Matrix metalloproteinases play an active role in Wnt1-induced mammary tumorigenesis

Prognostic value of different forms of serum MMP-2 and MMP-9 in dogs with mammary tumors; a longitudinal study

Gelatinases (MMP-2 and MMP-9) are related to tumor invasion and metastasis. In humans, the diagnostic value of serum levels of gelatinases has been confirmed in breast cancer, but their diagnostic value in canine mammary tumors is still unknown. This study aimed to determine the serum level of gelatinases in dogs with mammary tumors in order to determine their value in the diagnosis of malignancy or benign tumors and also in predicting the possibility of metastasis and recurrence. Frequent measurement of MMP-2 and MMP-9 by gelatin zymography in serum before and after surgical treatment has not previously been studied for monitoring mammary tumors in dogs. Thus, the serum levels of MMP-2 and MMP-9 in 26 dogs with mammary tumors before surgical treatment and then 1, 4 and 12 months after surgery were evaluated by gelatin zymography. Serum samples of 26 healthy dogs with normal conditions were used as control. Dogs with benign and malignant mammary tumors showed bands of pro-MMP-2, pro-MMP-9 and active MMP-9. However, only pro-MMP-2 and pro-MMP-9 bands appeared in the serum of control group. Our results showed that the presence of active MMP-9, regardless of its level, was prognostically important for metastasis and or recurrence (M/R). However, the presence of active MMP-2 band was more important for M/R than active MMP-9, as its presence coincides with definitive M/R. It seems that serum gelatin zymography could possibly be used at regular intervals before and after surgery to evaluate the probability of M/R in dogs with mammary tumors. More research is needed in this regard.

Anti-Angiogenic Effects of Natural Compounds in Diet-Associated Hepatic Inflammation

Alcoholic liver disease (ALD) and non-alcoholic fatty liver disease (NAFLD) are the most common causes of chronic liver disease and are increasingly emerging as a global health problem. Such disorders can lead to liver damage, resulting in the release of pro-inflammatory cytokines and the activation of infiltrating immune cells. These are some of the common features of ALD progression in ASH (alcoholic steatohepatitis) and NAFLD to NASH (non-alcoholic steatohepatitis). Hepatic steatosis, followed by fibrosis, lead to a continuous progression accompanied by angiogenesis. This process creates hypoxia, which activates vascular factors, initiating pathological angiogenesis and further fibrosis. This forms a vicious cycle of ongoing damage and progression. This condition further exacerbates liver injury and may contribute to the development of comorbidities, such as metabolic syndrome as well as hepatocellular carcinoma. Increasing evidence suggests that anti-angiogenic therapy may have beneficial effects on these hepatic disorders and their exacerbation. Therefore, there is a great interest to deepen the knowledge of the molecular mechanisms of natural anti-angiogenic products that could both prevent and control liver diseases. In this review, we focus on the role of major natural anti-angiogenic compounds against steatohepatitis and determine their potential therapeutic benefits in the treatment of liver inflammation caused by an imbalanced diet.

Research on the mechanism of berberine in the treatment of COVID-19 pneumonia pulmonary fibrosis using network pharmacology and molecular docking

Purpose Pulmonary fibrosis caused by COVID-19 pneumonia is a serious complication of COVID-19 infection, there is a lack of effective treatment methods clinically. This article explored the mechanism of action of berberine in the treatment of COVID-19 (Corona Virus Disease 2019, COVID-19) pneumonia pulmonary fibrosis with the help of the network pharmacology and molecular docking. Methods We predicted the role of berberine protein targets with the Pharmmapper database and the 3D structure of berberine in the Pubchem database. And GeneCards database was used in order to search disease target genes and screen common target genes. Then we used STRING web to construct PPI interaction network of common target protein. The common target genes were analyzed by GO and KEGG by DAVID database. The disease-core target gene-drug network was established and molecular docking was used for prediction. We also analyzed the binding free energy and simulates molecular dynamics of complexes. Results Berberine had 250 gene targets, COVID-19 pneumonia pulmonary fibrosis had 191 gene targets, the intersection of which was 23 in common gene targets. Molecular docking showed that berberine was associated with CCl2, IL-6, STAT3 and TNF-α. GO and KEGG analysis reveals that berberine mainly plays a vital role by the signaling pathways of influenza, inflammation and immune response. Conclusion Berberine acts on TNF-α, STAT3, IL-6, CCL2 and other targets to inhibit inflammation and the activation of fibrocytes to achieve the purpose of treating COVID-19 pneumonia pulmonary fibrosis.

