Obesity-associated epigenetic alterations and the obesity-breast cancer axis

Both breast cancer and obesity can regulate epigenetic changes or be regulated by epigenetic changes. Due to the well-established link between obesity and an increased risk of developing breast cancer, understanding how obesity-mediated epigenetic changes affect breast cancer pathogenesis is critical. Researchers have described how obesity and breast cancer modulate the epigenome individually and synergistically. In this review, the epigenetic alterations that occur in obesity, including DNA methylation, histone, and chromatin modification, accelerated epigenetic age, carcinogenesis, metastasis, and tumor microenvironment modulation, are discussed. Delineating the relationship between obesity and epigenetic regulation is vital to furthering our understanding of breast cancer pathogenesis.

The Non-Coding RNA Journal Club: Highlights on Recent Papers-13

We are delighted to share with you our thirteenth Journal Club and highlight some of the most interesting papers published recently [...].

Targeting Mcl-1 by a small molecule NSC260594 for triple-negative breast cancer therapy

Triple-negative breast cancers (TNBCs) are aggressive forms of breast cancer and tend to grow and spread more quickly than most other types of breast cancer. TNBCs can neither be targeted by hormonal therapies nor the antibody trastuzumab that targets the HER2 protein. There are urgent unmet medical needs to develop targeted drugs for TNBCs. We identified a small molecule NSC260594 from the NCI diversity set IV compound library. NSC260594 exhibited dramatic cytotoxicity in multiple TNBCs in a dose-and time-dependent manner. NSC260594 inhibited the Myeloid cell leukemia-1 (Mcl-1) expression through downregulation of Wnt signaling proteins. Consistent with this, NSC260594 treatment increased apoptosis, which was confirmed by using an Annexin-V/PI assay. Interestingly, NSC260594 treatment reduced the cancer stem cell (CSC) population in TNBCs. To make NSC260594 more clinically relevant, we treated NSC260594 with TNBC cell derived xenograft (CDX) mouse model, and with patient-derived xenograft (PDX) organoids. NSC260594 significantly suppressed MDA-MB-231 tumor growth in vivo, and furthermore, the combination treatment of NSC260594 and everolimus acted synergistically to decrease growth of TNBC PDX organoids. Together, we found that NSC260594 might serve as a lead compound for triple-negative breast cancer therapy through targeting Mcl-1.

17β-estradiol promotes extracellular vesicle release and selective miRNA loading in ERα-positive breast cancer

The causes and consequences of abnormal biogenesis of extracellular vesicles (EVs) are not yet well understood in malignancies, including in breast cancers (BCs). Given the hormonal signaling dependence of estrogen receptor-positive (ER+) BC, we hypothesized that 17β-estradiol (estrogen) might influence EV production and microRNA (miRNA) loading. We report that physiological doses of 17β-estradiol promote EV secretion specifically from ER+ BC cells via inhibition of miR-149-5p, hindering its regulatory activity on SP1, a transcription factor that regulates the EV biogenesis factor nSMase2. Additionally, miR-149-5p downregulation promotes hnRNPA1 expression, responsible for the loading of let-7's miRNAs into EVs. In multiple patient cohorts, we observed increased levels of let-7a-5p and let-7d-5p in EVs derived from the blood of premenopausal ER+ BC patients, and elevated EV levels in patients with high BMI, both conditions associated with higher levels of 17β-estradiol. In brief, we identified a unique estrogen-driven mechanism by which ER+ BC cells eliminate tumor suppressor miRNAs in EVs, with effects on modulating tumor-associated macrophages in the microenvironment.

The Non-Coding RNA Journal Club: Highlights on Recent Papers-12

We are delighted to share with you our twelfth Journal Club and highlight some of the most interesting papers published recently [...].

LKB1 Signaling and Patient Survival Outcomes in Hepatocellular Carcinoma

The liver is a major organ that is involved in essential biological functions such as digestion, nutrient storage, and detoxification. Furthermore, it is one of the most metabolically active organs with active roles in regulating carbohydrate, protein, and lipid metabolism. Hepatocellular carcinoma is a cancer of the liver that is associated in settings of chronic inflammation such as viral hepatitis, repeated toxin exposure, and fatty liver disease. Furthermore, liver cancer is the most common cause of death associated with cirrhosis and is the 3^rd leading cause of global cancer deaths. LKB1 signaling has been demonstrated to play a role in regulating cellular metabolism under normal and nutrient deficient conditions. Furthermore, LKB1 signaling has been found to be involved in many cancers with most reports identifying LKB1 to have a tumor suppressive role. In this review, we use the KMPlotter database to correlate RNA levels of LKB1 signaling genes and hepatocellular carcinoma patient survival outcomes with the hopes of identifying potential biomarkers clinical usage. Based on our results STRADß, CAB39L, AMPKα, MARK2, SIK1, SIK2, BRSK1, BRSK2, and SNRK expression has a statistically significant impact on patient survival.

Hippo signaling pathway: A comprehensive gene expression profile analysis in breast cancer

Breast cancer (BC) is the most frequently diagnosed malignancy in women and a major public health concern. The Hippo pathway is an evolutionarily conserved signaling pathway that serves as a key regulator for a wide variety of biological processes. Hippo signaling has been shown to have both oncogenic and tumor-suppressive functions in various cancers. Core components of the Hippo pathway consist of various kinases and downstream effectors such as YAP/TAZ. In the current report, differential expression of Hippo pathway elements as well as the correlation of Hippo pathway mRNAs with various clinicopathologic characteristics, including molecular subtypes, receptor status, and methylation status, has been investigated in BC using METABRIC and TCGA datasets. In this review, we note deregulation of several Hippo signaling elements in BC patients. Moreover, we see examples of negative correlations between methylation of Hippo genes and mRNA expression. The expression of Hippo genes significantly varies between different receptor subgroups. Because of the clear associations between mRNA expression and methylation status, DNA methylation may be one of the mechanisms that regulate the Hippo pathway in BC cells. Differential expression of Hippo genes among various BC molecular subtypes suggests that Hippo signaling may function differently in different subtypes of BC. Our data also highlights an interesting link between Hippo components' transcription and ER negativity in BC. In conclusion, substantial deregulation of Hippo signaling components suggests an important role of these genes in breast cancer.

Ceritinib is a novel triple negative breast cancer therapeutic agent

Background

Triple-negative breast cancers (TNBCs) are clinically aggressive subtypes of breast cancer. TNBC is difficult to treat with targeted agents due to the lack of commonly targeted therapies within this subtype. Androgen receptor (AR) has been detected in 12–55% of TNBCs. AR stimulates breast tumor growth in the absence of estrogen receptor (ER), and it has become an emerging molecular target in TNBC treatment.

Methods

Ceritinib is a small molecule inhibitor of tyrosine kinase and it is used in the therapy of non-small lung cancer patients. Enzalutamide is a small molecule compound targeting the androgen receptor and it is used to treat prostate cancer. Combination therapy of these drugs were investigated using AR positive breast cancer mouse xenograft models. Also, combination treatment of ceritinib and paclitaxel investigated using AR⁻ and AR low mouse xenograft and patient derived xenograft models.

