Suppression of SIN3A by miR-183 Promotes Breast Cancer Metastasis

Recent work has established that SWI-independent-3 (SIN3) chromatin modification complexes play key roles in cancer progression. We previously demonstrated that knockdown of SIN3A expression promotes human breast cancer cell invasion and metastasis; however, the levels of SIN3A in patient breast carcinoma are not known. We therefore examined SIN3A mRNA and protein in patient tissues and determined that SIN3A expression is lower in breast carcinoma relative to normal breast. Given the 3'-untranslated region (UTR) of SIN3A has several conserved binding sites for oncogenic miRNA, we hypothesized that SIN3A is targeted by miRNA and found that ectopic miR-183 results in decreased SIN3A in breast carcinoma cell lines. Functionally, we demonstrate that miR-183 promotes breast cancer cell migration and invasion in a SIN3A-dependent manner and ectopic miR-183 promotes metastasis in vivo. Patients with breast cancer with high levels of miR-183 and low levels of SIN3A have the shortest overall survival. Given the critical link between metastasis and survival in patients with breast cancer, it is of utmost importance to identify clinically relevant genes involved in metastasis. Here, we report for the first time the aberrant expression of the putative metastasis suppressing gene SIN3A in human breast cancers and propose a mechanism of SIN3A suppression by miR-183.

IMPLICATIONS

SIN3A expression is decreased in metastatic breast cancer in part due to miR-183.

Perturbation of BRMS1 interactome reveals pathways that impact metastasis

Breast Cancer Metastasis Suppressor 1 (BRMS1) expression is associated with longer patient survival in multiple cancer types. Understanding BRMS1 functionality will provide insights into both mechanism of action and will enhance potential therapeutic development. In this study, we confirmed that the C-terminus of BRMS1 is critical for metastasis suppression and hypothesized that critical protein interactions in this region would explain its function. Phosphorylation status at S237 regulates BRMS1 protein interactions related to a variety of biological processes, phenotypes [cell cycle (e.g., CDKN2A), DNA repair (e.g., BRCA1)], and metastasis [(e.g., TCF2 and POLE2)]. Presence of S237 also directly decreased MDA-MB-231 breast carcinoma migration in vitro and metastases in vivo. The results add significantly to our understanding of how BRMS1 interactions with Sin3/HDAC complexes regulate metastasis and expand insights into BRMS1's molecular role, as they demonstrate BRMS1 C-terminus involvement in distinct protein-protein interactions.

Collagen modifying enzyme P4HA1 is overexpressed and plays a role in lung adenocarcinoma

Lung cancer is the leading cause of cancer-related deaths globally and is histologically defined as either small cell lung cancer (SCLC) or non-small cell lung cancer (NSCLC), with the latter accounting for 80% of all lung cancers. The 5-year overall survival rate for lung cancer patients is low as it is often discovered at advanced stages when potential cure by surgical resection is no longer an option. To identify a biomarker and target for lung cancer, we performed analysis of multiple datasets of lung cancer gene expression data. Our analyses indicated that the collagen-modifying enzyme Prolyl 4-Hydroxylase Subunit Alpha 1 (P4HA1) is overexpressed in NSCLC. Furthermore, our investigation found that overexpression of enzymes involved in this pathway predicts poor outcome for patients with lung adenocarcinoma. Our functional studies using knockdown strategies in lung cancer cell lines in vitro indicated that P4HA1 is critical for lung cancer growth, migration, and invasion. Additionally, diethyl pythiDC (PythiDC), a small molecule inhibitor, decreased the malignant phenotypes of lung cancer cells. Moreover, we found that miR-124 regulates and targets P4HA1 in lung cancer cells. Thus, our study suggests that collagen-modifying enzymes play an important role in lung cancer aggressiveness. Furthermore, our studies showed that P4HA1 is required for lung cancer cell growth and invasion, suggesting its potential as a valid therapeutic target in lung adenocarcinoma.

miR-31 Displays Subtype Specificity in Lung Cancer

miRNA rarely possess pan-oncogenic or tumor-suppressive properties. Most miRNAs function under tissue-specific contexts, acting as either tumor suppressors in one tissue, promoting oncogenesis in another, or having no apparent role in the regulation of processes associated with the hallmarks of cancer. What has been less clear is the role of miRNAs within cell types of the same tissue and the ability within each cell type to contribute to oncogenesis. In this study, we characterize the role of one such tissue-specific miRNA, miR-31, recently identified as the most oncogenic miRNA in lung adenocarcinoma, across the histologic spectrum of human lung cancer. Compared with normal lung tissue, miR-31 was overexpressed in patient lung adenocarcinoma, squamous cell carcinoma, and large-cell neuroendocrine carcinoma, but not small-cell carcinoma or carcinoids. miR-31 promoted tumor growth in mice of xenografted human adenocarcinoma and squamous cell carcinoma cell lines, but not in large- or small-cell carcinoma lines. While miR-31 did not promote primary tumor growth of large- and small-cell carcinoma, it did promote spontaneous metastasis. Mechanistically, miR-31 altered distinct cellular signaling programs within each histologic subtype, resulting in distinct phenotypic differences. This is the first report distinguishing diverse functional roles for this miRNA across the spectrum of lung cancers and suggests that miR-31 has broad clinical value in human lung malignancy. SIGNIFICANCE: These findings demonstrate the oncogenic properties of miR-31 in specific subtypes of lung cancer and highlight it as a potential therapeutic target in these subtypes. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/81/8/1942/F1.large.jpg.

