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The heat shock protein 27 (Hsp27) has emerged as a principal factor of the castration-resistant prostate cancer (CRPC) progression. Also, an antisense oligonucleotide (ASO) against Hsp27 (OGX-427 or apatorsen) has been assessed in different clinical trials. Here, we illustrate that Hsp27 highly regulates the expression of the human DEAD-box protein 5 (DDX5), and we define DDX5 as a novel therapeutic target for CRPC treatment. DDX5 overexpression is strongly correlated with aggressive tumor features, notably with CRPC. DDX5 downregulation using a specific ASO-based inhibitor that acts on DDX5 mRNAs inhibits cell proliferation in preclinical models, and it particularly restores the treatment sensitivity of CRPC. Interestingly, through the identification and analysis of DDX5 protein interaction networks, we have identified some specific functions of DDX5 in CRPC that could contribute actively to tumor progression and therapeutic resistance. We first present the interactions of DDX5 and the Ku70/80 heterodimer and the transcription factor IIH, thereby uncovering DDX5 roles in different DNA repair pathways. Collectively, our study highlights critical functions of DDX5 contributing to CRPC progression and provides preclinical proof of concept that a combination of ASO-directed DDX5 inhibition with a DNA damage-inducing therapy can serve as a highly potential novel strategy to treat CRPC.

ObjectiveIntercellular communication within pancreatic ductal adenocarcinoma (PDAC) dramatically contributes to metastatic processes. The underlying mechanisms are poorly understood, resulting in a lack of targeted therapy to counteract stromal-induced cancer cell aggressiveness. Here, we investigated whether ion channels, which remain understudied in cancer biology, contribute to intercellular communication in PDAC.DesignWe evaluated the effects of conditioned media from patient-derived cancer-associated fibroblasts (CAFs) on electrical features of pancreatic cancer cells (PCC). The molecular mechanisms were deciphered using a combination of electrophysiology, bioinformatics, molecular and biochemistry techniques in cell lines and human samples. An orthotropic mouse model where CAF and PCC were co-injected was used to evaluate tumour growth and metastasis dissemination. Pharmacological studies were carried out in the Pdx1-Cre, Ink4afl/flLSL-KrasG12D(KICpdx1) mouse model.ResultsWe report that the K+channel SK2 expressed in PCC is stimulated by CAF-secreted cues (8.84 vs 2.49 pA/pF) promoting the phosphorylation of the channel through an integrin–epidermal growth factor receptor (EGFR)–AKT (Protein kinase B) axis. SK2 stimulation sets a positive feedback on the signalling pathway, increasing invasiveness in vitro (threefold) and metastasis formation in vivo. The CAF-dependent formation of the signalling hub associating SK2 and AKT requires the sigma-1 receptor chaperone. The pharmacological targeting of Sig-1R abolished CAF-induced activation of SK2, reduced tumour progression and extended the overall survival in mice (11.7 weeks vs 9.5 weeks).ConclusionWe establish a new paradigm in which an ion channel shifts the activation level of a signalling pathway in response to stromal cues, opening a new therapeutic window targeting the formation of ion channel-dependent signalling hubs.

Disease progression and therapeutic resistance of prostate cancer (PC) are linked to multiple molecular events that promote survival and plasticity. We previously showed that heat shock protein 27 (HSP27) acted as a driver of castration-resistant phenotype (CRPC) and developed an oligonucleotides antisense (ASO) against HSP27 with evidence of anti-cancer activity in men with CRPC. Here, we show that the tumor suppressor Menin (MEN1) is highly regulated by HSP27. Menin is overexpressed in high-grade PC and CRPC. High MEN1mRNA expression is associated with decreased biochemical relapse-free and overall survival. Silencing Menin with ASO technology inhibits CRPC cell proliferation, tumor growth, and restores chemotherapeutic sensitivity. ChIP-seq analysis revealed differential DNA binding sites of Menin in various prostatic cells, suggesting a switch from tumor suppressor to oncogenic functions in CRPC. These data support the evaluation of ASO against Menin for CRPC.

