| 1. |
- Achari, Chandrani, et al.
(author)
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Down Regulation of CLDND1 Induces Apoptosis in Breast Cancer Cells.
- 2015
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In: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 10:6
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Journal article (peer-reviewed)abstract
- Identification of targets for apoptosis induction is important to provide novel therapeutic approaches in breast cancer. Our earlier studies showed that down regulation of protein kinase C δ (PKCδ) induces death in breast cancer cells. In this study we set out to identify previously unrecognized apoptosis regulators in breast cancer cells. To identify candidates, global expression analysis with microarray was performed after down regulation of PKCδ in the basal-like breast cancer cell lines MDA-MB-231, MDA-MB-468 and BT-549. Genes that were down regulated in all cell lines were further studied for survival-supporting effects. The claudin-like CLDND1 was singled out since several independent siRNAs targeting CLDND1 induced cell death in several cell lines. The cell death induced by CLDND1 knockdown was caspase-dependent, suggesting induction of apoptosis. Nuclear fragmentation, cleavage of caspase-3 and PARP and release of cytochrome C from the mitochondria upon CLDND1 depletion demonstrated involvement of the intrinsic apoptotic pathway. Inhibition of MEK1/2 and JNK further potentiated the cell death induction by CLDND1 knockdown. However, CLDND1 down regulation augmented ERK1/2 phosphorylation, which thereby may protect against the apoptosis inducing effects of CLDND1 down regulation. A concomitant inhibition of MEK1/2 suppresses the ERK1/2 phosphorylation and markedly potentiates the cell death following CLDND1 siRNA treatment. There is today little information on the function of CLDND1. These data provide novel information on CLDND1 and highlight it as a novel survival factor in basal-like breast cancer cell lines.
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| 2. |
- Achari, Chandrani, et al.
(author)
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Expression of miR-34c induces G2/M cell cycle arrest in breast cancer cells
- 2014
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In: BMC Cancer. - : Springer Science and Business Media LLC. - 1471-2407. ; 14
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Journal article (peer-reviewed)abstract
- Background: MicroRNA-34 is a family of three miRNAs that have been reported to function as tumor suppressor miRNAs and show decreased expression in various cancers. Here, we examine functions of miR-34c in basal-like breast cancer cells. Methods: Data from The Cancer Genome Atlas (TCGA) were used for evaluation of expression in primary breast cancers. Cellular processes affected by miR-34c were investigated by thymidine incorporation, Annexin V-assays and cell cycle analysis using breast cancer cell lines. Effects on potential targets were analyzed with qPCR and Western blot. Results: TCGA data revealed that miR-34c was expressed at lower levels in basal-like breast cancer tumors and low expression was associated with poor prognosis. Ectopic expression of miR-34c in basal-like breast cancer cell lines resulted in suppressed proliferation and increased cell death. Additionally, miR-34c influenced the cell cycle mainly by inducing an arrest in the G2/M phase. We found that expression levels of the known cell cycle-regulating miR-34 targets CCND1, CDK4 and CDK6, were downregulated upon miR-34c expression in breast cancer cell lines. In addition, the levels of CDC23, an important mediator in mitotic progression, were suppressed following miR-34c expression, and siRNAs targeting CDC23 mimicked the effect of miR-34c on G2/M arrest. However, protein levels of PRKCA, a predicted miR-34c target and a known regulator of breast cancer cell proliferation were not influenced by miR-34c. Conclusions: Together, our results support the role of miR-34c as a tumor suppressor miRNA also in breast cancer.
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| 3. |
- Brauß, Thilo F., et al.
(author)
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The RNA-binding protein HuR inhibits expression of CCL5 and limits recruitment of macrophages into tumors
- 2017
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In: Molecular Carcinogenesis. - : Wiley. - 0899-1987. ; 56:12, s. 2620-2629
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Journal article (peer-reviewed)abstract
- The RNA-binding protein HuR promotes tumor growth by affecting proliferation, metastasis, apoptosis, and angiogenesis. Although immune cells, especially tumor-associated macrophages, are critical components of the tumor stroma, the influence of HuR in tumors on the recruitment of immune cells remains poorly understood. In the present study, we, therefore, aimed to elucidate the impact of tumor cell HuR on the interaction between tumor cells and macrophages. To this end, we stably depleted HuR in human MCF-7 breast cancer cells. We found that HuR-deficient cells not only showed reduced proliferation, they further expressed elevated levels of the chemokine CCL5. HuR-dependent repression of CCL5 was neither caused by altered CCL5 mRNA stability, nor by changes in CCL5 translation. Instead, loss of HuR augmented transcription of CCL5, which was mediated via an interferon-stimulated response element in the CCL5 promoter. Furthermore, HuR depletion enhanced macrophage recruitment into MCF-7 tumor spheroids, an effect which was completely lost upon neutralization of CCL5. HuR expression further negatively correlated with CCL5 expression and macrophage appearance in a cohort of breast tumors. Thus, while HuR is well-characterized to support various pro-tumorigenic features in tumor cells, we provide evidence that it limits the recruitment of macrophages into tumors by repressing CCL5. As macrophage infiltration is associated with poor prognosis, our findings underline the highly cell-type and context specific role of HuR in tumorigenesis.
