Master Transcription Factor Reprogramming Unleashes Selective Translation Promoting Castration Resistance and Immune Evasion in Lethal Prostate Cancer

Signaling rewiring allows tumors to survive therapy. Here we show that the decrease of the master regulator microphthalmia transcription factor (MITF) in lethal prostate cancer unleashes eukaryotic initiation factor 3B (eIF3B)-dependent translation reprogramming of key mRNAs conferring resistance to androgen deprivation therapy (ADT) and promoting immune evasion. Mechanistically, MITF represses through direct promoter binding eIF3B, which in turn regulates the translation of specific mRNAs. Genome-wide eIF3B enhanced cross-linking immunoprecipitation sequencing (eCLIP-seq) showed specialized binding to a UC-rich motif present in subsets of 5' untranslated regions. Indeed, translation of the androgen receptor and major histocompatibility complex I (MHC-I) through this motif is sensitive to eIF3B amount. Notably, pharmacologic targeting of eIF3B-dependent translation in preclinical models sensitizes prostate cancer to ADT and anti-PD-1 therapy. These findings uncover a hidden connection between transcriptional and translational rewiring promoting therapy-refractory lethal prostate cancer and provide a druggable mechanism that may transcend into effective combined therapeutic strategies.

SIGNIFICANCE

Our study shows that specialized eIF3B-dependent translation of specific mRNAs released upon downregulation of the master transcription factor MITF confers castration resistance and immune evasion in lethal prostate cancer. Pharmacologic targeting of this mechanism delays castration resistance and increases immune-checkpoint efficacy. This article is featured in Selected Articles from This Issue, p. 2489.

Harnessing transcriptionally driven chromosomal instability adaptation to target therapy-refractory lethal prostate cancer

Metastatic prostate cancer (PCa) inevitably acquires resistance to standard therapy preceding lethality. Here, we unveil a chromosomal instability (CIN) tolerance mechanism as a therapeutic vulnerability of therapy-refractory lethal PCa. Through genomic and transcriptomic analysis of patient datasets, we find that castration and chemotherapy-resistant tumors display the highest CIN and mitotic kinase levels. Functional genomics screening coupled with quantitative phosphoproteomics identify MASTL kinase as a survival vulnerability specific of chemotherapy-resistant PCa cells. Mechanistically, MASTL upregulation is driven by transcriptional rewiring mechanisms involving the non-canonical transcription factors androgen receptor splice variant 7 and E2F7 in a circuitry that restrains deleterious CIN and prevents cell death selectively in metastatic therapy-resistant PCa cells. Notably, MASTL pharmacological inhibition re-sensitizes tumors to standard therapy and improves survival of pre-clinical models. These results uncover a targetable mechanism promoting high CIN adaptation and survival of lethal PCa.

Targeting chemotherapy to de-condensed H3K27me3-marked chromatin of AML cells enhances leukemia suppression

Despite treatment with intensive chemotherapy, acute myeloid leukemia (AML) remains an aggressive malignancy with a dismal outcome in most patients. We found that AML cells exhibit an unusually rapid accumulation of the repressive histone mark H3K27me3 on nascent DNA. In cell lines, primary cells and xenograft mouse models, inhibition of the H3K27 histone methyltransferase EZH2 to de-condense the H3K27me3-marked chromatin of AML cells enhanced chromatin accessibility and chemotherapy-induced DNA damage, apoptosis, and leukemia suppression. These effects were further promoted when chromatin de-condensation of AML cells was induced upon S-phase entry after release from a transient G1 arrest mediated by CDK4/6 inhibition. In the p53-null KG-1 and THP-1 AML cell lines, EZH2 inhibitor and doxorubicin co-treatment induced transcriptional reprogramming that was, in part, dependent on de-repression of H3K27me3-marked gene promoters and led to increased expression of cell death-promoting and growth-inhibitory genes. In conclusion, decondensing H3K27me3-marked chromatin by EZH2 inhibition represents a promising approach to improve the efficacy of DNA-damaging cytotoxic agents in AML patients. This strategy might allow for a lowering of chemotherapy doses with a consequent reduction of treatment-related side effects in elderly AML patients or those with significant comorbidities.

IFN-β Acts on Monocytes to Ameliorate CNS Autoimmunity by Inhibiting Proinflammatory Cross-Talk Between Monocytes and Th Cells

IFN-β has been the treatment for multiple sclerosis (MS) for almost three decades, but understanding the mechanisms underlying its beneficial effects remains incomplete. We have shown that MS patients have increased numbers of GM-CSF+ Th cells in circulation, and that IFN-β therapy reduces their numbers. GM-CSF expression by myelin-specific Th cells is essential for the development of experimental autoimmune encephalomyelitis (EAE), an animal model of MS. These findings suggested that IFN-β therapy may function via suppression of GM-CSF production by Th cells. In the current study, we elucidated a feedback loop between monocytes and Th cells that amplifies autoimmune neuroinflammation, and found that IFN-β therapy ameliorates central nervous system (CNS) autoimmunity by inhibiting this proinflammatory loop. IFN-β suppressed GM-CSF production in Th cells indirectly by acting on monocytes, and IFN-β signaling in monocytes was required for EAE suppression. IFN-β increased IL-10 expression by monocytes, and IL-10 was required for the suppressive effects of IFN-β. IFN-β treatment suppressed IL-1β expression by monocytes in the CNS of mice with EAE. GM-CSF from Th cells induced IL-1β production by monocytes, and, in a positive feedback loop, IL-1β augmented GM-CSF production by Th cells. In addition to GM-CSF, TNF and FASL expression by Th cells was also necessary for IL-1β production by monocyte. IFN-β inhibited GM-CSF, TNF, and FASL expression by Th cells to suppress IL-1β secretion by monocytes. Overall, our study describes a positive feedback loop involving several Th cell- and monocyte-derived molecules, and IFN-β actions on monocytes disrupting this proinflammatory loop.

Abstract PS17-58: Pparg1 induces an EGF-EphA2 receptor tyrosine kinase module to promote ErbB2- mammary adenocarcinoma in mice

ErbB2 is overexpressed in approximately 25% of human breast cancers, associated with clinically aggressive disease. No soluble ligand has been identified and the receptor is regulated by heterodimerization with other ErbB family receptors, including EGFR, and other receptor tyrosine kinases including EphA2. EGFR is activated by seven different growth factors including EGF and Amphiregulin. Downstream signaling modules required for ErbB2 induced tumorigenesis in genetically engineered mouse models (GEMM) include the phosphatidylinositol 3-kinase/Akt (PKB) pathway, the Ras/Raf/MEK/ERK1/2 pathway and the phospholipase C (PLCγ) pathways.

ErbB2-mediated tumorigenesis involves activation of receptor tyrosine kinases, induction of cyclin D1/CDK activity, and functional restraint by tumor suppressors. The receptor tyrosine kinase EPH receptor A2 (EphA2), a member of the Eph RTK family, is overexpressed in aggressive breast cancer and EphA2 forms a complex with ErbB2 thereby enhancing ErbB2-induced tumor onset and progression.

The host immune system participates in the therapeutic response of HER2+ breast cancer. The tumor microenvironment (TME) is regulated by chemokines and their G protein coupled receptors binds several ligands, including Cxcl5 which binds Cxcr2, to augment the pro-tumor immune response, tumor growth and metastasis.

Identifying genetic programs that participate in ErbB2-induced tumors may provide the rational basis for co-extinction therapeutic approaches. Peroxisome proliferator-activated receptor γ (PPARγ), which is expressed in a variety of malignancies, governs biological functions through transcriptional programs.

Herein, genetic deletion of endogenous Pparγ1 restrained mammary tumor progression, lipogenesis, and induced local mammary tumor F4/80+ tumor-associated macrophage infiltration, without affecting other tissue hematopoietic stem cell pools. Pparγ1 induced peroxisomal target genes in the mammary tumors as evidenced by increased expression of PEX-11, together with PPARGC1 and ESRR induced regulator, muscle 1, Perm1 (PGC-1 and ERR-induced Regulator in Muscle 1). Peroxisomes induced by Pparγ1, activated Type1 interferons (IFNs) and IFN-stimulated gene expression, including Cxcl5. Endogenous Pparγ1 induced expression of both an EphA2-Amphiregulin and an inflammatory INFγ -Cxcl5 signaling module. Pparγ1 bound directly to growth promoting and proinflammatory target genes in the context of chromatin. We conclude Pparγ1 promotes ErbB2-induced tumor growth and inflammation and represents a relevant target for therapeutic coextinction.

Citation Format: Richard G Pestell, Xuanmao Jiao, Andrew V Kossenkov, Adam Ertel, Wei Tong, Zhao Zhang, Peter A McCue. Pparg1 induces an EGF-EphA2 receptor tyrosine kinase module to promote ErbB2- mammary adenocarcinoma in mice [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 PS17-58.