Results

We screened 133 FDA approved drugs that have a therapeutic effect of AR⁺ TNBC cells. From the screen, we identified two drugs, ceritinib and crizotinib. Since ceritinib has a well- defined role in androgen independent AR signaling pathways, we further investigated the effect of ceritinib. Ceritinib treatment inhibited RTK/ACK/AR pathway and other downstream pathways in AR⁺ TNBC cells. The combination of ceritinib and enzalutamide showed a robust inhibitory effect on cell growth of AR⁺ TNBC cells in vitro and in vivo. Interestingly Ceritinib inhibits FAK-YB-1 signaling pathway that leads to paclitaxel resistance in all types of TNBC cells. The combination of paclitaxel and ceritinib showed drastic inhibition of tumor growth compared to a single drug alone.

Conclusions

To improve the response of AR antagonist in AR positive TNBC, we designed a novel combinational strategy comprised of enzalutamide and ceritinib to treat AR⁺ TNBC tumors through the dual blockade of androgen-dependent and androgen-independent AR signaling pathways. Furthermore, we introduced a novel therapeutic combination of ceritinib and paclitaxel for AR negative or AR-low TNBCs and this combination inhibited tumor growth to a great extent. All agents used in our study are FDA-approved, and thus the proposed combination therapy will likely be useful in the clinic.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12943-022-01601-0.

Expression of Novel Kinase MAP3K19 in Various Cancers and Survival Correlations

Mitogen Activated Protein (MAP) kinases are a category of serine/threonine kinases that have been demonstrated to regulate intracellular events including stress responses, developmental processes, and cancer progression Although many MAP kinases have been extensively studied in various disease processes, MAP3K19 is an understudied kinase whose activities have been linked to lung disease and fibroblast development. In this manuscript, we use bioinformatics databases starBase, GEPIA, and KMPlotter, to establish baseline expressions of MAP3K19 in different tissue types and its correlation with patient survival in different cancers.

Abstract 1477: Circulating miR-125a-3p and miR-451a may be liquid biopsy biomarkers for the diagnosis of breast cancer

Background: Breast cancer is the most prevalent female cancer. Emerging evidence suggests that the unique serum miRNAs can assist in the early detection and diagnosis of breast cancer. Cell-free circulating miRNAs (about 22 nucleotides) are potential diagnostic tools and minimally invasive biomarkers for breast cancer detection. This study aimed to identify specific microRNAs in the serum of patients with breast cancer, which may serve as promising diagnostic and prognostic biomarkers and therapeutic targets.

Material and methods: Next-generation sequencing and quantitative real-time PCR (qRT-PCR) array analyses of microRNAs in sera from different subtypes of breast cancer patients and normal female individuals were performed. The differentially expressed microRNAs were verified in serum samples from 100 breast cancer patients. The predictive values of the selected microRNAs were statistically analyzed, determined by the correlation between microRNA expression and tumor parameters. Datasets were graphed using GraphPad Prism Software 8.0. and analysis was done using one-way ANOVA with unpaired two-tailed Student’s t-test.

Result: High serum levels of miR-125a-3p and miR-451a were found to be associated with breast cancer tumor subtype, size, and lymph node metastasis. Further functional in vitro experiments and enrichment analysis showed that overexpression and knockdown of miR-451 might significantly affect tumorigenic signaling pathways in TNBC cells.

Conclusion: Altogether, our data suggested that serum levels of microRNAs miR-125a-3p and miR-451a can potentially serve as liquid biopsy biomarkers in breast cancer.

Citation Format: Hassan Yousefi, Steven C. Eastlack, Jordyn T Fong, Samuel C. Okpechi, Jovanny Zabaleta, Lyndsey R. Buckner, Donnalee N Trapani, Erin Sims, Alison McDaniel McDaniel, Heather Scuderi, Meredith A. Lakey, John T. Cole, Suresh K. Alahari. Circulating miR-125a-3p and miR-451a may be liquid biopsy biomarkers for the diagnosis of breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1477.

NR4A Family Genes: A Review of Comprehensive Prognostic and Gene Expression Profile Analysis in Breast Cancer

This report analyzes nuclear receptor (NR) subfamily 4A’s potential role in treating those diagnosed with breast cancer. Here we reviewed the current literature on NR4 family members. We also examined the relative gene expression of the NR4A receptor subfamily in the basal, HER2 (human epidermal growth factor receptor 2) positive, luminal A, and luminal B subtypes using data from tumor samples in The Cancer Genome Atlas (TCGA) and Molecular Taxonomy of Breast Cancer International Consortium (METABRIC). These data showed a positive link between NR4A1-NR4A3 expression and increased overall survival and relapse-free survival in breast cancer patients. In addition, we observed that high expression of NR4A1, NR4A2, and NR4A3 led to better survival. Furthermore, NR4A family genes seem to play an essential regulatory role in glycolysis and oxidative phosphorylation in breast cancer. The novel prognostic role of the NR4A1–NR4A3 receptors implicates these receptors as important mediators controlling breast cancer metabolic reprograming and its progression. The review establishes a strong clinical basis for the investigation of the cellular, molecular, and physiological roles of NR4A genes in breast cancer.

Nischarin Deletion Reduces Oxidative Metabolism and Overall ATP: A Study Using a Novel NISCHΔ5-6 Knockout Mouse Model

Nischarin (Nisch) is a cytosolic scaffolding protein that harbors tumor-suppressor-like characteristics. Previous studies have shown that Nisch functions as a scaffolding protein and regulates multiple biological activities. In the current study, we prepared a complete Nisch knockout model, for the first time, by deletion of exons 5 and 6. This knockout model was confirmed by Qrt–PCR and Western blotting with products from mouse embryonic fibroblast (MEF) cells. Embryos and adult mice of knockouts are significantly smaller than their wild-type counterparts. Deletion of Nisch enhanced cell migration, as demonstrated by wound type and transwell migration assays. Since the animals were small in size, we investigated Nisch’s effect on metabolism by conducting several assays using the Seahorse analyzer system. These data indicate that Nisch null cells have lower oxygen consumption rates, lower ATP production, and lower levels of proton leak. We examined the expression of 15 genes involved in lipid and fat metabolism, as well as cell growth, and noted a significant increase in expression for many genes in Nischarin null animals. In summary, our results show that Nischarin plays an important physiological role in metabolic homeostasis.

Hippo pathway: Regulation, deregulation and potential therapeutic targets in cancer

Hippo pathway is a master regulator of development, cell proliferation, stem cell function, tissue regeneration, homeostasis, and organ size control. Hippo pathway relays signals from different extracellular and intracellular events to regulate cell behavior and functions. Hippo pathway is conserved from Protista to eukaryotes. Deregulation of the Hippo pathway is associated with numerous cancers. Alteration of the Hippo pathway results in cell invasion, migration, disease progression, and therapy resistance in cancers. However, the function of the various components of the mammalian Hippo pathway is yet to be elucidated in detail especially concerning tumor biology. In the present review, we focused on the Hippo pathway in different model organisms, its regulation and deregulation, and possible therapeutic targets for cancer treatment.

Global Sex Disparity of COVID-19: A Descriptive Review of Sex Hormones and Consideration for the Potential Therapeutic Use of Hormone Replacement Therapy in Older Adults

The 2019-2020 SARS-related coronavirus-2 (SARS-CoV-2) pandemic has brought unprecedented challenges to healthcare sectors around the world. As of November 2020, there have been over 64 million confirmed cases and approaching 2 million deaths globally. Despite the large number of positive cases, there are very limited established standards of care and therapeutic options available. To date, there is still no Food and Drug Administration (FDA) approved vaccine for COVID-19, although there are several options in various clinical trial stages. Herein, we have performed a global review evaluating the roles of age and sex on COVID-19 hospitalizations, ICU admissions, deaths in hospitals, and deaths in nursing homes. We have identified a trend in which elderly and male patients are significantly affected by adverse outcomes. There is evidence suggesting that sex hormone levels can influence immune system function against SARS-CoV-2 infection, thus reducing the adverse effects of COVID-19. Since older adults have lower levels of these sex hormones, we therefore speculate, within rational scientific context, that sex steroids, such as estrogen and progesterone, needs further consideration for use as alternative therapeutic option for treating COVID-19 elderly patients. To our knowledge, this is the first comprehensive article evaluating the significance of sex hormones in COVID-19 outcomes in older adults.