Chromosomal instability (CIN), a feature of most adult neoplasms from their early stages onward, is a driver of tumorigenesis. However, several malignancy subtypes, including some triple-negative breast cancers, display a paucity of genomic aberrations, thus suggesting that tumor development may occur in the absence of CIN. Here we show that the differentiation status of normal human mammary epithelial cells dictates cell behavior after an oncogenic event and predetermines the genetic routes toward malignancy. Whereas oncogene induction in differentiated cells induces massive DNA damage, mammary stem cells are resistant, owing to a preemptive program driven by the transcription factor ZEB1 and the methionine sulfoxide reductase MSRB3. The prevention of oncogene-induced DNA damage precludes induction of the oncosuppressive p53-dependent DNA-damage response, thereby increasing stem cells' intrinsic susceptibility to malignant transformation. In accord with this model, a subclass of breast neoplasms exhibit unique pathological features, including high ZEB1 expression, a low frequency of TP53 mutations and low CIN.

Breast cancer stem cells (bCSCs) have been implicated in tumor progression and therapeutic resistance; however, the molecular mechanisms that define this state are unclear. We have performed two microRNA (miRNA) gain- and loss-of-function screens to identify miRNAs that regulate the choice between bCSC self-renewal and differentiation. We find that micro-RNA (miR)-600 silencing results in bCSC expansion, while its overexpression reduces bCSC self-renewal, leading to decreased in vivo tumorigenicity. miR-600 targets stearoyl desaturase 1 (SCD1), an enzyme required to produce active, lipid-modified WNT proteins. In the absence of miR-600, WNT signaling is active and promotes self-renewal, whereas overexpression of miR-600 inhibits the production of active WNT and promotes bCSC differentiation. In a series of 120 breast tumors, we found that a low level of miR-600 is correlated with active WNT signaling and a poor prognosis. These findings highlight a miR-600-centered signaling network that governs bCSC-fate decisions and influences tumor progression.

Hematopoietic stem cells (HSCs) give rise to all blood populations due to their long-term self-renewal and multipotent differentiation capacities. Because they have to persist throughout an organism’s life span, HSCs tightly regulate the balance between proliferation and quiescence. Here, we investigated the role of the transcription factor promyelocytic leukemia zinc finger (plzf) in HSC fate using the Zbtb16lu/lu mouse model, which harbors a natural spontaneous mutation that inactivates plzf. Regenerative stress revealed that Zbtb16lu/lu HSCs had a lineage-skewing potential from lymphopoiesis toward myelopoiesis, an increase in the long-term-HSC pool, and a decreased repopulation potential. Furthermore, old plzf-mutant HSCs present an amplified aging phenotype, suggesting that plzf controls age-related pathway. We found that Zbtb16lu/lu HSCs harbor a transcriptional signature associated with a loss of stemness and cell cycle deregulation. Lastly, cell cycle analyses revealed an important role for plzf in the regulation of the G1-S transition of HSCs. Our study reveals a new role for plzf in regulating HSC function that is linked to cell cycle regulation, and positions plzf as a key player in controlling HSC homeostasis.

In pancreatic ductal adenocarcinoma (PDAC), signaling from stromal cells is implicated in metastatic progression. Tumor-stroma cross-talk is often mediated through extracellular vesicles (EVs). We previously reported that EVs derived from cancer-associated stromal fibroblasts (CAFs) that are abundant in annexin A6 (ANXA6+EVs) support tumor cell aggressiveness in PDAC. Here, we found that the cell surface glycoprotein and tetraspanin CD9 is a key component of CAF-derived ANXA6+EVs for mediating this cross-talk. CD9 was abundant on the surface of ANXA6+CAFs isolated from patient PDAC samples and from various mouse models of PDAC. CD9 colocalized with CAF markers in the tumor stroma, and CD9 abundance correlated with tumor stage. Blocking CD9 impaired the uptake of ANXA6+EVs into cultured PDAC cells. Signaling pathway arrays and further analyses revealed that the uptake of CD9+ANXA6+EVs induced mitogen-activated protein kinase (MAPK) pathway activity, cell migration, and epithelial-to-mesenchymal transition (EMT). Blocking either CD9 or p38 MAPK signaling impaired CD9+ANXA6+EV–induced cell migration and EMT in PDAC cells. Analysis of bioinformatic datasets indicated that CD9 abundance was an independent marker of poor prognosis in patients with PDAC. Our findings suggest that CD9-mediated stromal cell signaling promotes PDAC progression.