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| 4. |
- Kobayashi, Tamae, et al.
(author)
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PKCα Binds G3BP2 and Regulates Stress Granule Formation Following Cellular Stress
- 2012
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In: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 7:4, s. e35820-
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Journal article (peer-reviewed)abstract
- Protein kinase C (PKC) isoforms regulate a number of processes crucial for the fate of a cell. In this study we identify previously unrecognized interaction partners of PKCα and a novel role for PKCα in the regulation of stress granule formation during cellular stress. Three RNA-binding proteins, cytoplasmic poly(A)(+) binding protein (PABPC1), IGF-II mRNA binding protein 3 (IGF2BP3), and RasGAP binding protein 2 (G3BP2) all co-precipitate with PKCα. RNase treatment abolished the association with IGF2BP3 and PABPC1 whereas the PKCα-G3BP2 interaction was largely resistant to this. Furthermore, interactions between recombinant PKCα and G3BP2 indicated that the interaction is direct and PKCα can phosphorylate G3BP2 in vitro. The binding is mediated via the regulatory domain of PKCα and the C-terminal RNA-binding domain of G3BP2. Both proteins relocate to and co-localize in stress granules, but not to P-bodies, when cells are subjected to stress. Heat shock-induced stress granule assembly and phosphorylation of eIF2α are suppressed following downregulation of PKCα by siRNA. In conclusion this study identifies novel interaction partners of PKCα and a novel role for PKCα in regulation of stress granules.
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| 5. |
- Larsson, Christer, et al.
(author)
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Prognostic implications of the expression levels of different immunoglobulin heavy chain-encoding RNAs in early breast cancer
- 2020
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In: npj Breast Cancer. - : Springer Science and Business Media LLC. - 2374-4677. ; 6:1
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Journal article (peer-reviewed)abstract
- The extent and composition of the immune response in a breast cancer is one important prognostic factor for the disease. The aim of the current work was to refine the analysis of the humoral component of an immune response in breast tumors by quantifying mRNA expression of different immunoglobulin classes and study their association with prognosis. We used RNA-Seq data from two local population-based breast cancer cohorts to determine the expression of IGJ and immunoglobulin heavy (IGH) chain-encoding RNAs. The association with prognosis was investigated and public data sets were used to corroborate the findings. Except for IGHE and IGHD, mRNAs encoding heavy chains were generally detected at substantial levels and correlated with other immune-related genes. High IGHG1 mRNA was associated with factors related to poor prognosis such as estrogen receptor negativity, HER2 amplification, and high grade, whereas high IGHA2 mRNA levels were primarily associated with lower age at diagnosis. High IGHA2 and IGJ mRNA levels were associated with a more favorable prognosis both in univariable and multivariable Cox models. When adjusting for other prognostic factors, high IGHG1 mRNA levels were positively associated with improved prognosis. To our knowledge, these results are the first to demonstrate that expression of individual Ig class types has prognostic implications in breast cancer.
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| 6. |
- Mertens, Christina, et al.
(author)
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Macrophage-derived lipocalin-2 transports iron in the tumor microenvironment
- 2018
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In: OncoImmunology. - 2162-4011. ; 7:3
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Journal article (peer-reviewed)abstract
- While the importance of iron for tumor development is widely appreciated, the exact sources of tumor-supporting iron largely remain elusive. The possibility that iron might be provided by stromal cells in the tumor microenvironment was not taken into account so far. In the present study, we show that tumor-associated macrophages (TAM) acquire an iron-release phenotype upon their interaction with tumor cells, thereby increasing the availability of iron in the tumor microenvironment. Mechanistically, TAM expressed elevated levels of the high-affinity iron-binding protein lipocalin-2 (LCN-2), which appeared to be critical for the export of iron from TAM, and in turn enhanced tumor cell proliferation. Moreover, in PyMT-mouse tumors as well as in primary human breast tumors LCN-2 was predominantly expressed in the tumor stroma as compared to tumor cells. LCN-2 expression in the stroma further correlated with enhanced tumor proliferation in vivo. Our data suggest a dominant role of TAM in the tumor iron-management and identify LCN-2 as a critical iron transporter in this context. Targeting the LCN-2 iron export mechanism selectively in stromal cells might open for future iron-targeted tumor therapeutic approaches.
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| 7. |
- Winslow, Sofia, et al.
(author)
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Prognostic stromal gene signatures in breast cancer.