Repurposing existing drugs for the treatment of COVID-19/SARS-CoV-2 infection: A review describing drug mechanisms of action

The outbreak of a novel coronavirus (SARS-CoV-2) has caused a major public health concern across the globe. SARS-CoV-2 is the seventh coronavirus that is known to cause human disease. As of September 2020, SARS-CoV-2 has been reported in 213 countries and more than 31 million cases have been confirmed, with an estimated mortality rate of ∼3%. Unfortunately, a drug or vaccine is yet to be discovered to treat COVID-19. Thus, repurposing of existing cancer drugs will be a novel approach in treating COVID-19 patients. These drugs target viral replication cycle, viral entry and translocation to the nucleus. Some can enhance innate antiviral immune response as well. Hence this review focuses on comprehensive list of 22 drugs that work against COVID-19 infection. These drugs include fingolimod, colchicine, N4-hydroxycytidine, remdesivir, methylprednisone, oseltamivir, icatibant, perphanizine, viracept, emetine, homoharringtonine, aloxistatin, ribavirin, valrubicin, famotidine, almitrine, amprenavir, hesperidin, biorobin, cromolyn sodium, and antibodies- tocilzumab and sarilumab. Also, we provide a list of 31 drugs that are predicted to function against SARS-CoV-2 infection. In summary, we provide succinct overview of various therapeutic modalities. Among these 53 drugs, based on various clinical trials and literature, remdesivir, nelfinavir, methylpredinosolone, colchicine, famotidine and emetine may be used for COVID-19. SIGNIFICANCE: It is of utmost important priority to develop novel therapies for COVID-19. Since the effect of SARS-CoV-2 is so severe, slowing the spread of diseases will help the health care system, especially the number of visits to Intensive Care Unit (ICU) of any country. Several clinical trials are in works around the globe. Moreover, NCI developed a recent and robust response to COVID-19 pandemic. One of the NCI's goals is to screen cancer related drugs for identification of new therapies for COVID-19. https://www.cancer.gov/news-events/cancer-currents-blog/2020/covid-19-cancer-nci-response?cid=eb_govdel.

SARS-CoV infection crosstalk with human host cell noncoding-RNA machinery: An in-silico approach

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Protein-protein interaction (PPI) network of the SARS-CoV and Homo sapiens was obtained.

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Based on Bioinformatic analysis, the TGF-beta signaling pathway with the largest numbers of involved genes may play key roles during SARS-CoV infection.

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An integrated network of mRNA/lncRNA/miRNA was created.

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In the network, SMAD2, SMAD3, SMAD4, SMAD7, and TGFBR1 with the highest number of interactions were identified as target hubs.

Although 70 % of the genome is transcribed to RNA in humans, only ∼2% of these transcripts are translated into proteins. The rest of the transcripts are defined as noncoding RNAs, including Long noncoding RNAs (LncRNAs) and MicroRNAs (miRNAs) that mostly function post-transcriptionally to regulate the gene expression. The outbreak of a novel coronavirus (SARS-CoV) has caused a major public health concern across the globe. The SARS-CoV is the seventh coronavirus that is known to cause human disease. There are currently no promising antiviral drugs with proven efficacy nor are there vaccines for its prevention. As of August 10, 2020, SARS-CoV has been infected more than 13 million cases in more than 213 countries, with an estimated mortality rate of ∼3 %. Thus, it is of utmost important priority to develop novel therapies for COVID-19. It is not fully investigated whether noncoding RNAs regulate signaling pathways that SARS-CoV involved in. Hence, computational analysis of the noncoding RNA interactions and determining importance of key regulatory noncoding RNAs in antiviral defense mechanisms will likely be helpful in developing new drugs to attack SARS-CoV infection. To elucidate this, we utilized bioinformatic approaches to find the interaction network of SARS-CoV/human proteins, miRNAs, and lncRNAs. We found TGF-beta signaling pathway as one of the potential interactive pathways. Furthermore, potential miRNAs/lncRNAs networks that the virus might engage during infection in human host cells have been shown. Altogether, TGF-beta signaling pathway as well as hub miRNAs, and LncRNAs involve during SARS-CoV pathogenesis can be considered as potential therapeutic targets.

Knockout model reveals the role of Nischarin in mammary gland development, breast tumorigenesis and response to metformin treatment

Previously, our lab discovered the protein Nischarin and uncovered its role in regulating cell migration and invasion via its interactions with several proteins. We subsequently described a role for Nischarin in breast cancer, in which it is frequently underexpressed. To characterize Nischarin's role in breast tumorigenesis and mammary gland development more completely, we deleted a critical region of the Nisch gene (exons 7-10) from the mouse genome and observed the effects. Mammary glands in mutant animals showed delayed terminal end bud formation but did not develop breast tumors spontaneously. Therefore, we interbred the animals with transgenic mice expressing the mouse mammary tumor virus-polyoma middle T-antigen (MMTV-PyMT) oncogene. The MMTV-PyMT mammary glands lacking Nischarin showed increased hyperplasia compared to wild-type animal tissues. Furthermore, we observed significantly increased tumor growth and metastasis in Nischarin mutant animals. Surprisingly, Nischarin deletion decreased activity of AMPK and subsequently its downstream effectors. Given this finding, we treated these animals with metformin, which enhances AMPK activity. Here, we show for the first time, metformin activates AMPK signaling and inhibits tumor growth of Nischarin lacking PyMT tumors suggesting a potential use for metformin as a cancer therapeutic, particularly in the case of Nischarin-deficient breast cancers.

Long noncoding RNAs and exosomal lncRNAs: classification, and mechanisms in breast cancer metastasis and drug resistance

Breast cancer is the most common cancer, and the second cause of cancer-related deaths (after lung cancer) among women. Developing tumor metastasis and invasion is the most important cause of death in breast cancer patients. Several key factors participate in breast cancer metastasis including long noncoding RNAs (lncRNAs). lncRNAs are a category of cellular RNAs that are longer than 200 nucleotides in length. Accumulating evidence suggests that lncRNAs have the potential to be promising diagnostic, prognostic biomarkers and therapeutic targets in breast cancer. Understanding the role of lncRNAs and their mechanisms of functions might help to further discovery of breast cancer biological characteristics. In this review, we discuss physiological functions, epigenetic regulation, transcriptional regulation of lncRNAs, and their important role in tumor progression and metastasis. Some lncRNAs function as oncogenes and some function as tumor suppressors. Interestingly, recent reports depict that hypomethylation of promoters of lncRNAs play a pivotal role in cancer progression, suggesting the importance of epigenetic regulation. Furthermore, we discuss the role of lncRNAs in exosomes and their function in drug resistance, and therapeutic importance of exosomal lncRNAs in cancer biology. In summary, lncRNAs have a great potential to consider them as novel prognostic biomarkers as well as new therapeutic targets in breast cancer.

