Search

Mutations in U2AF1 are relatively common in myelodysplastic neoplasms (MDS) and are associated with an inferior prognosis, but the molecular mechanisms underlying this are not fully elucidated. Circular RNAs (circRNAs) have been implicated in cancer, but it is unknown how mutations in splicing factors may impact on circRNA biogenesis. Here, we used RNA-sequencing to investigate the effects of U2AF1 mutations on circRNA expression in K562 cells with a doxycycline-inducible U2AF1 S34 mutation, in a mouse model with a doxycycline-inducible U2AF1 S34 mutation, and in FACS-sorted CD34+ bone marrow cells from MDS patients with either U2AF1 S34 or U2AF1 Q157 mutations. In all contexts, we found an increase in global circRNA levels in the U2AF1-mutated setting, which was independent of expression changes in the cognate linear host genes. In patients, the U2AF1 S34 and U2AF1 Q157 mutations were both associated with an overall increased expression of circRNAs. circRNAs generated by a non-Alu-mediated mechanism generally showed the largest increase in expression levels. Several well-described cancer-associated circRNAs, including circZNF609 and circCSNK1G3, were upregulated in MDS patients with U2AF1 mutations compared to U2AF1-wildtype MDS controls. In conclusion, high circRNA expression is observed in association with U2AF1 mutations in three biological systems, presenting an interesting possibility for biomarker and therapeutic investigation.

Purpose: Carcinoma progression is linked to a partially dedifferentiated epithelial cell phenotype. As previously suggested, this regulation could involve transcription factors, Snail and Slug, known to promote epithelial-mesenchymal transitions during development. Here, we investigate the role of Snail and Slug in human breast cancer progression.Experimental Design: We analyzed Snail, Slug, and E-cadherin RNA expression levels and protein localization in large numbers of transformed cell lines and breast carcinomas, examined the correlation with tumor histologic features, and described, at the cellular level, Snail and Slug localization in carcinomas using combined in situ hybridization and immunolocalization.Results: In contrast with transformed cell lines, Slug was found to colocalize with E-cadherin at the cellular level in normal mammary epithelial cells and all tested carcinomas. Snail also colocalized at the cellular level with E-cadherin in tumors expressing high levels of Snail RNA. In addition, Snail was significantly expressed in tumor stroma, varying with tumors. Slug and Snail genes were significantly overexpressed in tumors associated with lymph node metastasis. Finally, the presence of semidifferentiated tubules within ductal carcinomas was linked to Slug expression levels similar to or above normal breast samples.Conclusions: These results suggest that Snail or Slug expression in carcinoma cells does not generally preclude significant E-cadherin expression. They emphasize a link between Snail, Slug, and lymph node metastasis in a large sampling of mammary carcinomas, and suggest a role for Slug in the maintenance of semidifferentiated structures. Snail and Slug proteins seem to support distinct tumor invasion modes and could provide new therapeutic targets.

Supplementary Tables 2-3 from Snail and Slug Play Distinct Roles during Breast Carcinoma Progression

Supplementary Figures 2-3 from Snail and Slug Play Distinct Roles during Breast Carcinoma Progression

Supplementary Figure 1 from Snail and Slug Play Distinct Roles during Breast Carcinoma Progression

Supplementary Data from CIP2A Is Associated with Human Breast Cancer Aggressivity

No description supplied

Background: The thioredoxin-interacting protein (TXNIP) is involved in cellular metabolism and cell proliferation, and recently, deficient expression of TXNIP has been associated with progression and poor outcome for cancer patients. Objectives: To assess TXNIP expression and function in malignant T cells from cutaneous T-cell lymphoma (CTCL). Methods: CTCL-derived malignant (MyLa2059, PB2B) and non-malignant (MyLa1850) cell lines were analysed by Western blotting and qPCR for TXNIP expression. Subsequently, the malignant CTCL cell lines were treated with GSK126 – an inhibitor of enhancer of zeste homolog 2 (EZH2) methyltransferase activity or assessed by bisulphite sequencing for TXNIP promoter methylation. Methylation was also assessed with the demethylating agent 5-azacytidine (5AZA). Finally, TXNIP was overexpressed in the malignant PB2B cell line via plasmid transduction, and the effect of TXNIP was further analysed by flow cytometry. Results: We report on low expression of TXNIP protein in all cell lines representing different subtypes and stages of CTCL when compared to non-malignant T cells. Epigenetic silencing and other mechanisms were involved in the repression of TXNIP whereas forced expression of TXNIP strongly inhibited proliferation of malignant T cells. Conclusions: Epigenetic silencing and other as yet unknown mechanisms repress TXNIP expression in malignant T cells. As forced expression of TXNIP inhibits malignant proliferation, we propose that TXNIP is a putative tumour suppressor in CTCL.