Development of nanotechnology-mediated precision radiotherapy for anti-metastasis and radioprotection

Radiotherapy (RT), including external beam RT and internal radiation therapy, uses high-energy ionizing radiation to kill tumor cells.

Effect of Nanog overexpression on the metastatic potential of a mouse melanoma cell line B16-BL6

Nanog, a marker and regulator of the undifferentiated state in embryonic stem cells were anticipated to be an effective enhancer of cancer metastasis. We have developed a Nanog overexpressing mouse melanoma cell line B16-BL6 (BL6). BL6 was well recognized as a cell line with a high metastatic potential. In vitro tests revealed the enhancement of cell proliferation, wound healing activity, and matrix metalloproteinase 9 (MMP9) activity. Nanog-induced up- or down-regulated genes were comprehensively analyzed by transcriptome sequencing using Nanog⁺BL6 and wild-type BL6. Principally, up-regulated genes were involved in vesicle-aided glucose transport and oxidative phosphorylation, while down-regulated genes were associated with immunosuppression and apoptosis. A marked finding was that TGF-β1 was down-regulated, because TGF-β1 has been well discussed about its suppressive/progressive dual role in cancer. In vivo test showed that the number and volume of metastatic colonies of BL6 to lung were as high as 115 colonies/lung and 5.6 mm³/lung. Under this condition, Nanog overexpression caused a progressive effect (150 colonies/lung, p = 0.25; 9.2 mm³/lung, p = 0.13) rather than a suppressive effect on the metastasis. In this study, the effectiveness of Nanog overexpression in enhancing the metastatic potential of melanoma cell lines has been demonstrated for the first time.

Membrane-type matrix metalloproteases as diverse effectors of cancer progression

Membrane-type matrix metalloproteases (MT-MMP) are pivotal regulators of cell invasion, growth and survival. Tethered to the cell membranes by a transmembrane domain or GPI-anchor, the six MT-MMPs can exert these functions via cell surface-associated extracellular matrix degradation or proteolytic protein processing, including shedding or release of signaling receptors, adhesion molecules, growth factors and other pericellular proteins. By interactions with signaling scaffold or cytoskeleton, the C-terminal cytoplasmic tail of the transmembrane MT-MMPs further extends their functionality to signaling or structural relay. MT-MMPs are differentially expressed in cancer. The most extensively studied MMP14/MT1-MMP is induced in various cancers along malignant transformation via pathways activated by mutations in tumor suppressors or proto-oncogenes and changes in tumor microenvironment including cellular heterogeneity, extracellular matrix composition, tissue oxygenation, and inflammation. Classically such induction involves transcriptional programs related to epithelial-to-mesenchymal transition. Besides inhibition by endogenous tissue inhibitors, MT-MMP activities are spatially and timely regulated at multiple levels by microtubular vesicular trafficking, dimerization/oligomerization, other interactions and localization in the actin-based invadosomes, in both tumor and the stroma. The functions of MT-MMPs are multifaceted within reciprocal cellular responses in the evolving tumor microenvironment, which poses the importance of these proteases beyond the central function as matrix scissors, and necessitates us to rethink MT-MMPs as dynamic signaling proteases of cancer. This article is part of a Special Issue entitled: Matrix Metalloproteinases edited by Rafael Fridman.

