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Intratumoral heterogeneity drastically impacts the success or failure of anti-cancer therapies. Here, we investigated the evolution and mechanistic heterogeneity in clonal populations of cell models for estrogen receptor positive breast cancer. To this end, we established barcoded models of luminal breast cancer and rendered them resistant to commonly applied first line endocrine therapies. By deconvoluting complex resistant cell pools and characterizing replicates of individual clones we observed inter- (between cell lines) and intra-tumor (between different clones from the same cell line) heterogeneity. Molecular characterization at RNA and phospho-proteomic levels revealed private clonal activation of the unfolded protein response and respective sensitivity to inhibition of the proteasome, and shared sensitivities for repression of protein kinase C. Our in vitro findings mirror the tumor-heterogeneity that is observed in breast cancer patients thus highlighting the urgent need to uncover heterogeneity at an individual patient level and to adjust therapies accordingly.

Plakophilin (PKP1) 1 is a member of the arm-repeat family of catenins and acts as a structural component of desmosomes, which are important stabilizers of cell-cell adhesion. Besides this, PKP1 also occurs in a non-junctional, cytoplasmic form contributing to post-transcriptional regulation of gene expression. Moreover, PKP1 is expressed in the prostate epithelium but its expression is frequently downregulated in prostate cancers with a more aggressive phenotype. This observation may imply a tumour-suppressive role of PKP1. We found that, in prostatic adenocarcinomas with PKP1 deficiency, the occurrence of T-cells, B-cells, macrophages and neutrophils were significantly increased. In a PKP1-deficient prostatic cancer cell line expressing IL8, these levels were statistically meaningfully reduced upon PKP1 re-expression. When analysing prostatic PKP1 knockdown cell lines, the mRNA and protein levels of additional cytokines, namely CXCL1 and IL6, were upregulated. The effect was rescued upon re-expression of a PKP1 RNAi-resistant form. The corresponding mRNAs were co-precipitated with cytoplasmic PKP1, indicating that they are components of PKP1-containing mRNA ribonucleoprotein particles. Moreover, the mRNA half-lives of CXCL1, IL8 and IL6 were significantly increased in PKP1-deficient cells, showing that these mRNAs were stabilized by PKP1. In an in vitro migration assay, the higher cytokine concentrations led to higher migration rates of THP1 and PBMC cells. This finding implies that PKP1 loss of expression in vivo correlates with the recruitment of immune cells into the tumour area to set up a tumour-specific environment. One may speculate that this newly established tumour environment has tumour-suppressive characteristics and thereby accelerates tumour progression and metastasis.

Anticancer therapies have been limited by the emergence of mutations and other adaptations. In bacteria, antibiotics activate the SOS response, which mobilizes error-prone factors that allow for continuous replication at the cost of mutagenesis. We investigated whether the treatment of lung cancer with EGFR inhibitors (EGFRi) similarly engages hypermutators. In cycling drug-tolerant persister (DTP) cells and in EGFRi-treated patients presenting residual disease, we observed upregulation of GAS6, whereas ablation of GAS6's receptor, AXL, eradicated resistance. Reciprocally, AXL overexpression enhanced DTP survival and accelerated the emergence of T790M, an EGFR mutation typical to resistant cells. Mechanistically, AXL induces low-fidelity DNA polymerases and activates their organizer, RAD18, by promoting neddylation. Metabolomics uncovered another hypermutator, AXL-driven activation of MYC, and increased purine synthesis that is unbalanced by pyrimidines. Aligning anti-AXL combination treatments with the transition from DTPs to resistant cells cured patient-derived xenografts. Hence, similar to bacteria, tumors tolerate therapy by engaging pharmacologically targetable endogenous mutators.Significance:EGFR-mutant lung cancers treated with kinase inhibitors often evolve resistance due to secondary mutations. We report that in similarity to the bacterial SOS response stimulated by antibiotics, endogenous mutators are activated in drug-treated cells, and this heralds tolerance. Blocking the process prevented resistance in xenograft models, which offers new treatment strategies.This article is highlighted in the In This Issue feature, p. 2483

Supplementary Figure from AXL and Error-Prone DNA Replication Confer Drug Resistance and Offer Strategies to Treat EGFR-Mutant Lung Cancer

Supplementary Data from AXL and Error-Prone DNA Replication Confer Drug Resistance and Offer Strategies to Treat EGFR-Mutant Lung Cancer

Primary tumors and distant site metastases form a bidirectionally communicating system. Yet, the molecular mechanisms of this crosstalk are poorly understood. Here, we identified the proteolytically cleaved fragments of angiopoietin-like 4 (ANGPTL4) as contextually active protumorigenic and antitumorigenic contributors in this communication ecosystem. Preclinical studies in multiple tumor models revealed that the C-terminal fragment (cANGPTL4) promoted tumor growth and metastasis. In contrast, the N-terminal fragment of ANGPTL4 (nANGPTL4) inhibited metastasis and enhanced overall survival in a postsurgical metastasis model by inhibiting WNT signaling and reducing vascularity at the metastatic site. Tracing ANGPTL4 and its fragments in tumor patients detected full-length ANGPTL4 primarily in tumor tissues, whereas nANGPTL4 predominated in systemic circulation and correlated inversely with disease progression. The study highlights the spatial context of the proteolytic cleavage-dependent pro- and antitumorigenic functions of ANGPTL4 and identifies and validates nANGPTL4 as a novel biomarker of tumor progression and antimetastatic therapeutic agent.