Cancer cells are addicted to ribosome biogenesis and high levels of translation. Thus, differential inhibition of cancer cells can be achieved by targeting aspects of ribosome biogenesis or ribosome function. Using RiboMeth-seq for profiling of the ∼112 2′-O-Me sites in human ribosomal RNA, we demonstrated pronounced hypomethylation at several sites in patient-derived diffuse large B-cell lymphoma (DLBCL) cell lines with a more severe perturbation in ABC-DLBCL compared to GBC-DLBCL. We extended our analysis to tumor samples from patients and demonstrated significant changes to the ribosomal modification pattern that appeared to consist of cell growth-related as well as tumor-specific changes. Sites of hypomethylation in patient samples are discussed as potential drug targets, using as an example a site in the small subunit (SSU-C1440) located in a ribosomal substructure that can be linked to DLBCL pathogenesis.

Diffuse large B-cell lymphoma (DLBCL) is the most common B-cell non-Hodgkin lymphoma. To treat this aggressive disease, R-CHOP, a combination of immunotherapy (R; rituximab) and chemotherapy (CHOP; cyclophosphamide, doxorubicin, vincristine, and prednisone), remains the most commonly used regimen for newly diagnosed DLBCLs. However, up to one-third of patients ultimately becomes refractory to initial therapy or relapses after treatment, and the high mortality rate highlights the urgent need for novel therapeutic approaches based upon selective molecular targets. In order to understand the molecular mechanisms underlying relapsed DLBCL, we studied differences in the lipid and metabolic composition of nontreated and R-CHOP-resistant tumors, using a combination of in vivo DLBCL xenograft models and mass spectrometry imaging. Together, these techniques provide information regarding analyte composition and molecular distributions of therapy-resistant and sensitive areas. We found specific lipid and metabolic profiles for R-CHOP-resistant tumors, such as a higher presence of phosphatidylinositol and sphingomyelin fragments. In addition, we investigated intratumor heterogeneity and identified specific lipid markers of viable and necrotic areas. Furthermore, we could monitor metabolic changes and found reduced adenosine triphosphate and increased adenosine monophosphate in the R CHOP-resistant tumors. This work highlights the power of combining in vivo imaging and MSI to track molecular signatures in DLBCL, which has potential application for other diseases.

The PR-domain (PRDM) family of genes encodes transcriptional regulators, several of which are deregulated in cancer. By using a functional screening approach, we sought to identify novel tumor suppressors among the PRDMs. Here we demonstrate oncogenic collaboration between depletion of the previously uncharacterized PR-domain family member Prdm11 and overexpression of MYC. Overexpression of PRDM11 inhibits proliferation and induces apoptosis. Prdm11 knockout mice are viable, and loss of Prdm11 accelerates MYC-driven lymphomagenesis in the Eµ-Myc mouse model. Moreover, we show that patients with PRDM11-deficient diffuse large B-cell lymphomas (DLBCLs) have poorer overall survival and belong to the nongerminal center B-cell-like subtype. Mechanistically, genome-wide mapping of PRDM11 binding sites coupled with transcriptome sequencing in human DLBCL cells evidenced that PRDM11 associates with transcriptional start sites of target genes and regulates important oncogenes such as FOS and JUN. Hence, we characterize PRDM11 as a putative novel tumor suppressor that controls the expression of key oncogenes, and we add new mechanistic insight into B-cell lymphomagenesis.