TIMPs: versatile extracellular regulators in cancer

A compelling long-term goal of cancer biology is to understand the crucial players during tumorigenesis in order to develop new interventions. Here, we review how the four non-redundant tissue inhibitors of metalloproteinases (TIMPs) regulate the pericellular proteolysis of a vast range of matrix and cell surface proteins, generating simultaneous effects on tumour architecture and cell signalling. Experimental studies demonstrate the contribution of TIMPs to the majority of cancer hallmarks, and human cancers invariably show TIMP deregulation in the tumour or stroma. Of the four TIMPs, TIMP1 overexpression or TIMP3 silencing is consistently associated with cancer progression or poor patient prognosis. Future efforts will align mouse model systems with changes in TIMPs in patients, will delineate protease-independent TIMP function, will pinpoint therapeutic targets within the TIMP-metalloproteinase-substrate network and will use TIMPs in liquid biopsy samples as biomarkers for cancer prognosis.

Antitumour and antiangiogenic activities of [Pt(O,O'-acac)(γ-acac)(DMS)] in a xenograft model of human renal cell carcinoma

BACKGROUND AND PURPOSE

It is thought that the mechanism of action of anticancer chemotherapeutic agents is mainly due to a direct inhibition of tumour cell proliferation. In tumour specimens, the endothelial cell proliferation rate increases, suggesting that the therapeutic effects of anticancer agents could also be attributed to inhibition of tumour angiogenesis. Hence, we investigated the potential effects of [Pt(O,O'-acac)(γ-acac)(DMS)] ([Pt(DMS)]), a new platinum drug for non-genomic targets, on human renal carcinoma and compared them with those of the well-established anticancer drug, cisplatin.

EXPERIMENTAL APPROACH

Tumour growth, tumour cell proliferation and microvessel density were investigated in a xenograft model of renal cell carcinoma, developed by injecting Caki-1 cells into BALB/c nude mice. The antiangiogenic potential of compounds was also investigated using HUVECs.

KEY RESULTS

Treatment of the Caki-1 cells with cisplatin or [Pt(DMS)] resulted in a dose-dependent inhibition of cell survival, but the cytotoxicity of [Pt(DMS)] was approximately fivefold greater than that of cisplatin. [Pt(DMS)] was much more effective than cisplatin at inhibiting tumour growth, proliferation and angiogenesis in vivo, as well as migration, tube formation and MMP1, MMP2 and MMP9 secretion of endothelial cells in vitro. Whereas, cisplatin exerted a greater cytotoxic effect on HUVECs, but did not affect tube formation or the migration of endothelial cells. In addition, treatment of the xenograft mice with [Pt(DMS)] decreased VEGF, MMP1 and MMP2 expressions in tumours.

CONCLUSIONS AND IMPLICATIONS

The antiangiogenic and antitumour activities of [Pt(DMS)] provide a solid starting point for its validation as a suitable candidate for further pharmacological testing.

Wnt1 Participates in Inflammation Induced by Lipopolysaccharide Through Upregulating Scavenger Receptor A and NF-kB

The study investigated the role of wnt1 in the inflammatory response initiated by lipolysaccharide (LPS), and analyzed the association between wnt1, NF-KB, and inflammatory factors. THP-1 cells were activated with phorbol-12-myristate-13-acetate (PMA) and treated with LPS to induce inflammation. THP-1 cells were transfected with wnt1siRNA and overexpression plasmid to explore the relationship among wnt1, SRA, and NF-KB. Inhibitor of β-catenin and siRNA of FZD1were used to investigate the signaling events involved in SRA activation induced by wnt1. Levels of NF-kB protein and inflammatory cytokines were assessed followingwnt1 siRNA and LPS treatment. PMA activation and LPS treatment of THP-1 cells increased wnt1 protein levels. Wnt1 promoted SRA expression through activation of canonical wnt pathway. Wnt1 increased NF-kB protein levels and enhanced the secretion of IL-6, TNF-α, and iNOS through binding to SRA. These findings suggest that wnt1 increased SRA and NF-kB protein levels and participated in the inflammatory response.