Previously, we identified the stress-induced chaperone, Hsp27, as highly overexpressed in castration-resistant prostate cancer and developed an Hsp27 inhibitor (OGX-427) currently tested in phase I/II clinical trials as a chemosensitizing agent in different cancers. To better understand the Hsp27 poorly-defined cytoprotective functions in cancers and increase the OGX-427 pharmacological safety, we established the Hsp27-protein interaction network using a yeast two-hybrid approach and identified 226 interaction partners. As an example, we showed that targeting Hsp27 interaction with TCTP, a partner protein identified in our screen increases therapy sensitivity, opening a new promising field of research for therapeutic approaches that could decrease or abolish toxicity for normal cells. Results of an in-depth bioinformatics network analysis allying the Hsp27 interaction map into the human interactome underlined the multifunctional character of this protein. We identified interactions of Hsp27 with proteins involved in eight well known functions previously related to Hsp27 and uncovered 17 potential new ones, such as DNA repair and RNA splicing. Validation of Hsp27 involvement in both processes in human prostate cancer cells supports our system biology-predicted functions and provides new insights into Hsp27 roles in cancer cells.

Self‐renewal and differentiation are two epigenetic programs that regulate stem cells fate. Dysregulation of these two programs leads to the development of cancer stem cells (CSCs). Recent evidence suggests that CSCs are relatively resistant to conventional therapies and responsible for metastasis formation. Deciphering these processes will help understand oncogenesis and allow the development of new targeted therapies. Here, we have used a whole genome promoter microarray to establish the DNA methylation portraits of breast cancer stem cells (bCSCs) and non‐bCSCs. A total of 68 differentially methylated regions (DMRs) were more hypomethylated in bCSCs than in non‐bCSCs. Using a differentiation assay we demonstrated that DMRs are rapidly hypermethylated within the first 6 hours following induction of CSC differentiation whereas the cells reached the steady‐state within 6 days, suggesting that these DMRs are linked to early CSC epigenetic regulation. These DMRs were significantly enriched in genes coding for TGF‐β signaling‐related proteins. Interestingly, DMRs hypomethylation was correlated to an overexpression of TGF‐β signaling genes in a series of 109 breast tumors. Moreover, patients with tumors harboring the bCSC DMRs signature had a worse prognosis than those with non‐bCSC DMRs signature. Our results show that bCSCs have a distinct DNA methylation landscape with TGF‐β signaling as a key epigenetic regulator of bCSCs differentiation. StemCells2014;32:3031–3036

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There is increasing evidence that breast tumors are organized in a hierarchy, with a subpopulation of tumorigenic cancer cells, the cancer stem cells (CSCs), which sustain tumor growth. The characterization of protein networks that govern CSC behavior is paramount to design new therapeutic strategies targeting this subpopulation of cells. We have sought to identify specific molecular pathways of CSCs isolated from 13 different breast cancer cell lines of luminal or basal/mesenchymal subtypes. We compared the gene expression profiling of cancer cells grown in adherent conditions to those of matched tumorsphere cultures. No specific pathway was identified to be commonly regulated in luminal tumorspheres, resulting from a minor CSC enrichment in tumorsphere passages from luminal cell lines. However, in basal/mesenchymal tumorspheres, the enzymes of the mevalonate metabolic pathway were overexpressed compared to those in cognate adherent cells. Inhibition of this pathway with hydroxy‐3‐methylglutaryl CoA reductase blockers resulted in a reduction of breast CSC independent of inhibition of cholesterol biosynthesis and of protein farnesylation. Further modulation of this metabolic pathway demonstrated that protein geranylgeranylation (GG) is critical to breast CSC maintenance. A small molecule inhibitor of the geranylgeranyl transferase I (GGTI) enzyme reduced the breast CSC subpopulation both in vitro and in primary breast cancer xenografts. We found that the GGTI effect on the CSC subpopulation is mediated by inactivation of Ras homolog family member A (RHOA) and increased accumulation of P27kip1in the nucleus. The identification of protein GG as a major contributor to CSC maintenance opens promising perspectives for CSC targeted therapy in basal breast cancer. STEMCELLS2012;30:1327–1337