We currently have limited knowledge of the involvement of long non-coding RNAs (lncRNAs) in normal cellular processes and pathologies. Here, we identify and characterize SNHG5 as a stable cytoplasmic lncRNA with up-regulated expression in colorectal cancer. Depletion of SNHG5 induces cell cycle arrest and apoptosis in vitro and limits tumour outgrowth in vivo, whereas SNHG5 overexpression counteracts oxaliplatin-induced apoptosis. Using an unbiased approach, we identify 121 transcript sites interacting with SNHG5 in the cytoplasm. Importantly, knockdown of key SNHG5 target transcripts, including SPATS2, induces apoptosis and thus mimics the effect seen following SNHG5 depletion. Mechanistically, we suggest that SNHG5 stabilizes the target transcripts by blocking their degradation by STAU1. Accordingly, depletion of STAU1 rescues the apoptosis induced after SNHG5 knockdown. Hence, we characterize SNHG5 as a lncRNA promoting tumour cell survival in colorectal cancer and delineate a novel mechanism in which a cytoplasmic lncRNA functions through blocking the action of STAU1., Several lncRNAs have been linked to cancer. Here, the authors identify SNHG5 as a long non-coding RNA promoting proliferation and survival of colorectal cancer cells by protecting specific mRNAs from STAU1-mediated degradation.

INTRODUCTION: Circular RNAs (circRNAs) are covalently closed endogenous RNA molecules with tissue- and disease specific expression patterns, that are emerging as potential diagnostic and prognostic biomarkers. These molecules exert diverse regulatory functions, and several studies have reported prognostic relevance and functional significance of circRNAs in cancer. However, no studies have yet examined the role of circRNAs in Mantle Cell Lymphoma (MCL). We have previously shown that the Nanostring nCounter technology enables specific, sensitive and accurate quantification of circRNAs in formalin-fixed, paraffin-embedded (FFPE) tissue samples from patients (Dahl et al, 2018). Here, we quantified circRNA expression in MCL tumors to address whether certain circRNAs could serve as prognostic markers in MCL. Samples were obtained from patients treated in the two Nordic clinical trials MCL2 and MCL3, all treated with immuno-chemotherapy and autologous stem cell transplant, which due to the improved prognosis observed with this regimen, remains the current standard of care. MATERIALS AND METHODS: We profiled the genome-wide circRNA expression in MCL using high-throughput RNA-sequencing (RNA-seq) of 14 diagnostic MCL samples, from which high-quality RNA from lymph nodes with MCL tumor infiltration was available. Based on these data, we designed assays for analyses of 41 differentially expressed circRNAs and quantified the expression using the NanoString nCounter technology. We examined the prognostic potential of individual circRNAs in a training cohort of 75 patients (MCL2) and confirmed these results in an independent, but similarly treated, validation cohort of 90 patients (MCL3). RESULTS: The total cohort consisted of 165 previously untreated MCL patients In our training cohort we identified seven circRNAs that were significantly associated with both progression-free survival (PFS), TTP, overall survival (OS) and lymphoma specific survival (LSS). We dichotomized expression values of each individual circRNA and examined the prognostic value in the validation cohort MCL3. Only one (circRAB11FIP1) of the seven circRNAs identified in MCL2 retained prognostic value in MCL3. As shown in Figure 1, univariate analysis revealed that low circRAB11FIP1 expression was significantly associated with TTP in MCL2 (HR=5.1, [2.5;10.4], p Finally, we performed a multivariate cox regression analysis of the entire cohort and found that circRAB11FIP1 was an independent prognostic factor for TTP, even when adjusting for MIPI and ki67-index (HR=2.36[1.3;4.4], p CONCLUSION: Our study showed that low circRAB11FIP1 was significantly associated with shorter TTP, even when adjusting for known prognostic factors, indicating that circRAB11FIP1 could play a specific role in the pathogenesis of MCL. CircRAB11FIP1 originates from exon 2 of the host gene RAB11-Family Interacting Protein 1 located on chromosome 8, and no studies have yet examined the functional role of this circRNA. Interestingly, we found that low circRAB11FIP1 was significantly associated with the presence of TP53 mutations. This warrants future studies to examine whether there is a functional link between circRAB11FIP1 and TP53 in MCL, which may help explain why patients with TP53 mutations have an exceedingly poor prognosis. Figure Disclosures Kolstad: Merck: Research Funding; Nordic Nanovector: Membership on an entity's Board of Directors or advisory committees, Research Funding. Jerkeman:Janssen: Honoraria, Research Funding; Gilead: Honoraria, Research Funding; Acerta: Honoraria, Research Funding; Celgene: Honoraria, Research Funding; Roche: Honoraria, Research Funding.

