein, we explore the role of TLR3-triggered apoptosis in HCC cells. METHODS: Quantitative reverse transcription PCR, western blotting, immunohistochemistry and comparative genomic hybridization were used to analyze human and mouse HCC cell lines, as well as surgically resected primary human HCCs, and to study the impact of TLR3 expression on patient outcomes. Functional analyses were performed in HCC cells, following the restoration of TLR3 by lentiviral transduction. The role of TLR3-triggered apoptosis in HCC was analyzed in vivo in a transgenic mouse model of HCC. RESULTS: Lower expression of TLR3 in tumor compared to non-tumor matched tissue was observed at both mRNA and protein levels in primary HCC, and was predictive of shorter recurrence-free survival after surgical resection in both univariate (hazard ratio [HR] 1.79; 95% CI 1.04-3.06; p = 0.03) and multivariate analyses (HR 1.73; CI 1.01-2.97; p = 0.04). Immunohistochemistry confirmed frequent downregulation of TLR3 in human and mouse primary HCC cells. None of the 6 human HCC cell lines analyzed expressed TLR3, and ectopic expression of TLR3 following lentiviral transduction not only restored the inflammatory response but also sensitized cells to TLR3-triggered apoptosis. Lastly, in the transgenic mouse model of HCC, absence of TLR3 expression was accompanied by a lower rate of preneoplastic hepatocyte apoptosis and accelerated hepatocarcinogenesis without altering the tumor immune infiltrate. CONCLUSION: Downregulation of TLR3 protects transforming hepatocytes from direct TLR3-triggered apoptosis, thereby contributing to hepatocarcinogenesis and poor patient outcome. LAY SUMMARY: Hepatocellular carcinoma (HCC) is a heterogeneous disease associated with a poor prognosis. In patients with HCC, TLR3 downregulation is associated with reduced survival. Herein, we show that the absence of TLR3 is associated with a lower rate of apoptosis, and subsequently more rapid hepatocarcinogenesis, without any change to the immune infiltrate in the liver. Therefore, the poor prognosis associated with low TLR3 expression in HCC is likely linked to tumors ability to escape apoptosis. TLR3 may become a promising therapeutic target in TLR3-positive HCC.

Release of c-FLIP brake selectively sensitizes human cancer cells to TLR3-mediated apoptosis.

Toll-like receptor 3 (TLR3) mediates innate immune responses by sensing viral dsRNA, but also induces apoptosis selectively in cancer cells. Our analysis by immunohistochemistry revealed that TLR3 is frequently overexpressed in 130 non-small cell lung cancer (NSCLC) patients' samples compared with normal bronchial epithelium (P < 0.0001, Mann-Whitney test), supporting the therapeutic potential of TLR3 ligand for this type of cancer. However, a proportion of TLR3-expressing cancer cell lines, including NSCLC, remain resistant to TLR3-mediated apoptosis, and the underlying mechanism of resistance remains unclear. We here investigated the molecular basis conferring resistance to non-transformed vs. transformed cells against TLR3-mediated cell death. In non-transformed epithelial cells cellular FLICE-like inhibitory protein (c-FLIP) and cellular Inhibitor of APoptosis (cIAPs) ubiquitin ligases exerted an efficient double brake on apoptosis signaling. In contrast, releasing only one of these two brakes was sufficient to overcome the resistance of 8/8 cancer cell lines tested. Remarkably, the release of the c-FLIP, but not cIAPs, brake only results in the sensitization of all human cancer cells to TLR3-mediated apoptosis. Taking advantage of the difference between transformed and non-transformed cells, we developed a rational strategy by combining the chemotherapeutic agent paclitaxel, which decreases c-FLIP expression, with TLR3 ligand. This combination was highly synergistic for triggering apoptosis in cancer cells but not in non-transformed cells. In vivo, the combination of paclitaxel with dsRNA delayed tumor growth and prolonged survival in a mouse xenograft lung tumor model. In conclusion, combining the release of the c-FLIP brake with TLR3 ligand synergizes to selectively kill cancer cells, and could represent an efficient and safe therapy against TLR3-expressing cancers such as NSCLC.