Perfusion and Inflation of the Mouse Lung for Tumor Histology

The ability to evaluate lung histology is critical for the fields of lung cancer research and cancer metastasis. It is equally important to perform necropsies rapidly and efficiently from studies without sacrificing the quality of the tissues procured. The goal of this protocol is to present a method to rapidly perfuse, inflate, and fix mouse lungs for downstream histological analysis. This method does not standardize lung inflation; thus, it does not require any special procedures or equipment and instead simply instills fixative directly through the trachea following perfusion through the heart. This allows for sufficient estimation of tumor size, histology, and scoring. This also allows for the collection of frozen tissue prior to lung tissue fixation. This method is limited in that it does not allow for later morphometric quantification of the lung; however, it is more than sufficient for lung tumor analysis from genetically engineered mouse models (GEMMs), syngeneic models, as well as xenograft tumor and metastasis studies.

Targeting of SGK1 by miR-576-3p Inhibits Lung Adenocarcinoma Migration and Invasion

Metastatic lung cancer is common in patients with lung adenocarcinoma, but the molecular mechanisms of metastasis remain incompletely resolved. miRNA regulate gene expression and contribute to cancer development and progression. This report identifies miR-576-3p and its mechanism of action in lung cancer progression. miR-576-3p was determined to be significantly decreased in clinical specimens of late-stage lung adenocarcinoma. Overexpression of miR-576-3p in lung adenocarcinoma cells decreased mesenchymal marker expression and inhibited migration and invasion. Inhibition of miR-576-3p in nonmalignant lung epithelial cells increased migration and invasion as well as mesenchymal markers. Serum/glucocorticoid-regulated kinase 1 (SGK1) was a direct target of miR-576-3p, and modulation of miR-576-3p levels led to alterations in SGK1 protein and mRNA as well as changes in activation of its downstream target linked to metastasis, N-myc downstream regulated 1 (NDRG1). Loss of the ability of miR-576-3p to bind the 3'-UTR of SGK1 rescued the inhibition in migration and invasion observed with miR-576-3p overexpression. In addition, increased SGK1 levels were detected in lung adenocarcinoma patient samples expressing mesenchymal markers, and pharmacologic inhibition of SGK1 resulted in a similar inhibition of migration and invasion of lung adenocarcinoma cells as observed with miR-576-3p overexpression. Together, these results reveal miR-576-3p downregulation is selected for in late-stage lung adenocarcinoma due to its ability to inhibit migration and invasion by targeting SGK1. Furthermore, these results also support targeting SGK1 as a potential therapeutic for lung adenocarcinoma. IMPLICATIONS: This study reveals SGK1 inhibition with miR-576-3p or pharmacologically inhibits migration and invasion of lung adenocarcinoma, providing mechanistic insights into late-stage lung adenocarcinoma and a potential new treatment avenue.

Hiding in Plain Sight: Rediscovering the Importance of Noncoding RNA in Human Malignancy

At the time of its construction in the 1950s, the central dogma of molecular biology was a useful model that represented the current state of knowledge for the flow of genetic information after a period of prolific scientific discovery. Unknowingly, it also biased many of our assumptions going forward. Whether intentional or not, genomic elements not fitting into this paradigm were deemed unimportant and emphasis on the study of protein-coding genes prevailed for decades. The phrase "Junk DNA," first popularized in the 1960s, is still used with alarming frequency to describe the entirety of noncoding DNA. It has since become apparent that RNA molecules not coding for protein are vitally important in both normal development and human malignancy. Cancer researchers have been pioneers in determining noncoding RNA function and developing new technologies to study these molecules. In this review, we will discuss well known and newly emerging species of noncoding RNAs, their functions in cancer, and new technologies being utilized to understand their mechanisms of action in cancer. Cancer Res; 78(9); 2149-58. ©2018 AACR.