The spliced human papillomavirus 16 (HPV16) E1C RNA is associated with high-grade precursor lesions and cervical cancer. This qualifies E1C as a biomarker for high-grade lesions in HPV-based cervical cancer precursor screening. Here, we aimed to characterize the biological activity of HPV16 E1C RNA. In HEK-293T cells overexpressing HPV16 E1C RNA, we detected 9 kDa E1C protein in the cytoplasm using immunological assays with a newly generated E1C-specific monoclonal antibody or in mass spectrometry only after proteasome inhibition with MG132, indicating instability of the E1C protein. In HPV16-transformed cervical cancer cell lines in which the level of endogenous E1C RNA is much lower, E1C protein was not detected even after proteasome inhibition. Transient E1C overexpression in HEK-293T cells, co-transfected with a firefly luciferase reporter gene under the control of the HPV16 upstream regulatory region (URR), activated the HPV16 URR by 38%. This activation was also present when E1C translation was abolished by mutation. However, a construct expressing a random RNA sequence with similar GC content and 45% homology to the E1C RNA sequence also stimulated URR activity, indicating that special E1C RNA motifs might be responsible for the activation. In HPV16-transformed cell lines W12-episomal (W12-epi), W12-integrated HPV (W12-int), CaSki and SiHa stably overexpressing E1C RNA from lentiviral transduction, levels of endogenous HPV16 RNAs E6*I and E7 remained unchanged, while E1^E4 levels were significantly reduced by 20–30% in W12-epi, W12-int and CaSki cells. Overall, our study shows that E1C RNA is active and might contribute to transformation independent of the E6*I or E7 pathways. However, E1C overexpression resulted in only subtle changes in HPV16 RNA expression and very low copies of endogenous E1C RNA were detected in cervical cancer cell lines. This could weigh towards a less prominent role of E1C RNA in natural HPV transformation.

Anticancer therapies have been limited by the emergence of mutations and other adaptations. In bacteria, antibiotics activate the SOS response, which mobilizes error-prone factors that allow for continuous replication at the cost of mutagenesis. We investigated whether the treatment of lung cancer with EGFR inhibitors (EGFRi) similarly engages hypermutators. In cycling drug-tolerant persister (DTP) cells and in EGFRi-treated patients presenting residual disease, we observed upregulation of GAS6, whereas ablation of GAS6's receptor, AXL, eradicated resistance. Reciprocally, AXL overexpression enhanced DTP survival and accelerated the emergence of T790M, an EGFR mutation typical to resistant cells. Mechanistically, AXL induces low-fidelity DNA polymerases and activates their organizer, RAD18, by promoting neddylation. Metabolomics uncovered another hypermutator, AXL-driven activation of MYC, and increased purine synthesis that is unbalanced by pyrimidines. Aligning anti-AXL combination treatments with the transition from DTPs to resistant cells cured patient-derived xenografts. Hence, similar to bacteria, tumors tolerate therapy by engaging pharmacologically targetable endogenous mutators. Significance: EGFR-mutant lung cancers treated with kinase inhibitors often evolve resistance due to secondary mutations. We report that in similarity to the bacterial SOS response stimulated by antibiotics, endogenous mutators are activated in drug-treated cells, and this heralds tolerance. Blocking the process prevented resistance in xenograft models, which offers new treatment strategies. This article is highlighted in the In This Issue feature, p. 2483

Chemotherapy (CTX) remains the standard of care for most aggressive tumours, including breast cancer (BC). In BC chemotherapeutic regimens, the maximum tolerated dose of cytotoxic drugs is administered at regular intervals, and cancer cells can re‐grow or adapt during the resting periods between cycles. The impact of the tumour microenvironment on the fate of cancer cells after CTX remains poorly understood. Here, we show that paracrine signalling from CTX‐treated cancer cells to stromal fibroblasts can drive cancer cell recovery after cytotoxic drug withdrawal. Interferon β1 (IFNβ1) secreted by cancer cells following treatment with high doses of CTX instigates the acquisition of an anti‐viral state in stromal fibroblasts. This state is associated with an expression pattern here referred to as interferon signature (IFNS), which encompasses several interferon‐stimulated genes (ISGs), including numerous pro‐inflammatory cytokine genes. This crosstalk is an important driver of the expansion of BC cells after CTX, and IFNβ1 blockade in tumour cells abrogated their fibroblast‐dependent recovery potential. Analysis of human breast carcinomas supported a link between CTX‐induced IFNS in tumour stroma and poor response to CTX treatment. First, IFNβ1 expression in human breast carcinomas was found to inversely correlate with recurrence free survival (RFS). Second, using laser capture microdissection data sets, we show a higher expression of IFNS in the stromal tumour compartment compared to the epithelial one and this signature was found to be more prominent in more aggressive subtypes of BC (basal‐like), pointing to a pro‐tumorigenic role of this signature. Moreover, IFNS was associated with higher recurrence rates and a worse outcome in BC patients. Our study unravels a novel form of paracrine communication between cancer cells and fibroblasts that ultimately results in CTX resistance. Targeting this axis has the potential to improve CTX outcomes in patients with BC., Treatment with high doses of chemotherapy leads to the secretion of IFNβ1 into the tumour microenvironment. Exposure of stromal fibroblasts to IFNβ1 induces an anti‐viral, pro‐inflammatory signature associated with the expression of several interferon stimulated genes. This reprogramming drives a pro‐tumorigenic state in fibroblasts that facilitates cancer cell recovery after treatment and promotes cancer relapse in patients with breast cancer.