Exosomes: composition, biogenesis, and mechanisms in cancer metastasis and drug resistance

Tumor-derived exosomes (TDEs) participate in formation and progression of different cancer processes, including tumor microenvironment (TME) remodeling, angiogenesis, invasion, metastasis and drug-resistance. Exosomes initiate or suppress various signaling pathways in the recipient cells via transmitting heterogeneous cargoes. In this review we discuss exosome biogenesis, exosome mediated metastasis and chemoresistance. Furthermore, tumor derived exosomes role in tumor microenvironment remodeling, and angiogenesis is reviewed. Also, exosome induction of epithelial mesenchymal transition (EMT) is highlighted. More importantly, we discuss extensively how exosomes regulate drug resistance in several cancers. Thus, understanding exosome biogenesis, their contents and the molecular mechanisms and signaling pathways that are responsible for metastasis and drug-resistance mediated by TDEs may help to devise novel therapeutic approaches for cancer progression particularly to overcome therapy-resistance and preventing metastasis as major factors of cancer mortality.

Exosomes from Nischarin-Expressing Cells Reduce Breast Cancer Cell Motility and Tumor Growth

Exosomes are small extracellular microvesicles that are secreted by cells when intracellular multivesicular bodies fuse with the plasma membrane. We have previously demonstrated that Nischarin inhibits focal adhesion formation, cell migration, and invasion, leading to reduced activation of focal adhesion kinase. In this study, we propose that the tumor suppressor Nischarin regulates the release of exosomes. When cocultured on exosomes from Nischarin-positive cells, breast cancer cells exhibited reduced survival, migration, adhesion, and spreading. The same cocultures formed xenograft tumors of significantly reduced volume following injection into mice. Exosomes secreted by Nischarin-expressing tumors inhibited tumor growth. Expression of only one allele of Nischarin increased secretion of exosomes, and Rab14 activity modulated exosome secretions and cell growth. Taken together, this study reveals a novel role for Nischarin in preventing cancer cell motility, which contributes to our understanding of exosome biology. SIGNIFICANCE: Regulation of Nischarin-mediated exosome secretion by Rab14 seems to play an important role in controlling tumor growth and migration.See related commentary by McAndrews and Kalluri, p. 2099.

Suppression of PDHX by microRNA-27b deregulates cell metabolism and promotes growth in breast cancer

BACKGROUND

The disruption of normal gene regulation due to microRNA dysfunction is a common event in cancer pathogenesis. MicroRNA-27b is an example of an oncogenic miRNA, and it is frequently upregulated in breast cancer. MicroRNAs have been found to deregulate tumor metabolism, which typically manifests as heightened cellular glucose uptake in consort with increased flux through glycolysis, followed by the preferential conversion of glycolytic pyruvate into lactate (a phenomenon known as the Warburg Effect). Pyruvate Dehydrogenase, an enzyme complex linking glycolysis with downstream oxidative metabolism, represents a key location where regulation of metabolism occurs; PDHX is a key structural component of this complex and is essential for its function.

METHODS

We sought to characterize the role of miR-27b in breast cancer by identifying novel transcripts under its control. We began by utilizing luciferase, RNA, and protein assays to establish PDHX as a novel target of miR-27b. We then tested whether miR-27b could alter metabolism using several metabolite assay kits and performed a seahorse analysis. We also examined how the altered metabolism might affect cell proliferation. Lastly, we confirmed the relevance of our findings in human breast tumor samples.

RESULTS

Our data indicate that Pyruvate Dehydrogenase Protein X is a credible target of miR-27b in breast cancer. Mechanistically, by suppressing PDHX, miR-27b altered levels of pyruvate, lactate and citrate, as well as reducing mitochondrial oxidation and promoting extracellular acidification. These changes corresponded with an increased capacity for cell proliferation. In human breast tumor samples, PDHX expression was deficient, and low levels of PDHX were associated with reduced patient survival.

CONCLUSIONS

MicroRNA-27b targets PDHX, resulting in an altered metabolic configuration that is better suited to fuel biosynthetic processes and cell proliferation, thereby promoting breast cancer progression.

Expression of long noncoding RNA MALAT1 correlates with increased levels of Nischarin and inhibits oncogenic cell functions in breast cancer

Malat1 is a long noncoding RNA with a wide array of functions, including roles in regulating cancer cell migration and metastasis. However, the nature of its involvement in control of these oncogenic processes is incompletely understood. In the present study, we investigate the role of Malat1 and the effects of Malat1 KO in a breast cancer cell model. Our selection of Malat1 as the subject of inquiry followed initial screening experiments seeking to identify lncRNAs which are altered in the presence or absence of Nischarin, a gene of interest previously discovered by our lab. Nischarin is a well characterized tumor suppressor protein and actively represses cell proliferation, migration, and invasion in breast cancer. Our microarray screen for lncRNAs revealed multiple lncRNAs to be significantly elevated in cells ectopically expressing Nischarin compared to control cancer cells, which have only marginal Nisch expression. Using these cells, we assess how the link between Nischarin and Malat1 affects cancer cell function, finding that Malat1 confers an inhibitory effect on cell growth and migration which is lost following Malat1 KO, but in a Nisch-dependent context. Specifically, Malat1 KO in the background of low Nischarin expression had a limited effect on cell functions, while Malat1 KO in cells with high levels of Nischarin led to significant increases in cell proliferation and migration. In summary, this project provides further clarity concerning the function of Malat1, specifically in breast cancer, while also indicating that the Nischarin expression context is an important factor in the determining how Malat1 activity is governed in breast cancer.

Cell matrix adhesions in cancer: The proteins that form the glue

The main purposes of Integrin-mediated cell contacts are to interpret bi-directional signals between the extracellular environment and intracellular proteins, as well as, anchor the cell to a matrix. Many cell adhesion molecules have been discovered with a wide spectrum of responsibilities, including recruiting, activating, elongating, and maintaining. This review will perlustrate some of the key incidences that precede focal adhesion formation. Tyrosine phosphorylation is a key signaling initiation event that leads to the recruitment of multiple proteins to focal adhesion sites. Recruitment and concentration of proteins such as Paxillin and Vinculin to Integrin clutches is necessary for focal adhesion development. The assembled networks are responsible for transmitting signals back and forth from the extracellular matrix (ECM) to Actin and its binding proteins. Cancer cells exhibit highly altered focal adhesion dynamics. This review will highlight some key discoveries in cancer cell adhesion, as well as, identify current gaps in knowledge.

FACS-based Glucose Uptake Assay of Mouse Embryonic Fibroblasts and Breast Cancer Cells Using 2-NBDG Probe

This is a flow cytometry-based protocol to measure glucose uptake of mouse embryonic fibroblasts (MEFs) and breast cancer cells in vitro. The method is a slightly modified and updated version as previously described ( Dong et al., 2017 ). Briefly, the target cells are incubated with the fluorescently tagged 2-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-2-deoxyglucose (2-NBDG) for 2 h or 30 min, and the efficiency of glucose uptake is examined using a flow cytometer. This method can be adapted to measure a variety of adipocytes, immune cells, MEFs and cancer cells.

Nischarin regulates focal adhesion and Invadopodia formation in breast cancer cells

Background

During metastasis, tumor cells move through the tracks of extracellular matrix (ECM). Focal adhesions (FAs) are the protein complexes that link the cell cytoskeleton to the ECM and their presence is necessary for cell attachment. The tumor suppressor Nischarin interacts with a number of signaling proteins such as Integrin α5, PAK1, LIMK1, LKB1, and Rac1 to prevent cancer cell migration. Although previous findings have shown that Nischarin exerts this migratory inhibition by interacting with other proteins, the effects of these interactions on the entire FA machinery are unknown.