N-glycosylation of mouse TRAIL-R restrains TRAIL-induced apoptosis.

The sensitivity of cells to death receptor-induced apoptosis is commonly controlled by multiple checkpoints in order to limit induction of excessive or unnecessary death. Although cytotoxic in various cancer cells, tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) does not trigger apoptosis in most non-transformed cells. The molecular nature of the checkpoints that normally protect the cells from TRAIL-induced death are not fully understood. Endoplasmic reticulum (ER) stress has been reported to switch the sensitivity of human cells to the cytotoxic effect of TRAIL, suggesting that this cellular state perturbs some of these protective mechanisms. We found that tunicamycin (TU), but no other ER stress inducers, sensitized mouse fibroblasts and hippocampal neuronal cells to TRAIL-induced apoptosis. Importantly, the sensitization was specific to TRAIL and not caused by differences in ER stress induction. Instead, it relied on the inhibition of N-glycosylation of the mouse TRAIL receptor (mTRAIL-R). Inhibition of N-glycosylation did not alter cell surface expression of mTRAIL-R but enhanced its ability to bind TRAIL, and facilitated mTRAIL-R oligomerization, which resulted in enhanced death-inducing signaling complex (DISC) formation and caspase-8 activation. Remarkably, reconstitution of mTRAIL-R-deficient cells with a version of mTRAIL-R mutated for the three N-glycosylation sites identified in its ectodomain confirmed higher sensitivity to TRAIL-induced apoptosis. Together, our results demonstrate that inhibition of N-glycosylation of mTRAIL-R, and not ER stress induction, sensitizes mouse cells to TRAIL-induced apoptosis. We therefore reveal a new mechanism restraining TRAIL cytotoxicity in mouse cells.

Whole exome sequencing in three families segregating a pediatric case of sarcoidosis.

BACKGROUND: Sarcoidosis (OMIM 181000) is a multi-systemic granulomatous disorder of unknown origin. Despite multiple genome-wide association (GWAS) studies, no major pathogenic pathways have been identified to date. To find out relevant sarcoidosis predisposing genes, we searched for de novo and recessive mutations in 3 young probands with sarcoidosis and their healthy parents using a whole-exome sequencing (WES) methodology. METHODS: From the SARCFAM project based on a national network collecting familial cases of sarcoidosis, we selected three families (trios) in which a child, despite healthy parents, develop the disease before age 15 yr. Each trio was genotyped by WES (Illumina HiSEQ 2500) and we selected the gene variants segregating as 1) new mutations only occurring in affected children and 2) as recessive traits transmitted from each parents. The identified coding variants were compared between the three families. Allelic frequencies and in silico functional results were analyzed using ExAC, SIFT and Polyphenv2 databases. The clinical and genetic studies were registered by the ClinicalTrials.gov - Protocol Registration and Results System (PRS) ( https://clinicaltrials.gov ) receipt under the reference NCT02829853 and has been approved by the ethical committee (CPP LYON SUD EST - 2 - REF IRB 00009118 - September 21, 2016). RESULTS: We identified 37 genes sharing coding variants occurring either as recessive mutations in at least 2 trios or de novo mutations in one of the three affected children. The genes were classified according to their potential roles in immunity related pathways: 9 to autophagy and intracellular trafficking, 6 to G-proteins regulation, 4 to T-cell activation, 4 to cell cycle and immune synapse, 2 to innate immunity. Ten of the 37 genes were studied in a bibliographic way to evaluate the functional link with sarcoidosis. CONCLUSIONS: Whole exome analysis of case-parent trios is useful for the identification of genes predisposing to complex genetic diseases as sarcoidosis. Our data identified 37 genes that could be putatively linked to a pediatric form of sarcoidosis in three trios. Our in-depth focus on 10 of these 37 genes may suggest that the formation of the characteristic lesion in sarcoidosis, granuloma, results from combined deficits in autophagy and intracellular trafficking (ex: Sec16A, AP5B1 and RREB1), G-proteins regulation (ex: OBSCN, CTTND2 and DNAH11), T-cell activation (ex: IDO2, IGSF3), mitosis and/or immune synapse (ex: SPICE1 and KNL1). The significance of these findings needs to be confirmed by functional tests on selected gene variants.