Solitary fibrous tumors (SFTs) harbor recurrent NAB2-STAT6 gene fusions, promoting constitutional up-regulation of oncogenic early growth response 1 (EGR1)-dependent gene expression. SFTs with the most common canonical NAB2 exon 4-STAT6 exon 2 fusion variant are often located in the thorax (pleuropulmonary) and are less cellular with abundant collagen. In contrast, SFTs with NAB2 exon 6-STAT6 exon 16/17 fusion variants typically display a cellular round to ovoid cell morphology and are often located in the deep soft tissue of the retroperitoneum and intra-abdominal pelvic region or in the meninges. Here, we employed next-generation sequencing-based gene expression profiling to identify significant differences in gene expression associated with anatomic localization and NAB2-STAT6 gene fusion variants. SFTs with the NAB2 exon 4-STAT6 exon 2 fusion variant showed a transcriptional signature enriched for genes involved in DNA binding, gene transcription, and nuclear localization, whereas SFTs with the NAB2 exon 6-STAT6 exon 16/17 fusion variants were enriched for genes involved in tyrosine kinase signaling, cell proliferation, and cytoplasmic localization. Specific transcription factor binding motifs were enriched among differentially expressed genes in SFTs with different fusion variants, implicating co-transcription factors in the modification of chimeric NGFI-A binding protein 2 (NAB2)-STAT6-dependent deregulation of EGR1-dependent gene expression. In summary, this study establishes a potential molecular biologic basis for clinicopathologic differences in SFTs with distinct NAB2-STAT6 gene fusion variants.

Visual Abstract, Highlights • FYCO1, a component of the autophagic machinery, is highly expressed in the heart and a potent inducer of cardiomyocyte autophagy. • Loss of FYCO1 in vivo inhibits adaptation to starvation or biomechanical stress of the heart by an abrogated increase of autophagic flux and results in contractile dysfunction. • Heart specific overexpression of FYCO1 improves autophagic flux and rescues contractile dysfunction following pressure overload., Summary Autophagy is a cellular degradation process that has been implicated in diverse disease processes. The authors provide evidence that FYCO1, a component of the autophagic machinery, is essential for adaptation to cardiac stress. Although the absence of FYCO1 does not affect basal autophagy in isolated cardiomyocytes, it abolishes induction of autophagy after glucose deprivation. Likewise, Fyco1-deficient mice subjected to starvation or pressure overload are unable to respond with induction of autophagy and develop impaired cardiac function. FYCO1 overexpression leads to induction of autophagy in isolated cardiomyocytes and transgenic mouse hearts, thereby rescuing cardiac dysfunction in response to biomechanical stress.

Introduction: The main cause of death for cancer patients is the development of metastasis. These arise mainly due to irresponsiveness of cancer cells to the administered therapy, which then fails to eliminate all cancer cells present in the patient. To overcome this problem, it is essential to understand which mechanisms are involved in the lack of treatment response. We are investigating how the tumour microenvironment (TME) affects the response of cancer cells to chemotherapy (CTX) and how it can be modulated to improve the outcome of patients to therapy. Materials and Methods: Co-culture of chemotherapy-treated breast cancer cell lines with primary fibroblasts isolated from breast cancer patients was performed to investigate if fibroblasts affect the response of tumour cells to commonly used agents, such as epirubicin and paclitaxel. Recovery of cells was assessed using colony formation assays (CFA) and cell cycle profiling by EdU and the FUCCI system. To further explore the complex crosstalk between cancer cells and fibroblasts in the context of CTX, gene expression analysis of both cell types was done using next generation sequencing. Validation and evaluation of the biological impact of the identified pathways was done using RT-qPCR, western-blot and perturbation experiments. Lastly, publicly available datasets for breast cancer were used to investigate the clinical relevance of our findings. Results and Discussion: We show that cancer cells utilize paracrine signalling with stromal fibroblasts to drive their recovery after treatment withdrawal. Cell cycle analysis and RNA-sequencing revealed an increase in cell cycle re-entry of CTX-treated cancer cells in co-culture with fibroblasts. In addition, we have successfully shown that treated cancer cells upregulate an important secreted factor that modulates fibroblasts into a pro-tumorigenic state. Moreover, analysis of human breast carcinomas supported the proposed role of the identified factor since its expression is inversely correlated with recurrence free survival (RFS). Moreover, expression of the gene signature identified in stromal fibroblasts in co-culture with CTX-treated cancer cells was equally associated with higher recurrence rates and a worse outcome in breast cancer patients. Conclusion: CTX-induced secretory profile of cancer cells orchestrates the reprogramming of stromal fibroblasts into a pro-tumorigenic state, which drives the expansion of cancer cells. Our study unravels a novel paracrine communication between cancer cells and stromal fibroblasts that ultimately results in the escape of malignant cells to treatment, highlighting the importance of the TME in drug response. Targeting of this axis could potentially improve the outcome of breast cancer patients to CTX treatment. Citation Format: Ana Maia, Zuguang Gu, André Koch, Mireia Berdiel-Acer, Rainer Will, Matthias Schlesner, Stefan Wiemann. Paracrine signalling with stromal fibroblasts drives recovery of cancer cells after chemotherapy treatment [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS16-36.