Methods

RT-PCR, Western Blotting, invadopodia assays, and immunofluorescence were used to examine FA gene expression and determine whether Nischarin affects cell attachment, as well as the proteins that regulate it.

Results

Our data show that Nischarin prevents cell migration and invasion by altering the expression of key focal adhesion proteins. Furthermore, we have found that Nischarin-expressing cells have reduced ability to attach the ECM, which in turn leads to a decrease in invadopodia-mediated matrix degradation.

Conclusions

These experiments demonstrate an important role of Nischarin in regulating cell attachment, which adds to our understanding of the early events of the metastatic process in breast cancer.

Electronic supplementary material

The online version of this article (10.1186/s12943-018-0764-6) contains supplementary material, which is available to authorized users.

Nischarin inhibition alters energy metabolism by activating AMP-activated protein kinase

Nischarin (Nisch) is a key protein functioning as a molecular scaffold and thereby hosting interactions with several protein partners. To explore the physiological importance of Nisch, here we generated Nisch loss-of-function mutant mice and analyzed their metabolic phenotype. Nisch-mutant embryos exhibited delayed development, characterized by small size and attenuated weight gain. We uncovered the reason for this phenotype by showing that Nisch binds to and inhibits the activity of AMP-activated protein kinase (AMPK), which regulates energy homeostasis by suppressing anabolic and activating catabolic processes. The Nisch mutations enhanced AMPK activation and inhibited mechanistic target of rapamycin signaling in mouse embryonic fibroblasts as well as in muscle and liver tissues of mutant mice. Nisch-mutant mice also exhibited increased rates of glucose oxidation with increased energy expenditure, despite reduced overall food intake. Moreover, the Nisch-mutant mice had reduced expression of liver markers of gluconeogenesis associated with increased glucose tolerance. As a result, these mice displayed decreased growth and body weight. Taken together, our results indicate that Nisch is an important AMPK inhibitor and a critical regulator of energy homeostasis, including lipid and glucose metabolism.

Abstract P4-07-05: MicroRNA-27b mediates deregulation of energy metabolism in breast cancer

MicroRNAs (miRNAs) are a class of small, non-coding RNA which participate in gene regulation by targeted silencing of specific mRNA transcripts. Recently, it has become clear that dysfunctional miRNA expression is an important contributor to the deregulation of key signaling pathways underlying carcinogenesis. MicroRNA-27b is an example of one such pro-oncogenic miRNA, and correspondingly, its expression has been found to be upregulated in breast cancer cells and tissues. In this regard, several targets of miR-27b have previously been verified, and implicate miR-27b in multiple neoplastic processes including migration, invasion and metastasis. In order to enable future development of miRNA-based cancer therapies, the putative targets of each miRNA must be mapped more comprehensively. Such awareness is necessary in order to make informed choices regarding whether a miRNA-based therapy is likely to be effective and what side-effects should be anticipated. Therefore, this project seeks to further establish the role of miR-27b in the context of breast cancer, specifically by identifying novel target transcripts under its control. Using target prediction algorithms and breast cancer cell culture models, initial evidence has implicated Pyruvate Dehydrogenase Protein X (PDHX) to be a probable target. As a structural component of the Pyruvate Dehydrogenase Complex, the role of PDHX in linking the end products of glycolytic reactions with subsequent oxidative phosphorylation pathways is indispensable. However, a hallmark of cancer cell metabolism is the propensity to consume glucose aerobically, which liberates additional carbon skeletons for use in biosynthetic reactions that are crucial for tumor growth. In this way, miR-27b overexpression appears to sever the link between glycolysis and subsequent catabolic pathways, thus conferring a pro-growth advantage to the cancer cells. Expression profiling of PDHX using both breast cancer cell lines and human breast tissues (which overexpress miR-27b) reveal that PDHX levels are indeed significantly reduced, thus supporting the notion that miR-27b alters cancer cell metabolism specifically by targeting this gene in breast cancer. Improving the current understanding of miR-27b's functions will lay the necessary ground work to evaluate its potential as a novel target for cancer therapy. Similarly, the awareness of the expression status of miR-27b and its targets in breast cancer tumors will further efforts to find suitable miRNA tissue biomarkers to enhance screening and prognosis. In this way, microRNA-based approaches offer the distinct potential to improve cancer detection as well as treatment, making them a dynamic method to improve management of breast cancer patients in the future.

Citation Format: Eastlack SC, Alahari SK, Dong S, Cole JT. MicroRNA-27b mediates deregulation of energy metabolism in breast cancer [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P4-07-05.

The roles of oncogenic miRNAs and their therapeutic importance in breast cancer

Since the discovery of tumour suppressive miRNA in 2002, the dysregulation of miRNAs was implicated in many cancers, exhibiting both tumour suppressive and oncogenic roles. Dysregulation of miRNAs was found to be involved in the initiation of oncogenesis, as well as the progression, invasion and metastasis of cancers. While normal miRNA inhibitory functions help regulate gene expression in the cell, oncogenic miRNA, when dysregulated can lead to suppression of critical pathways that control apoptosis, cell cycle progression, growth and proliferation. This suppression allows for the upregulation of pro-oncogenic factors that drive cell survival, growth and proliferation. Due to emerging discoveries, oncogenic miRNAs are proving to be a critical component in cancers, such as breast cancer, and may provide novel avenues for cancer treatment. In this article, we discuss the roles of the most studied oncogenic miRNAs in breast cancer including clusters and families involved as well as the less studied and recently discovered oncogenic miRNAs. These miRNAs provide valuable information into the complexity of regulatory elements affected by their overexpression and the overall impact in the progression of breast cancer. Also, identifying miRNAs causing or leading to resistance or sensitivity to current anti-cancer drugs prior to treatment may lead to an improvement in treatment selection and overall patient response. This review summarizes known and recently discovered miRNAs in literature found to have oncogenic roles in breast cancer initiation and the progression, invasion and metastasis of the disease.

Abstract 3681: Nischarin disruption promotes breast tumor development in mouse models

Nischarin is a novel tumor suppressor that was first discovered and characterized in our laboratory. The accumulating evidence suggests that Nischarin is a critical regulator of cell migration and breast tumor growth, metastasis and invasion. However, little is known about the exact function of Nischarin in in vivo physiological conditions, probably due to lack of any transgenic Nischarin animals. We recently generated Nischarin knockout mouse. This Nischarin knockout mouse has a dramatic unusual phenotype of mammary development and overall growth defect. Nischarin knockout mice do not spontaneously develop breast tumors. To determine the importance of Nischarin in regulation of breast cancer development, we bred Nischarin knockout virgin mice with PyMT (polyoma middle T antigen) and Neu background mice and the progeny produced tumors exclusively in the mammary gland. We found Nischarin knockout virgins with PyMT accelerated breast cancer onset and progression, which further suggests Nischarin inhibits tumor growth. Mammary epithelial cells (MECs) are surrounded by basement membrane, which mainly consists of extracellular matrix. We noted that the basement membrane of Nischarin knockout virgins contain much more collagen and fibronectin than those of wild type virgins. In addition, we observed that Nischarin disruption significantly changed extracellular acidification rates (ECAR) in mouse primary breast tumour cells. We suspected that this changed acidic microenvironment might facilitate breast tumor progression. Recent studies indicated that clinical anti-diabetic drug Metformin, an AMPK activator, inhibits breast cancer cell growth. Our data show that Het-PyMT and Null-PyMT primary cells were much more sensitive for metformin treatment. Thus we examined the importance of AMPK signaling in our mouse models. Interestingly, both tumor tissues and primary cells derived from Null-PyMT breast tumors had lower AMPK activity. Together, our data strongly support that Nischarin disruption promotes breast tumor development and AMPK signaling is important for Nischarin-mediated suppression of breast tumor.