Compared with adults, pediatric mastocytosis has a relatively favorable prognosis. Interestingly, a difference was also observed in the status of c-kit mutations according to the age of onset. Although most adult patients have a D816V mutation in phosphotransferase domain (PTD), we have described that half of the children carry mutations in extracellular domain (ECD). KIT-ECD versus KIT-PTD mutants were introduced into rodent Ba/F3, EML, Rat2, and human TF1 cells to investigate their biologic effect. Both ECD and PTD mutations induced constitutive receptor autophosphorylation and ligand-independent proliferation of the 3 hematopoietic cells. Unlike ECD mutants, PTD mutants enhanced cluster formation and up-regulated several mast cell-related antigens in Ba/F3 cells. PTD mutants failed to support colony formation and erythropoietin-mediated erythroid differentiation. ECD and PTD mutants also displayed distinct whole-genome transcriptional profiles in EML cells. We observed differences in their signaling properties: they both activated STAT, whereas AKT was only activated by ECD mutants. Consistently, AKT inhibitor suppressed ECD mutant-dependent proliferation, clonogenicity, and erythroid differentiation. Expression of myristoylated AKT restored erythroid differentiation in EML-PTD cells, suggesting the differential role of AKT in those mutants. Overall, our study implied different pathogenesis of pediatric versus adult mastocytosis, which might explain their diverse phenotypes.

The cancer stem cell (CSC) hypothesis implicates the development of new therapeutic approaches to target the CSC population. Characterization of the pathways that regulate CSCs activity will facilitate the development of targeted therapies. We recently reported that the enzymatic activity of ALDH1, as measured by the ALDELFUOR assay, can be utilized to isolate normal and malignant breast stem cells in both primary tumors and cell lines. In this study, utilizing a tumorsphere assay, we have demonstrated the role of retinoid signaling in the regulation of breast CSCs self-renewal and differentiation. Utilizing the gene set enrichment analysis (GSEA) algorithm we identified gene sets and pathways associated with retinoid signaling. These pathways regulate breast CSCs biology and their inhibition may provide novel therapeutic approaches to target breast CSCs.

Metastasis is a complex process involving loss of adhesion, migration, invasion and proliferation of cancer cells. Cell adhesion molecules play a pivotal role in this phenomenon by regulating cell–cell and cell–matrix interactions. CD146 (MCAM) is associated with an advanced tumor stage in melanoma, prostate cancer and ovarian cancer. Studies of CD146 expression and function in breast cancer remain scarce except for a report concluding that CD146 could act as a tumor suppressor in breast carcinogenesis. To resolve these apparent discrepancies in the role of CD146 in tumor cells, we looked at the association of CD146 expression with histoclinical features in human primary breast cancers using DNA and tissue microarrays. By flow cytometry, we characterized CD146 expression on different breast cancer cell lines. Using siRNA or shRNA technology, we studied functional consequences of CD146 downmodulation of MDA-MB-231 cells in migration assays. Wild-type, mock-transfected and downmodulated transfected cells were profiled using whole-genome DNA microarrays to identify genes whose expression was modified by CD146 downregulation. Microarray studies revealed the association of higher levels of CD146 with histoclinical features that belong to the basal cluster of human tumors. Expression of CD146 protein on epithelial cells was detected in a small subset of cancers with histoclinical features of basal tumors. CD146+cell lines displayed a mesenchymal phenotype. Downmodulation of CD146 expression in the MDA-MB-231 cell line resulted in downmodulation of vimentin, as well as of a set of genes that include both genes associated with a poor prognosis in a variety of cancers and genes known to promote cell motility. In vitrofunctional assays revealed decreased migration abilities associated with decreased CD146 expression. In addition to its expression in the vascular compartment, CD146 is expressed on a subset of epithelial cells in malignant breast. CD146 may directly or indirectly contribute to tumor aggressiveness by promoting malignant cell motility. Changes in molecular signatures following downmodulation of CD146 expression suggest that CD146 downmodulation is associated with the reversal of several biological characteristics associated with epithelial to mesenchymal transition, and the phenomenon associated with the metastatic process.