While for photon radiation hypofractionation has been reported to induce enhanced immunomodulatory effects, little is known about the immunomodulatory potential of carbon ion radiotherapy (CIRT). We thus compared the radio-immunogenic effects of photon and carbon ion irradiation on two murine cancer cell lines of different tumor entities. We first calculated the biological equivalent doses of carbon ions corresponding to photon doses of 1, 3, 5, and 10 Gy of the murine breast cancer cell line EO771 and the OVA-expressing pancreatic cancer cell line PDA30364/OVA by clonogenic survival assays. We compared the potential of photon and carbon ion radiation to induce cell cycle arrest, altered surface expression of immunomodulatory molecules and changes in the susceptibility of cancer cells to cytotoxic T cell (CTL) mediated killing. Irradiation induced a dose-dependent G2/M arrest in both cell lines irrespective from the irradiation source applied. Likewise, surface expression of the immunomodulatory molecules PD-L1, CD73, H2-Db and H2-Kb was increased in a dose-dependent manner. Both radiation modalities enhanced the susceptibility of tumor cells to CTL lysis, which was more pronounced in EO771/Luci/OVA cells than in PDA30364/OVA cells. Overall, compared to photon radiation, the effects of carbon ion radiation appeared to be enhanced at higher dose range for EO771 cells and extenuated at lower dose range for PDA30364/OVA cells. Our data show for the first time that equivalent doses of carbon ion and photon irradiation exert similar immunomodulating effects on the cell lines of both tumor entities, highlighted by an enhanced susceptibility to CTL mediated cytolysis in vitro.

Autophagy is an intracellular degradation process that maintains the cellular homeostasis and it is regulated in multiple ways, both in health and disease. Assessment of autophagic flux in cells is an important approach for understanding the function of autophagy in biological contexts. Here, we describe a new tool for the qualitative and quantitative determination of autophagic flux using a dual lentiviral reporter system that generates a fusion HiBiT-GFP-LC3B protein suitable for generating stable cell lines.

Tumor cell extensions called tumor microtubes (TMs) in glioma resemble neurites during neurodevelopment and connect glioma cells to a network that has considerable relevance for tumor progression and therapy resistance. The determination of interconnectivity in individual tumors has been challenging and the impact of tumor cell connectivity on patient survival remained unresolved so far. Here, a connectivity signature from single-cell RNA-sequenced (scRNA-Seq) xenografted primary glioblastoma (GB) cells was established and clinically validated. Thirty-four of 40 connectivity genes were related to neurogenesis, neural tube development or glioma progression, including the TM-network-relevant GAP43 gene. Astrocytic-like and mesenchymal-like GB cells had the highest connectivity signature scores in scRNA-Seq data of patient-derived xenografts and patient samples. In 230 human GBs, high connectivity correlated with the mesenchymal expression subtype, TP53 wildtype, and with dismal patient survival. CHI3L1 was identified as a robust molecular marker of connectivity. Thus, the connectivity signature allows novel insights into brain tumor biology, provides a proof-of-principle that tumor cell connectivity is relevant for patients’ prognosis, and serves as a robust biomarker that can be used for future clinical trials.Statement of significanceIntegration of GB cells into functional networks drives tumor progression and resistance. Here, we established and validated a novel connectivity gene expression signature of single GB cells and whole tumors that can be easily applied to clinical and preclinical samples. It is shown that connectivity is determining prognosis combining molecular, functional and clinical insights into the disease.

Chemotherapy is still the standard of care for a large number of aggressive tumours including breast cancer. In breast cancer, chemotherapeutic regimens are administered in intervaled cycles of the maximum tolerated dose, allowing cancer cells to re-grow or adapt during the resting periods between cycles. However, how stromal fibroblasts impact the fate of cancer cells after chemotherapy treatment remains poorly understood. We show that cancer cells utilize paracrine signalling with stromal fibroblasts to drive their recovery after treatment withdrawal. Secretion of IFNβ1 by cancer cells after treatment with high doses of chemotherapy instigates the acquisition of an anti-viral state in stromal fibroblasts associated with the expression of several interferon stimulated genes (ISGs), including numerous pro-inflammatory cytokines. This crosstalk is an important driver of the expansion of breast cancer cells after chemotherapy and blocking of IFNβ1 in tumour cells abrogated their increased recovery potential. Analysis of human breast carcinomas supports the proposed role of IFNβ1 since its expression is inversely correlated with recurrence free survival (RFS). Moreover, expression of the interferon signature identified in stromal fibroblasts is equally associated with higher recurrence rates and a worse outcome in breast cancer patients. Our study unravels a novel paracrine communication between cancer cells and fibroblasts that ultimately results in the escape of malignant cells to treatment. Targeting of this axis could potentially improve the outcome of breast cancer patients to chemotherapy treatment.

Breast cancer is one of the leading causes of death for women worldwide. Patients whose tumors express Estrogen Receptor α (ERα) account for around 70% of cases and are mostly treated with targeted endocrine therapy. However, 40% of these tumors eventually relapse due to resistance development and further treatment of these patients is highly ineffective. In this study we profiled the early phases of the resistance development process to uncover drivers of this phenomenon. Time-resolved analysis revealed that ATF3, a member of the ATF/CREB family of transcription factors, acts as a novel regulator of the response to therapy via rewiring of central signaling processes towards the adaptation to endocrine treatment. ATF3 was found to be essential in controlling crucial processes such as proliferation, cell cycle and apoptosis during the early response to treatment through the regulation of MAPK/AKT signaling pathways. Its essential role was confirmed in vivo in a mouse model and elevated expression of ATF3 was verified in patient datasets, adding clinical relevance to our findings. This study proposes ATF3 as a novel mediator of endocrine resistance development in breast cancer and elucidates its role in the regulation of downstream pathways activities.