Nanodiamonds coupled with 5,7-dimethoxycoumarin, a plant bioactive metabolite, interfere with the mitotic process in B16F10 cells altering the actin organization

For the first time, we coupled reduced detonation nanodiamonds (NDs) with a plant secondary metabolite, citropten (5,7-dimethoxycoumarin), and demonstrated how this complex was able to reduce B16F10 tumor cell growth more effectively than treatment with the pure molecule. These results encouraged us to find out the specific mechanism underlying this phenomenon. Internalization kinetics and quantification of citropten in cells after treatment with its pure or ND-conjugated form were measured, and it was revealed that the coupling between NDs and citropten was essential for the biological properties of the complex. We showed that the adduct was not able to induce apoptosis, senescence, or differentiation, but it determined cell cycle arrest, morphological changes, and alteration of mRNA levels of the cytoskeletal-related genes. The identification of metaphasic nuclei and irregular disposition of β-actin in the cell cytoplasm supported the hypothesis that citropten conjugated with NDs showed antimitotic properties in B16F10 cells. This work can be considered a pioneering piece of research that could promote and support the biomedical use of plant drug-functionalized NDs in cancer therapy.

Merging allosteric and active site binding motifs: de novo generation of target selectivity and potency via natural-product-derived fragments

The de novo design of molecules from scratch with tailored biological activity is still the major intellectual challenge in chemical biology and drug discovery. Herein we validate natural-product-derived fragments (NPDFs) as excellent molecular seeds for the targeted de novo discovery of lead structures for the modulation of therapeutically relevant proteins. The application of this de novo approach delivered, in synergy with the combination of allosteric and active site binding motifs, highly selective and ligand-efficient non-zinc-binding (3: 4-{[5-(2-{[(3-methoxyphenyl)methyl]carbamoyl}eth-1-yn-1-yl)-2,4-dioxo-1,2,3,4-tetrahydropyrimidin-1-yl]methyl}benzoic acid) as well as zinc-binding (4: 4-({5-[2-({[3-(3-carboxypropoxy)phenyl]methyl}carbamoyl)eth-1-yn-1-yl]-2,4-dioxo-1,2,3,4-tetrahydropyrimidin-1-yl}methyl)benzoic acid) uracil-based MMP-13 inhibitors presenting IC₅₀ values of 11 nm (3: LE=0.35) and 6 nm (4: LE=0.31).

Remodeling of endogenous mammary epithelium by breast cancer stem cells

Poorly regulated tissue remodeling results in increased breast cancer risk, yet how breast cancer stem cells (CSC) participate in remodeling is unknown. We performed in vivo imaging of changes in fluorescent, endogenous duct architecture as a metric for remodeling. First, we quantitatively imaged physiologic remodeling of primary branches of the developing and regenerating mammary tree. To assess CSC-specific remodeling events, we isolated CSC from MMTV-Wnt1 (mouse mammary tumor virus long-term repeat enhancer driving Wnt1 oncogene) breast tumors, a well studied model in which tissue remodeling affects tumorigenesis. We confirm that CSC drive tumorigenesis, suggesting a link between CSC and remodeling. We find that normal, regenerating, and developing gland maintain a specific branching pattern. In contrast, transplantation of CSC results in changes in the branching patterns of endogenous ducts while non-CSC do not. Specifically, in the presence of CSC, we identified an increased number of branches, branch points, ducts which have greater than 40 branches (5/33 for CSC and 0/39 for non-CSC), and histological evidence of increased branching. Moreover, we demonstrate that only CSC implants invade into surrounding stroma with structures similar to developing mammary ducts (nine for CSC and one for non-CSC). Overall, we demonstrate a novel approach for imaging physiologic and pathological remodeling. Furthermore, we identify unique, CSC-specific, remodeling events. Our data suggest that CSC interact with the microenvironment differently than non-CSC, and that this could eventually be a therapeutic approach for targeting CSC.

