SMARCD1 is a "Goldilocks" metastasis modifier

Breast cancer is the most frequently diagnosed cancer worldwide, constituting around 15% of all diagnosed cancers in 2023. The predominant cause of breast cancer-related mortality is metastasis to distant essential organs, and a lack of metastasis-targeted therapies perpetuates dismal outcomes for late-stage patients. However, through our use of meiotic genetics to study inherited transcriptional network regulation, we have identified a new class of "Goldilocks" genes that are promising candidates for the development of metastasis-targeted therapeutics. Building upon previous work that implicated the CCR4-NOT RNA deadenylase complex in metastasis, we now demonstrate that the RNA-binding proteins (RNA-BPs) NANOS1, PUM2, and CPSF4 also regulate metastatic potential. Using cell lines, 3D culture, mouse models, and clinical data, we pinpoint Smarcd1 mRNA as a key target of all three RNA-BPs. Strikingly, both high and low expression of Smarcd1 is associated with positive clinical outcomes, while intermediate expression significantly reduces the probability of survival. Applying the theory of "essential genes" from evolution, we identify an additional 50 genes that span several cellular processes and must be maintained within a discrete window of expression for metastasis to occur. In the case of Smarcd1, small perturbations in its expression level significantly reduce metastasis in laboratory mouse models and alter splicing programs relevant to the ER+/HER2-enriched breast cancer subtype. The identification of subtype-specific "Goldilocks" metastasis modifier genes introduces a new class of genes and potential catalogue of novel targets that, when therapeutically "nudged" in either direction, may significantly improve late-stage patient outcomes.

Loss of NAT10 disrupts enhancer organization via p300 mislocalization and suppresses transcription of genes necessary for metastasis progression

Acetylation of protein and RNA represent a critical event for development and cancer progression. NAT10 is the only known RNA acetylase that catalyzes the N4-actylcytidine (ac4C) modification of RNAs. Here, we show that the loss of NAT10 significantly decreases lung metastasis in allograft and genetically engineered mouse models of breast cancer. NAT10 interacts with a mechanosensitive, metastasis susceptibility protein complex at the nuclear pore. In addition to its canonical role in RNA acetylation, we find that NAT10 interacts with p300 at gene enhancers. NAT10 loss is associated with p300 mislocalization into heterochromatin regions. NAT10 depletion disrupts enhancer organization, leading to alteration of gene transcription necessary for metastatic progression, including reduced myeloid cell-recruiting chemokines that results in a less metastasis-prone tumor microenvironment. Our study uncovers a distinct role of NAT10 in enhancer organization of metastatic tumor cells and suggests its involvement in the tumor-immune crosstalk dictating metastatic outcomes.

Self-organized yolk sac-like organoids allow for scalable generation of multipotent hematopoietic progenitor cells from induced pluripotent stem cells

Although the differentiation of human induced pluripotent stem cells (hiPSCs) into various types of blood cells has been well established, approaches for clinical-scale production of multipotent hematopoietic progenitor cells (HPCs) remain challenging. We found that hiPSCs cocultured with stromal cells as spheroids (hematopoietic spheroids [Hp-spheroids]) can grow in a stirred bioreactor and develop into yolk sac-like organoids without the addition of exogenous factors. Hp-spheroid-induced organoids recapitulated a yolk sac-characteristic cellular complement and structures as well as the functional ability to generate HPCs with lympho-myeloid potential. Moreover, sequential hemato-vascular ontogenesis could also be observed during organoid formation. We demonstrated that organoid-induced HPCs can be differentiated into erythroid cells, macrophages, and T lymphocytes with current maturation protocols. Notably, the Hp-spheroid system can be performed in an autologous and xeno-free manner, thereby improving the feasibility of bulk production of hiPSC-derived HPCs in clinical, therapeutic contexts.