Senescence induction contributes to cancer therapy responses and is crucial for p53-mediated tumor suppression. However, whether p53 inactivation actively suppresses senescence induction has been unclear. Here, we show that E2F1 overexpression, due to p53 or p21 inactivation, promotes expression of human oncoprotein CIP2A, which in turn, by inhibiting PP2A activity, increases stabilizing serine 364 phosphorylation of E2F1. Several lines of evidence show that increased activity of E2F1-CIP2A feedback renders breast cancer cells resistant to senescence induction. Importantly, mammary tumorigenesis is impaired in a CIP2A-deficient mouse model, and CIP2A-deficient tumors display markers of senescence induction. Moreover, high CIP2A expression predicts for poor prognosis in a subgroup of patients with breast cancer treated with senescence-inducing chemotherapy. Together, these results implicate the E2F1-CIP2A feedback loop as a key determinant of breast cancer cell sensitivity to senescence induction. This feedback loop also constitutes a promising prosenescence target for therapy of cancers with an inactivated p53–p21 pathway. Significance: It has been recently realized that most currently used chemotherapies exert their therapeutic effect at least partly by induction of terminal cell arrest, senescence. However, the mechanisms by which cell-intrinsic senescence sensitivity is determined are poorly understood. Results of this study identify the E2F1-CIP2A positive feedback loop as a key determinant of breast cancer cell sensitivity to senescence and growth arrest induction. Our data also indicate that this newly characterized interplay between 2 frequently overexpressed oncoproteins constitutes a promising prosenescence target for therapy of cancers with inactivated p53 and p21. Finally, these results may also facilitate novel stratification strategies for selection of patients to receive senescence-inducing cancer therapies. Cancer Discov; 3(2); 182–97. ©2013 AACR. This article is highlighted in the In This Issue feature, p. 125

The oncoprotein Cancerous Inhibitor of Protein Phosphatase 2A ( CIP2A) is overexpressed in most malignancies and is an obvious candidate target protein for future cancer therapies. However, the physiological importance of CIP2A-mediated PP2A inhibition is largely unknown. As PP2A regulates immune responses, we investigated the role of CIP2A in normal immune system development and during immune response in vivo. We show that CIP2A-deficient mice (CIP2A(HOZ)) present a normal immune system development and function in unchallenged conditions. However when challenged with Listeria monocytogenes, CIP2A(HOZ) mice display an impaired adaptive immune response that is combined with decreased frequency of both CD4(+) T-cells and CD8(+) effector T-cells. Importantly, the cell autonomous effect of CIP2A deficiency for T-cell activation was confirmed. Induction of CIP2A expression during T-cell activation was dependent on Zap70 activity. Thus, we reveal CIP2A as a hitherto unrecognized mediator of T-cell activation during adaptive immune response. These results also reveal CIP2A(HOZ) as a possible novel mouse model for studying the role of PP2A activity in immune regulation. On the other hand, the results also indicate that CIP2A targeting cancer therapies would not cause serious immunological side-effects.

Purpose: To investigate the clinical relevance of the recently characterized human oncoprotein cancerous inhibitor of protein phosphatase 2A (CIP2A) in human breast cancer. Experimental Design: CIP2A expression (mRNA and protein) was measured in three different sets of human mammary tumors and compared with clinicopathologic variables. The functional role of CIP2A in breast cancer cells was evaluated by small interfering RNA–mediated depletion of the protein followed by an analysis of cell proliferation, migration, anchorage-independent growth, and xenograft growth. Results: CIP2A mRNA is overexpressed (n = 159) and correlates with higher Scarff-Bloom-Richardson grades (n = 251) in samples from two independent human breast cancer patients. CIP2A protein was found to be overexpressed in 39% of 33 human breast cancer samples. Furthermore, CIP2A mRNA expression positively correlated with lymph node positivity of the patients and with the expression of proliferation markers and p53 mutations in the tumor samples. Moreover, CIP2A protein expression was induced in breast cancer mouse models presenting mammary gland–specific depletion of p53 and either BRCA1 or BRCA2. Functionally, CIP2A depletion was shown to inhibit the expression of its target protein c-Myc. Loss of CIP2A also inhibited anchorage-independent growth in breast cancer cells. Finally, CIP2A was shown to support MDA-MB-231 xenograft growth in nude mice. Conclusions: Our data show that CIP2A is associated with clinical aggressivity in human breast cancer and promotes the malignant growth of breast cancer cells. Thus, these results validate the role of CIP2A as a clinically relevant human oncoprotein and warrant further investigation of CIP2A as a therapeutic target in breast cancer treatment. (Clin Cancer Res 2009;15(16):5092–100)