Abstract 5469: iCVA- A knowledge-based cancer variation annotation application

A typical genomic sequencing experiment results in a long list of statistically significant variant candidates among protein-coding genes without any unifying biological theme. This leads to a daunting task of identifying the causal variants and genes to accurately diagnose the disease for clinical or research utility. While a number of downstream tools exist to aid in cancer genome annotation and interpretation, including Clinical Interpretations of Variants in Cancer (CIViC), ClinGen, Database of Curated Mutations (DoCM), Oncotator, and Variant Interpretation for Cancer (VIC), these only provide selective information (somatic/germline/gene-variant specific) or are time/resource consuming. To address this challenge, we developed a software called iCVA using the following methodology: 1) we obtained a priori defined gene sets for different cancer-inducing mechanisms such as pro-oncogenesis, tumor-suppression, DNA repair, angiogenesis, inflammation, metabolism, hypoxia, cell cycle and immune system. 2) genomic variation data were integrated from 1000 Genome, Exome Sequencing Project, Exome Aggregation Consortium (ExAC), ClinVar, dbSNP, GNOMAD, The Cancer Genome Atlas (TCGA), the Catalogue of Somatic Mutations in Cancer (COSMIC) and the International Cancer Gene Census (ICGC), and re-classified into a consensus classification according to ACMG guidelines. 3) Finally, we devised a reporting system to process mutation data from a sequencing experiment to utilize the harmonized pathway and mutational information integrated in a local database to identify and classify cancer-specific gene mutations. The iCVA reporting system classifies mutations as germline or somatic and then sub-classifies these into different cancer-specific mechanisms, including those known to be targetable through existing therapies. To our knowledge, iCVA is the first tool to provide a comprehensive report on cancer variants in a simplified and faster manner, to accelerate the genomic characterization of cancer samples analyzed by high-throughput DNA sequencing.

Citation Format: Gaurav Kumar, Melanie Kelly, Paolo Fortina, Adam Ertel. iCVA- A knowledge-based cancer variation annotation application [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5469.

iSeqQC: a tool for expression-based quality control in RNA sequencing

Background

Quality Control in any high-throughput sequencing technology is a critical step, which if overlooked can compromise an experiment and the resulting conclusions. A number of methods exist to identify biases during sequencing or alignment, yet not many tools exist to interpret biases due to outliers.

Results

Hence, we developed iSeqQC, an expression-based QC tool that detects outliers either produced due to variable laboratory conditions or due to dissimilarity within a phenotypic group. iSeqQC implements various statistical approaches including unsupervised clustering, agglomerative hierarchical clustering and correlation coefficients to provide insight into outliers. It can be utilized through command-line (Github: https://github.com/gkumar09/iSeqQC) or web-interface (http://cancerwebpa.jefferson.edu/iSeqQC). A local shiny installation can also be obtained from github (https://github.com/gkumar09/iSeqQC).

Conclusion

iSeqQC is a fast, light-weight, expression-based QC tool that detects outliers by implementing various statistical approaches.

Abstract 1730: DACH1 gene deletion extends portraits of human prostate cancer

Purpose of the study: This study was conducted to define the role of Dachshund in prostate cancer, through assessing human prostate cancer samples and through genetic deletion in the mouse. Prostate cancer (PCa), the second leading cause of death in American men, is a genetically heterogeneous disease, likely representing distinct genetic drivers, with terminal events caused primarily by metastasis. Substratification of PCa into genetic subtypes, forms the basis of rational therapy for PCa. A better molecular understanding of the disease is necessary in order to develop novel targeted therapies of metastatic PCa. Known genetic drivers to tumor initiation include PTEN and NKX3.1 deletions, rearrangements of the TMPRSS2 gene to the oncogenic ETS transcription factor, ERG, and genetic predisposing factors include germline DNA-repair gene mutations. The DACH1 gene, initially cloned as an inhibitor of Elipse, the hyperactive epidermal growth factor (EGFR) in Drosophila, was found to be reduced in abundance in several malignancies including breast and prostate cancer.

Results: In order to determine whether the DACH1 gene is deleted or mutated in prostate cancer we interrogated the genomic sequencing analysis of over 490 patients from 5 population cohorts. Homozygous deletion of DACH1 was identified in 18% (N=61), 11% (N=136), 10% (N=492), 7% (N=103) and 3% (N=150) of prostate cancer in 5 distinct cohorts. The prevalence of DACH1 gene deep deletions was higher in the metastasis than in the primary tumors. The Transgenic Adenocarcinoma Mouse Prostate (TRAMP) transgenic, Dach1fl/fl, and Probasin-Cre, ROSA26mT/mG transgenic mice were used to generate a prostate epithelial cell specific Dach1 gene knockout mouse (Probasin-Cre-Dach1fl/fl ROSA26mT/mG-TRAMP) lines. Prostate specific deletion of the murine Dach1 gene enhanced progression of prostatic intraepithelial neoplasia (PIN), associated with increased prostate epithelial cell proliferation, epithelial mesenchymal transition (EMT), DNA damage and inflammation.

Conclusions: DACH1 gene deletion may define a distinct subclass of prostate cancer that may benefit from PARP inhibitors, and platinum-based chemotherapy.

Citation Format: Xuanmao Jiao, Gabriele Di Sante, Zhiping Li, Agnese Di Rocco, Min Wang, Adam Ertel, Peter A. McCue, Andrew P. South, Carlos Cordon-Cardo, Matthew P. Stokes, Marco Marra, Steven J. Jones, Andrew Kossenkov, Richard G. Pestell. DACH1 gene deletion extends portraits of human prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1730.

Cyclin D1 integrates G9a-mediated histone methylation

Lysine methylation of histones and non-histone substrates by the SET domain containing protein lysine methyltransferase (KMT) G9a/EHMT2 governs transcription contributing to apoptosis, aberrant cell growth, and pluripotency. The positioning of chromosomes within the nuclear three-dimensional space involves interactions between nuclear lamina (NL) and the lamina-associated domains (LAD). Contact of individual LADs with the NL are dependent upon H3K9me2 introduced by G9a. The mechanisms governing the recruitment of G9a to distinct subcellular sites, into chromatin or to LAD, is not known. The cyclin D1 gene product encodes the regulatory subunit of the holoenzyme that phosphorylates pRB and NRF1 thereby governing cell-cycle progression and mitochondrial metabolism. Herein, we show that cyclin D1 enhanced H3K9 dimethylation though direct association with G9a. Endogenous cyclin D1 was required for the recruitment of G9a to target genes in chromatin, for G9a-induced H3K9me2 of histones, and for NL-LAD interaction. The finding that cyclin D1 is required for recruitment of G9a to target genes in chromatin and for H3K9 dimethylation, identifies a novel mechanism coordinating protein methylation.

Gene expression signatures for HOXA4, HOXA9, and HOXD10 reveal alterations in transcriptional regulatory networks in colon cancer

We previously reported that HOXA4, HOXA9, and HOXD10 are selectively expressed in colonic stem cells (SCs) and their overexpression contributes to colorectal cancer (CRC). Our goals here were to determine how these HOX genes are transcriptionally regulated and whether transcriptional dysregulation of HOX genes occurs in CRC. Accordingly, we used correlation analysis to identify genes that are expression-correlated or anticorrelated with HOXA4, HOXA9, and HOXD10. We then used Gene Ontology (GO) analysis to functionally classify these genes. The GO results for both HOXA4 and HOXD10 correlated gene sets for normal colon and CRC show functions mostly classified as developmental, transcriptional regulation, and DNA binding. This raised the question: Are these gene sets regulated by the same transcription factors (TFs)? Consequently, we used promoter analysis and interaction network toolset (PAINT) to identify commonly shared transcription response elements. The results indicated that completely different sets of TFs coregulate HOXA4 and HOXD10 (but not HOXA9) and their expression-correlated genes. And predicted TFs are altered in CRC compared with normal colon. Taken together, analysis of gene signatures correlated with expression of HOXA4 and HOXD10 indicates how these HOX genes are: (a) transcriptionally regulated in the normal colon; (b) dysregulated in CRC. This discovery provides a mechanism for targeting CRC SCs.

Nuclear Pores Promote Lethal Prostate Cancer by Increasing POM121-Driven E2F1, MYC, and AR Nuclear Import

Nuclear pore complexes (NPCs) regulate nuclear-cytoplasmic transport, transcription, and genome integrity in eukaryotic cells. However, their functional roles in cancer remain poorly understood. We interrogated the evolutionary transcriptomic landscape of NPC components, nucleoporins (Nups), from primary to advanced metastatic human prostate cancer (PC). Focused loss-of-function genetic screen of top-upregulated Nups in aggressive PC models identified POM121 as a key contributor to PC aggressiveness. Mechanistically, POM121 promoted PC progression by enhancing importin-dependent nuclear transport of key oncogenic (E2F1, MYC) and PC-specific (AR-GATA2) transcription factors, uncovering a pharmacologically targetable axis that, when inhibited, decreased tumor growth, restored standard therapy efficacy, and improved survival in patient-derived pre-clinical models. Our studies molecularly establish a role of NPCs in PC progression and give a rationale for NPC-regulated nuclear import targeting as a therapeutic strategy for lethal PC. These findings may have implications for understanding how NPC deregulation contributes to the pathogenesis of other tumor types.

Exosomal αvβ6 integrin is required for monocyte M2 polarization in prostate cancer

Therapeutic approaches aimed at curing prostate cancer are only partially successful given the occurrence of highly metastatic resistant phenotypes that frequently develop in response to therapies. Recently, we have described αvβ6, a surface receptor of the integrin family as a novel therapeutic target for prostate cancer; this epithelial-specific molecule is an ideal target since, unlike other integrins, it is found in different types of cancer but not in normal tissues. We describe a novel αvβ6-mediated signaling pathway that has profound effects on the microenvironment. We show that αvβ6 is transferred from cancer cells to monocytes, including β6-null monocytes, by exosomes and that monocytes from prostate cancer patients, but not from healthy volunteers, express αvβ6. Cancer cell exosomes, purified via density gradients, promote M2 polarization, whereas αvβ6 down-regulation in exosomes inhibits M2 polarization in recipient monocytes. Also, as evaluated by our proteomic analysis, αvβ6 down-regulation causes a significant increase in donor cancer cells, and their exosomes, of two molecules that have a tumor suppressive role, STAT1 and MX1/2. Finally, using the Pten^pc-/- prostate cancer mouse model, which carries a prostate epithelial-specific Pten deletion, we demonstrate that αvβ6 inhibition in vivo causes up-regulation of STAT1 in cancer cells. Our results provide evidence of a novel mechanism that regulates M2 polarization and prostate cancer progression through transfer of αvβ6 from cancer cells to monocytes through exosomes.