The outcome of classical Hodgkin lymphoma (cHL) patients may be related to the tumor microenvironment, which in turn may be influenced by Epstein-Barr virus (EBV) infection. To characterize the cHL microenvironment, a set of 63 cHL tissue samples was profiled using DNA microarrays. Their gene expression profile differed from that of histiocyte T cell–rich B-cell lymphoma (H/TCRBCL) samples that were used as controls, mainly due to high expression of PDCD1/PD-1 in H/TCRBCL. EBV+ cHL tissues could be distinguished from EBV− samples by a gene signature characteristic of Th1 and antiviral responses. Samples from cHL patients with favorable outcome overexpressed genes specific for B cells and genes involved in apoptotic pathways. An independent set of 146 cHL samples was analyzed using immunohistochemistry. It showed a significant adverse value in case of high percentage of either TIA-1+-reactive cells or topoisomerase-2+ tumor cells, whereas high numbers of BCL11A+, FOXP3+, or CD20+ reactive cells had a favorable influence. Our results suggest an antitumoral role for B cells in the cHL microenvironment and a stronger stromal influence of the PD1 pathway in H/TCRBCL than cHL. The observation of Th1/ antiviral response in EBV+ cHL tissues provides a basis for novel treatment strategies.

L’hétérogénéité histologique et clinique du cancer du sein, en partie responsable des échecs thérapeutiques, reflète sa nature moléculaire complexe et combinatoire jusqu’à présent mal documentée par les outils classiques de biologie. Une caractérisation moléculaire approfondie est indispensable. L’avènement des puces à ADN a permis de progresser dans ce sens. Une nouvelle classification moléculaire du cancer du sein a été définie, des signatures pronostiques ou prédictives de la réponse thérapeutique ont été identifiées, dont certaines sont actuellement en phase ultime de validation dans des essais cliniques prospectifs. Nous présentons dans cet article les principaux résultats publiés et leurs applications cliniques potentielles. Nous discutons leurs limites actuelles et retombées futures dans la prise en charge thérapeutique des patientes.

Pathologic and clinical heterogeneity of breast cancer reflects the poorly documented, complex, and combinatory molecular basis of the disease and is in part responsible for therapeutic failures. The DNA microarray technique allows the analysis of RNA expression of several thousands of genes simultaneously in a sample. There are multiple potential applications of the technique in cancer research. A number of recent studies have shown the promising role of gene expression profiling in breast cancer by identifying new prognostic subclasses unidentifiable by conventional parameters and new prognostic and/or predictive gene signatures, whose predictive impact is superior to conventional histoclinical prognostic factors. In this review we describe current use of DNA microarrays in the prognosis of breast cancer. We also discuss issues that need to be addressed in the near future to allow the method to reach its full potential.