Abstract LB-168: MicroRNA-31 initiates lung tumorigenesis and promotes mutant KRAS-driven lung cancer

Lung cancer is the leading cause of cancer deaths and yet the genes that drive this malignancy are not entirely known. MicroRNA (miRNA) are important regulators of gene expression and aberrant miRNA expression has been linked to lung oncogenesis; however, little known about their contribution in tumor initiation. We’ve determined that miR-31 is overexpressed in human lung adenocarcinoma and this overexpression independently correlates with decreased patient survival. miR-31 promotes lung cell proliferation and adenocarcinoma growth in vivo. We also developed a transgenic mouse model that allows for lung-specific expression of miR-31 to test the oncogenic potential of miR-31 in the lung. Using this model, we observed that miR-31 induction results in lung hyperplasia, followed by adenoma formation and later adenocarcinoma development. We identified 6 negative regulators of RAS/MAPK signaling (RASA1, SPRED1, SPRED2, SPRY1, SPRY3, SPRY4) as direct targets of miR-31. Analysis of human lung adenocarcinoma revealed that high miR-31 expression correlated to decreased target mRNA expression. miR-31 overexpression in lung cells results in increased RAS signaling and pharmacologic inhibition of MEK ablates miR-31 induced lung cell proliferation. Induced expression of miR-31 in mice cooperated with mutant KRAS to accelerate lung tumorigenesis. Our study demonstrates for the first time that a miRNA can drive an epithelial cancer. Specifically we identified miR-31 as a driver of lung tumorigenesis that promotes mutant KRAS-mediated oncogenesis and demonstrate that miR-31 directly targets and reduces expression of negative regulators of RAS/MAPK signaling.

Citation Format: Mick D. Edmonds, Kelli L. Boyd, Tamara K. Moyo, Ramkrishna Mitra, Robert J. Duszynski, Maria P. Arrate, Xi Chen, Zhongming Zhao, Timothy S. Blackwell, Christine M. Eischen. MicroRNA-31 initiates lung tumorigenesis and promotes mutant KRAS-driven lung cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-168.

MicroRNA-31 initiates lung tumorigenesis and promotes mutant KRAS-driven lung cancer

MicroRNA (miR) are important regulators of gene expression, and aberrant miR expression has been linked to oncogenesis; however, little is understood about their contribution to lung tumorigenesis. Here, we determined that miR-31 is overexpressed in human lung adenocarcinoma and this overexpression independently correlates with decreased patient survival. We developed a transgenic mouse model that allows for lung-specific expression of miR-31 to test the oncogenic potential of miR-31 in the lung. Using this model, we observed that miR-31 induction results in lung hyperplasia, followed by adenoma formation and later adenocarcinoma development. Moreover, induced expression of miR-31 in mice cooperated with mutant KRAS to accelerate lung tumorigenesis. We determined that miR-31 regulates lung epithelial cell growth and identified 6 negative regulators of RAS/MAPK signaling as direct targets of miR-31. Our study distinguishes miR-31 as a driver of lung tumorigenesis that promotes mutant KRAS-mediated oncogenesis and reveals that miR-31 directly targets and reduces expression of negative regulators of RAS/MAPK signaling.

miR-31 and miR-17-5p levels change during transformation of follicular lymphoma

The 30% of patients whose indolent follicular lymphoma transforms to aggressive diffuse large B-cell lymphoma (DLBCL) have poor survival. Reliable predictors of follicular B-cell lymphoma transformation to DLBCL are lacking, and diagnosis of those that will progress is challenging. MicroRNA, which regulates gene expression, has critical functions in the growth and progression of many cancers and contributes to the pathogenesis of lymphoma. Using 5 paired samples from patients who presented with follicular lymphoma and progressed to DLBCL, we identified specific microRNA differentially expressed between the two. Specifically, miR-17-5p levels were low in follicular lymphoma and increased as the disease transformed. In contrast, miR-31 expression was high in follicular lymphoma and decreased as the lymphoma progressed. These results were confirmed in additional unpaired cases of low-grade follicular lymphoma (n = 13) and high-grade follicular lymphoma grade 3 or DLBCL (n = 17). Loss of miR-31 expression in DLBCL was not due to deletion of the locus. Changes in miR-17-5p and miR-31 were not correlated with immunophenotype, genetics, or status of the MYC oncogene. However, increased miR-17-5p expression did significantly correlate with increased expression of p53 protein, which is indicative of mutant TP53. Two pro-proliferative genes, E2F2 and PI3KC2A, were identified as direct messenger RNA targets of miR-31, suggesting that these may contribute to follicular lymphoma transformation. Our results indicate that changes in miR-31 and miR-17-5p reflect the transformation of follicular lymphoma to an aggressive large B-cell lymphoma and may, along with their targets, be viable markers for this process.

Reproducible combinatorial regulatory networks elucidate novel oncogenic microRNAs in non-small cell lung cancer

While previous studies reported aberrant expression of microRNAs (miRNAs) in non-small cell lung cancer (NSCLC), little is known about which miRNAs play central roles in NSCLC's pathogenesis and its regulatory mechanisms. To address this issue, we presented a robust computational framework that integrated matched miRNA and mRNA expression profiles in NSCLC using feed-forward loops. The network consists of miRNAs, transcription factors (TFs), and their common predicted target genes. To discern the biological meaning of their associations, we introduced the direction of regulation. A network edge validation strategy using three independent NSCLC expression profiling data sets pinpointed reproducible biological regulations. Reproducible regulation, which may reflect the true molecular interaction, has not been applied to miRNA-TF co-regulatory network analyses in cancer or other diseases yet. We revealed eight hub miRNAs that connected to a higher proportion of targets validated by independent data sets. Network analyses showed that these miRNAs might have strong oncogenic characteristics. Furthermore, we identified a novel miRNA-TF co-regulatory module that potentially suppresses the tumor suppressor activity of the TGF-β pathway by targeting a core pathway molecule (TGFBR2). Follow-up experiments showed two miRNAs (miR-9-5p and miR-130b-3p) in this module had increased expression while their target gene TGFBR2 had decreased expression in a cohort of human NSCLC. Moreover, we demonstrated these two miRNAs directly bind to the 3' untranslated region of TGFBR2. This study enhanced our understanding of miRNA-TF co-regulatory mechanisms in NSCLC. The combined bioinformatics and validation approach we described can be applied to study other types of diseases.