Betaine inhibits in vitro and in vivo angiogenesis through suppression of the NF-κB and Akt signaling pathways

Angiogenesis is defined as the formation of new blood vessels form existing vessels surrounding a tumor. The process of angiogenesis is an important step for tumor growth and metastasis, as is inflammation. Thus, angiogenesis inhibitors that suppress inflammation have been studied as an anticancer treatment. Recently, many research groups have investigated the anti-angiogenic activity of natural compounds since some have been demonstrated to have anticancer properties. Among many natural compounds, we focused on betaine, which is known to suppress inflammation. Betaine, trimethylglycine (TMG), was first discovered in the juice of sugar beets and was later shown to be present in wheat, shellfish and spinach. In Southeast Asia, betaine is used in traditional oriental medicine for the treatment of hepatic disorders. Here, we report the anti-angiogenic action of betaine. Betaine inhibited in vitro angiogenic cascade, tube formation, migration and invasion of human umbilical vein endothelial cells (HUVECs). Betaine also inhibited in vivo angiogenesis in the mouse Matrigel plug assay. The mRNA expression levels of basic fibroblast growth factor (bFGF), matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9) in HUVECs were decreased by betaine treatment. In addition, betaine suppressed NF-κB and Akt activation.

The history of matrix metalloproteinases: milestones, myths, and misperceptions

Since the discovery of tadpole collagenase in 1962, the matrix metalloproteinase (MMP) family has emerged as a significant proteinase group with recognized effects on the cardiovascular system. Over the last 40 years, many milestones have been achieved, from the identification of the first MMP, to the generation of the first MMP cDNA clone and null mouse, to the clinical approval of the first MMP inhibitor. Over the years, a few myths and misunderstandings have interwoven into the truths. In this review, we will discuss the major milestones of MMP research, as well as review the misinterpretations and misperceptions that have evolved. Clarifying the confusions and dispelling the myths will both provide a better understanding of MMP properties and functions and focus the cardiovascular field on the outstanding research questions that need to be addressed.

Genome-wide analysis of HMGA2 transcription factor binding sites by ChIP on chip in gastric carcinoma cells

High mobility group protein A2 (HMGA2) is an architectural transcription factor that plays an important role in development and progression of malignant neoplasias. Recently, some studies reported that HMGA2 is also implicated in epithelial-mesenchymal transitions (EMT) and cancer stem cells. But the underlying mechanisms of these conditions are poorly understood. Therefore, we established an EMT model of gastric carcinoma cells by overexpressing HMGA2 in vitro, then global mapping of HMGA2 potential transcription factor binding sites was identified by promoter microarray in these cells, and the date obtained from the microarrays were validated via chromatin immunoprecipitation-PCR (ChIP-PCR) and real-time PCR. HMGA2 potential target genes were classified in KEGG database and Gene Ontology (GO) analyses. To our knowledge, this is the first report on the genome-wide analysis of HMGA2 downstream direct targets, and these findings will be valuable in understanding the roles of HMGA2 in EMT.

Matrix metalloproteinases: protective roles in cancer

The original notion that matrix metalloproteinases (MMPs) act as tumour and metastasis-promoting enzymes by clearing a path for tumour cells to invade and metastasize has been challenged in the last decade. It has become clear that MMPs are involved in numerous steps of tumour progression and metastasis, and hence are now considered to be multifaceted proteases. Moreover, more recent experimental evidence indicates that some members of the MMP family behave as tumour-suppressor enzymes and should therefore be regarded as anti-targets in cancer therapy. The complexity of the pro- and anti-tumorigenic and -metastatic functions might partly explain why broad-spectrum MMP inhibitors failed in phase III clinical trials. This review will provide a focussed overview of the published data on the tumour-suppressive behaviour of MMPs.