BACKGROUND The application of personalized vaccines has shown to be effective in patients with newly diagnosed glioblastoma in phase 1 clinical trials. Responses of CD8 T cells directed against the glioma-associated antigen Neuroligin-4, X-linked (NLGN4X) were reported in multipeptide vaccine trials in patients with glioblastoma. Here, we characterized the functional status of NLGN4X TCR transgenic T cells in vitro and assessed their therapeutic capacity in vivo. METHODS TCR encoding sequences were delivered by lentiviral transduction to activated T cells from healthy donors. After confirmation of TCR surface expression T cells were used for a functional in vitro characterization. For in vivo assessment of NLGN4X-specific TCR transgenic T cells, NLGN4X-expressing U87 glioma cells were injected into the flank of NSG MHCI/MHC II knockout mice, which do not develop graft versus host disease. TCR transgenic T cells were injected intravenously on day 11 and day 18 and tumor size was monitored. RESULTS TCR transgenic T cells depicted stable surface expression for at least 11 days in vitro after transduction. Thereby, murine TCR beta constant region positive T cells featured a polyfunctional phenotype demonstrated by a significant increase of Interferon-γ and TNF-α and remained reactive to the NLGN4X epitope for at least 7 days. Additionally, NLGN4X TCR transgenic T cells showed significantly increased antigen-specific production of the cytolytic protein granzyme B and elevated levels of perforin. In a novel xenograft mouse model NLGN4X TCR transgenic T cells slowed the tumor growth compared to the initial tumor size until day 25 after tumor inoculation. DISCUSSION We demonstrate that NLGN4X TCR transgenic T cells specifically and consistently recognize their corresponding immunogenic sequence and target antigen-overexpressing glioma cells. We present first evidence of in vivo reactivity, while further experiments are required to assess the full therapeutic potential of NLGN4X-TCR-transgenic T cell therapy for glioma patients.

Several mechanisms of action have been proposed for DNA methyltransferase and histone deacetylase inhibitors (DNMTi and HDACi), primarily based on candidate-gene approaches. However, less is known about their genome-wide transcriptional and epigenomic consequences. By mapping global transcription start site (TSS) and chromatin dynamics, we observed the cryptic transcription of thousands of treatment-induced non-annotated TSSs (TINATs) following DNMTi and HDACi treatment. The resulting transcripts frequently splice into protein-coding exons and encode truncated or chimeric ORFs translated into products with predicted abnormal or immunogenic functions. TINAT transcription after DNMTi treatment coincided with DNA hypomethylation and gain of classical promoter histone marks, while HDACi specifically induced a subset of TINATs in association with H2AK9ac, H3K14ac, and H3K23ac. Despite this mechanistic difference, both inhibitors convergently induced transcription from identical sites, as we found TINATs to be encoded in solitary long terminal repeats of the ERV9/LTR12 family, which are epigenetically repressed in virtually all normal cells.

Rationale: The emerging role of the ubiquitin–proteasome system in cardiomyocyte function and homeostasis implies the necessity of tight regulation of protein degradation. However, little is known about cardiac components of this machinery. Objective: We sought to determine whether molecules exist that control turnover of cardiac-specific proteins. Methods and Results: Using a bioinformatic approach to identify novel cardiac-enriched sarcomere proteins, we identified F-box and leucine-rich repeat protein 22 (Fbxl22). Tissue-specific expression was confirmed by multiple tissue Northern and Western Blot analyses as well as quantitative reverse-transcriptase polymerase chain reaction on a human cDNA library. Immunocolocalization experiments in neonatal and adult rat ventricular cardiomyocytes as well as murine heart tissue located Fbxl22 to the sarcomeric z-disc. To detect cardiac protein interaction partners, we performed a yeast 2-hybrid screen using Fbxl22 as bait. Coimmunoprecipitation confirmed the identified interactions of Fbxl22 with S-phase kinase-associated protein 1 and Cullin1, 2 critical components of SCF (Skp1/Cul1/F-box) E3- ligases. Moreover, we identified several potential substrates, including the z-disc proteins α-actinin and filamin C. Consistently, in vitro overexpression of Fbxl22-mediated degradation of both substrates in a dose-dependent fashion, whereas proteasome inhibition with MG-132 markedly attenuated degradation of both α-actinin and filamin C. Finally, targeted knockdown of Fbxl22 in rat cardiomyocytes as well as zebrafish embryos results in the accumulation of α-actinin associated with severely impaired contractile function and cardiomyopathy in vivo. Conclusions: These findings reveal the previously uncharacterized cardiac-specific F-box protein Fbxl22 as a component of a novel cardiac E3 ligase. Fbxl22 promotes the proteasome-dependent degradation of key sarcomeric proteins, such as α-actinin and filamin C, and is essential for maintenance of normal contractile function in vivo.

Cholangiocarcinoma (CC) is a rare malignancy of the extrahepatic or intrahepatic biliary tract with an outstanding poor prognosis. Non-surgical therapeutic regimens result in minimally improved survival of CC patients. Global genomic analyses identified a few recurrently mutated genes, some of them in genes involved in epigenetic patterning. In a previous study, we demonstrated global DNA methylation changes in CC, indicating major contribution of epigenetic alterations to cholangiocarcinogenesis. Here, we aimed at the identification and characterization of CC-related, differentially methylated regions (DMRs) in potential microRNA promoters and of genes targeted by identified microRNAs. Twenty-seven hypermethylated and 13 hypomethylated potential promoter regions of microRNAs, known to be associated with cancer-related pathways like Wnt, ErbB, and PI3K-Akt signaling, were identified. Selected DMRs were confirmed in 2 independent patient cohorts. Inverse correlation between promoter methylation and expression suggested miR-129-2 and members of the miR-200 family (miR-200a, miR-200b, and miR-429) as novel tumor suppressors and oncomiRs, respectively, in CC. Tumor suppressor genes deleted in liver cancer 1 (DLC1), F-box/WD-repeat-containing protein 7 (FBXW7), and cadherin-6 (CDH6) were identified as presumed targets in CC. Tissue microarrays of a representative and well-characterized cohort of biliary tract cancers (n=212) displayed stepwise downregulation of CDH6 and association with poor patient outcome. Ectopic expression of CDH6 on the other hand, delayed growth in the CC cell lines EGI-1 and TFK-1, together suggesting a tumor suppressive function of CDH6. Our work represents a valuable repository for the study of epigenetically altered miRNAs in cholangiocarcinogenesis and novel putative, CC-related tumor suppressive miRNAs and oncomiRs.