Abstract A012: NAT10 promotes metastasis through enhancer remodeling of cancer cells

Distant organ metastases account for the majority of the cancer-related death. However, the detailed mechanism underlying the metastatic potential of cancer cells is poorly understood. We have previously shown than NUP210-dependent nuclear pore-associated chromatin-bound protein complex is involved in cellular mechanotransduction and metastasis in breast cancer. Although NAT10, an RNA cytidine acetyl transferase has been shown to interact with this protein complex, specific function of NAT10 in metastasis is not well understood. Using allograft and genetically engineered highly metastatic PyMT mouse model, we found that the loss of NAT10 significantly decreases lung metastasis in mice. NAT10 is mainly localized to the nucleolus and nucleoplasmic compartment of the cancer cells. Current understanding suggests a role of NAT10 in acetylation of mRNAs and ribosomal RNAs. In contrast to its role as an RNA acetylase, we uncovered a new mechanism of NAT10 in cancer cells. Using co-immunoprecipitation followed by mass spectrometry and chromatin immunoprecipitation followed by high throughput sequencing (ChIP-seq), we found that NAT10 is interacting with super-enhancer associated protein complex. RNA-seq analysis revealed that the loss of NAT10 leads to dramatic transcriptional suppression of super-enhancer driven genes including MYC. Mechanistically, using mass spectrometry-based quantification of protein acetylation, we showed that the loss of NAT10 leads to decreased acetylation of enhancer-associated Histone H4 and H3 modification. NAT10 loss also leads to increased heterochromatin-forming histone methylation within the cell nuclei. Our study revealed a distinct role of NAT10 as an enhancer remodeler in metastatic cancer cells. Therefore, NAT10 could be a potential therapeutic target in preventing metastatic disease.

Citation Format: Ruhul Amin, Ngoc-Han Ha, Jordan L. Meier, Kent W. Hunter. NAT10 promotes metastasis through enhancer remodeling of cancer cells [abstract]. In: Proceedings of the AACR Special Conference: Cancer Metastasis; 2022 Nov 14-17; Portland, OR. Philadelphia (PA): AACR; Cancer Res 2022;83(2 Suppl_2):Abstract nr A012.

Abstract A54: Epi-RTM (epigenetic reprogramming) technology improves stemness, preserves polyclonality and enhances antitumor functionality of tumor infiltrating lymphocytes in nonclinical studies

Background: Adoptive cell therapy (ACT) is an evolving area for drug development in advanced solid tumors. Tumor infiltrating lymphocyte (TIL) therapy as an autologous ACT has shown promising efficacy in select solid tumor types, eliciting clinical responses through tumor specific antigen recognition and maintaining T-cell receptor (TCR) diversity. Growing evidence indicates that TIL products with increased T-cell stemness, tumor antigen recognition, and clonal diversity may result in improved clinical outcomes. Epi-R reprogramming technology is designed to improve T-cell stemness, polyclonality, and antitumor functionality in ACT products, including TIL. Method: The Epi-R protocol is composed of an extensively formulated proprietary cell culture media and well-defined cytokines with specific cell activation and expansion manufacturing parameters and methods. In nonclinical experiments, research-scale TIL products were produced from 3 different tumor types (melanoma, lung, and colorectal cancer) using either the Epi-R technology or a standard protocol (control TIL). Characteristics of the resulting products were compared using flow cytometry to assess stemness markers. An autologous cell line was generated from a melanoma patient tumor, and antitumor function and cytokine production were measured upon co-culture with the TIL products. Clonal diversity was assessed using TCR Vbeta sequencing. Results: Nonclinical evaluations of Epi-R TIL demonstrated increased stemness, functional cytokine production and antitumor activity compared to control TIL. Epi-R TIL products were enriched for CD8+ T cells, co-receptor (CD27 and CD28) positive CD8+ T cells, and stem-like CD8+ T cells, as demonstrated by enrichment for CD39-CD69- T cells compared to control TIL. Epi-R TIL demonstrated superior functionality by IFNg response upon co-culture with an autologous melanoma tumor cell line. Polyclonality was preserved in Epi-R TIL as measured by Simpson clonality index using bulk TCR Vbeta sequencing data. Conclusion: Results from research-scale TIL productions demonstrated that Epi-R reprogramming technology enables successful TIL expansion while maintaining a greater proportion of stem-like and co-stimulatory positive CD8+ TIL with preserved polyclonality compared to control TIL. Moreover, Epi-R TIL show improved antitumor activity compared to control TIL product in a melanoma tumor cell line. Further studies of Epi-R TIL using RNA sequencing will allow further characterization of this product and determine whether key product attributes are maintained at large-scale TIL manufacturing. An Investigational New Drug (IND) submission for LYL845, our autologous TIL product manufactured with Epi-R reprogramming technology, for melanoma and other advanced solid tumors is anticipated to occur in the second half of 2022.