In Vivo E2F Reporting Reveals Efficacious Schedules of MEK1/2-CDK4/6 Targeting and mTOR-S6 Resistance Mechanisms

Targeting cyclin-dependent kinases 4/6 (CDK4/6) represents a therapeutic option in combination with BRAF inhibitor and/or MEK inhibitor (MEKi) in melanoma; however, continuous dosing elicits toxicities in patients. Using quantitative and temporal in vivo reporting, we show that continuous MEKi with intermittent CDK4/6 inhibitor (CDK4/6i) led to more complete tumor responses versus other combination schedules. Nevertheless, some tumors acquired resistance that was associated with enhanced phosphorylation of ribosomal S6 protein. These data were supported by phospho-S6 staining of melanoma biopsies from patients treated with CDK4/6i plus targeted inhibitors. Enhanced phospho-S6 in resistant tumors provided a therapeutic window for the mTORC1/2 inhibitor AZD2014. Mechanistically, upregulation or mutation of NRAS was associated with resistance in in vivo models and patient samples, respectively, and mutant NRAS was sufficient to enhance resistance. This study utilizes an in vivo reporter model to optimize schedules and supports targeting mTORC1/2 to overcome MEKi plus CDK4/6i resistance.Significance: Mutant BRAF and NRAS melanomas acquire resistance to combined MEK and CDK4/6 inhibition via upregulation of mTOR pathway signaling. This resistance mechanism provides the preclinical basis to utilize mTORC1/2 inhibitors to improve MEKi plus CDK4/6i drug regimens. Cancer Discov; 8(5); 568-81. ©2018 AACR.See related commentary by Sullivan, p. 532See related article by Romano et al., p. 556This article is highlighted in the In This Issue feature, p. 517.

Blockade of Tumor-Expressed PD-1 promotes lung cancer growth

Anti-PD-1 immunotherapy is the standard of care for treating many patients with non-small cell lung cancer (NSCLC), yet mechanisms of treatment failure are emerging. We present a case of NSCLC, who rapidly progressed during a trial (NCT02318771) combining palliative radiotherapy and pembrolizumab. Planned tumor biopsy demonstrated PD-1 expression by NSCLC cells. We validated this observation by detecting PD-1 transcript in lung cancer cells and by co-localizing PD-1 and lung cancer-specific markers in resected lung cancer tissues. We further investigated the biological role of cancer-intrinsic PD-1 in a mouse lung cancer cell line, M109. Knockout or antibody blockade of PD-1 enhanced M109 viability in-vitro, while PD-1 overexpression and exposure to recombinant PD-L1 diminished viability. PD-1 blockade accelerated growth of M109-xenograft tumors with increased proliferation and decreased apoptosis in immune-deficient mice. This represents a first-time report of NSCLC-intrinsic PD-1 expression and a potential mechanism by which PD-1 blockade may promote cancer growth.

Therapeutic Challenge with a CDK 4/6 Inhibitor Induces an RB-Dependent SMAC-Mediated Apoptotic Response in Non-Small Cell Lung Cancer

Purpose: The retinoblastoma tumor suppressor (RB), a key regulator of cell-cycle progression and proliferation, is functionally suppressed in up to 50% of non-small cell lung cancer (NSCLC). RB function is exquisitely controlled by a series of proteins, including the CyclinD-CDK4/6 complex. In this study, we interrogated the capacity of a CDK4/6 inhibitor, palbociclib, to activate RB function.Experimental Design and Results: We employed multiple isogenic RB-proficient and -deficient NSCLC lines to interrogate the cytostatic and cytotoxic capacity of CDK 4/6 inhibition in vitro and in vivo We demonstrate that while short-term exposure to palbociclib induces cellular senescence, prolonged exposure results in inhibition of tumor growth. Mechanistically, CDK 4/6 inhibition induces a proapoptotic transcriptional program through suppression of IAPs FOXM1 and Survivin, while simultaneously augmenting expression of SMAC and caspase-3 in an RB-dependent manner.Conclusions: This study uncovers a novel function of RB activation to induce cellular apoptosis through therapeutic administration of a palbociclib and provides a rationale for the clinical evaluation of CDK 4/6 inhibitors in the treatment of patients with NSCLC. Clin Cancer Res; 24(6); 1402-14. ©2018 AACR.

The Chemokine Receptor CXCR3 Promotes CD8+ T Cell Accumulation in Uninfected Salivary Glands but Is Not Necessary after Murine Cytomegalovirus Infection

Recent work indicates that salivary glands are able to constitutively recruit CD8⁺ T cells and retain them as tissue-resident memory T cells, independently of local infection, inflammation, or Ag. To understand the mechanisms supporting T cell recruitment to the salivary gland, we compared T cell migration to the salivary gland in mice that were infected or not with murine CMV (MCMV), a herpesvirus that infects the salivary gland and promotes the accumulation of salivary gland tissue-resident memory T cells. We found that acute MCMV infection increased rapid T cell recruitment to the salivary gland but that equal numbers of activated CD8⁺ T cells eventually accumulated in infected and uninfected glands. T cell recruitment to uninfected salivary glands depended on chemokines and the integrin α₄ Several chemokines were expressed in the salivary glands of infected and uninfected mice, and many of these could promote the migration of MCMV-specific T cells in vitro. MCMV infection increased the expression of chemokines that interact with the receptors CXCR3 and CCR5, but neither receptor was needed for T cell recruitment to the salivary gland during MCMV infection. Unexpectedly, however, the chemokine receptor CXCR3 was critical for T cell accumulation in uninfected salivary glands. Together, these data suggest that CXCR3 and the integrin α₄ mediate T cell recruitment to uninfected salivary glands but that redundant mechanisms mediate T cell recruitment after MCMV infection.

Recessive mutation in tetraspanin CD151 causes Kindler syndrome-like epidermolysis bullosa with multi-systemic manifestations including nephropathy

Epidermolysis bullosa (EB) is caused by mutations in as many as 19 distinct genes. We have developed a next-generation sequencing (NGS) panel targeting genes known to be mutated in skin fragility disorders, including tetraspanin CD151 expressed in keratinocytes at the dermal-epidermal junction. The NGS panel was applied to a cohort of 92 consanguineous families of unknown subtype of EB. In one family, a homozygous donor splice site mutation in CD151 (NM_139029; c.351+2T>C) at the exon 5/intron 5 border was identified, and RT-PCR and whole transcriptome analysis by RNA-seq confirmed deletion of the entire exon 5 encoding 25 amino acids. Immunofluorescence of proband's skin and Western blot of skin proteins with a monoclonal antibody revealed complete absence of CD151. Transmission electron microscopy showed intracellular disruption and cell-cell dysadhesion of keratinocytes in the lower epidermis. Clinical examination of the 33-year old proband, initially diagnosed as Kindler syndrome, revealed widespread blistering, particularly on pretibial areas, poikiloderma, nail dystrophy, loss of teeth, early onset alopecia, and esophageal webbing and strictures. The patient also had history of nephropathy with proteinuria. Collectively, the results suggest that biallelic loss-of-function mutations in CD151 underlie an autosomal recessive mechano-bullous disease with systemic features. Thus, CD151 should be considered as the 20th causative, EB-associated gene.

Stromal cyclin D1 promotes heterotypic immune signaling and breast cancer growth

The cyclin D1 gene encodes the regulatory subunit of a holoenzyme that drives cell autonomous cell cycle progression and proliferation. Herein we show cyclin D1 abundance is increased >30-fold in the stromal fibroblasts of patients with invasive breast cancer, associated with poor outcome. Cyclin D1 transformed hTERT human fibroblast to a cancer-associated fibroblast phenotype. Stromal fibroblast expression of cyclin D1 (cyclin D1^Stroma) in vivo, enhanced breast epithelial cancer tumor growth, restrained apoptosis, and increased autophagy. Cyclin D1^Stroma had profound effects on the breast tumor microenvironment increasing the recruitment of F4/80⁺ and CD11b⁺ macrophages and increasing angiogenesis. Cyclin D1^Stroma induced secretion of factors that promoted expansion of stem cells (breast stem-like cells, embryonic stem cells and bone marrow derived stem cells). Cyclin D1^Stroma resulted in increased secretion of proinflammatory cytokines (CCL2, CCL7, CCL11, CXCL1, CXCL5, CXCL9, CXCL12), CSF (CSF1, GM-CSF1) and osteopontin (OPN) (30-fold). OPN was induced by cyclin D1 in fibroblasts, breast epithelial cells and in the murine transgenic mammary gland and OPN was sufficient to induce stem cell expansion. These results demonstrate that cyclin D1^Stroma drives tumor microenvironment heterocellular signaling, promoting several key hallmarks of cancer.