ABSTRACTBackground. Anti-PD1/PDL1 immune checkpoint inhibitors (ICIs) showed promising results in breast cancer, and exploration of additional actionable immune checkpoints is ongoing. Inflammatory breast cancer (IBC) is an aggressive form of disease, the immune tumor microenvironment (TME) of which is poorly known. We aimed at providing the first comprehensive immune portrait of IBCs. Methods. From the gene expression profiles of 137 IBC and 252 non-IBC clinical samples, we measured the fractions of 22 immune cell types, expression of signatures associated with tertiary lymphoid structures (TLS) and with the response to ICIs (T cell-inflamed signature: TIS) and of 18 genes coding for major actionable immune checkpoints. The IBC/non-IBC comparison was adjusted upon the clinicopathological variables. Results. The immune profiles of IBCs were heterogeneous. CIBERSORT analysis showed profiles rich in macrophages, CD8+ and CD4 + T-cells, with remarkable similarity with melanoma TME. The comparison with non-IBCs showed significant enrichment in M1 macrophages, γδ T-cells, and memory B-cells. IBCs showed higher expression of TLS and TIS signatures. The TIS signature displayed values in IBCs close to those observed in other cancers sensitive to ICIs. Two-thirds of actionable immune genes (HAVCR2/TIM3, CD27, CD70, CTLA4, ICOS, IDO1, LAG3, PDCD1, TNFRSF9, PVRIG, CD274/PDL1, and TIGIT) were overexpressed in IBCs as compared to normal breast and two-thirds were overexpressed in IBCs versusnon-IBCs, with very frequent co-overexpression. For most of them, the overexpression was associated with better pathological response to chemotherapy. Conclusion. Our results suggest the potential higher vulnerability of IBC to ICIs. Clinical trials.

ABSTRACTAdrenocortical carcinomas (ACCs) are heterogeneous cancers associated with a very poor prognosis. The improvement of prognostic tools and systemic therapy are urgently needed. Targeting the immune system using checkpoint inhibitors such as PD1/PDL1 inhibitors is an attractive novel therapeutic strategy for poor-prognosis tumors. Multiple clinical trials are ongoing, including in advanced ACC. However, PDL1 expression has been studied in ACC in only one heterogeneous series of 28 clinical samples. Here, we have retrospectively analyzed PDL1mRNA expression in 146 clinical ACC samples and searched for correlations between expression and biological and clinicopathological data, including post-operative disease-free survival (DFS). PDL1mRNA expression was heterogeneous across samples. “PDL1-high” tumors were not associated with the classical prognostic variables but were associated with longer DFS in both uni- and multivariate analyses. High PDL1 mRNA expression was associated with biological signs of the cytotoxic local immune response. Supervised analysis between “PDL1-high” and “PDL1-low” tumors identified a robust 370-gene signature whose ontology analysis suggested the existence in “PDL1-high” tumors of a cytotoxic T-cell response, however, associated with some degree of T-cell exhaustion. In conclusion, PDL1mRNA expression refines the prognostication in ACC and high expression is associated with longer DFS. Clinical validation at the protein level and functional validation are required to fully understand the role of PDL1 in ACC. Reactivation of dormant tumor-infiltrating lymphocytes by PDL1-inhibitors could represent a promising strategy in “PDL1-high” ACCs, supporting the ongoing clinical trials.

ABSTRACTSoft-tissue sarcomas (STS) are a group of rare, heterogeneous, and aggressive tumors, with high metastatic risk and relatively few efficient systemic therapies. In the quest for new treatments, the immune system represents an attractive therapeutic target. Recently, PD1/PDL1 inhibitors showed very promising results in patients with solid tumors. PDL1 expression has been rarely studied in STS, in small series only, by using immunohistochemistry (IHC), and with non-concordant prognostic implications. Here, we have analyzed PDL1mRNA expression in 758 clinical STS samples retrospectively profiled using DNA microarrays and RNAseq, and searched for correlations with clinicopathological variables including metastasis-free survival (MFS) after surgery. PDL1expression was heterogeneous across the samples. PDL1-high samples (41%) were more frequently leiomyosarcomas and liposarcomas, and showed more frequently a complex genetic profile and a high-risk CINSARC signature. No correlation existed with other clinicopathological features such as tumor site, depth, and pathological tumor grade and size. In multivariate prognostic analysis, the PDL1-high class was associated with shorter MFS, independently of the pathological type and the CINSARC signature. Analysis of correlations with biological factors suggested the existence in tumors of the PDL1-high class of a strong and efficient cytotoxic T-cell response, however associated with some degree of T-cell exhaustion and negative regulation. In conclusion, we show that PDL1expression refines the prediction of metastatic relapse in operated localized STS, and that PD1/PDL1 blockade holds potential to improve patient survival by reactivating inhibited T cells to increase the antitumor immune in PDL1-high tumors.