We established a selection strategy to identify new models for an altered airway inflammatory response from a large compendium of mutant mouse lines that were systemically phenotyped in the German Mouse Clinic (GMC). As selection criteria we included published gene functional data, as well as immunological and transcriptome data from GMC phenotyping screens under standard conditions. Applying these criteria we identified a few from several hundred mutant mouse lines and further characterized the Cox4i2tm1Hutt, Ifit2tm1.1Ebsb, and Prdm11tm1.1ahl lines following ovalbumin (OVA) sensitization and repeated OVA airway challenge. Challenged Prdm11tm1.1ahl mice exhibited changes in B cell counts, CD4+ T cell counts, and in the number of neutrophils in bronchoalveolar lavages, whereas challenged Ifit2tm1.1Ebsb mice displayed alterations in plasma IgE, IgG1, IgG3, and IgM levels compared to the challenged wild type littermates. In contrast, challenged Cox4i2tm1Hutt mutant mice did not show alterations in the humoral or cellular immune response compared to challenged wild type mice. Transcriptome analyses from lungs of the challenged mutant mouse lines showed extensive changes in gene expression in Prdm11tm1.1ahl mice. Functional annotations of regulated genes of all three mutant mouse lines were primarily related to inflammation and airway smooth muscle (ASM) remodeling. We were thus able to define an effective selection strategy to identify new candidate genes for the predisposition to an altered airway inflammatory response under OVA challenge conditions. Similar selection strategies may be used for the analysis of additional genotype - envirotype interactions for other diseases.

International audience; To investigate the molecular events controlling myelination of the peripheral nervous system, we compared gene expression of normal mouse sciatic nerves to that of the trembler mouse, whose Schwann cells are blocked in a pre-myelinating phenotype. Using cDNA array, we assessed expression levels of 1176 genes, and we found that delta-like protein (dlk), an epidermal growth factor-like homeotic protein, was expressed in the normal developing nerves, but at a low level in the dysmyelinating mutant trembler. Moreover, dlk expression was down-regulated when myelin protein expression was up-regulated, and no expression was observed in the developing brain. These results suggest that dlk expression is required for Schwann cell acquisition of the myelinating phenotype.

An understanding of the mechanisms determining MYC's transcriptional and proliferation-promoting activities in vivo could facilitate approaches for MYC targeting. However, post-translational mechanisms that control MYC function in vivo are poorly understood. Here, we demonstrate that MYC phosphorylation at serine 62 enhances MYC accumulation on Lamin A/C-associated nuclear structures and that the protein phosphatase 2A (PP2A) inhibitor protein CIP2A is required for this process. CIP2A is also critical for serum-induced MYC phosphorylation and for MYC-elicited proliferation induction in vitro. Complementary transgenic approaches and an intestinal regeneration model further demonstrated the in vivo importance of CIP2A and serine 62 phosphorylation for MYC activity upon DNA damage. However, targeting of CIP2A did not influence the normal function of intestinal crypt cells. These data underline the importance of nuclear organization in the regulation of MYC phosphorylation, leading to an in vivo demonstration of a strategy for inhibiting MYC activity without detrimental physiological effects.