Citation Format: Yogin Patel, Ngoc-Han Ha, Melissa Bedard, Joanna Kritikou, Rigel Kishton, Suman Kumar Vodnala. Epi-RTM (epigenetic reprogramming) technology improves stemness, preserves polyclonality and enhances antitumor functionality of tumor infiltrating lymphocytes in nonclinical studies [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy; 2022 Oct 21-24; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2022;10(12 Suppl):Abstract nr A54.

Intercomparison of Geant4 low energy electromagnetic models in 90Y dosimetry

This work shows the comparison between Geant4 low energy electromagnetic physics lists G4EmLi-vermorePhysics, G4EmPenelopePhysics, G4EmLowEPPhysics, and G4EmDNAPhysics_option2 when simulating the energy deposition of low mono-energetic electrons and β^- emitted from ⁹⁰Y isotope. The simulation time and influence of production cut were considered. In the sense of balance between the accuracy and computer resource, G4EmPenelopePhysics can be proposed as the best physics model for our future Treatment Planning System (TPS) for treating liver cancer using ⁹⁰Y microsphere radioembolization therapy.

T cell stemness and dysfunction in tumors are triggered by a common mechanism

A paradox of tumor immunology is that tumor-infiltrating lymphocytes are dysfunctional in situ, yet are capable of stem cell-like behavior including self-renewal, expansion, and multipotency, resulting in the eradication of large metastatic tumors. We find that the overabundance of potassium in the tumor microenvironment underlies this dichotomy, triggering suppression of T cell effector function while preserving stemness. High levels of extracellular potassium constrain T cell effector programs by limiting nutrient uptake, thereby inducing autophagy and reduction of histone acetylation at effector and exhaustion loci, which in turn produces CD8⁺ T cells with improved in vivo persistence, multipotency, and tumor clearance. This mechanistic knowledge advances our understanding of T cell dysfunction and may lead to novel approaches that enable the development of enhanced T cell strategies for cancer immunotherapy.

Genetic insights into the morass of metastatic heterogeneity

Tumour heterogeneity poses a substantial problem for the clinical management of cancer. Somatic evolution of the cancer genome results in genetically distinct subclones in the primary tumour with different biological properties and therapeutic sensitivities. The problem of heterogeneity is compounded in metastatic disease owing to the complexity of the metastatic process and the multiple biological hurdles that the tumour cell must overcome to establish a clinically overt metastatic lesion. New advances in sequencing technology and clinical sample acquisition are providing insights into the phylogenetic relationship of metastases and primary tumours at the level of somatic tumour genetics while also illuminating fundamental mechanisms of the metastatic process. In addition to somatically acquired genetic heterogeneity in the tumour cells, inherited population-based genetic heterogeneity can profoundly modify metastatic biology and further complicate the development of effective, broadly applicable antimetastatic therapies. Here, we examine how genetic heterogeneity impacts metastatic disease and the implications of current knowledge for future research endeavours and therapeutic interventions.

Abstract 3050: Polymorphisms in the arntl2 promoter affect breast cancer metastasis susceptibility