Differences in miRNA expression in early stage lung adenocarcinomas that did and did not relapse

Relapse of adenocarcinoma, the most common non-small cell lung cancer (NSCLC), is a major clinical challenge to improving survival. To gain insight into the early molecular events that contribute to lung adenocarcinoma relapse, and taking into consideration potential cell type specificity, we used stringent criteria for sample selection. We measured miRNA expression only from flash frozen stage I lung adenocarcinomas, excluding other NSCLC subtypes. We compared miRNA expression in lung adenocarcinomas that relapsed within two years to those that did not relapse within three years after surgical resection prior to adjuvant therapy. The most significant differences in mRNA expression for recurrent tumors compared to non-recurrent tumors were decreases in miR-106b*, -187, -205, -449b, -774* and increases in miR-151-3p, let-7b, miR-215, -520b, and -512-3p. A unique comparison between adjacent normal lung tissue from relapse and non-relapse groups revealed dramatically different miRNA expression, suggesting dysregulation of miRNA in the environment around the tumor. To assess patient-to-patient variability, miRNA levels in the tumors were normalized to levels in matched adjacent normal lung tissue. This analysis revealed a different set of significantly altered miRNA in tumors that recurred compared to tumors that did not. Together our analyses elucidated miRNA not previously linked to lung adenocarcinoma that likely have important roles in its development and progression. Our results also highlight the differences in miRNA expression in normal lung tissue in adenocarcinomas that do and do not recur. Most notably, our data identified those miRNA that distinguish early stage tumors likely to relapse prior to treatment and miRNA that could be further studied for use as biomarkers for prognosis, patient monitoring, and/or treatment decisions.

Feeding performance, carcass characteristics, and tenderness attributes of steers sorted by the Igenity tenderness panel and fed zilpaterol hydrochloride

Steers (n = 560; initial BW = 420 ± 26 kg) were selected from a pool of 1,040, using the IGENITY Profile DNA test for tenderness, sorted into 1 of 4 tenderness genotype (TG) groups [140 tough (TUF), 140 intermediate (INT), 140 tender (TEND), or 140 mixed (MXD)], and subsequently allocated into 56 pens at random, of which one-half (28 pens, 7 pens from each TG) were supplemented the β-adrenergic agonist zilpaterol hydrochloride (ZH) and the balance fed a control ration. No TG × ZH interaction (P ≥ 0.15) occurred for any measured trait. Cattle from INT TG had less (P < 0.05) DMI during pretreatment (d 0 to 118) and entire trial (d 0 to 143) periods than other TG. Cattle fed ZH had greater (P < 0.01) ADG and G:F, and decreased (P < 0.01) DMI during the treatment period (d 119 to 143). Cattle from the TEND group had greater (P < 0.01) marbling scores, increased (P < 0.02) calculated USDA yield grades (YG), and more (P < 0.02) calculated empty body fat (EBF) than TUF cattle. Cattle receiving ZH during the treatment period had increased (P < 0.01) HCW, dressed yield, and LM area. Additionally, cattle fed ZH exhibited decreased (P < 0.01) EBF, marbling, KPH, and calculated USDA YG. No difference (P > 0.06) in YG distributions were detected among TG, yet TEND cattle were represented by a greater (P < 0.01) proportion of Prime and premium Choice carcasses. Cattle fed ZH exhibited increased (P < 0.01) frequencies of YG 2 carcasses and fewer (P < 0.01) YG 3, 4, and 5 carcasses concurrent with an increase (P < 0.04) in the percentage of Select carcasses. Longissimus steaks from TUF cattle had greater (P < 0.03) Warner-Bratzler Shear Force (WBSF) values at 7 and 14 d postmortem than steaks from INT or TEND cattle. Furthermore, ZH-fed cattle had increased (P < 0.01) WBSF values for all aging periods compared with control cattle. Frequency of steaks with WBSF values <3.9 kg (certified tender) were less (P < 0.05) for the TUF group. Feeding ZH resulted in fewer longissimus steaks (P < 0.01) with WBSF values <3.0 kg (guaranteed tender) across all aging periods; however, no difference in the frequency of steaks with WBSF values <3.9 kg was found after 21 d of aging. Igenity Profile tenderness scores were correlated (P < 0.05) to carcass finish attributes and WBSF values. Commercially available tenderness panels may have the potential to allow for antemortem sorting of cattle into expected tenderness groupings, which could augment feeding management strategies and ultimately lead to increased marketing value for the beef system.