Cell cycle-coupled expansion of AR activity promotes cancer progression

The androgen receptor (AR) is required for prostate cancer (PCa) survival and progression, and ablation of AR activity is the first line of therapeutic intervention for disseminated disease. While initially effective, recurrent tumors ultimately arise for which there is no durable cure. Despite the dependence of PCa on AR activity throughout the course of disease, delineation of the AR-dependent transcriptional network that governs disease progression remains elusive, and the function of AR in mitotically active cells is not well understood. Analyzing AR activity as a function of cell cycle revealed an unexpected and highly expanded repertoire of AR-regulated gene networks in actively cycling cells. New AR functions segregated into two major clusters: those that are specific to cycling cells and retained throughout the mitotic cell cycle ('Cell Cycle Common'), versus those that were specifically enriched in a subset of cell cycle phases ('Phase Restricted'). Further analyses identified previously unrecognized AR functions in major pathways associated with clinical PCa progression. Illustrating the impact of these unmasked AR-driven pathways, dihydroceramide desaturase 1 was identified as an AR-regulated gene in mitotically active cells that promoted pro-metastatic phenotypes, and in advanced PCa proved to be highly associated with development of metastases, recurrence after therapeutic intervention and reduced overall survival. Taken together, these findings delineate AR function in mitotically active tumor cells, thus providing critical insight into the molecular basis by which AR promotes development of lethal PCa and nominate new avenues for therapeutic intervention.

RB Loss Promotes Prostate Cancer Metastasis

RB loss occurs commonly in neoplasia but its contributions to advanced cancer have not been assessed directly. Here we show that RB loss in multiple murine models of cancer produces a prometastatic phenotype. Gene expression analyses showed that regulation of the cell motility receptor RHAMM by the RB/E2F pathway was critical for epithelial-mesenchymal transition, motility, and invasion by cancer cells. Genetic modulation or pharmacologic inhibition of RHAMM activity was sufficient and necessary for metastatic phenotypes induced by RB loss in prostate cancer. Mechanistic studies in this setting established that RHAMM stabilized F-actin polymerization by controlling ROCK signaling. Collectively, our findings show how RB loss drives metastatic capacity and highlight RHAMM as a candidate therapeutic target for treating advanced prostate cancer. Cancer Res; 77(4); 982-95. ©2016 AACR.

Abstract B33: The membrane associated cyclin D1 promotes contact-independent growth via phosphorylation of Akt1 Ser 473

The serine threonine kinase Akt plays a pivotal role in the control of cellular metabolism, survival, growth and cellular migration. Cyclin D1 encodes the regulatory subunit of a holoenzyme that phosphorylates and inactivates pRb, to promote cell cycle progression and functions as a nuclear collaborative oncogene. Herein, genetic deletion of cyclin D1 reduced and overexpression induced Akt1 activity in tissue culture and in vivo. Endogenous cyclin D1 augmented both the rate of onset and maximal cellular Akt1 activity. The cytoplasmic membrane-associated pool of cyclin D1, augmented Akt1 kinase activity, to thereby induce cell cycle progression, cellular migration, proliferation and contact independent growth. The induction of Akt1 kinase activity, via Ser 473, was dependent upon a single residue of cyclin D1 (K112) in vitro, and in vivo in mammary epithelial cell targets tissue specific transgenic mice. Distinct subcellular compartments of cell cycle proteins convey distinct functions to augment cellular growth.

Our data identified the function of the membrane associated cyclin D1 pool is to phosphorylate and activate AKT1, thereby, inducing cell cycle progression, contact independent growth and cellular migration. Membrane mounted cyclin D1 is a novel targetable vulnerability aberrant growth control.

Citation Format: Xuanmao Jiao, Ke Chen, Shaohua Xu, Xiaoming Ju, Adam Ertel, Lifeng Tian, Zuoren Yu, Gabriele Di Sante, Min Wang, Zhiping Li, Timothy Pestell, Mathew Casimiro, Duanwen Shen, Samuel Achilefu, Richard Pestell. The membrane associated cyclin D1 promotes contact-independent growth via phosphorylation of Akt1 Ser 473. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Cancer Cell Cycle - Tumor Progression and Therapeutic Response; Feb 28-Mar 2, 2016; Orlando, FL. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(11_Suppl):Abstract nr B33.

v-Src Oncogene Induces Trop2 Proteolytic Activation via Cyclin D1

Proteomic analysis of castration-resistant prostate cancer demonstrated the enrichment of Src tyrosine kinase activity in approximately 90% of patients. Src is known to induce cyclin D1, and a cyclin D1-regulated gene expression module predicts poor outcome in human prostate cancer. The tumor-associated calcium signal transducer 2 (TACSTD2/Trop2/M1S1) is enriched in the prostate, promoting prostate stem cell self-renewal upon proteolytic activation via a γ-secretase cleavage complex (PS1, PS2) and TACE (ADAM17), which releases the Trop2 intracellular domain (Trop2 ICD). Herein, v-Src transformation of primary murine prostate epithelial cells increased the proportion of prostate cancer stem cells as characterized by gene expression, epitope characteristics, and prostatosphere formation. Cyclin D1 was induced by v-Src, and Src kinase induction of Trop2 ICD nuclear accumulation required cyclin D1. Cyclin D1 induced abundance of the Trop2 proteolytic cleavage activation components (PS2, TACE) and restrained expression of the inhibitory component of the Trop2 proteolytic complex (Numb). Patients with prostate cancer with increased nuclear Trop2 ICD and cyclin D1, and reduced Numb, had reduced recurrence-free survival probability (HR = 4.35). Cyclin D1, therefore, serves as a transducer of v-Src-mediated induction of Trop2 ICD by enhancing abundance of the Trop2 proteolytic activation complex. Cancer Res; 76(22); 6723-34. ©2016 AACR.

Genome-wide redistribution of MeCP2 in dorsal root ganglia after peripheral nerve injury

Background

Methyl-CpG-binding protein 2 (MeCP2), a protein with affinity for methylated cytosines, is crucial for neuronal development and function. MeCP2 regulates gene expression through activation, repression and chromatin remodeling. Mutations in MeCP2 cause Rett syndrome, and these patients display impaired nociception. We observed an increase in MeCP2 expression in mouse dorsal root ganglia (DRG) after peripheral nerve injury. The functional implication of increased MeCP2 is largely unknown. To identify regions of the genome bound by MeCP2 in the DRG and the changes induced by nerve injury, a chromatin immunoprecipitation of MeCP2 followed by sequencing (ChIP-seq) was performed 4 weeks after spared nerve injury (SNI).

Results

While the number of binding sites across the genome remained similar in the SNI model and sham control, SNI induced the redistribution of MeCP2 to transcriptionally relevant regions. To determine how differential binding of MeCP2 can affect gene expression in the DRG, we investigated mmu-miR-126, a microRNA locus that had enriched MeCP2 binding in the SNI model. Enriched MeCP2 binding to miR-126 locus after nerve injury repressed miR-126 expression, and this was not mediated by alterations in methylation pattern at the miR-126 locus. Downregulation of miR-126 resulted in the upregulation of its two target genes Dnmt1 and Vegfa in Neuro 2A cells and in SNI model compared to control. These target genes were significantly downregulated in Mecp2-null mice compared to wild-type littermates, indicating a regulatory role for MeCP2 in activating Dnmt1 and Vegfa expression. Intrathecal delivery of miR-126 was not sufficient to reverse nerve injury-induced mechanical and thermal hypersensitivity, but decreased Dnmt1 and Vegfa expression in the DRG.

Conclusions

Our study shows a regulatory role for MeCP2 in that changes in global redistribution can result in direct and indirect modulation of gene expression in the DRG. Alterations in genome-wide binding of MeCP2 therefore provide a molecular basis for a better understanding of epigenetic regulation-induced molecular changes underlying nerve injury.

Electronic supplementary material

The online version of this article (doi:10.1186/s13072-016-0073-5) contains supplementary material, which is available to authorized users.

Abstract B10: Cyclin D1 restrains oncogene-induced autophagy via phosphorylation of LKB1

Cyclin D1 is an important molecular driver of many human cancers. The cyclin D1 gene is amplified or overexpressed in up to half of human breast cancers and mammary-targeted overexpression of cyclin D1 is sufficient to induce mammary tumorigenesis in mice. Cyclin D1 encodes the regulatory subunit of the cyclin-dependent kinase (CDK) holoenzyme that phosphorylates several substrates including the retinoblastoma protein (pRb) to advance the G1S cell cycle checkpoint and promote DNA synthesis. Recent studies have implicated cell cycle regulators that govern G1S transition, in regulating cellular metabolism. Cyclin D1 phosphorylates and inactivates a nuclear encoded protein essential for mitochondrial biogenesis, Nrf1. In this manner cyclin D1 coordinates both nuclear and mitochondrial functions. Consistent with cyclin D1-dependent inhibition of mitochondrial biogenesis, pRB promotes and E2F-1 inhibits mitochondrial biogenesis. In addition to inhibiting mitochondrial biogenesis, cyclin D1 inhibits mitochondrial membrane potential, which may be in part due to binding VDAC.

Autophagy is a catabolic pathway activated in response to cellular stress such as oxidative or nutritional stress. It mitigates cellular damage via removal of insoluble and damaged proteins, lipids and organelles. Autophagy is enhanced by the phosphorylated and activated form of 5’-AMP-activated protein kinase (AMPK). We initiated the following study to directly test the effect of cyclin D1 has on cellular metabolism and autophagy. Herein, endogenous cyclin D1 restrained autophagy in breast cancer cells in tissue culture and in the mammary gland of mice. Using mammary epithelial-targeted deletion of cyclin D1 we show cyclin D1 restrains autophagy by reducing AMPK activation. Cyclin D1 may serve to couple cellular proliferation to cellular energy homeostasis.