ABSTRACTCancer immunotherapy is revolutionizing the clinical management of several tumors, but has demonstrated limited activity in breast cancer. The development of more effective treatments is hindered by incomplete knowledge of the genetic determinant of immune responsiveness. To fill this gap, we mined copy number alteration, somatic mutation, and expression data from The Cancer Genome Atlas (TCGA). By using RNA-sequencing data from 1,004 breast cancers, we defined distinct immune phenotypes characterized by progressive expression of transcripts previously associated with immune-mediated rejection. The T helper 1 (Th-1) phenotype (ICR4), which also displays upregulation of immune-regulatory transcripts such as PDL1, PD1, FOXP3, IDO1, and CTLA4, was associated with prolonged patients' survival. We validated these findings in an independent meta-cohort of 1,954 breast cancer gene expression data. Chromosome segment 4q21, which includes genes encoding for the Th-1 chemokines CXCL9-11, was significantly amplified only in the immune favorable phenotype (ICR4). The mutation and neoantigen load progressively decreased from ICR4 to ICR1 but could not fully explain immune phenotypic differences. Mutations of TP53were enriched in the immune favorable phenotype (ICR4). Conversely, the presence of MAP3K1and MAP2K4mutations were tightly associated with an immune-unfavorable phenotype (ICR1). Using both the TCGA and the validation dataset, the degree of MAPK deregulation segregates breast tumors according to their immune disposition. These findings suggest that mutation-driven perturbations of MAPK pathways are linked to the negative regulation of intratumoral immune response in breast cancer. Modulations of MAPK pathways could be experimentally tested to enhance breast cancer immune sensitivity.

ABSTRACTAnalysis of PDL1mRNA expression in ∼5,500 breast cancers showed PDL1upregulation in 38% of basal tumors and 38% of inflammatory breast cancers (IBC). Upregulation, associated with signs of strong cytotoxic local immune response, was associated with a better survival in the basal or triple-negative subtypes, and with a better pathological response to chemotherapy in these subtypes and IBC. Reactivation of dormant tumor-infiltrating lymphocytes (TILs) by PD1/PDL1-inhibitors represents a promising strategy in these aggressive tumors.

Gastrointestinal stromal tumors (GIST) are the most frequently occurring digestive sarcomas. The prognosis of localized GIST is heterogeneous, notably for patients with an Armed Forces Institute of Pathology (AFIP) intermediate or high risk of relapse. Despite imatinib effectiveness, it is crucial to develop therapies able to overcome the resistance mechanisms. The immune system represents an attractive prognostic and therapeutic target. The Programmed cell Death 1 (PD1)/programmed cell death ligand 1 (PDL1) pathway is a key inhibitor of the immune response; recently, anti-PD1 and anti-PDL1 drugs showed very promising results in patients with solid tumors. However, PDL1 expression has never been studied in GIST. Our objective was to analyze PDL1 expression in a large series of clinical samples. We analyzed mRNA expression data of 139 operated imatinib-untreated localized GIST profiled using DNA microarrays and searched for correlations with histoclinical features including postoperative metastatic relapse. PDL1expression was heterogeneous across tumors and was higher in AFIP low-risk than in high-risk samples, and in samples without than with metastatic relapse. PDL1expression was associated with immunity-related parameters such as T–cell-specific and CD8+T–cell-specific gene expression signatures and probabilities of activation of interferon α (IFNα), IFNγ, and tumor necrosis factor α (TNFα) pathways, suggesting positive correlation with a cytotoxic T-cell response. In multivariate analysis, the PDL1-low group was associated with a higher metastatic risk independently of the AFIP classification and the KITmutational status. In conclusion, PDL1expression refines the prediction of metastatic relapse in localized GIST and might improve our ability to better tailor adjuvant imatinib. In the metastatic setting, PDL1expression might guide the use of PDL1 inhibitors, alone or associated with tyrosine kinase inhibitors.