Abstract 3416: Ubiquitous Brms1 expression is critical for mammary carcinoma metastasis suppression via promotion of apoptosis

Morbidity and mortality in breast cancer patients are drastically increased when primary tumor cells are able to spread to distant sites and proliferate to become secondary lesions. Effective treatment of metastatic disease has been limited; therefore, increased molecular understanding to identify biomarkers and targets is needed. We have previously shown that breast cancer metastasis suppressor 1 (Brms1) can suppress development of pulmonary metastases when expressed in a variety of cancer types, including metastatic mammary carcinoma. Our lab has developed two transgenic Brms1 mouse models, one which expresses murine Brms1 cDNA specifically in mammary tissue (expression by the mouse mammary tumor virus (MMTV) promoter) and a ubiquitous Brms1 expression model (expression by the chicken beta actin promoter). The goal of this study was to investigate mechanisms of Brms1-mediated metastasis suppression in transgenic mice that express Brms1 using a polyoma middle T (PyMT) oncogene-induced model. Brms1 expression, either ubiquitously or predominantly in the mammary gland, did not significantly alter growth of the primary tumor, confirming earlier studies. When expressed ubiquitously, Brms1 suppressed pulmonary metastasis and promoted tumor cell apoptosis in the lung but not in the mammary gland. However, selective expression of Brms1 in the mammary gland using the MMTV promoter did not significantly block metastasis nor did it promote apoptosis in mammary glands or lungs despite increased expression within primary tumors and the lungs. These results suggest tissue- or cell-type specific expression of Brms1 is a critical determinant for Brms1-mediated metastasis suppression.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3416. doi:1538-7445.AM2012-3416

Subsets of ATP-sensitive potassium channel (KATP) inhibitors increase gap junctional intercellular communication in metastatic cancer cell lines independent of SUR expression

Gap junctional intercellular communication (GJIC) regulates cellular homeostasis by propagating signaling molecules, exchanging cellular metabolites, and coupling electrical signals. In cancer, cells exhibit altered rates of GJIC which may play a role in neoplastic progression. K(ATP) channels help maintain membrane polarity and linkages between K(ATP) channel activity and rates of GJIC have been established. The mechanistic relationship has not been fully elucidated. We report the effects of treatment with multiple K(ATP) antagonist compounds on GJIC in metastatic cell lines demonstrating an increase in communication rates following treatment with compounds possessing specificities towards the SUR2 subunit of K(ATP). These effects remained consistent using cell lines with different expression levels of SUR1 and SUR2, suggesting possible off target effects on GJIC by these compounds.

Abstract 1437: Coordinate regulation of miR-183-96-182 and miR10b by Breast Cancer Metastasis Suppressor 1 results in a decrease in migration and invasion of metastatic breast cancer cells

To date more than 30 metastasis suppressors have been identified by functional assays. BReast cancer Metastasis Suppressor 1 (BRMS1) suppresses metastasis of multiple tumor types by hindering the ability to colonize ectopic tissues without blocking tumorigenesis. BRMS1 interacts with SIN3:histone deacetylase complexes which can lead to metastasis suppression through epigenetic regulation of metastasis-associated gene transcription. In addition to regulating protein-coding genes (EGFR, OPN, TWIST), we showed that BRMS1 coordinately regulates metastasis-associated miRNA, e.g., increases metastasis-suppressing miRNA (miR-183-96-182, miR-146a/b, miR-335) and decreases metastasis-promoting miRNA (miR-10b, miR-373, miR-520c). We also observed significant upregulation of miR-96, which is part of the miR-183-96-182 cluster (miR-183C). In this study, we hypothesized that miR-96 could inhibit metastasis-associated processes and that restoration of miR-10b expression in BRMS1-expressing cells would restore metastatic efficiency. Over-expression of miR-96 (and individual miRNA within miR-183C) in metastatic MDA-MB-231 (231) breast cancer cells decreased invasion (∼50%) and migration (∼40%). Knockdown of individual miRNA in 231 or MDA-MB-435 (435) cells expressing BRMS1 (231B; 435B) increased motility, migration, and invasion in vitro (P&lt;0.05). Pilot in vivo metastasis assays showed a trend toward decreased metastasis with miR-183C components, but fully powered studies are underway. Re-expression of miR-10b in 231B cells partially restored motility and invasion in vitro (P&lt;0.02) but the effect on metastasis, while not statistically significant, did modestly increase. These results are consistent with the hypothesis that metastamiR are downstream mediators of BRMS1 metastasis suppression; however, coordinated expression changes are necessary to achieve significant in vivo biological effects. Given that over-expression of individual miR-183C components leads to nearly identical suppression of migration and invasion, we asked whether exogenous over-expression of one of the miR-183C miRNA affected expression of the other endogenous miR-183C miRNA (e.g., Does miR-96 over-expression change miR-182 or miR-183 expression?). Ectopic expression of individual miR-183C members led to increased expression of the other miRNA within the cluster. These findings imply feedback mechanisms for miRNA within miR-183C which may explain discordant data in other cancers where miR-183C exerted tissue-selective metastasis-promoting or -suppressing actions. The linked expression of miRNA within a cluster advise caution when designing and interpreting results from a single miRNA.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1437. doi:10.1158/1538-7445.AM2011-1437