Breast cancer mortality is primarily due to metastatic lesions rather than primary tumors, yet relatively little is known regarding the mechanisms of metastatic breast cancer, making it difficult to identify patients who are at risk for metastatic disease. Our hypothesis suggests that inherited germline mutations contribute to metastatic disease and that these single nucleotide polymorphisms (SNPs) could be used to predict outcome in breast cancer patients. To investigate the effect of inherited SNPs on metastasis, we used a mouse genetics approach comparing strains with high (FVB) and low (MOLF) metastatic phenotypes and identified Arntl2, a circadian rhythm transcription factor, as a gene whose differential expression predicted outcome in breast cancer patients. To identify SNP differences in Arntl2 between MOLF and FVB, we performed whole genome sequencing of MOLF and compared it to the FVB genome. Overlapping the data with DNase hypersensitivity sites revealed 10 SNPs in the predicted promoter of Arntl2. To test the causative role of the SNPs on Arntl2 expression in vivo, metastatic cell lines were engineered using the CRISPR-Cas9 approach to specifically replace the FVB Arntl2 promoter with that of MOLF. In agreement with our hypothesis, substitution of the MOLF promoter reduced Arntl2 transcript levels and subsequently decreased lung metastases in orthotopic implantation assays. In vitro pulldown experiments with strain-specific promoter probes revealed potential differential binding of chromatin modifier proteins, demonstrating the significance of the SNPs in regulating Arntl2 transcription. Finally, analysis of SNPs associated with Arntl2 expression in a cohort of Chinese breast cancer patients revealed significant correlation of Arntl2 expression with overall survival, validating this gene as a marker in humans. Since Arntl2 is a transcription factor, current studies are focused on identifying Arntl2-regulated genes to investigate downstream pathways involved in metastasis. This study has important implications regarding the role of circadian rhythm in cancer progression and provides a potential mechanism to explain the increased risk of breast cancers in nightshift workers. Furthermore, this provides the first evidence that transcriptional control elements can be engineered using CRISPR-Cas9 to establish the causative role of SNPs in inherited susceptibility to cancer metastasis.

Citation Format: Ngoc-Han Ha, Kent Hunter. Polymorphisms in the arntl2 promoter affect breast cancer metastasis susceptibility [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3050. doi:10.1158/1538-7445.AM2017-3050

The Circadian Rhythm Gene Arntl2 Is a Metastasis Susceptibility Gene for Estrogen Receptor-Negative Breast Cancer

Breast cancer mortality is primarily due to metastasis rather than primary tumors, yet relatively little is understood regarding the etiology of metastatic breast cancer. Previously, using a mouse genetics approach, we demonstrated that inherited germline polymorphisms contribute to metastatic disease, and that these single nucleotide polymorphisms (SNPs) could be used to predict outcome in breast cancer patients. In this study, a backcross between a highly metastatic (FVB/NJ) and low metastatic (MOLF/EiJ) mouse strain identified Arntl2, a gene encoding a circadian rhythm transcription factor, as a metastasis susceptibility gene associated with progression, specifically in estrogen receptor-negative breast cancer patients. Integrated whole genome sequence analysis with DNase hypersensitivity sites reveals SNPs in the predicted promoter of Arntl2. Using CRISPR/Cas9-mediated substitution of the MOLF promoter, we demonstrate that the SNPs regulate Arntl2 transcription and affect metastatic burden. Finally, analysis of SNPs associated with ARNTL2 expression in human breast cancer patients revealed reproducible associations of ARNTL2 expression quantitative trait loci (eQTL) SNPs with disease-free survival, consistent with the mouse studies.

Estrogen receptor-negative (ER-) breast cancer is a highly malignant form of breast cancer with poor prognosis. Like most solid tumors, the mortality associated with ER- breast cancer is due to the development of secondary tumors, or metastases, in vital organs distant from the original breast tumor. ER- breast tumors, particularly those also lacking HER (human epidermal growth factor receptor) expression, are particularly deadly because unlike ER+ or HER+ breast cancers, targeted therapies have not yet been developed that can effectively reduce or eliminate tumor cells that have disseminated throughout the patient. Therefore, better understanding of the etiology of metastasis in ER- patients would potentially have a large clinical benefit by providing new targets to eradicate single tumor cells before they develop into metastases. A better understanding of metastasis etiology may also provide methods to prevent the conversion of these disseminated cells into life-threatening lesions. In this study, we demonstrate that a commonly used model of metastatic breast cancer is capable of identifying genes that play a role in the metastatic progression of ER- breast cancers. Furthermore, we identify the circadian rhythm gene, Arntl2, as a gene associated with inherited susceptibility for the development of metastatic lesions. These studies provide additional information regarding the mechanisms associated with metastasis in ER- breast cancers.