Citation Format: Mathew Casimiro, Gabriele Di Sante, Emanuele Loro, Timothy Pestell, Sara Bisetto, Marco Velasco-Velázquez, Xuanmao Jiao, Zhiping Li, Chenguang Wang, Daniel Ly, Bin Zheng, Shen Che-Hung, Adam Ertel, Richard G. Pestell. Cyclin D1 restrains oncogene-induced autophagy via phosphorylation of LKB1. [abstract]. In: Proceedings of the Fourth AACR International Conference on Frontiers in Basic Cancer Research; 2015 Oct 23-26; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2016;76(3 Suppl):Abstract nr B10.

RB loss contributes to aggressive tumor phenotypes in MYC-driven triple negative breast cancer

Triple negative breast cancer (TNBC) is characterized by multiple genetic events occurring in concert to drive pathogenic features of the disease. Here we interrogated the coordinate impact of p53, RB, and MYC in a genetic model of TNBC, in parallel with the analysis of clinical specimens. Primary mouse mammary epithelial cells (mMEC) with defined genetic features were used to delineate the combined action of RB and/or p53 in the genesis of TNBC. In this context, the deletion of either RB or p53 alone and in combination increased the proliferation of mMEC; however, the cells did not have the capacity to invade in matrigel. Gene expression profiling revealed that loss of each tumor suppressor has effects related to proliferation, but RB loss in particular leads to alterations in gene expression associated with the epithelial-to-mesenchymal transition. The overexpression of MYC in combination with p53 loss or combined RB/p53 loss drove rapid cell growth. While the effects of MYC overexpression had a dominant impact on gene expression, loss of RB further enhanced the deregulation of a gene expression signature associated with invasion. Specific RB loss lead to enhanced invasion in boyden chambers assays and gave rise to tumors with minimal epithelial characteristics relative to RB-proficient models. Therapeutic screening revealed that RB-deficient cells were particularly resistant to agents targeting PI3K and MEK pathway. Consistent with the aggressive behavior of the preclinical models of MYC overexpression and RB loss, human TNBC tumors that express high levels of MYC and are devoid of RB have a particularly poor outcome. Together these results underscore the potency of tumor suppressor pathways in specifying the biology of breast cancer. Further, they demonstrate that MYC overexpression in concert with RB can promote a particularly aggressive form of TNBC.

Abstract 1844: Genome wide analysis of AR-cell cycle interplay reveals novel functions in cancer

The androgen receptor (AR) plays a vital role in prostate cancer (PCa) due in part to its ability to interact with cell cycle components in order to drive cell cycle transition. Numerous points of cross-talk have been identified, wherein specific components of the cell cycle machinery “feed back” to modulate AR function, and these interactions are thought to be altered in human malignancies. Despite these observations, the majority of genome wide analyses for AR have been performed in cells that have exited cell cycle (G0). Here, the cell cycle dependent AR transcriptome and cistrome was identified, revealing new and unexpected functions for AR in cycling tumor cells. In studies to be discussed, cells were arrested in 5 distinct phases of the cell cycle, stimulated with androgen, and AR activity assessed through gene expression and ChIP-Seq analyses. In AR binding analyses, significant overlap was seen with previously identified sites, but were accompanied by novel binding events that could be segregated into those that are specific to cycling cells and occur in all phases (“cell cycle common”) or show cell cycle stage specific binding (“phase exclusive”). Over 50% of the cell cycle common sites, and up to 95% of the phases exclusive sites were novel AR occupied sites. Additionally, using a “guilty by association” approach to determine potentially AR regulated genes from this novel cistromic data, it was determined that close to 50% of cell cycle common, and 70% of phase exclusive binding uncover novel candidates for AR regulation. Cistrome data was therefore overlaid with microarray data, to prioritize discovery of meaningful, cell cycle specific AR binding events. Analyses to be discussed reveal striking new insight into disease relevant AR function. In sum, these data rigorously demonstrate that AR acts in a cell cycle dependent manner, and that these functions of AR have a major impact on tumor cell phenotypes.

Citation Format: Christopher McNair, Jonathan Goodwin, Michael Augello, Alfonso Urbanucci, Matthew Schiewer, Clay Comstock, Adam Ertel, Liguo Wang, Qianben Wang, Ian Mills, Wei Li, Jason Carroll, Karen Knudsen. Genome wide analysis of AR-cell cycle interplay reveals novel functions in cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1844. doi:10.1158/1538-7445.AM2015-1844

Monocyte-macrophage differentiation of acute myeloid leukemia cell lines by small molecules identified through interrogation of the Connectivity Map database

The transcription factor C/EBPα is required for granulocytic differentiation of normal myeloid progenitors and is frequently inactivated in acute myeloid leukemia (AML) cells. Ectopic expression of C/EBPα in AML cells suppresses proliferation and induces differentiation suggesting that restoring C/EBPα expression/activity in AML cells could be therapeutically useful. Unfortunately, current approaches of gene or protein delivery in leukemic cells are unsatisfactory. However, "drug repurposing" is becoming a very attractive strategy to identify potential new uses for existing drugs. In this study, we assessed the biological effects of candidate C/EBPα-mimetics identified by interrogation of the Connectivity Map database. We found that amantadine, an antiviral and anti-Parkinson agent, induced a monocyte-macrophage-like differentiation of HL60, U937, Kasumi-1 myeloid leukemia cell lines, as indicated by morphology and differentiation antigen expression, when used in combination with suboptimal concentration of all trans retinoic acid (ATRA) or Vit D3. The effect of amantadine depends, in part, on increased activity of the vitamin D receptor (VDR), since it induced VDR expression and amantadine-dependent monocyte-macrophage differentiation of HL60 cells was blocked by expression of dominant-negative VDR. These results reveal a new function for amantadine and support the concept that screening of the Connectivity Map database can identify small molecules that mimic the effect of transcription factors required for myelo-monocytic differentiation.

Structure-Based Screen Identifies a Potent Small Molecule Inhibitor of Stat5a/b with Therapeutic Potential for Prostate Cancer and Chronic Myeloid Leukemia

Bypassing tyrosine kinases responsible for Stat5a/b phosphorylation would be advantageous for therapy development for Stat5a/b-regulated cancers. Here, we sought to identify small molecule inhibitors of Stat5a/b for lead optimization and therapy development for prostate cancer and Bcr-Abl-driven leukemias. In silico screening of chemical structure databases combined with medicinal chemistry was used for identification of a panel of small molecule inhibitors to block SH2 domain-mediated docking of Stat5a/b to the receptor-kinase complex and subsequent phosphorylation and dimerization. We tested the efficacy of the lead compound IST5-002 in experimental models and patient samples of two known Stat5a/b-driven cancers, prostate cancer and chronic myeloid leukemia (CML). The lead compound inhibitor of Stat5-002 (IST5-002) prevented both Jak2 and Bcr-Abl-mediated phosphorylation and dimerization of Stat5a/b, and selectively inhibited transcriptional activity of Stat5a (IC50 = 1.5μmol/L) and Stat5b (IC50 = 3.5 μmol/L). IST5-002 suppressed nuclear translocation of Stat5a/b, binding to DNA and Stat5a/b target gene expression. IST5-002 induced extensive apoptosis of prostate cancer cells, impaired growth of prostate cancer xenograft tumors, and induced cell death in patient-derived prostate cancers when tested ex vivo in explant organ cultures. Importantly, IST5-002 induced robust apoptotic death not only of imatinib-sensitive but also of imatinib-resistant CML cell lines and primary CML cells from patients. IST5-002 provides a lead structure for further chemical modifications for clinical development for Stat5a/b-driven solid tumors and hematologic malignancies.

The endogenous cell-fate factor dachshund restrains prostate epithelial cell migration via repression of cytokine secretion via a cxcl signaling module

Prostate cancer is the second leading form of cancer-related death in men. In a subset of prostate cancer patients, increased chemokine signaling IL8 and IL6 correlates with castrate-resistant prostate cancer (CRPC). IL8 and IL6 are produced by prostate epithelial cells and promote prostate cancer cell invasion; however, the mechanisms restraining prostate epithelial cell cytokine secretion are poorly understood. Herein, the cell-fate determinant factor DACH1 inhibited CRPC tumor growth in mice. Using Dach1(fl/fl)/Probasin-Cre bitransgenic mice, we show IL8 and IL6 secretion was altered by approximately 1,000-fold by endogenous Dach1. Endogenous Dach1 is shown to serve as a key endogenous restraint to prostate epithelial cell growth and restrains migration via CXCL signaling. DACH1 inhibited expression, transcription, and secretion of the CXCL genes (IL8 and IL6) by binding to their promoter regulatory regions in chromatin. DACH1 is thus a newly defined determinant of benign and malignant prostate epithelium cellular growth, migration, and cytokine abundance in vivo.

CCR5 receptor antagonists block metastasis to bone of v-Src oncogene-transformed metastatic prostate cancer cell lines

Src family kinases (SFK) integrate signal transduction for multiple receptors, regulating cellular proliferation, invasion, and metastasis in human cancer. Although Src is rarely mutated in human prostate cancer, SFK activity is increased in the majority of human prostate cancers. To determine the molecular mechanisms governing prostate cancer bone metastasis, FVB murine prostate epithelium was transduced with oncogenic v-Src. The prostate cancer cell lines metastasized in FVB mice to brain and bone. Gene expression profiling of the tumors identified activation of a CCR5 signaling module when the prostate epithelial cell lines were grown in vivo versus tissue cultures. The whole body, bone, and brain metastatic prostate cancer burden was reduced by oral CCR5 antagonist. Clinical trials of CCR5 inhibitors may warrant consideration in patients with CCR5 activation in their tumors.