Citation Format: Shengli Dong, Suresh K. Alahari. Nischarin disruption promotes breast tumor development in mouse models. [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 3681.

Abstract 1177: The role of nischarin in the breast tumor microenvironment

Women with denser breasts, have a higher risk of developing breast cancer. Breast density reflects the amount of connective tissue and collagen present. During metastasis, tumor cells move through tracks of extracellular matrix (ECM). A stiff and ordered tissue microenvironment is necessary for tumor cell invasiveness. Matrix stiffness is mediated by ECM fiber organization and cell-matrix adhesions. Our lab is investigating a tumor suppressor that contributes to ECM organization. The protein Nischarin interacts with a number of signaling proteins such as integrin α5, PAK1, LIMK1, LKB1, MLCK, ERK and Rac1 to prevent cancer cell migration. Our data shows that spontaneous breast tumors from wild-type (WT) animals have reduced ECM fiber expression and organization compared to those from homozygous Nischarin Null mice. Furthermore, we have found Nischarin to alter integrin and focal adhesion signaling, therefore affecting cell-matrix adhesions. We hypothesize that the absence of Nischarin in the breast tumor leads to increased matrix stiffness, through increased fiber organization, and altered cell-matrix adhesions. Since no breast tumor suppressors have been linked to collagen and fibronectin ECM remodeling, we present a novel role for Nischarin in organizing the ECM. By integrating cell signaling with optical and computational instrumentation, we will assess the role of Nischarin in the bidirectional cellular/matrix crosstalk, which will add to our understanding of the metastatic process in breast cancer.

Citation Format: Mazvita Maziveyi, Shengli Dong, Suresh K. Alahari. The role of nischarin in the breast tumor microenvironment. [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 1177.

Regulation of epithelial-mesenchymal transition through epigenetic and post-translational modifications

The epithelial to mesenchymal transition (EMT) is a biological process in which a non-motile epithelial cell changes to a mesenchymal phenotype with invasive capacities. This phenomenon has been well documented in multiple biological processes including embryogenesis, fibrosis, tumor progression and metastasis. The hallmark of EMT is the loss of epithelial surface markers, most notably E-cadherin, and the acquisition of mesenchymal markers including vimentin and N-cadherin. The downregulation of E-cadherin during EMT can be mediated by its transcriptional repression through the binding of EMT transcription factors (EMT-TFs) such as SNAIL, SLUG and TWIST to E-boxes present in the E-cadherin promoter. Additionally, EMT-TFs can also cooperate with several enzymes to repress the expression of E-cadherin and regulate EMT at the epigenetic and post- translational level. In this review, we will focus on epigenetic and post- translational modifications that are important in EMT. In addition, we will provide an overview of the various therapeutic approaches currently being investigated to undermine EMT and hence, the metastatic progression of cancer as well.

Breast Cancer Tumor Suppressors: A Special Emphasis on Novel Protein Nischarin

Tumor suppressor genes regulate cell growth and prevent spontaneous proliferation that could lead to aberrant tissue function. Deletions and mutations of these genes typically lead to progression through the cell-cycle checkpoints, as well as increased cell migration. Studies of these proteins are important as they may provide potential treatments for breast cancers. In this review, we discuss a comprehensive overview on Nischarin, a novel protein discovered by our laboratory. Nischarin, or imidazoline receptor antisera-selected protein, is a protein involved in a vast number of cellular processes, including neuronal protection and hypotension. The NISCH promoter experiences hypermethylation in several cancers, whereas some highly aggressive breast cancer cells exhibit genomic loss of the NISCH locus. Furthermore, we discuss data illustrating a novel role of Nischarin as a tumor suppressor in breast cancer. Analysis of this new paradigm may shed light on various clinical questions. Finally, the therapeutic potential of Nischarin is discussed.

Primary Tumor and MEF Cell Isolation to Study Lung Metastasis

In breast tumorigenesis, the metastatic stage of the disease poses the greatest threat to the affected individual. Normal breast cells with altered genotypes now possess the ability to invade and survive in other tissues. In this protocol, mouse mammary tumors are removed and primary cells are prepared from tumors. The cells isolated from this procedure are then available for gene profiling experiments. For successful metastasis, these cells must be able to intravasate, survive in circulation, extravasate to distant organs, and survive in that new organ system. The lungs are the typical target of breast cancer metastasis. A set of genes have been discovered that mediates the selectivity of metastasis to the lung. Here we describe a method of studying lung metastasis from a genetically engineered mouse model.. Furthermore, another protocol for analyzing mouse embryonic fibroblasts (MEFs) from the mouse embryo is included. MEF cells from the same animal type provide a clue of non-cancer cell gene expression. Together, these techniques are useful in studying mouse mammary tumorigenesis, its associated signaling mechanisms and pathways of the abnormalities in embryos.

Are macrophages in tumors good targets for novel therapeutic approaches?

The development of cancer has been an extensively researched topic over the past few decades. Although great strides have been made in cancer prevention, diagnosis, and treatment, there is still much to be learned about cancer's micro-environmental mechanisms that contribute to cancer formation and aggressiveness. Macrophages, lymphocytes which originate from monocytes, are involved in the inflammatory response and often dispersed to areas of infection to fight harmful antigens and mutated cells in tissues. Macrophages have a plethora of roles including tissue development and repair, immune system functions, and inflammation. We discuss various pathways by which macrophages get activated, various approaches that can regulate the function of macrophages, and how these approaches can be helpful in developing new cancer therapies.

Integrin-binding protein nischarin interacts with tumor suppressor liver kinase B1 (LKB1) to regulate cell migration of breast epithelial cells

Biallelic inactivation of LKB1, a serine/threonine kinase, has been detected in 30% of lung adenocarcinomas, and inhibition of breast tumor growth has been demonstrated. We have identified the tumor suppressor, Nischarin, as a novel binding partner of LKB1. Our mapping analysis shows that the N terminus of Nischarin interacts with amino acids 44-436 of LKB1. Time lapse microscopy and Transwell migration data show that the absence of both Nischarin and LKB1 from an invasive breast cancer cell line (MDA-MB-231) enhances migration as measured by increased distance and speed of migrating cells. Our data suggest that this is a result of elevated PAK1 and LIMK1 phosphorylation. Moreover, the absence of Nischarin and LKB1 increased tumor growth in vivo. Consistent with this, the percentage of S phase cells was increased, as demonstrated by flow cytometry and enhanced cyclin D1. The absence of Nischarin and LKB1 also led to a dramatic increase in the formation of lung metastases. Our studies, for the first time, demonstrate functional interaction between LKB1 and Nischarin to inhibit cell migration and breast tumor progression. Mechanistically, we show that these two proteins together regulate PAK-LIMK-Cofilin and cyclin D1/CDK4 pathways.