Mutated proteins arising from somatic mutations in tumors are promising targets for cancer immunotherapy. They represent true tumor-specific antigens (TSAs) as they are exclusively expressed in tumors, reduce the risk of autoimmunity and are more likely to overcome tolerance compared to wild-type (wt) sequences. Hence, we designed a panel of long peptides (LPs, 28–35 aa) comprising driver gene mutations in TP35 and KRAS frequently found in gastrointestinal tumors to test their combined immunotherapeutic potential. We found increased numbers of T cells responsive against respective mutated and wt peptides in colorectal cancer patients that carry the tested mutations in their tumors than patients with other mutations. Further, active immunization of HLA(-A2/DR1)-humanized mice with mixes of the same mutated LPs yielded simultaneous, polyvalent CD8+/CD4+ T cell responses against the majority of peptides. Peptide-specific T cells possessed a multifunctional cytokine profile with CD4+ T cells showing a TH1-like phenotype. Two mutated peptides (Kras[G12V], p53[R248W]) induced significantly higher T cell responses than corresponding wt sequences and comprised HLA-A2/DR1-restricted mutated epitopes. However, vaccination with the same highly immunogenic LPs strongly increased systemic regulatory T cells (Treg) numbers in a syngeneic sarcoma model over-expressing these mutated protein variants and resulted in accelerated tumor outgrowth. In contrast, tumor outgrowth was delayed when vaccination was directed against tumor-intrinsic Kras/Tp53 mutations of lower immunogenicity. Conclusively, we show that LP vaccination targeting multiple mutated TSAs elicits polyvalent, multifunctional, and mutation-specific effector T cells capable of targeting tumors. However, the success of this therapeutic approach can be hampered by vaccination-induced, TSA-specific Tregs.

Rationale : The intercalated disc (ID) is a highly specialized cell-cell contact structure that ensures mechanical and electric coupling of contracting cardiomyocytes. Recently, the ID has been recognized to be a hot spot of cardiac disease, in particular inherited cardiomyopathy. Objective : Given its complex structure and function we hypothesized that important molecular constituents of the ID still remain unknown. Methods and Results : Using a bioinformatics screen, we discovered and cloned a previously uncharacterized 54 kDa cardiac protein which we termed Myozap (Myocardium-enriched zonula occludens-1–associated protein). Myozap is strongly expressed in the heart and lung. In cardiac tissue it localized to the ID and directly binds to desmoplakin and zonula occludens-1. In a yeast 2-hybrid screen for additional binding partners of Myozap we identified myosin phosphatase–RhoA interacting protein (MRIP), a negative regulator of Rho activity. Myozap, in turn, strongly activates SRF-dependent transcription through its ERM (Ezrin/radixin/moesin)-like domain in a Rho-dependent fashion. Finally, in vivo knockdown of the Myozap ortholog in zebrafish led to severe contractile dysfunction and cardiomyopathy. Conclusions : Taken together, these findings reveal Myozap as a previously unrecognized component of a Rho-dependent signaling pathway that links the intercalated disc to cardiac gene regulation. Moreover, its subcellular localization and the observation of a severe cardiac phenotype in zebrafish, implicate Myozap in the pathogenesis of cardiomyopathy.

Background— We have previously shown that deficiency for the z-disc protein calsarcin-1 (CS1) sensitizes the heart to calcineurin signaling and to stimuli of pathological hypertrophy. In the present study we asked whether overexpression of CS1 might exhibit antihypertrophic effects, and therefore we tested this hypothesis both in vitro and in vivo. Methods and Results— Adenoviral gene transfer of CS1 into neonatal cardiomyocytes inhibited hypertrophy as a result of Gq-agonist stimulation, including angiotensin-II (Ang-II), endothelin-1, and phenylephrine. Consistently, Adenoviral gene transfer of CS1 also led to the reduction of increased levels of atrial natriuretic factor (mRNA) and the calcineurin-sensitive gene MCIP1.4, suggesting that CS1 inhibits calcineurin-dependent signaling. Furthermore, we generated CS1-overexpressing transgenic mice (CS1Tg). Unchallenged CS1Tg mice did not exhibit a pathological phenotype as assessed by echocardiography and analysis of cardiac gene expression. Likewise, when subjected to long-term infusion of Ang-II, both CS1Tg and wild-type mice developed a similar degree of arterial hypertension. Yet, in contrast to wild-type mice, Ang-II–treated CS1Tg animals did not display cardiac hypertrophy. Despite the absence of hypertrophy, both fractional shortening and dP/dt max were preserved in CS1Tg Ang-II–treated mice as assessed by echocardiography and cardiac catherization, respectively. Moreover, induction of the hypertrophic gene program (atrial natriuretic factor, brain natriuretic peptide) was markedly blunted, and expression of the calcineurin-dependent gene MCIP1.4 was significantly reduced in CS1Tg mice, again consistent with an inhibitory role of CS1 on calcineurin. Conclusions— The sarcomeric protein CS1 prevents Ang-II–induced cardiomyocyte hypertrophy at least in part via inhibition of calcineurin signaling. Thus, overexpression of CS1 might represent a novel approach to attenuate pathological cardiac hypertrophy.