Retinoblastoma protein potentiates the innate immune response in hepatocytes: significance for hepatocellular carcinoma

Cancers mediated by viral etiology must exhibit deregulated cellular proliferation and evade immune recognition. The role of the retinoblastoma tumor suppressor (RB) pathway, which is lost at relatively high frequency in hepatocellular carcinoma (HCC), has recently been expanded to include the regulation of innate immune responsiveness. In this study we investigated the coordinate impact of RB-loss on cell cycle control and immune function in the liver. We found that RB depletion in hepatoma cells resulted in a compromised immunological response to multiple stimuli and reduced the potential of these cells to recruit myeloid cells. Viral-mediated liver-specific RB deletion in vivo led to the induction of genes associated with proliferation and cell cycle entry as well as the significant attenuation of genes associated with immune function, as evidenced by decreases in cytokine and chemokine expression, leukocyte recruitment, and hepatic inflammation. To determine if these changes in gene expression were instructive in human disease, we compared our liver-specific RB-loss gene signature to existing profiles of HCC and found that this signature was associated with disease progression and confers a worse prognosis.

CONCLUSION

Our data confirm that RB participates in the regulation of innate immunity in liver parenchymal cells both in vitro and in vivo and to our knowledge describes the first gene signature associated with HCC that includes both immunoregulatory and proliferative genes and that can also be attributed to the alteration of a single gene in vitro.

The retinoblastoma tumor suppressor modulates DNA repair and radioresponsiveness

PURPOSE

Perturbations in the retinoblastoma pathway are over-represented in advanced prostate cancer; retinoblastoma loss promotes bypass of first-line hormone therapy. Conversely, preliminary studies suggested that retinoblastoma-deficient tumors may become sensitized to a subset of DNA-damaging agents. Here, the molecular and in vivo consequence of retinoblastoma status was analyzed in models of clinical relevance.

EXPERIMENTAL DESIGN

Experimental work was performed with multiple isogenic prostate cancer cell lines (hormone sensitive: LNCaP and LAPC4 cells and hormone resistant C42, 22Rv1 cells; stable knockdown of retinoblastoma using shRNA). Multiple mechanisms were interrogated including cell cycle, apoptosis, and DNA damage repair. Transcriptome analysis was performed, validated, and mechanisms discerned. Cell survival was measured using clonogenic cell survival assay and in vivo analysis was performed in nude mice with human derived tumor xenografts.

RESULTS

Loss of retinoblastoma enhanced the radioresponsiveness of both hormone-sensitive and castrate-resistant prostate cancer. Hypersensitivity to ionizing radiation was not mediated by cell cycle or p53. Retinoblastoma loss led to alteration in DNA damage repair and activation of the NF-κB pathway and subsequent cellular apoptosis through PLK3. In vivo xenografts of retinoblastoma-deficient tumors exhibited diminished tumor mass, lower PSA kinetics, and decreased tumor growth after treatment with ionizing radiation (P < 0.05).

CONCLUSIONS

Loss of retinoblastoma confers increased radiosensitivity in prostate cancer. This hypersensitization was mediated by alterations in apoptotic signaling. Combined, these not only provide insight into the molecular consequence of retinoblastoma loss, but also credential retinoblastoma status as a putative biomarker for predicting response to radiotherapy.

Cyclin D1 induction of Dicer governs microRNA processing and expression in breast cancer

Cyclin D1 encodes the regulatory subunit of a holoenzyme that phosphorylates the pRB protein and promotes G₁/S cell cycle progression and oncogenesis. Dicer is a central regulator of miRNA maturation, encoding an enzyme that cleaves double strand RNA or stem-loop-stem RNA into 20–25 nucleotide long small RNA, governing sequence specific gene silencing and heterochromatin methylation. The mechanism by which the cell cycle directly controls the non-coding genome is poorly understood. Here we show that cyclin D1^−/− cells are defective in pre-miRNA processing which is restored by cyclin D1a rescue. Cyclin D1 induces Dicer expression in vitro and in vivo. Dicer is transcriptionally targeted by cyclin D1, via a cdk-independent mechanism. Cyclin D1 and Dicer expression significantly correlates in luminal A and basal-like subtypes of human breast cancer. Cyclin D1 and Dicer maintain heterochromatic histone modification (Tri-m-H3K9). Cyclin D1-mediated cellular proliferation and migration is Dicer-dependent. We conclude that cyclin D1 induction of Dicer coordinates microRNA biogenesis.

Acetylation of the cell-fate factor dachshund determines p53 binding and signaling modules in breast cancer

Breast cancer is a leading form of cancer in the world. The Drosophila Dac gene was cloned as an inhibitor of the hyperactive epidermal growth factor (EGFR), ellipse. Herein, endogenous DACH1 co-localized with p53 in a nuclear, extranucleolar compartment and bound to p53 in human breast cancer cell lines, p53 and DACH1 bound common genes in Chip-Seq. Full inhibition of breast cancer contact-independent growth by DACH1 required p53. The p53 breast cancer mutants R248Q and R273H, evaded DACH1 binding. DACH1 phosphorylation at serine residue (S439) inhibited p53 binding and phosphorylation at p53 amino-terminal sites (S15, S20) enhanced DACH1 binding. DACH1 binding to p53 was inhibited by NAD-dependent deacetylation via DACH1 K628. DACH1 repressed p21^CIP1 and induced RAD51, an association found in basal breast cancer. DACH1 inhibits breast cancer cellular growth in an NAD and p53-dependent manner through direct protein-protein association.

Functional significance of macrophage-derived exosomes in inflammation and pain

Exosomes, secreted microvesicles transporting microRNAs (miRNAs), mRNAs, and proteins through bodily fluids, facilitate intercellular communication and elicit immune responses. Exosomal contents vary, depending on the source and the physiological conditions of cells, and can provide insights into how cells and systems cope with physiological perturbations. Previous analysis of circulating miRNAs in patients with complex regional pain syndrome (CRPS), a debilitating chronic pain disorder, revealed a subset of miRNAs in whole blood that are altered in the disease. To determine functional consequences of alterations in exosomal biomolecules in inflammation and pain, we investigated exosome-mediated information transfer in vitro, in a rodent model of inflammatory pain, and in exosomes from patients with CRPS. Mouse macrophage cells stimulated with lipopolysaccharides secrete exosomes containing elevated levels of cytokines and miRNAs that mediate inflammation. Transcriptome sequencing of exosomal RNA revealed global alterations in both innate and adaptive immune pathways. Exosomes from lipopolysaccharide-stimulated cells were sufficient to cause nuclear factor-κB activation in naive cells, indicating functionality in recipient cells. A single injection of exosomes attenuated thermal hyperalgesia in a murine model of inflammatory pain, suggesting an immunoprotective role for macrophage-derived exosomes. Macrophage-derived exosomes carry a protective signature that is altered when secreting cells are exposed to an inflammatory stimulus. We also show that circulating miRNAs altered in patients with complex regional pain syndrome are trafficked by exosomes. With their systemic signaling capabilities, exosomes can induce pleiotropic effects potentially mediating the multifactorial pathology underlying chronic pain, and should be explored for their therapeutic utility.

Abstract P4-07-05: Cyclin D1 induction of dicer governs microRNA processing and expression in breast cancer

MicroRNAs (miRNAs), a class of non-coding small RNA, regulate gene expression through base-pairing binding to the complementary sequence in the 3’ untranslated region (3’ UTR) of mRNA. miRNAs contribute to the timing of development, apoptosis, cell cycle progression, cellular proliferation, stem cell self-renewal, cancer initiation and metastasis. The expression of miRNA is regulated during cell-cycle transition and cellular contact in part via active degradation. Aberrant expression of miRNAs or mutations of miRNA genes have been described in many types of tumors, including mammary tumors. The RNase III endoribonuclease Dicer cleaves long double-stranded RNA (dsRNA) or stem-loop-stem structured pre-miRNA to form mature miRNAs. RNAi-mediated knock-down of Dicer in human cells led to defects in both miRNA production and shRNA-mediated RNAi.

Initially cloned as a breakpoint rearrangement in parathyroid adenoma, the cyclin D1 gene encodes the regulatory subunit of the holoenzyme that phosphorylates and inactivates both the pRb tumor suppressor and the key inducer of mitochondrial biogenesis NRF-1. In addition, a DNA bound form of cyclin D1 regulates gene expression. Cyclin D1 expression is induced during mammary gland and retinal differentiation, and deletion of the murine cyclin D1 gene resulted in failed terminal alveolar breast bud development and retinal degeneration. Diverse biological functions regulated by cyclin D1 include the induction of cellular proliferation, angiogenesis, cellular migration, DNA damage repair, mitochondrial biogenesis, stem cell maintenance, and miRNA expression. Cyclin D1 was shown to regulate the miR-17/20 locus and found to bind the miR-17/20 regulatory region.