Prooncogenic factors miR-23b and miR-27b are regulated by Her2/Neu, EGF, and TNF-α in breast cancer

miRNAs (miR) are a critical class of small (21-25 nucleotides) noncoding endogenous RNAs implicated in gene expression regulation. We identified miR-23b and miR-27b as miRNAs that are highly upregulated in human breast cancer. We found that engineered knockdown of miR-23b and miR-27b substantially repressed breast cancer growth. Nischarin (NISCH) expression was augmented by knockdown of miR-23b as well as miR-27b. Notably, these miRNAs and Nischarin were inversely expressed in human breast cancers, underscoring their biologic relevance. We showed the clinical relevance of the expression of these miRNAs and showed that high expression of miR-23b and miR-27b correlates with poor outcome in breast cancer. Moreover, intraperitoneally delivered anti-miR-27b restored Nischarin expression and decreased tumor burden in a mouse xenograft model of human mammary tumor. Also, we report for the first time that HER2/neu (ERBB2), EGF, and TNF-α promote miR-23b/27b expression through the AKT/NF-κB signaling cascade. Nischarin was found to regulate miR-27b/23b expression through a feedback loop mechanism by suppressing NF-κB phosphorylation. Because anti-miR-27b compounds that suppress miR-27b inhibit tumor growth, the anti-miR-27b seems to be a good candidate for the development of new antitumor therapies.

Quantitative analysis of random migration of cells using time-lapse video microscopy

Cell migration is a dynamic process, which is important for embryonic development, tissue repair, immune system function, and tumor invasion (1, 2). During directional migration, cells move rapidly in response to an extracellular chemotactic signal, or in response to intrinsic cues (3) provided by the basic motility machinery. Random migration occurs when a cell possesses low intrinsic directionality, allowing the cells to explore their local environment. Cell migration is a complex process, in the initial response cell undergoes polarization and extends protrusions in the direction of migration (2). Traditional methods to measure migration such as the Boyden chamber migration assay is an easy method to measure chemotaxis in vitro, which allows measuring migration as an end point result. However, this approach neither allows measurement of individual migration parameters, nor does it allow to visualization of morphological changes that cell undergoes during migration. Here, we present a method that allows us to monitor migrating cells in real time using video - time lapse microscopy. Since cell migration and invasion are hallmarks of cancer, this method will be applicable in studying cancer cell migration and invasion in vitro. Random migration of platelets has been considered as one of the parameters of platelet function (4), hence this method could also be helpful in studying platelet functions. This assay has the advantage of being rapid, reliable, reproducible, and does not require optimization of cell numbers. In order to maintain physiologically suitable conditions for cells, the microscope is equipped with CO(2) supply and temperature thermostat. Cell movement is monitored by taking pictures using a camera fitted to the microscope at regular intervals. Cell migration can be calculated by measuring average speed and average displacement, which is calculated by Slidebook software.

Rho GTPase effector functions in tumor cell invasion and metastasis

Rho GTPases (Ras homologous family) comprise the largest subfamily cluster of the Ras-homology superfamily. Rho GTPases exist in inactive GDP and active GTP forms. The active forms of the Rho family members bind with numerous effector proteins that are crucial for various biological processes. Accumulating evidence exemplifies the importance of Rho effector proteins in various steps of cancer progression. Here, we highlight the actions of various effectors of Rho members in cancer invasion and metastasis.

Molecular characterization of the tumor-suppressive function of nischarin in breast cancer

BACKGROUND

Nischarin (encoded by NISCH), an α5 integrin-binding protein, has been identified as a regulator of breast cancer cell invasion. We hypothesized that it might be a tumor suppressor and were interested in its regulation.

METHODS

We examined nischarin expression in approximately 300 human breast cancer and normal tissues using quantitative polymerase chain reaction and immunohistochemistry. Loss of heterozygosity analysis was performed by examining three microsatellite markers located near the NISCH locus in normal and tumor tissues. We generated derivatives of MDA-MB-231 human metastatic breast cancer cells that overexpressed nischarin and measured tumor growth from these cells as xenografts in mice; metastasis by these cells after tail vein injection; and α5 integrin expression, Rac, and focal adhesion kinase (FAK) signaling using western blotting. We also generated clones of MCF-7 human breast cancer cells in which nischarin expression was silenced and measured tumor growth in mouse xenograft models (n = 5 for all mouse experiments). P values were from two-sided Student t tests in pairwise comparisons.

RESULTS

Normal human breast tissue samples had statistically significantly higher expression of nischarin mRNA compared with tumor tissue samples (mean level in normal breast = 50.7 [arbitrary units], in breast tumor = 16.49 [arbitrary units], difference = 34.21, 95% confidence interval [CI] = 11.63 to 56.79, P = .003), and loss of heterozygosity was associated with loss of nischarin expression. MDA-MB-231 cells in which nischarin was overexpressed had statistically significantly reduced tumor growth and metastasis compared with parental MDA-MB-231 cells (mean volume at day 40, control vs nischarin-expressing tumors, 1977 vs 42.27 mm(3), difference = 1935 mm(3), 95% CI = 395 to 3475 mm(3), P = .025). Moreover, MCF-7 tumor xenografts in which nischarin expression was silenced grew statistically significantly faster than parental cells (mean volume at day 63, tumors with scrambled short hairpin RNA [shRNA] vs with nischarin shRNA, 224 vs 1262 mm(3), difference = 1038 mm(3), 95% CI = 899.6 to 1176 mm(3), P < .001). Overexpression of nischarin was associated with decreased α5 integrin expression, FAK phosphorylation, and Rac activation.

CONCLUSION

Nischarin may be a novel tumor suppressor that limits breast cancer progression by regulating α5 integrin expression and subsequently α5 integrin-, FAK-, and Rac-mediated signaling.

Integrin subunits alpha5 and alpha6 regulate cell cycle by modulating the chk1 and Rb/E2F pathways to affect breast cancer metastasis

Background

Although integrins have been implicated in the progression of breast cancer, the exact mechanism whereby they exert this regulation is clearly not understood. To understand the role of integrins in breast cancer, we examined the expression levels of several integrins in mouse breast cancer cell lines by flow cytometry and the data were validated by Western and RT-PCR analysis. The importance of integrins in cell migration and cell invasion was examined by in vitro assays. Further the effect of integrins on metastasis was investigated by in vivo experimental metastasis assays using mouse models.

Results

Integrin α5 subunit is highly expressed in the nonmetastatic cell line 67NR and is significantly low in the highly invasive cell line 4T1. In contrast, expression levels of integrin α6 subunit are high in 4T1 cells and low in 67NR cells. In vitro data indicated that overexpression of α5 subunit and knockdown of α6 integrin subunit inhibited cell proliferation, migration, and invasion. Our in vivo findings indicated that overexpression of integrin α5 subunit and knockdown of α6 subunit decreased the pulmonary metastasis property of 4T1 cells. Our data also indicated that overexpression of alpha 5 integrin subunit and suppression of alpha6 integrin subunit inhibited cells entering into S phase by up-regulating p27, which results in downregulation of cyclinE/CDK2 complexes, This suggests that these integrins regulate cell growth through their effects on cell-cycle-regulated proteins. We also found that modulation of these integrins upregulates E2F, which may induce the expression of chk1 to regulate cdc25A/cyclin E/CDK2/Rb in a feedback loop mechanism.

Conclusion

This study indicates that Integrin α5 subunit functions as a potential metastasis suppressor, while α6 subunit functions as a metastasis promoter. The modulation of integrins reduces cdc25 A, another possible mechanism for downregulation of CDK2. Taken together we demonstrate a link between integrins and the chk1-cdc25-cyclin E/CDK2-Rb pathway.