Metastamir: the field of metastasis-regulatory microRNA is spreading

Despite advancements in knowledge from more than a century of metastasis research, the genetic programs and molecular mechanisms required for cancer metastasis are still incompletely understood. Genes that specifically regulate the process of metastasis are useful tools to elucidate molecular mechanisms and may become markers and/or targets for antimetastatic therapy. Recently, several noncoding regulatory RNA genes, microRNA (miRNA), were identified, which play roles in various steps of metastasis, some without obvious roles in tumorigenesis. Understanding how these metastasis-associated miRNA, which we term metastamir, are involved in metastasis will help identify possible biomarkers or targets for the most lethal attribute of cancer: metastasis.

Breast cancer metastasis suppressor 1 coordinately regulates metastasis-associated microRNA expression

Breast cancer metastasis suppressor 1 (BRMS1) suppresses metastasis of multiple tumor types without blocking tumorigenesis. BRMS1 forms complexes with SIN3, histone deacetylases and selected transcription factors that modify metastasis-associated gene expression (e.g., EGFR, OPN, PI4P5K1A, PLAU). microRNA (miRNA) are a recently discovered class of regulatory, noncoding RNA, some of which are involved in neoplastic progression. Based on these data, we hypothesized that BRMS1 may also exert some of its antimetastatic effects by regulating miRNA expression. MicroRNA arrays were done comparing small RNAs that were purified from metastatic MDA-MB-231 and MDA-MB-435 and their nonmetastatic BRMS1-transfected counterparts. miRNA expression changed by BRMS1 were validated using SYBR Green RT-PCR. BRMS1 decreased metastasis-promoting (miR-10b, -373 and -520c) miRNA, with corresponding reduction of their downstream targets (e.g., RhoC which is downstream of miR-10b). Concurrently, BRMS1 increased expression of metastasis suppressing miRNA (miR-146a, -146b and -335). Collectively, these data show that BRMS1 coordinately regulates expression of multiple metastasis-associated miRNA and suggests that recruitment of BRMS1-containing SIN3:HDAC complexes to, as yet undefined, miRNA promoters might be involved in the regulation of cancer metastasis.

Linking metastasis suppression with metastamiR regulation

Cancer metastasis requires the coordinate expression of multiple genes during every step of the metastatic cascade. Molecules that regulate these genetic programs have the potential to impact metastasis at multiple levels. Breast cancer metastasis suppressor 1 (BRMS1) suppresses metastasis by inhibiting multiple steps in the cascade through regulation of many protein-encoding, metastasis-associated genes as well as metastasis-regulatory microRNA, termed metastamiR. In this Feature , we will highlight connections between BRMS1 biology and regulation of metastamiR.

A shift from nuclear to cytoplasmic breast cancer metastasis suppressor 1 expression is associated with highly proliferative estrogen receptor-negative breast cancers

BACKGROUND/AIMS

To determine breast cancer metastasis suppressor 1 (BRMS1) expression in breast cancers and the efficacy of BRMS1 as a prognostic indicator, BRMS1 expression was assessed in two sets of breast cancer tissues.

METHODS

Epithelial cells from 36 frozen samples of breast cancers and corresponding normal breast were collected by laser capture microdissection and assessed for BRMS1 by quantitative RT-PCR and immunohistochemistry. BRMS1 was also evaluated by immunohistochemistry in a tissue microarray of 209 breast cancers and correlated with indicators of prognosis [estrogen receptor (ER), progesterone receptor (PR), ErbB2, p53, p27(Kip1), Bcl2 and Ki-67].

RESULTS

BRMS1 mRNA and protein were higher in 94 and 81%, respectively, of breast cancers than in corresponding normal epithelium. BRMS1 localization was predominantly nuclear, but 60-70% of cancers also exhibited cytoplasmic immunostaining. Breast cancers with lower nuclear than cytoplasmic BRMS1 (nuclear score - cytoplasmic score < or =0; 11% of cancers) had lower ER, lower PR and higher Ki-67 expression. There was also a trend toward poorer overall survival in this group of cancers, but this was only of borderline significance (p = 0.073). In Cox proportional hazards models, loss of nuclear BRMS1 was not a significant predictor of overall survival.

CONCLUSIONS

Loss of nuclear BRMS1 was associated with ER-negative cancers and a high rate of proliferation, but was not an independent indicator of prognosis.