In order to determine further the mechanism by which cyclin D1 regulates non-coding RNA, we conducted studies of miRNA processing. We established cyclin D1-/- mouse embryonic fibroblasts cells (MEFs) and cyclin D1 knockdown (KD) MCF-7 human breast cancer cells. miRNA analysis indicated an induction of mature miRNA expression in cyclin D1 overexpressing cells. Analysis of the miRNA processing regulators demonstrated the selective induction of Dicer expression by cyclin D1. In cyclin D1-/- cells the reduction of Dicer abundance was accompanied by impairment of pre-miRNA to mature miRNA processing, which was restored with cyclin D1 rescue. Transient transgenic expression of cyclin D1 in the mouse mammary gland, or sustained transgenic expression of cyclin D1 induced mouse mammary gland tumors, recapitulated the induction of Dicer expression. Cyclin D1 and Dicer expression were correlated in luminal A and basal-like human breast cancer. Cyclin D1 regulation of cellular proliferation and migration was dependent upon Dicer. By demonstrating cyclin D1 induced Dicer abundance and function in tissue culture and in vivo, we provide evidence for novel crosstalk between the cell-cycle and non-coding miRNA biogenesis.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P4-07-05.

Abstract P5-07-06: Kinase-independent role of cyclin D1 in chromosomal instability and mammary tumorigenesis

Cyclin D1 is an important molecular driver of human breast cancer but better understanding of its oncogenic mechanisms is needed, especially to enhance efforts in targeted therapeutics. Activation of the cyclin D1 oncogene, often by amplification or rearrangement, is a major driver of multiple types of human tumors including breast and squamous cell cancers, B-cell lymphoma, myeloma, and parathyroid adenoma. The cyclin D1 gene is amplified or overexpressed in up to half of human breast cancers and its mammary-targeted overexpression induces mammary tumorigenesis in mice. Cyclin D1 encodes the regulatory subunit of the cyclin-dependent kinase (CDK) holoenzyme that phosphorylates several substrates including the retinoblastoma protein (pRb) to advance the G1S cell cycle checkpoint, promote DNA synthesis and regulate NRF-1 to inhibit mitochondrial biogenesis thereby coordinating nuclear and mitochondrial functions.

In addition to cyclin D1's function as a regulatory subunit of a CDK holoenzyme, several CDK-independent functions have been identified. Tumors overexpressing cyclin D1 tend to display normal levels of proliferation and expression of E2F target genes, which contrasts with tumors overexpressing cyclin E or an activator for pRb. Breast cancers overexpressing cyclin D1 that are wild type for pRb have relatively normal proliferation rates, in contrast to those caused by genetic inactivation of pRb, which show significantly increased proliferation rates. Furthermore, the alternate splice form of cyclin D1, (cyclin D1b), has potent transforming ability, which does not correlate with the ability to phosphorylate the pRb protein. Several other properties of cyclin D1 have been identified including the induction of cellular migration and enhanced angiogenesis, inhibition of mitochondrial biogenesis, and mediating DNA-damage repair signaling. Cyclin D1 binding proteins participating in these putatively CDK-independent functions include PACSIN2, NRF1, and p27KIP1; binding to p27KIP1 and PACSIN2 contribute to the pro-migratory function of cyclin D1.

Currently, pharmaceutical initiatives to inhibit cyclin D1 are focused on the catalytic component since the transforming capacity is thought to reside in the cyclin D1/CDK activity. We initiated the following study to directly test the oncogenic potential of catalytically inactive cyclin D1 in an in vivo mouse model that is relevant to breast cancer. Herein, transduction of cyclin D1-/- mouse embryonic fibroblasts (MEFs) with the kinase dead KE mutant of cyclin D1 led to aneuploidy, abnormalities in mitotic spindle formation, autosome amplification, and chromosomal instability (CIN) by gene expression profiling. Acute transgenic expression of either cyclin D1WT or cyclin D1KE in the mammary gland was sufficient to induce the CIN signature within 7 days. Sustained expression of cyclin D1KE induced mammary adenocarcinoma with similar kinetics to that of the wild-type cyclin D1. ChIP-Seq studies demonstrated recruitment of cyclin D1WT and cyclin D1KE to the genes governing CIN. We conclude that the CDK-activating function of cyclin D1 is not necessary to induce either chromosomal instability or mammary tumorigenesis.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-07-06.

Abstract P1-07-05: The cell fate factor DACH1 represses YB-1-mediated oncogenic transcription and translation

The epithelial-mesenchymal transition (EMT) enhances cellular invasiveness and confers tumor cells with cancer stem cell like characteristics, through transcriptional and translational mechanisms. The mechanisms maintaining transcriptional and translational repression of EMT and cellular invasion are poorly understood. The Drosophila homologue of DACH1, the Dac gene is a key member of the retinal determination gene network that specifies organismal development. The dachshund (dac), eya1, eyes-absent (eya), twin of eyeless (toy), teashirt (tsh) and sinoculues (so) are expressed in progenitor cells, contributing to development of the eye and genitalia. Loss of DACH1 expression contributes to the expansion of neural progenitors, muscle satellite cell differentiation and breast cancer stem cells. In recent studies Dachshund repressed breast cancer stem cell expansion. DACH1 expression is reduced in a variety of human cancers including prostate, ovarian and human breast cancer.

Herein, the cell fate-determination factor Dachshund (DACH1), suppressed EMT via repression of cytoplasmic translational induction of Snail by inactivating the Y box-binding protein (YB-1). In the nucleus, DACH1 antagonized YB-1-mediated oncogenic transcriptional modules governing cell invasion. DACH1 blocked YB-1-induced mammary tumor growth and EMT in mice. In basal-like breast cancer (BLBC) the reduced expression of DACH1 and increased YB-1, correlated with poor metastasis free survival. The loss of DACH1 suppression of both cytoplasmic translational and nuclear transcriptional events governing EMT and tumor invasion may contribute to poor prognosis in BLBC.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-07-05.

Abstract P2-06-02: Pparg deacetylation by SIRT1 determines breast tumor lipid synthesis and growth

Peroxisome proliferator-activated receptorg (Pparγ) is a member of the nuclear receptor (NR) superfamily, which regulates diverse biological functions including lipogenesis and differentiation, anti-inflammation, insulin sensitivity, cellular proliferation, and autophagy. Independent lines of evidence support a role for Pparγ as either a collaborative oncogene or as a tumor suppressor. Heterozygous mutations of Pparγ have been detected in 4/55 patients with colon cancer and a chromosomal translocation between PAX8 and Pparγ in follicular thyroid cancer appeared to serve as a dominant inhibitor of endogenous Pparγ expression. Pparγ agonists reduced tumorigenesis in several in vivo models. In contrast, several studies suggest Pparγ may enhance tumor growth. Pparγ ligands increased polyp numbers in the Apc mouse model of familial adenomatosis. Pparγ and its ligands inhibit breast tumor growth; however, constitutively active Pparγ collaborated in mammary oncogenesis with polyoma middle T antigen or oncogenic ErbB2.

Pparγ activation involves post-translational modifications including phosphorylation and sumoylation upon growth factor or ligand stimulus. Mutation of the Pparγ1 sumoylation site at K77 and K365 demonstrated that K77 may either reduce Pparγ-dependent gene induction and enhance repression or reduce repression, depending upon the synthetic reporter gene used. Lysine residues of nuclear receptors also serve as substrates for acetylation and Pparγ binds co-activators and co-repressors with intrinsic or associated histone acetylase or deacetylase activity including NCoR, SMRT, SIRT1, and p300. Initially characterized for the ERα, AR and, subsequently, the orphan nuclear receptor steroidogenic factor 1 (SF-1), acetylation occurs at a conserved lysine motif shared amongst evolutionarily related nuclear receptors. Several nuclear receptors and co-integrators involved in lipid metabolism are regulated by acetylation including p300, PGC1α, FXR, LXR and RAR. Both TSA- and NAD-sensitive HDACs (e.g. SIRT1) regulate Pparγ function and SIRT1 inhibits Pparγ-dependent adipocyte differentiation. Whether Pparγ is acetylated in cancer cells and how Pparγ exerts it's crucial, though controversial, function in tumorigenesis have not been established.

Pparγ induces gene transcription through binding specific NR half-sites and through non-canonical binding sequences (such as CREB/AP-1 sites). Transcriptional repression involves Pparγ sumoylation at lysine 77 (K77). Herein, Pparγ was shown to be acetylated at nine distinct lysine residues. SIRT1 bound and deacetylated Pparγ at K154/155. ChIP-Seq analysis for genome-wide DNA binding demonstrated the acetylation site was required for binding NR half-sites, but was not required for non-canonical site binding. Breast tumor growth, de novo lipid synthesis, induction of autophagy and evasion of apoptosis was promoted by K154/155 and inhibited by K77 in vivo. Pparγ acetylation induced a gene signature that was increased in breast cancer, associated with a reduction in SIRT1 abundance and poor outcome. The Pparγ acetylation site determines binding to autophagy and apoptosis signaling to regulate breast tumor lipid metabolism and growth.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P2-06-02.

Abstract P5-11-04: Post-translational modification of the cell-fate factor Dachshund determines p53 binding and signaling modules in breast cancer

Breast cancer is a leading form of cancer in the world. Initially cloned as a dominant inhibitor of the hyperactive EGFR, Ellipse, in Drosophila, the mammalian DACH1 regulates expression of target genes in part through interacting with DNA-binding transcription factors (c-Jun, Smads, Six, ERα), and in part through intrinsic DNA-sequence specific binding to Forkhead binding sites. The Drosophila dac gene is a key member of the retinal determination gene network (RDGN), which also includes eyes absent (eya), ey, twin of eyeless (toy), teashirt (tsh) and sin oculis (so), that specifies eye tissue identity.