Role of Rho GTPases and their regulators in cancer progression

Rho family of GTPases is an ubiquitiously expressed and evolutionarily conserved family of GTP binding proteins that regulate actin dynamics and intracellular signaling. Among the Rho family GTPases, three members RhoA, Rac1 and CDC42 have been well characterized. They each play pivotal roles in gene expression, cell proliferation, apoptosis and various cellular functions. They are driven by signaling from RhoGDIs, RhoGEFs, RhoGAPs and cell surface receptors. Abnormalities in Rho GTPase function have major consequences on cell behavior. Over expression of Rho GTPases is associated with reorganization of actin cytoskeleton, an increase in cell migration, invasion and metastasis which are important aspects of cancer progression. This review will explore these Rho GTPases and the function of their associated signaling pathways in different types of cancers.

Abstract 2196: Tumor suppressor LKB1 cooperates with the integrin-binding protein Nischarin to inhibit breast cancer

Tumor metastasis still remains the main cause of breast cancer death. Although with chemotherapy and radiation therapy, the prognosis has improved in some cases, these approaches often result in severe side effects. It is therefore imperative to elucidate the molecular targets which can prevent metastasis. Two tumor suppressor proteins, Nischarin and LKB1, have been implicated in suppressing metastasis. A novel protein, Nischarin has an inhibitory role in cancer cell migration and invasion; it affects the process of cytoskeletal regulation mediated by Rac and PAK [1]. Nischarin binds to PAK1 and inhibits the kinase activity of PAK1. Nischarin also suppresses breast tumor growth and metastasis in vivo (unpublished results). LKB1 is a serine/threonine kinase involved in the progression of Peutz-Jegher syndrome (PJS) and is also known to play a role in the suppression of breast cancer [2]. Since Nischarin has structural similarities with LKB1 interacting protein (LIP1)[3], we hypothesized that Nischarin interacts with LKB1. Using co-immunoprecipitation assays we have shown that Nischarin interacts with LKB1 in breast cancer cell lines. Our confocal microscopy data confirm that endogenous Nischarin and LKB1 co-localize in the cytosol. Furthermore, we demonstrate that the amino-terminus of Nischarin binds to the kinase domain of LKB1. Nischarin is expressed primarily in the cytoplasm whereas LKB1 is predominantly nuclear with only a small portion of it being in the cytosol, and the cytoplasmic fraction of LKB1 is important for its tumor suppressor function. Our preliminary biochemical fractionation data indicate that Nischarin expression leads to cytoplasmic relocalization of LKB1 suggesting that Nischarin may regulate LKB1 function by regulating its sub cellular localization. Moreover, our random cell migration data using time-lapse microcopy indicate that cancer cell displacement and speed is greatly reduced when both Nischarin and LKB1 are expressed. Hence, it appears that LKB1 cooperates with Nischarin to inhibit breast cancer tumor growth and metastasis. Thus, the studies will be important in determining the role of the LKB-Nischarin interaction in breast cancer, and will likely provide a foundation for subsequent preclinical and clinical studies.

This work was supported by the grant from NIH 5RO1CA115706.

1. Alahari, S.K., Nischarin inhibits Rac induced migration and invasion of epithelial cells by affecting signaling cascades involving PAK. Exp Cell Res, 2003. 288(2): p. 415-24.

2. Zhuang, Z.G., et al., Enhanced expression of LKB1 in breast cancer cells attenuates angiogenesis, invasion, and metastatic potential. Mol Cancer Res, 2006. 4(11): p. 843-9.

3. Smith, D.P., et al., LIP1, a cytoplasmic protein functionally linked to the Peutz-Jeghers syndrome kinase LKB1. Hum Mol Genet, 2001. 10(25): p. 2869-77.

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 2196. doi:10.1158/1538-7445.AM2011-2196

Breast cancer stem cells: a new challenge for breast cancer treatment

The biggest challenge for cancer research is relapses that occur in patients undergoing chemotherapy and radiotherapy, suggesting that some cells in tumors escape targeted treatment. Key questions are why relapses occur and why current therapies fail to remove all cancer cells. The cancer stem-cell hypothesisis based on the fact that not all cells within a tumor are similar. Other than tumorigenesis and metastasis, cancer stem cells have some properties that are similar to those of normal stem cells, such as self-renewal and differentiation. Accordingly, breast cancer stem cells may arise from mutation of normal mammary stem cells or progenitor cells. Cancer stem cell regulation involves several factors, such as Wnt, Notch, and Hedgehog, mutations of which endow cancer stem cells with the capacity for self-renewal. Moreover, epithelial mesenchymal transition and microRNAs recently have been shown to regulate the "stemness " of cancer cells. Targeting cancer stem cells could prevent relapse and provide new hope for cancer prevention.

Integrin-mediated function of Rab GTPases in cancer progression

The RAS (rat sarcoma) superfamily of small GTPases is broadly subdivided into five groups: Ras, Rho, Rab, Ran, and Arf. Rab family proteins are important in regulating signal transduction and cellular processes such as differentiation, proliferation, vesicle transport, nuclear assembly, and cytoskeleton formation. However, some Rab proteins have been reported to be necessary for the adhesion and migration of cancer cells. Although Ras and Rho family members have been strongly implicated in cancer progression, knowledge of Rabs action in this regard is limited. Some reports have also linked Rab GTPases with cancer cell migration and invasiveness. This review discusses the implications of the involvement of Rabs in malignant transformation and cancer therapy through integrin-mediated signaling events, with particular emphasis on breast cancer.

miRNA control of tumor cell invasion and metastasis

MicroRNAs have emerged as a novel class of noncoding RNAs that regulate gene expression at the post-translational level in almost every biological event. A large body of evidence indicates that microRNAs regulate the expression of different genes that play an important role in cancer cell invasion, migration and metastasis. In this review, we briefly describe the role of various miRNAs in invasion, migration and metastasis which are essential steps during cancer progression.

ST14 (suppression of tumorigenicity 14) gene is a target for miR-27b, and the inhibitory effect of ST14 on cell growth is independent of miR-27b regulation

MicroRNAs are noncoding, endogenous small RNAs that regulate target genes by cleavage of the targeted mRNA or translational repression. We investigated the microRNAome using 2-color microarrays in a highly invasive human breast cancer cell line, MDA-MB-231 (subline 4175) and a noninvasive breast epithelial cell line, MCF10A. We found 13 microRNAs that were up-regulated, and nine were down-regulated significantly in 4175 cells (p < 0.05, -fold change >2) compared with MCF10A cells. Interestingly, miR-27b and its putative target gene, ST14 (suppressor of tumorigenicity 14), had inverse expression pattern in breast cancer cells. The 3'-untranslated region of ST14 contains a regulatory element for miR-27b, and our luciferase experiments indicate that antisense miR-27b enhances ST14 expression in cancer cells. Furthermore, antagomir of miR-27b suppressed cell invasion in 4175 cells, whereas pre-miR-27b stimulated invasion in moderately invasive ZR75 breast cancer cells. In addition, ST14 reduces cell proliferation as well as cell migration and invasion. Analysis of human breast tumors revealed that miR-27b expression increases during cancer progression, paralleling a decrease in ST14 expression. Furthermore, our data indicate that ST14 inhibits cells from entering into S phase by up-regulating p27, which results in down-regulation of cyclin E-CDK2 complexes, suggesting ST14 reduces cell growth through its effects on cell cycle-related proteins. Introduction of miR-27b into ST14-expressing cells did not suppress the effect on cell growth. These findings suggest that ST14 plays an important role in several biological processes, and some effects are not completely dependent on miR-27b regulation.