An Integrated Genome-Wide Systems Genetics Screen for Breast Cancer Metastasis Susceptibility Genes

Metastasis remains the primary cause of patient morbidity and mortality in solid tumors and is due to the action of a large number of tumor-autonomous and non-autonomous factors. Here we report the results of a genome-wide integrated strategy to identify novel metastasis susceptibility candidate genes and molecular pathways in breast cancer metastasis. This analysis implicates a number of transcriptional regulators and suggests cell-mediated immunity is an important determinant. Moreover, the analysis identified novel or FDA-approved drugs as potentially useful for anti-metastatic therapy. Further explorations implementing this strategy may therefore provide a variety of information for clinical applications in the control and treatment of advanced neoplastic disease.

Metastasis, the spread and growth of tumor cells from the original tumor to secondary sites throughout the body, is the primary cause of cancer-related death for most solid tumor types. The process of metastasis is very complex, requiring multiple individual steps and the cooperation of different cell types during the dissemination and proliferation steps. Many genes are involved in this process, but at present few have been identified and characterized. In this study, we have integrated multiple genome-wide analysis methods to try to identify large numbers of candidate metastasis-associated genes and pathways based on a highly metastatic mouse model. Using this strategy, we have identified a number of genes that predict outcome of human breast cancer. These genes implicate specific molecular and cellular pathways in the metastatic process that might be used to intervene in the process. Furthermore, this integrated analysis implicates pre-existing drugs that might be re-purposed to help prevent or reduce metastatic burden in patients. The combined results obtained from this analytical strategy therefore provide an important platform for further genome-wide analysis into the etiology of metastatic disease.

Abstract B12: Polymorphisms in the Arntl2 promoter affect metastatic susceptibility in breast cancer

Metastasis accounts for the majority of cancer-related deaths. Although exact mechanisms are unknown, studies in our laboratory have demonstrated that germline polymorphisms could alter tumorigenesis and metastasis. Our lab developed a mouse genetics approach to investigate the effect of inherited single nucleotide polymorphisms (SNPs) on metastasis by crossing inbred mice of various backgrounds and subsequent mapping of quantitative trait loci (QTL) responsible for the phenotype. Using this approach, we crossed a highly metastatic (FVB) and low metastatic (MOLF) mouse strain and identified Arntl2, a circadian rhythm transcription factor, as a gene with differential expression that predicted distant metastasis-free survival in breast cancer patients. shRNA-mediated reduction in Arntl2 expression suppressed lung metastases, establishing Arntl2 as a metastasis modifier. Initial analysis revealed no polymorphisms in coding regions that could account for the differential expression in FVB and MOLF. Therefore, we performed whole genome sequencing of MOLF to identify SNP differences between MOLF and FVB. Overlapping this analysis with DNAse hypersensitivity sites in mouse mammary tumor cell lines revealed 13 polymorphisms in the predicted promoter region of Arntl2. FVB and MOLF promoters exhibited differential promoter activity in vitro, suggesting that these SNPs could explain the difference in Arntl2 expression between these two strains. In order to validate the causative role of the SNPs in vivo, metastatic cell lines were engineered using CRISPR technology to specifically replace the FVB with the MOLF promoter. Substitution of this promoter reduced Arntl2 transcript levels and subsequently decreased pulmonary metastases, as expected. Since Arntl2 is a transcription factor, current studies are focused on identifying Arntl2-regulated genes to investigate the pathways that are involved in modulating metastasis. This study will have important implications regarding the function of circadian rhythm in cancer progression and provide a potential molecular mechanism to explain the increased risk of breast cancers in nightshift workers. Furthermore, to the best of our knowledge this would be the first example of genome editing to validate polymorphisms in transcriptional control elements associated with inherited susceptibility for metastasis.

Citation Format: Ngoc-Han Ha, Kent W. Hunter. Polymorphisms in the Arntl2 promoter affect metastatic susceptibility in breast cancer. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Metastasis; 2015 Nov 30-Dec 3; Austin, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(7 Suppl):Abstract nr B12.