Several lines of evidence suggest DACH1 may function as a tumor suppressor. Clinical studies have demonstrated a correlation between poor prognosis and reduced expression of the cell-fate determination factor DACH1 in breast cancer, and loss of DACH1 expression has been observed in prostate and endometrial cancer. DACH1 inhibits breast cancer tumor metastasis and reduces breast cancer stem cell expansion via Sox2/Nanog. Although these studies suggest DACH1 may function as a tumor suppressor, the molecular mechanisms remain poorly defined. Herein, endogenous DACH1 co-localized with p53 in a nuclear, extranucleolar compartment and bound to p53 in human breast cancer cell lines, p53 and DACH1 bound common genes in ChIP-Seq. Full inhibition of breast cancer contact-independent growth by DACH1 required p53. The p53 breast cancer mutants R248Q and R273H, evaded DACH1 binding. DACH1 phosphorylation at serine residue (S439) inhibited p53 binding and phosphorylation at p53 amino-terminal sites (S15, S20) enhanced DACH1 binding. DACH1 binding to p53 was inhibited by NAD-dependent deacetylation via DACH1 K628. DACH1 repressed p21CIP1 and induced RAD51, an association found in basal breast cancer. DACH1 inhibits breast cancer cellular growth in an NAD and p53 dependent manner through direct protein-protein association.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-11-04.

Abstract P5-04-04: CCR5 antagonists block basal breast cancer and prostate cancer metastasis in vivo

The identification of new therapeutic targets and treatments to reduce tumor metastasis homing requires alternative interrogation approaches. The roles of the chemokine CCL5 and its receptor CCR5 in breast cancer progression are controversial. Cancer metastasis is regulated by chemokines in the microenvironment. Chemokines bind to cell surface receptors that belong to the G-protein-coupled receptor family (GPCRs), controlling diverse biological and pathological processes from immune surveillance, inflammation, and cancer. Previous studies of human breast cancer and breast cancer cell lines demonstrated that the chemokine receptors CXCR4 and CCR7 are expressed in breast cancer cells, malignant breast tumors, and metastasis. Their related ligands, CXCL12 (SDF1) and CCL21, are also expressed at the site of metastasis. Subsequent studies identified altered expression of CCL5 (RANTES) in breast cancer patients, correlating with disease progression. CCL5 can be expressed and secreted either by breast cancer cells or by non-malignant stromal cells at the primary or metastatic sites. However, the roles of CCL5 and its receptors in breast cancer are not fully understood. CCL5 facilitates disease progression by recruiting and modulating the activity of inflammatory cells, which subsequently remodel the tumor microenvironment. Accordingly, inhibition of CCR5 by a peptide antagonist reduced leukocyte infiltration and reduced tumor growth after subcutaneous injection of 410.4 mammary carcinoma cells into immunocompetent mice. Our recent microarray analysis of 2,254 human breast cancers demonstrated increased expression of CCL5 and its receptor CCR5, but not CCR3, in the basal and HER-2 genetic subtypes of breast cancer. Interrogation of pathways activated in patient normal breast vs. tumor identified up regulation of a CCR5 signaling module. At the same time, we also extended our research to prostate cancers. Using isogenic oncogene transformed breast and prostate cancer cell lines we show oncogene transformation induces CCR5 expression in breast and prostate epithelial cells. Further we show that the subpopulation of cells that express functional CCR5 display increased invasiveness. Studies in vivo demonstrated that CCR5 promoted metastasis homing. The FDA approved CCR5 antagonists Maraviroc or Vicriviroc, developed to block CCR5 HIV co-receptor function, reduced in vitro invasion of basal breast cancer and prostate cancer cell lines without affecting cell proliferation or viability. In a series of preclinical mouse models, used at equivalent doses to those used in treatment of humans for HIV, Maraviroc decreased breast pulmonary metastasis. The isogenic prostate cancer cell lines metastasized to bones in immune-competent mice representing an ideal model for testing anti-metastasis therapies. CCR5 was expressed in the metastasis in the bones. Maraviroc reduced prostate cancer metastasis to brain, bones and lungs. Our findings provide evidence for a key role of CCL5/CCR5 in the metastasis of basal breast cancer and prostate cancer cell lines and suggest that CCR5 antagonists may be used as an adjuvant therapy to reduce the risk of metastasis in patients with the basal breast cancer subtype and prostate cancer.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-04-04.

Abstract P3-02-03: The phosphatase function of the eyes absent (EYA) homolog is required for the induction of breast cancer cellular proliferation via cyclin D1

The Drosophila Eyes Absent Homologue 1 (EYA1) is a component of the retinal determination gene network (RDGN) and serves as an H2AX phosphatase. The cell fate determination gene network includes the dachshund (dac), twin-of-eyeless (toy), eye absent (eya), teashirt (tsh) and sine oculis (So). In Drosophila, mutations of the RDGN leads to failure of eye formation, whereas, forced expression induces ectopic eye formation. EYA functions as a transcriptional co-activator being recruited in the context of local chromatin, but lacking intrinsic DNA binding activity. EYA family members EYA 1-4 are defined by a 275 amino acid carboxyl-terminal motif that is conserved between species, referred to as the EYA domain (ED). The human homologs EYA 1-4 are highly conserved in their EYA domain and amino termini, with the exception of a small tyrosine rich residue region named EYA domain II.

Altered expression or functional activity of the RDGN has been documented in a variety of malignancies. DACH1 expression is reduced in breast, prostate, endometrial and brain cancer. EYA2 is up regulated in ovarian cancer, promoting tumor growth. EYA1 and EYA2 enhanced survival in response to DNA damage producing agents in HEK293 cells. Eya2 was required for Six1/TGFb signals that govern a prometastatic phenotype and epithelial mesenchymal transition (EMT). Although EYA proteins are expressed in human breast cancer, the relationship to molecular genetic subtype, prognosis and the molecular mechanisms governing contact-independent growth are not known.

The cyclin D1 gene encodes the regulatory subunits of a holoenzyme that phosphorylates and inactivates the pRb protein. Herein, comparison with normal breast demonstrated EYA1 is overexpressed with cyclin D1 in luminal B breast cancer subtype. EYA1 enhanced breast tumor growth in mice in vivo requiring the phosphatase domain. EYA1 enhanced cellular proliferation, inhibited apoptosis, and induced contact-independent growth and cyclin D1 abundance. The induction of cellular proliferation and cyclin D1 abundance, but not apoptosis, was dependent upon the EYA1 phosphatase domain. The EYA1-mediated transcriptional induction of cyclin D1 occurred via the AP-1 binding site at -953 and required the EYA1 phosphatase function. The AP-1 mutation did not affect SIX1-dependent activation of cyclin D1. EYA1 was recruited in the context of local chromatin to the cyclin D1 AP-1 site. The EYA1 phosphatase function determined the recruitment of CBP, RNA polymerase II and acetylation of H3K9 at the cyclin D1 gene AP-1 site regulatory region in the context of local chromatin. The EYA1 phosphatase regulates cell cycle control via transcriptional complex formation at the cyclin D1 promoter.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P3-02-03.

Cell fate factor DACH1 represses YB-1-mediated oncogenic transcription and translation

The epithelial-mesenchymal transition (EMT) enhances cellular invasiveness and confers tumor cells with cancer stem cell-like characteristics, through transcriptional and translational mechanisms. The mechanisms maintaining transcriptional and translational repression of EMT and cellular invasion are poorly understood. Herein, the cell fate determination factor Dachshund (DACH1), suppressed EMT via repression of cytoplasmic translational induction of Snail by inactivating the Y box-binding protein (YB-1). In the nucleus, DACH1 antagonized YB-1-mediated oncogenic transcriptional modules governing cell invasion. DACH1 blocked YB-1-induced mammary tumor growth and EMT in mice. In basal-like breast cancer, the reduced expression of DACH1 and increased YB-1 correlated with poor metastasis-free survival. The loss of DACH1 suppression of both cytoplasmic translational and nuclear transcriptional events governing EMT and tumor invasion may contribute to poor prognosis in basal-like forms of breast cancer, a relatively aggressive disease subtype.

Identification of a cyclin D1 network in prostate cancer that antagonizes epithelial-mesenchymal restraint

Improved clinical management of prostate cancer has been impeded by an inadequate understanding of molecular genetic elements governing tumor progression. Gene signatures have provided improved prognostic indicators of human prostate cancer. The TGF-β/BMP-SMAD4 signaling pathway, which induces epithelial-mesenchymal transition (EMT), is known to constrain prostate cancer progression induced by Pten deletion. Herein, cyclin D1 inactivation reduced cellular proliferation in the murine prostate in vivo and in isogenic oncogene-transformed prostate cancer cell lines. The in vivo cyclin D1-mediated molecular signature predicted poor outcome of recurrence-free survival for patients with prostate cancer (K-means HR, 3.75, P = 0.02) and demonstrated that endogenous cyclin D1 restrains TGF-β, Snail, Twist, and Goosecoid signaling. Endogenous cyclin D1 enhanced Wnt and ES cell gene expression and expanded a prostate stem cell population. In chromatin immunoprecipitation sequencing, cyclin D1 occupied genes governing stem cell expansion and induced their transcription. The coordination of EMT restraining and stem cell expanding gene expression by cyclin D1 in the prostate may contribute to its strong prognostic value for poor outcome in biochemical-free recurrence in human prostate cancer.