Granulomatous lung inflammation is nanoparticle type-dependent.

BACKGROUND: Nanoparticles are increasingly suspected as a strong etiologic factor of granuloma formation. AIM OF THE STUDY: The aim of our study was to compare lung inflammatory response and histology changes following exposure of mice to two widely used nanoparticles: carbon nanotubes (MWCNT) and cadmium-based nanoparticles (QDOT705) in an attempt to better our understanding of granulomatous inflammation. MATERIALS AND METHODS: Various groups of mice were included: control mice and mice that were intranasally instilled with QDOT or MWCNT. At defined time points post-challenge, bronchoalveolar lavages (BALs) and lung tissues were collected to study inflammatory and histologic changes. RESULTS: Analyses of lung BAL fluids and tissues of nanoparticles-challenged mice in comparison to controls found: (1) increased cellularity in BALs, (2) increase of total protein concentration, LDH activity and proteolytic activity in BALs; (3) patchy granulomas, (4) macrophages, CD3 ± T, Treg and B cell infiltration in granulomatous areas; and (5) altered regulation of key inflammatory mediators and receptors. Importantly, these changes were nanoparticle type-dependent. CONCLUSION: Our work enhances understanding of nanoparticles-induced lung inflammatory and histological changes that result in granuloma formation. We provide compelling evidence that not only exposure to nanoparticles leads to granulomatous lung inflammation, but the severity of this latter is nanostructure type-dependent. Of importance, while nanotechnology has the potential to revolutionize various fields including medicine, nanoparticles form the potential for an entirely new lung health risk that it is necessary to take seriously into consideration by setting up and/or reinforcing adequate safety measures.

Familial vs. sporadic sarcoidosis: BTNL2 polymorphisms, clinical presentations, and outcomes in a French cohort.

BACKGROUND: The occurrence of familial forms of sarcoidosis (OMIM 181100) suggests a genetic predisposition. The involvement of butyrophilin-like 2 (BTNL2) gene (rs2076530 variant) has to be investigated. RESULTS: The study performed independent analyses of BTNL2 polymorphism, clinical phenotypes, and outcomes in familial vs. sporadic presentations in 256 sporadic and 207 familial cases from 140 families. The logistic multivariate model showed that a young age at diagnosis and the combination of lung and skin involvement at diagnosis may distinguish sporadic from familial sarcoidosis (p = 0.016 and p = 0.041). We observed also that Sarcoid Clinical Activity Classification (SCAC) profiles were significantly different between familial and sporadic cases (p = 0.0497). Variant rs2076530 was more frequent in patients than in controls (OR = 2.02; 95% CI: [1.32-3.09]) but showed no difference between sporadic and familial cases and no difference according to the clinical phenotype or the outcome. CONCLUSION: Despite a significant difference in BTNL2 polymorphism between sarcoid patients and controls, there was no such difference between familial and sporadic sarcoidosis cases and no correlation between BTNL2 polymorphism and disease severity or outcome. Thus, BTNL2 difference cannot be considered as a key marker for disease classification or patient management.

Nutrient shortage triggers the hexosamine biosynthetic pathway via the GCN2-ATF4 signalling pathway.

The hexosamine biosynthetic pathway (HBP) is a nutrient-sensing metabolic pathway that produces the activated amino sugar UDP-N-acetylglucosamine, a critical substrate for protein glycosylation. Despite its biological significance, little is known about the regulation of HBP flux during nutrient limitation. Here, we report that amino acid or glucose shortage increase GFAT1 production, the first and rate-limiting enzyme of the HBP. GFAT1 is a transcriptional target of the activating transcription factor 4 (ATF4) induced by the GCN2-eIF2α signalling pathway. The increased production of GFAT1 stimulates HBP flux and results in an increase in O-linked ß-N-acetylglucosamine protein modifications. Taken together, these findings demonstrate that ATF4 provides a link between nutritional stress and the HBP for the regulation of the O-GlcNAcylation-dependent cellular signalling.