Hematopoietic stem cells (HSC)11Hematopoietic stem cell (HSC), hematopoietic stem and progenitor cell (HSPC), bone marrow (BM), bone marrow transplantation (BMT), acute myeloid leukemia (AML), peripheral blood (PB), multipotent progenitor (MPP), pre-megakaryocyte/erythroid (preMegE), megakaryocytic progenitor (MkP), pre-granulocyte/macrophage (preGM), granulocyte/macrophage progenitors (GMP), common lymphoid progenitors (CLP), colony forming unit erythroid (CFU-E), proErythroid (proE), colony forming unit megakaryocyte (CFU-Mk), colony forming unit granulocyte macrophage (CFU-GM), megakaryocyte (Mk), LSK (Lineage−, Sca1+, c-Kithi). supply organisms with life-long output of mature blood cells. To do so, the HSC pool size has to be maintained by HSC self-renewing divisions. PRDM3 and PRDM16 have been documented to regulate HSC self-renewal, maintenance and function. We found Prdm11 to have similar expression patterns in the hematopoietic stem and progenitor cell (HSPC) compartments as Prdm3 and Prdm16. Therefore, we undertook experiments to test if PRDM11 regulates HSC self-renewal, maintenance and function by investigating the Prdm11−/− mice. Our data shows that phenotypic HSPCs are intact in bone marrow (BM) of one-year-old Prdm11−/− mice. In addition, Prdm11−/− mice were able to fully regenerate the hematopoietic system upon BM transplantation (BMT) into lethally irradiated mice with a mild drop in lymphoid output only. Taken together, this suggests that PRDM11, in contrast to PRDM3 and PRDM16, is not directly involved in regulation of HSPCs in mice.

International audience; BACKGROUND: Morphogenesis results from the coordination of distinct cell signaling pathways controlling migration, differentiation, apoptosis, and proliferation, along stem/progenitor cell dynamics. To decipher this puzzle, we focused on epithelial-mesenchymal transition (EMT) "master genes". EMT has emerged as a unifying concept, involving cell-cell adhesion, migration and apoptotic pathways. EMT also appears to mingle with stemness. However, very little is known on the physiological role and relevance of EMT master-genes. We addressed this question during mammary morphogenesis. Recently, a link between Slug/Snai2 and stemness has been described in mammary epithelial cells, but EMT master genes actual localization, role and targets during mammary gland morphogenesis are not known and we focused on this basic question. METHODOLOGY/PRINCIPAL FINDINGS: Using a Slug-lacZ transgenic model and immunolocalization, we located Slug in a distinct subpopulation covering about 10-20% basal cap and duct cells, mostly cycling cells, coexpressed with basal markers P-cadherin, CK5 and CD49f. During puberty, Slug-deficient mammary epithelium exhibited a delayed development after transplantation, contained less cycling cells, and overexpressed CK8/18, ER, GATA3 and BMI1 genes, linked to luminal lineage. Other EMT master genes were overexpressed, suggesting compensation mechanisms. Gain/loss-of-function in vitro experiments confirmed Slug control of mammary epithelial cell luminal differentiation and proliferation. In addition, they showed that Slug enhances specifically clonal mammosphere emergence and growth, cell motility, and represses apoptosis. Strikingly, Slug-deprived mammary epithelial cells lost their potential to generate secondary clonal mammospheres. CONCLUSIONS/SIGNIFICANCE: We conclude that Slug pathway controls the growth dynamics of a subpopulation of cycling progenitor basal cells during mammary morphogenesis. Overall, our data better define a key mechanism coordinating cell lineage dynamics and morphogenesis, and provide physiological relevance to broadening EMT pathways.