Breast cancer metastasis suppressor 1 up-regulates miR-146, which suppresses breast cancer metastasis

Breast cancer metastasis suppressor 1 (BRMS1) is a predominantly nuclear protein that differentially regulates expression of multiple genes, leading to suppression of metastasis without blocking orthotopic tumor growth in multiple human and murine cancer cells of diverse origins. We hypothesized that miR-146 may be involved in the ability of BRMS1 to supress metastasis because miR-146 expression is altered by BRMS1 and because BRMS1 and miR-146 are both associated with decreased signaling through the nuclear factor-kappaB pathway. BRMS1 significantly up-regulates miR-146a by 6- to 60-fold in metastatic MDA-MB-231 and MDA-MB-435 cells, respectively, and miR-146b by 40-fold in MDA-MB-435 as measured by real-time quantitative reverse transcription-PCR. Transduction of miR-146a or miR-146b into MDA-MB-231 down-regulated expression of epidermal growth factor receptor, inhibited invasion and migration in vitro, and suppressed experimental lung metastasis by 69% and 84%, respectively (mean +/- SE: empty vector = 39 +/- 6, miR-146a = 12 +/- 1, miR-146b = 6 +/- 1). These results further support the recent notion that modulating the levels of miR-146a or miR-146b could have a therapeutic potential to suppress breast cancer metastasis.

Pathogenicity and protective activity in pregnant goats of a Brucella melitensis Deltaomp25 deletion mutant

The Brucella melitensis mutant BM 25, which lacks the major 25 kDa outer membrane protein Omp25, has previously been found to be attenuated in the murine brucellosis model. In the present study, the capacity of the Deltaomp25 mutant to colonise and cause abortions in the caprine host was evaluated. The vaccine potential of BM 25 was also investigated in goats. Inoculation of nine pregnant goats in late gestation with the B. melitensis mutant resulted in 0/9 abortions, while the virulent parental strain, B. melitensis 16M, induced 6/6 dams to abort (P<0.001, n=6). BM 25 also colonised fewer adults (P<0.05, n=6) and kids (P<0.01, n=6) than strain 16M. The Deltaomp25 mutant was found capable of transient in vivo colonisation of non-pregnant goats for two weeks post-infection. Owing to the ability of BM 25 to colonise both non-pregnant and pregnant adults without inducing abortions, a vaccine efficacy study was performed. Vaccination of goats prior to breeding with either BM 25 or the current caprine vaccine B. melitensis strain Rev. 1 resulted in 100 per cent protection against abortion following challenge in late gestation with virulent strain 16M (P<0.05, n=7). However, unlike strain Rev. 1, BM 25 does not appear to cause abortions in late gestation based on this study with a small number of animals. The B. melitensis Deltaomp25 mutant, BM 25, may be a safe and efficacious alternative to strain Rev. 1 when dealing with goat herds of mixed age and pregnancy status.

Re-examination of the role of the Brucella melitensis HtrA stress response protease in virulence in pregnant goats

Based on previously reported studies describing the experimental infection of pregnant goats with B. melitensis strain RWP5, we proposed that the HtrA protease plays an important role in the virulence of B. melitensis in its natural ruminant host. Subsequent studies, however, have shown that RWP5 is actually an htrA cycL double mutant. In order to definitively evaluate the role of the B. melitensis htrA in virulence, we constructed an authentic htrA mutant and examined this strain in pregnant goats. The findings of these studies indicate that the contribution of the htrA gene product to the virulence of B. melitensis in its natural host is not as great as was previously proposed.

Attenuation of a Brucella abortus mutant lacking a major 25 kDa outer membrane protein in cattle

OBJECTIVE

To determine the virulence of a Brucella abortus mutant, BA25, lacking a major 25 kd outer membrane protein (Omp25) in cattle.

ANIMALS

20 mixed-breed heifers in late gestation.

PROCEDURE

10 heifers were inoculated with 1 x 10(7) colony-forming units of the Omp25 mutant via the conjunctival sac, and an equal number were infected with the virulent parental strain B. abortus 2308. The delivery status of the dams was recorded, and colonization was assessed following necropsy. The ability of BA25 to replicate inside bovine phagocytes and chorionic trophoblasts was also evaluated in vitro because of the propensity of virulent brucellae to replicate inside these cells in vivo.

RESULTS

The parental strain induced abortions in 5 of 10 inoculated cattle, whereas only 1 of 10 dams exposed to BA25 aborted. Brucella abortus strain 2308 colonized all of the cow-calf pairs and induced Brucella-specific antibodies in 100% of the dams. In contrast, BA25 was isolated by bacteriologic cultural technique from 30% of the calves and 50% of the inoculated dams (n = 10). Of the 10 heifers inoculated with BA25, 4 did not develop Brucella-specific antibodies nor were they colonized by the mutant strain. In bovine macrophages and chorionic trophoblasts, BA25 replicated in significantly lower numbers than the virulent parental strain (n = 3).

CONCLUSIONS AND CLINICAL RELEVANCE

The 25 kd outer membrane protein may be an important virulence factor for B. abortus in cattle. The attenuation of the Omp25 mutant in cattle may involve the inability of BA25 to replicate efficiently in bovine phagocytes and chorionic trophoblasts.

Oral vaccination of sexually mature pigs with Brucella abortus vaccine strain RB51

OBJECTIVE

To develop a novel oral vaccine delivery system for swine, using the rough vaccine strain of Brucella abortus.