- 2015
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In: Breast Cancer Research. - : Springer Science and Business Media LLC. - 1465-5411 .- 1465-542X. ; 17:1
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Journal article (peer-reviewed)abstract
- Global gene expression analysis of tumor samples has been a valuable tool to subgroup tumors and has the potential to be of prognostic and predictive value. However, tumors are heterogeneous, and homogenates will consist of several different cell types. This study was designed to obtain more refined expression data representing different compartments of the tumor.
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| 8. |
- Winslow, Sofia
(author)
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Regulation of cellular growth and identification of stromal gene signatures in breast cancer
- 2014
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Doctoral thesis (other academic/artistic)abstract
- Normal tissue is tightly controlled to keep a balance between reproduction and elimination of cells. In cancer, these regulated processes are disrupted, resulting in uncontrolled cell growth. Regulation of RNA stability and turnover is important to maintain cellular homeostasis and can be controlled by various mechanisms. During stress, the cell can form cytoplasmic complexes of proteins and RNAs, called stress granules, to inhibit translation of proteins unnecessary for the cell during harmful conditions and focus translation on stress-related proteins. In neuroblastoma and breast cancer cell lines, we have found that the protein kinase Cα (PKCα) isoform can influence stress granule formation in a stress inducer-specific way. Depletion of PKCα led to a delayed stress response along with an initial loss of eIF2α phosphorylation in heat shock, but not arsenite, treated cells. G3BP proteins are well-known stress inducers and we identified a direct interaction between PKCα and the G3BP2 isoform. G3BP2 belongs to a family of three homologous proteins with RNA-regulating capacities. With the aim to identify specific RNA targets, we performed a gene expression analysis and detected a negative regulation of the peripheral myelin protein (PMP22) by the G3BP1 isoform. The previously reported growth suppressing effects by PMP22 was here verified in breast cancer cells and we could show that G3BP1 influences growth regulation by reducing PMP22 expression, although not through mRNA destabilizing mechanisms. Another RNA regulating mechanism that can promote or prevent tumor progression are mRNA silencing through miRNA. We analyzed miR-34c and its function in breast cancer and identified impaired cell growth, induced apoptosis and cell cycle G2/M arrest, which might be due to regulation of the anaphase-promoting complex protein Cdc23. The tumor is not a homogenous compartment, but consists of various different cell types, both among the cancer cells as well as in the surrounding stroma. We have developed a methodological procedure for isolation and characterization of cancer- and stroma-specific genes using laser capture microdissection on FFPE triple negative breast cancers. Gene expression microarrays of these samples revealed compartment specific gene expression and enabled identification of stromal-specific gene signatures with tumor-predictive capacity.
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| 9. |
- Winslow, Sofia, et al.
(author)
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Regulation of PMP22 mRNA by G3BP1 affects cell proliferation in breast cancer cells.
- 2013
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In: Molecular Cancer. - : Springer Science and Business Media LLC. - 1476-4598. ; 12:1
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Journal article (peer-reviewed)abstract
- Regulation of mRNAs is one way to control protein levels and thereby important cellular processes such as growth, invasion and apoptosis. G3BPs constitute a family of mRNA-binding proteins, shown to be overexpressed in several cancer types, including breast, colon and pancreas cancer. G3BP has been reported to both stabilize and induce degradation of specific mRNAs.
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| 10. |
- Winslow, Sofia, et al.
(author)
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The expression pattern of matrix-producing tumor stroma is of prognostic importance in breast cancer
- 2016
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In: Bmc Cancer. - : Springer Science and Business Media LLC. - 1471-2407. ; 16
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Journal article (peer-reviewed)abstract
- Background: There are several indications that the composition of the tumor stroma can contribute to the malignancy of a tumor. Here we utilized expression data sets to identify metagenes that may serve as surrogate marker for the extent of matrix production and vascularization of a tumor and to characterize prognostic molecular components of the stroma. Methods: TCGA data sets from six cancer forms, two breast cancer microarray sets and one mRNA data set of xenografted tumors were downloaded. Using the mean correlation as distance measure compact clusters with genes representing extracellular matrix production (ECM metagene) and vascularization (endothelial metagene) were defined. Explorative Cox modeling was used to identify prognostic stromal gene sets. Results: Clustering of stromal genes in six cancer data sets resulted in metagenes, each containing three genes, representing matrix production and vascularization. The ECM metagene was associated with poor prognosis in renal clear cell carcinoma and in lung adenocarcinoma but not in other cancers investigated. Explorative Cox modeling using gene pairs identified gene sets that in multivariate models were prognostic in breast cancer. This was validated in two microarray sets. Two notable genes are TCF4 and P4HA3 which were included in the sets associated with positive and negative prognosis, respectively. Data from laser-microdissected tumors, a xenografted tumor data set and from correlation analyses demonstrate the stroma specificity of the genes. Conclusions: It is possible to construct ECM and endothelial metagenes common for several cancer forms. The molecular composition of matrix-producing cells, rather than the extent of matrix production seem to be important for breast cancer prognosis.
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