Abstract IA21: An integrated genome-wide systems genetics screen for breast cancer metastasis susceptibility genes

Metastasis remains the primary cause of patient morbidity and mortality in solid tumors and is due to the action of a large number of tumor-autonomous and non-autonomous factors. Hundreds or thousands of genes are thought to be associated with metastasis however how many of these genes contribute etiologically to tumor progression is not currently known. Identification of the genes contributing mechanistically to the metastatic processes will not only deepen our understanding of how metastases occur, but also provide novel targets for either preventing their formation or combatting their life-threatening effects. Previously our laboratory demonstrated that inbred mice of distinct phylogenetic lineages possess distinct propensity for metastatic disease, indicating that inherited susceptibility for metastasis exists and that polymorphisms can both mark and functionally effect genes within the metastatic cascade. Here we report the results of a genome-wide integrated strategy to identify novel metastasis susceptibility candidate genes and molecular pathways which implicates a number of transcriptional regulators and suggests cell-mediated immunity is an important determinant. The strategy described integrates meiotic genetic screens with epigenetic control of gene expression and three dimensional chromatin structure analyses to identify genes, molecular and cellular pathways likely to be important in metastatic disease. Moreover, the analysis identified novel or FDA-approved drugs as potentially useful for anti-metastatic therapy. Further explorations implementing this strategy may therefore provide a variety of information for clinical applications in the control and treatment of advanced neoplastic disease.

Citation Format: Kent W. Hunter, Ling Bai, Howard H. Yang, Ying Hu, Anjali Shukla, Ngoc-Han Ha, Anthony Doran, Farhoud Faraji, Natalie Goldberger, Maxwell P. Lee, Thomas Keane. An integrated genome-wide systems genetics screen for breast cancer metastasis susceptibility genes. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Metastasis; 2015 Nov 30-Dec 3; Austin, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(7 Suppl):Abstract nr IA21.

Functional analysis of prognostic gene expression network genes in metastatic breast cancer models

Identification of conserved co-expression networks is a useful tool for clustering groups of genes enriched for common molecular or cellular functions [1]. The relative importance of genes within networks can frequently be inferred by the degree of connectivity, with those displaying high connectivity being significantly more likely to be associated with specific molecular functions [2]. Previously we utilized cross-species network analysis to identify two network modules that were significantly associated with distant metastasis free survival in breast cancer. Here, we validate one of the highly connected genes as a metastasis associated gene. Tpx2, the most highly connected gene within a proliferation network specifically prognostic for estrogen receptor positive (ER+) breast cancers, enhances metastatic disease, but in a tumor autonomous, proliferation-independent manner. Histologic analysis suggests instead that variation of TPX2 levels within disseminated tumor cells may influence the transition between dormant to actively proliferating cells in the secondary site. These results support the co-expression network approach for identification of new metastasis-associated genes to provide new information regarding the etiology of breast cancer progression and metastatic disease.

BRD4 short isoform interacts with RRP1B, SIPA1 and components of the LINC complex at the inner face of the nuclear membrane

Recent studies suggest that BET inhibitors are effective anti-cancer therapeutics. Here we show that BET inhibitors are effective against murine primary mammary tumors, but not pulmonary metastases. BRD4, a target of BET inhibitors, encodes two isoforms with opposite effects on tumor progression. To gain insights into why BET inhibition was ineffective against metastases the pro-metastatic short isoform of BRD4 was characterized using mass spectrometry and cellular fractionation. Our data show that the pro-metastatic short isoform interacts with the LINC complex and the metastasis-associated proteins RRP1B and SIPA1 at the inner face of the nuclear membrane. Furthermore, histone binding arrays revealed that the short isoform has a broader acetylated histone binding pattern relative to the long isoform. These differential biochemical and nuclear localization properties revealed in our study provide novel insights into the opposing roles of BRD4 isoforms in metastatic breast cancer progression.

Using a systems biology approach to understand and study the mechanisms of metastasis

Metastasis remains the main cause for cancer-related deaths due to the lack of effective therapy. The clonal selection model has long been thought to be the primary mechanism of metastatic progression but many different mechanisms have been hypothesized for the progression from tumorigenesis to the successful dissemination and expansion of tumor cells at the secondary site. MicroRNAs, germline polymorphisms in combination with the tumor microenvironment are few of the different pathways to explain the metastatic cascade. Technological advances for high-throughput screening of cells such as expression profiling, next generation sequencing, as well as global network analyses have advanced the studies of these mechanisms. Combined with new insights into the various mechanisms of metastasis a systems biology approach has also been shown to be useful in identifying metastasis-specific gene signatures as well as predicting disease outcome. Furthermore, the results of these studies have been relevant for identifying biomarkers for metastatic disease.