Immune biomarkers PD-1/PD-L1 and TLR3 in malignant pleural mesotheliomas.

Malignant pleural mesothelioma (MPM) is an aggressive tumor with no effective therapy. However PD-L1/PD-1 immunity checkpoint therapies gave encouraging results; TLR3 is a programmed death factor, which triggering up-regulates PD-L1. As PD-1/PD-L1 blocking antibodies could restore antitumor immune responses alone or in combination with TLR3 agonists, we investigated PD-L1/PD-1 and TLR3 expressions in MPM to select patients for immunotherapy. Sixty-eight pleural surgical specimens, including 58 MPM (epithelioid, n = 34; biphasic, n = 11; sarcomatoid, n = 13) and 10 benign lesions, were studied. PD-L1 expression was assessed using E1L3N and SP142 clones in tumor cells (TCs) and in tumor-infiltrating lymphocytes (TILs) (positivity threshold of 1%), and compared with overall survival. PD-1, CD3 and CD8 expression by TILs, and TLR3 expression by TCs were analyzed concomitantly. PD-L1 was more expressed by sarcomatoid subtype than by other MPM (62% versus 23% and 9% for E1L3N; 38% versus 11% for SP142) (P = .01 and .04, respectively). Specificity and sensitivity of E1L3N and SP142 were of 53% and 98%, and 90% and 86%, respectively. PD-L1 expression by TILs and TCs correlated for SP142 (P = .023), and PD-L1 SP142 expression by TCs was associated with shorter overall survival (P = .016). TLR3 was expressed in most MPM, but weakly in sarcomatoid MPM. We confirm by comparing two commercially available antibodies that PD-L1 expression is higher in sarcomatoid MPM and correlates with a shorter survival. Whereas TLR3 agonists could be tested in MPM expressing TLR3, the sarcomatoid subtype could benefit from anti-PD-L1/PD-1 therapies alone or in combination.

MyD88 in DNA repair and cancer cell resistance to genotoxic drugs.

BACKGROUND: MyD88 is an adaptor molecule in Toll-like receptor and interleukin 1 receptor signaling implicated in tumorigenesis through proinflammatory mechanisms. We have recently reported that MyD88 also directly promotes optimal activation of the Ras/Erk pathway. Here we investigate MyD88 implication in the maintenance of the transformation of Ras-dependent tumors. METHODS: RNA interference was used to inhibit MyD88 expression in the colon cancer cell lines HCT116 and LS513. Apoptosis, DNA damage, p53 function, ERCC1 levels, and Ras and inflammatory signaling pathways were analyzed. Using in vitro assays and xenotransplantation in nude mice (five per group), HCT116 tumor growth was assessed following MyD88 knockdown in presence or absence of chemotherapy. RESULTS: MyD88 exerts antiapoptotic functions in colon cancer cells via the Ras/Erk, but not the NF-κB, pathway. MyD88 inhibition leads to defective ERCC1-dependent DNA repair and to accumulation of DNA damage, resulting in cancer cell death via p53. Furthermore, we show that knocking down MyD88 sensitizes cancer cells to genotoxic agents such as platinum salts in vitro and in vivo. Indeed, HCT116 tumor growth following treatment with a combination of suboptimal MyD88 inhibition and suboptimal doses of cisplatin (fold tumor increase = 5.4 ± 1.6) was statistically significantly reduced in comparison to treatment with doxycycline alone (12.4 ± 3.1) or with cisplatin alone (12.5 ± 2.6) (P = .005 for both, one-sided Student t test). CONCLUSIONS: Collectively, these results indicate a novel and original link between inflammation, DNA repair, and cancer, and provide further rationale for MyD88 as a potential therapeutic target in Ras-dependent cancers, in the context of concomitant genotoxic chemotherapy.