ANIMALS

56 crossbred pigs from a brucellosis-free facility.

PROCEDURE

In 3 separate experiments, pigs were orally vaccinated with doses of 1 x 10(9) to > 1 x 10(11) CFU of strain RB51 vaccine. The vaccine was placed directly on the normal corn ration, placed inside a whole pecan, or mixed with cracked pecans and corn.

RESULTS

Oral vaccination of pigs with vaccine strain RB51 resulted in a humoral immune response to strain RB51 and short-term colonization of the regional lymph nodes.

CONCLUSIONS AND CLINICAL RELEVANCE

A viscous liquid such as Karo corn syrup in association with pecans that scarify the oral mucosa are necessary when placing the live vaccine directly onto corn or other food rations. Doses of > 1 x 10(11) CFU of RB51 organisms/pig in this mixture ensures 100% colonization of regional lymph nodes via the oral route. This method may allow an efficient and economical means to vaccinate feral swine for brucellosis.

Use of western immunoblot analysis for testing moose serum for Brucella suis biovar 4 specific antibodies

To determine if 12 moose (Alces alces) from northern Alaska with agglutinating antibodies specific for Brucella spp. had been exposed to either B. suis biovar 4 or B. abortus biovar 1, western immnnoblot serologic analysis was performed. Differential serologic responses to strain specific A and M antigenic variances of the lipopolysaccharide O-polysaccharide sugar allowed strain identification. Prior to examination, test sera were absorbed with killed whole cells from either B. abortus biovar 1, containing predominately A antigen (A+ M-); B. melitensis biovar 1, containing essentially M antigen (A- M+); or B. suis biovar 4, containing both antigenic tyes (A+ M+). The resulting sera were then examined by western immunoblot for recognition of either B. abortus biovar 1, B. melitensis biovar 1, or B. suis biovar 4 cell lysates. The results of this study indicate that these moose were exposed to B. suis biovar 4, a known pathogen of caribou (Rangifer tarandus) from arctic Alaska.

Biosafety of Brucella abortus strain RB51 for vaccination of mature bulls and pregnant heifers

OBJECTIVE

To determine shedding and colonization profiles in mature sexually intact bulls and pregnant heifers after vaccination with a standard calfhood dose of Brucella abortus strain RB51 (SRB51).

ANIMALS

6 sexually mature 3-year-old Jersey bulls and 7 mixed-breed heifers in midgestation.

PROCEDURE

Bulls and pregnant heifers were vaccinated IM with the standard calfhood dose of 3x10(10) colony-forming units of SRB51. After vaccination, selected body fluids were monitored weekly for vaccine organism shedding. Pathogenesis was monitored in bulls by weekly breeding soundness examination and, in heifers, by delivery status of the calf. Vaccine organism colonization was assessed by obtaining select tissues at necropsy for bacterial culture. Serologic analysis was performed by use of numerous tests, including complement fixation, an SRB51-based ELISA, and immunoblot analysis.

RESULTS

After vaccination, none of the vaccinated bulls or heifers shed SRB51 in their secretions. Results of breeding soundness examination for bulls were normal as was delivery status of the pregnant heifers (6 live births, 1 dystocia). At necropsy, SRB51 was not recovered from any of the selected tissues obtained from bulls, heifers, or calves; however, serologic analysis did detect SRB51-specific antibodies in all cattle.

CONCLUSIONS AND CLINICAL RELEVANCE

Vaccination with the standard calfhood dose of SRB51 administered IM was not associated with shedding or colonization in sexually mature bulls or pregnant heifers. Also, under conditions of this study with small numbers of animals, IM vaccination with SRB51 does not appear to cause any reproductive problems when administered to sexually mature cattle.

Safety of Brucella abortus strain RB51 in Bison

To determine the safety of Brucella abortus strain RB51 (SRB51) vaccine in American bison (Bison bison), 31 animals from a herd with brucellosis were used. In October 1996, 10 adult bison males and seven calves were vaccinated with the standard calfhood cattle dose of 1.8 x 10(10) colony forming units (CFU) of SRB51 subcutaneously while the adult females received the standard adult cattle dose of 1 x 10(9) CFU. Western immunoblot indicated the presence of SRB51 antibodies following vaccination. To evaluate prolonged bacterial colonization of tissues, the adult males, calves, and three adult females were divided into two groups which were slaughtered at either 13 or 16 wk post-vaccination. At necropsy, tissue samples were obtained for B. abortus culture from the liver, spleen, lymph nodes, and reproductive tract of each animal. While B. abortus field strain was cultured from one adult bull, no SRB51 was isolated from any of the animals. Seven pregnant females were monitored until parturition for signs of abortions and fetal lesions. Six cows delivered healthy calves and one delivered a dead full-term calf that was brucellae negative. Based on these results, administration of SRB51 to bison did not cause prolonged bacterial colonization of tissues in calves, adult males, or adult females. Furthermore, SRB51 did not induce abortions following vaccination in the second month of gestation.