Mechanism of MTA1 protein overexpression-linked invasion: MTA1 regulation of hyaluronan-mediated motility receptor (HMMR) expression and function

Even though the hyaluronan-mediated motility receptor (HMMR), a cell surface oncogenic protein, is widely up-regulated in human cancers and correlates well with cell motility and invasion, the underlying molecular and nature of its putative upstream regulation remain unknown. Here, we found for the first time that MTA1 (metastatic tumor antigen 1), a master chromatin modifier, regulates the expression of HMMR and, consequently, its function in breast cancer cell motility and invasiveness. We recognized a positive correlation between the levels of MTA1 and HMMR in human cancer. Furthermore, MTA1 is required for optimal expression of HMMR. The underlying mechanism includes interaction of the MTA1·RNA polymerase II·c-Jun coactivator complex with the HMMR promoter to stimulates its transcription. Accordingly, selective siRNA-mediated knockdown of HMMR in breast cancer cells substantially reduces the invasion and migration of cells. These findings reveal a regulatory role for MTA1 as an upstream coactivator of HMMR expression and resulting biological phenotypes.

Lactoferrin-endothelin-1 axis contributes to the development and invasiveness of triple-negative breast cancer phenotypes

Triple-negative breast cancer (TNBC) is characterized by the lack of expression of estrogen receptor-α (ER-α), progesterone receptor (PR), and human epidermal growth factor receptor-2 (HER-2). However, pathways responsible for downregulation of therapeutic receptors, as well as subsequent aggressiveness, remain unknown. In this study, we discovered that lactoferrin (Lf) efficiently downregulates levels of ER-α, PR, and HER-2 in a proteasome-dependent manner in breast cancer cells, and it accounts for the loss of responsiveness to ER- or HER-2-targeted therapies. Furthermore, we found that lactoferrin increases migration and invasiveness of both non-TNBC and TNBC cell lines. We discovered that lactoferrin directly stimulates the transcription of endothelin-1 (ET-1), a secreted proinvasive polypeptide that acts through a specific receptor, ET(A)R, leading to secretion of the bioactive ET-1 peptide. Interestingly, a therapeutic ET-1 receptor-antagonist blocked lactoferrin-dependent motility and invasiveness of breast cancer cells. The physiologic significance of this newly discovered Lf-ET-1 axis in the manifestation of TNBC phenotypes is revealed by elevated plasma and tissue lactoferrin and ET-1 levels in patients with TNBC compared with those in ER(+) cases. These findings describe the first physiologically relevant polypeptide as a functional determinant in downregulating all three therapeutic receptors in breast cancer, which uses another secreted ET-1 system to confer invasiveness. Results presented in this article provide proof-of-principle evidence in support of the therapeutic effectiveness of ET-1 receptor antagonist to completely block the lactoferrin-induced motility and invasiveness of the TNBC as well as non-TNBC cells, and thus, open a remarkable opportunity to treat TNBC by targeting the Lf-ET-1 axis using an approved developmental drug.

Phosphoproteomic identification of a PDX-1/14-3-3ε interaction in pancreatic beta cells

Glucose-dependent activation of the homeodomain transcription factor PDX-1 leads to its phosphorylation, to an increase in DNA binding capacity, and to NLS dependent translocation into the nucleus. To uncover unknown mediators of PDX-1 activation, PDX-1 interacting proteins were analysed by pull-down from (32)P-labelled, glucose-stimulated MIN6 cells. Recovered proteins were analysed by 2D gel electrophoresis and mass spectrometry. We identified 14-3-3ε as a novel PDX-1 binding protein and confirmed the interaction in vivo by Fluorescence Resonance Energy Transfer (FRET) analysis. We propose that 14-3-3ε interacts directly with PDX-1 to regulate its cellular distribution in pancreatic beta cells.