Targeting MYC function would be highly desirable for hyperproliferative diseases. As MYC itself is refractory to direct chemical inhibition, understanding of the mechanisms determining MYC's transcriptional and proliferation promoting activities in vivo would be critical for generation of alternative targeting strategies. However, despite 30 years of research, it is very poorly documented what post-translational mechanisms control MYC function in vivo. Here we demonstrate for the first time that Lamin A/C association is critical for MYC phosphorylation regulation. MYC phosphorylation at serine 62 enhances MYC recruitment to Lamin A/C-associated nuclear structures and the Protein Phosphatase 2A (PP2A) inhibitor protein CIP2A is required for retaining this phosphorylation and localization. CIP2A is also critical for serum induced MYC phosphorylation, and for MYC-elicited proliferation induction in vitro. Critically, using complementary transgenic approaches, and intestinal regeneration model, we demonstrate the in vivo importance of this mechanism for MYC´s transcriptional and proliferation promoting activities. However, targeting of this mechanism does not influence basal proliferation, or differentiation of intestinal crypt cells or mouse well-being. Together we discover unprecedented importance of nuclear organization of MYC for its phosphorylation regulation; leading to in vivo demonstration of a strategy for targeting of MYC activity without detrimental physiological effects. Citation Format: Kevin Myant, Xi Qiao, Tuuli Halonen, Christophe Come, Anni Laine, Johanna I. Partanen, Erinn-Lee Ogg, Tiina Laiterä, Mahnaz Janghorban, Juha Okkeri, Juha Klefström, Rosalie C. Sears, Owen J. Sansom, Jukka Westermarck. Serine 62 phosphorylated MYC associates with nuclear lamins and its regulation by CIP2A is essential for proliferation induction in vivo. [abstract]. In: Proceedings of the AACR Special Conference on Myc: From Biology to Therapy; Jan 7-10, 2015; La Jolla, CA. Philadelphia (PA): AACR; Mol Cancer Res 2015;13(10 Suppl):Abstract nr PR03.

Purpose: Carcinoma progression is linked to a partially dedifferentiated epithelial cell phenotype. As previously suggested, this regulation could involve transcription factors, Snail and Slug, known to promote epithelial-mesenchymal transitions during development. Here, we investigate the role of Snail and Slug in human breast cancer progression. Experimental Design: We analyzed Snail, Slug, and E-cadherin RNA expression levels and protein localization in large numbers of transformed cell lines and breast carcinomas, examined the correlation with tumor histologic features, and described, at the cellular level, Snail and Slug localization in carcinomas using combined in situ hybridization and immunolocalization. Results: In contrast with transformed cell lines, Slug was found to colocalize with E-cadherin at the cellular level in normal mammary epithelial cells and all tested carcinomas. Snail also colocalized at the cellular level with E-cadherin in tumors expressing high levels of Snail RNA. In addition, Snail was significantly expressed in tumor stroma, varying with tumors. Slug and Snail genes were significantly overexpressed in tumors associated with lymph node metastasis. Finally, the presence of semidifferentiated tubules within ductal carcinomas was linked to Slug expression levels similar to or above normal breast samples. Conclusions: These results suggest that Snail or Slug expression in carcinoma cells does not generally preclude significant E-cadherin expression. They emphasize a link between Snail, Slug, and lymph node metastasis in a large sampling of mammary carcinomas, and suggest a role for Slug in the maintenance of semidifferentiated structures. Snail and Slug proteins seem to support distinct tumor invasion modes and could provide new therapeutic targets.

Successful cutaneous wound repair occurs in a series of tightly coordinated and overlapping steps: (1) inflammation and clot formation, (2) keratinocyte activation and migration, (3) remodeling of the basement membrane and extracellular matrix, and (4) dermal and epidermal maturation. During the final three stages of cutaneous wound healing, restoration of an intact epidermis occurs via a complex process termed reepithelialization. In this chapter, we focus on the process of wound reepithelialization, emphasizing the resemblance of reepithelialization to epithelial-mesenchymal transition (EMT) occurring during development and tumor progression. Based on the many morphologic and molecular similarities between the two processes, we propose that wound reepithelialization represents a partial and reversible EMT.

Metastasis is a multistep process during which cancer cells disseminate from the site of primary tumors and establish secondary tumors in distant organs. In a search for key regulators of metastasis in a murine breast tumor model, we have found that the transcription factor Twist, a master regulator of embryonic morphogenesis, plays an essential role in metastasis. Suppression of Twist expression in highly metastatic mammary carcinoma cells specifically inhibits their ability to metastasize from the mammary gland to the lung. Ectopic expression of Twist results in loss of E-cadherin-mediated cell-cell adhesion, activation of mesenchymal markers, and induction of cell motility, suggesting that Twist contributes to metastasis by promoting an epithelial-mesenchymal transition (EMT). In human breast cancers, high level of Twist expression is correlated with invasive lobular carcinoma, a highly infiltrating tumor type associated with loss of E-cadherin expression. These results establish a mechanistic link between Twist, EMT, and tumor metastasis.