none 27 si Dissemination of primary tumor cells depends on migratory and invasive attributes. Here, we identify Navigator-3 (NAV3), a gene frequently mutated or deleted in human tumors, as a regulator of epithelial migration and invasion. Following induction by growth factors, NAV3 localizes to the plus ends of microtubules and enhances their polarized growth. Accordingly, NAV3 depletion trimmed microtubule growth, prolonged growth factor signaling, prevented apoptosis and enhanced random cell migration. Mathematical modeling suggested that NAV3-depleted cells acquire an advantage in terms of the way they explore their environment. In animal models, silencing NAV3 increased metastasis, whereas ectopic expression of the wild-type form, unlike expression of two, relatively unstable oncogenic mutants from human tumors, inhibited metastasis. Congruently, analyses of > 2,500 breast and lung cancer patients associated low NAV3 with shorter survival. We propose that NAV3 inhibits breast cancer progression by regulating microtubule dynamics, biasing directionally persistent rather than random migration, and inhibiting locomotion of initiated cells. Hadas Cohen-Dvashi1, Nir Ben-Chetrit1, Roslin Russell2, Silvia Carvalho1, Mattia Lauriola1,‡, Sophia Nisani1, Maicol Mancini1, Nishanth Nataraj1, Merav Kedmi1, Lee Roth1, Wolfgang Köstler1,†, Amit Zeisel3, Assif Yitzhaky3, Jacques Zylberg4, Gabi Tarcic1, Raya Eilam1, Yoav Wigelman1, Rainer Will5, Sara Lavi1, Ziv Porat6, Stefan Wiemann5, Sara Ricardo7, Fernando Schmitt7, Carlos Caldas2 & Yosef Yarden1,* Hadas Cohen-Dvashi1, Nir Ben-Chetrit1, Roslin Russell2, Silvia Carvalho1, Mattia Lauriola1,‡, Sophia Nisani1, Maicol Mancini1, Nishanth Nataraj1, Merav Kedmi1, Lee Roth1, Wolfgang Köstler1,†, Amit Zeisel3, Assif Yitzhaky3, Jacques Zylberg4, Gabi Tarcic1, Raya Eilam1, Yoav Wigelman1, Rainer Will5, Sara Lavi1, Ziv Porat6, Stefan Wiemann5, Sara Ricardo7, Fernando Schmitt7, Carlos Caldas2 & Yosef Yarden1,*

A novel peripheral membrane protein (2c18) that interacts directly with the gamma 'ear' domain of the adaptor protein complex 1 (AP-1) in vitro and in vivo is described. Ultrastructural analysis demonstrates a colocalization of 2c18 and gamma1-adaptin at the trans-Golgi network (TGN) and on vesicular profiles. Overexpression of 2c18 increases the fraction of membrane-bound gamma1-adaptin and inhibits its release from membranes in response to brefeldin A. Knockdown of 2c18 reduces the steady-state levels of gamma1-adaptin on membranes. Overexpression or downregulation of 2c18 leads to an increased secretion of the lysosomal hydrolase cathepsin D, which is sorted by the mannose-6-phosphate receptor at the TGN, which itself involves AP-1 function for trafficking between the TGN and endosomes. This suggests that the direct interaction of 2c18 and gamma1-adaptin is crucial for membrane association and thus the function of the AP-1 complex in living cells. We propose to name this protein gamma-BAR.

Cancer cells have high levels of thioredoxin (Trx) and of glyceraldehyde 3-phosphate dehydrogenase (GAPDH). Cells from patients with the cancer-prone disease Fanconi anemia (FA) exhibit reduced Trx levels. We found the activity of GAPDH to correlate directly with the endogenous Trx content and mRNA transcripts for GAPDH and TRx reduced in FA cells. The treatment of cells with reduced human Trx stimulated the synthesis of GAPDH mRNA. Similarly, the transfection of cells with an expression plasmid for Trx increased GAPDH mRNA synthesis. Trx treatment of cells and subsequent analysis of the differential gene expression by human cDNA arrays containing about 50 000 different PCR products resulted in more than 300 up- or downregulated genes. Two representative genes, GAPDH and IkappaBalpha/MAD-3, were further investigated to confirm their stimulation by Trx. Trx besides being the major carrier of redox potential of cells is also a regulator of gene expression on the transcriptional level. By regulation via Trx, cells are able to adapt to the prevailing redox conditions. These findings also enlighten the pathophysiology of FA in the respect that the characteristic diminution of Trx that results in the dysregulation of gene expression is a basis for the major symptoms of this disease.