Cleaved/associated TLR3 represents the primary form of the signaling receptor.

TLR3 belongs to the family of intracellular TLRs that recognize nucleic acids. Endolysosomal localization and cleavage of intracellular TLRs play pivotal roles in signaling and represent fail-safe mechanisms to prevent self-nucleic acid recognition. Indeed, cleavage by cathepsins is required for native TLR3 to signal in response to dsRNA. Using novel Abs generated against TLR3, we show that the conserved loop exposed in LRR12 is the single cleavage site that lies between the two dsRNA binding sites required for TLR3 dimerization and signaling. Accordingly, we found that the cleavage does not dissociate the C- and N-terminal fragments, but it generates a very stable "cleaved/associated" TLR3 present in endolysosomes that recognizes dsRNA and signals. Moreover, comparison of wild-type, noncleavable, and C-terminal-only mutants of TLR3 demonstrates that efficient signaling requires cleavage of the LRR12 loop but not dissociation of the fragments. Thus, the proteolytic cleavage of TLR3 appears to fulfill function(s) other than separating the two fragments to generate a functional receptor.

Targeting pattern recognition receptors in cancer immunotherapy.

Pattern recognition receptors (PRRs) are known for many years for their role in the recognition of microbial products and the subsequent activation of the immune system. The 2011 Nobel Prize for medicine indeed rewarded J. Hoffmann/B. Beutler and R. Steinman for their revolutionary findings concerning the activation of the immune system, thus stressing the significance of understanding the mechanisms of activation of the innate immunity. Such immunostimulatory activities are of major interest in the context of cancer to induce long-term antitumoral responses. Ligands for the toll-like receptors (TLRs), a well-known family of PRR, have been shown to have antitumoral activities in several cancers. Those ligands are now undergoing extensive clinical investigations both as immunostimulant molecules and as adjuvant along with vaccines. However, when considering the use of these ligands in tumor therapy, one shall consider the potential effect on the tumor cells themselves as well as on the entire organism. Recent data indeed demonstrate that TLR activation in tumor cells could trigger both pro- or antitumoral effect depending on the context. This review discusses this balance between the intrinsic activation of PRR in tumor cells and the extrinsic microenvironment activation in term of overall effect of PRR ligands on tumor development. We review recent advances in the field and underline appealing prospects for clinical development of PRR agonists in the light of our current knowledge on their expression and activation.

Prognostic value of the expression of C-Chemokine Receptor 6 and 7 and their ligands in non-metastatic breast cancer.

BACKGROUND: Chemokines and chemokine receptors are major actors of leukocytes trafficking and some have been shown to play an important role in cancer metastasis. Chemokines CCL19, CCL20 and CCL21 and their receptors CCR6 and CCR7, were assessed as potential biomarkers of metastatic dissemination in primary breast cancer. METHODS: Biomarker expression levels were evaluated using immunohistochemistry on paraffin-embedded tissue sections of breast cancer (n = 207). RESULTS: CCR6 was expressed by tumor cells in 35% of cases. CCR7 was expressed by spindle shaped stromal cells in 43% of cases but not by tumor cells in this series. CCL19 was the only chemokine found expressed in a significant number of breast cancers and was expressed by both tumor cells and dendritic cells (DC). CCR6, CCL19 and CCR7 expression correlated with histologic features of aggressive disease. CCR6 expression was associated with shorter relapse-free survival (RFS) in univariate and but not in multivariate analysis (p = 0.0316 and 0.055 respectively), and was not associated with shorter overall survival (OS). Expression of CCR7 was not significantly associated with shorter RFS or OS. The presence of CCL19-expressing DC was associated with shorter RFS in univariate and multivariate analysis (p = 0.042 and 0.020 respectively) but not with shorter OS. CONCLUSION: These results suggest a contribution of CCR6 expression on tumor cells and CCL19-expressing DC in breast cancer dissemination. In our series, unlike what was previously published, CCR7 was exclusively expressed on stromal cells and was not associated with survival.