Aggressive breast cancer is associated with poor patient outcome and characterized by the development of tumor cell variants that are able to escape from control of the immune system or are resistant to targeted therapies. The complex molecular mechanisms leading to immune escape and therapy resistance are incompletely understood. We have previously shown that high miR-519a-3p levels are associated with poor survival in breast cancer. Here, we demonstrate that miR-519a-3p confers resistance to apoptosis induced by TRAIL, FasL and granzyme B/perforin by interfering with apoptosis signaling in breast cancer cells. MiR-519a-3p diminished the expression of its direct target genes for TRAIL-R2 (TNFRSF10B) and for caspase-8 (CASP8) and its indirect target gene for caspase-7 (CASP7), resulting in reduced sensitivity and tumor cell apoptosis in response to apoptotic stimuli. Furthermore, miR-519a-3p impaired tumor cell killing by natural killer (NK) cells via downregulation of the NKG2D ligands ULBP2 and MICA on the surface of tumor cells that are crucial for the recognition of these tumor cells by NK cells. We determined that miR-519a-3p was overexpressed in more aggressive mutant TP53 breast cancer that was associated with poor survival. Furthermore, low levels of TRAIL-R2, caspase-7 and caspase-8 correlated with poor survival, suggesting that the inhibitory effect of miR-519a-3p on TRAIL-R2 and caspases may have direct clinical relevance in lowering patient’s prognosis. In conclusion, we demonstrate that miR-519a-3p is a critical factor in mediating resistance toward cancer cell apoptosis and impairing tumor cell recognition by NK cells. This joint regulation of apoptosis and immune cell recognition through miR-519a-3p supports the hypothesis that miRNAs are key regulators of cancer cell fate, facilitating cancer progression and evasion from immunosurveillance at multiple and interconnected levels.

Nuclear Factor kappa B (NF-κB) signaling is frequently deregulated in a variety of cancers and is constitutively active in estrogen receptor negative (ER-) breast cancer subtypes. These molecular subtypes of breast cancer are associated with poor overall survival. We focused on mechanisms of NF-κB regulation by microRNAs (miRNAs), which regulate eukaryotic gene expression at the post-transcriptional level. In a previous genome-wide miRNA screen, we had identified miR-30c-2-3p as one of the strongest negative regulators of NF-κB signaling. Here we have uncovered the underlying molecular mechanisms and its consequences in breast cancer. In vitro results show that miR-30c-2-3p directly targets both TNFRSF1A-associated via death domain (TRADD), an adaptor protein of the TNFR/NF-κB signaling pathway, and the cell cycle protein Cyclin E1 (CCNE1). Ectopic expression of miR-30c-2-3p downregulated essential cytokines IL8, IL6, CXCL1, and reduced cell proliferation as well as invasion in MDA-MB-231 breast cancer cells. RNA interference (RNAi) induced silencing of TRADD phenocopied the effects on invasion and cytokine expression caused by miR-30c-2-3p, while inhibition of CCNE1 phenocopied the effects on cell proliferation. We further confirmed the tumor suppressive role of this miRNA using a dataset of 781 breast tumors, where higher expression was associated with better survival in breast cancer patients. In summary we have elucidated the mechanism by which miR-30c-2-3p negatively regulates NF-κB signaling and cell cycle progression in breast cancer.

Rationale and Objective: The M-band represents a transverse structure in the center of the sarcomeric A-band and provides an anchor for the myosin-containing thick filaments. In contrast to other sarcomeric structures, eg, the Z-disc, only few M-band–specific proteins have been identified to date, and its exact molecular composition remains unclear. Methods and Results: Using a bioinformatic approach to identify novel heart- and muscle-specific genes, we found a leucine rich protein, myomasp ( Myo sin-interacting, M -band- a ssociated s tress-responsive p rotein)/LRRC39. RT-PCR and Northern and Western blot analyses confirmed a cardiac-enriched expression pattern, and immunolocalization of myomasp revealed a strong and specific signal at the sarcomeric M-band. Yeast 2-hybrid screens, as well as coimmunoprecipitation experiments, identified the C terminus of myosin heavy chain (MYH)7 as an interaction partner for myomasp. Knockdown of myomasp in neonatal rat ventricular myocytes (NRVCMs) led to a significant upregulation of the stretch-sensitive genes GDF-15 and BNP. Conversely, the expression of MYH7 and the M-band proteins myomesin-1 and -2 was found to be markedly reduced. Mechanistically, knockdown of myomasp in NRVCM led to a dose-dependent suppression of serum response factor–dependent gene expression, consistent with earlier observations linking the M-band to serum response factor–mediated signaling. Finally, downregulation of myomasp/LRRC39 in spontaneously beating engineered heart tissue constructs resulted in significantly lower force generation and reduced fractional shortening. Likewise, knockdown of the myomasp/LRRC39 ortholog in zebrafish resulted in severely impaired heart function and cardiomyopathy in vivo. Conclusions: These findings reveal myomasp as a previously unrecognized component of an M-band–associated signaling pathway that regulates cardiomyocyte gene expression in response to biomechanical stress.

Aims Left ventricular non-compaction (LVNC) is caused by mutations in multiple genes. It is still unclear whether LVNC is the primary determinant of cardiomyopathy or rather a secondary phenomenon with intrinsic cardiomyocyte dysfunction being the actual cause of the disease. Here, we describe a family with LVNC due to a novel missense mutation, pE96K, in the cardiac troponin T gene ( TNNT2 ). Methods and results The novel mutation was identified in the index patient and all affected relatives, but not in 430 healthy control individuals. Mutations in known LVNC-associated genes were excluded. To investigate the pathophysiological implications of the mutation, we generated transgenic mice expressing human wild-type cTNT (hcTNT) or a human troponin T harbouring the pE96K mutation (mut cTNT). Animals were characterized by echocardiography, histology, and gene expression analysis. Mut cTNT mice displayed an impaired left ventricular function and induction of marker genes of heart failure. Remarkably, left ventricular non-compaction was not observed. Conclusion Familial co-segregation and the cardiomyopathy phenotype of mut cTNT mice strongly support a causal relationship of the pE96K mutation and disease in our index patient. In addition, our data suggest that a non-compaction phenotype is not required for the development of cardiomyopathy in this specific TNNT2 mutation leading to LVNC.