The expression of interleukin (IL)-17 and IL-17 receptor and MMP-9 in human pituitary adenomas

The IL-17 plays a crucial role in the invasion of tumors. However, the effects of IL-17 on the invasion of human pituitary adenomas are still unknown. The current study is designed to investigate the possible involvement of IL-17 in the invasion of adenomas. By collecting invasive and non-invasive pituitary adenomas, the mRNA and protein levels of IL-17, IL-17R and MMP-9 are investigated. The results obtained from IHC showed that the strong positive rate and the total positive rate of IL-17, IL-17R and MMP-9 expression cells in the non-invasive group were 17.1 and 51.43%, 14.3 and 54.3%, 17.1 and 57.1%, respectively. In contrast, the strong positive rate and the total positive rate of the invasive group were significantly higher than that of the non-invasive group, which were 37.5 and 82.5%, 52.5 and 87.5%, 67.5 and 92.5%, respectively. Meanwhile, the serum IL-17 level in the invasive pituitary adenomas patients was significantly higher than in the non-invasive groups (P < 0.05). Furthermore, the mRNA levels of IL-17, IL-17R and MMP-9 were also higher in the invasive group than in the non-invasive group with statistical differences (P < 0.05), and where the expression levels of IL-17 and IL-17R had positive correlation with that of MMP-9 in the invasive group. These results suggested that IL-17 may promote the invasion of pituitary adenomas.

PPARgamma and Proline Oxidase in Cancer

Proline is metabolized by its own specialized enzymes with their own tissue and subcellular localizations and mechanisms of regulation. The central enzyme in this metabolic system is proline oxidase, a flavin adenine dinucleotide-containing enzyme which is tightly bound to mitochondrial inner membranes. The electrons from proline can be used to generate ATP or can directly reduce oxygen to form superoxide. Although proline may be derived from the diet and biosynthesized endogenously, an important source in the microenvironment is from degradation of extracellular matrix by matrix metalloproteinases. Previous studies showed that proline oxidase is a p53-induced gene and its overexpression can initiate proline-dependent apoptosis by both intrinsic and extrinsic pathways. Another important factor regulating proline oxidase is peroxisome proliferator activated receptor gamma (PPARγ). Importantly, in several cancer cells, proline oxidase may be an important mediator of the PPARγ-stimulated generation of ROS and induction of apoptosis. Knockdown of proline oxidase expression by antisense RNA markedly decreased these PPARγ-stimulated effects. These findings suggest an important role in the proposed antitumor effects of PPARγ. Moreover, it is possible that proline oxidase may contribute to the other metabolic effects of PPARγ.

Matrix metalloproteinases as master regulators of the vicious cycle of bone metastasis

Bone remodeling is a delicate balancing act between the bone matrix synthesizing osteoblasts and bone resorbing osteoclasts. Active bone metastases typically subvert this process to generate lesions that are comprised of extensive areas of pathological osteogenesis and osteolysis. The resultant increase in bone matrix remodeling enhances cytokine/growth factor bioavailability thus creating a vicious cycle that stimulates tumor progression. Given the extent of matrix remodeling occurring in the tumor-bone microenvironment, the expression of matrix metalloproteinases (MMPs) would be expected, since collectively they have the ability to degrade all components of the extracellular matrix (ECM). However, in addition to being "matrix bulldozers", MMPs control the bioavailability and bioactivity of factors such as RANKL and TGFβ that have been described as crucial for tumor-bone interaction, thus implicating MMPs as key regulators of the vicious cycle of bone metastases.

Stromelysin-1 (MMP-3) is a target and a regulator of Wnt1-induced epithelial-mesenchymal transition (EMT)

Matrix metalloproteinases (MMPs) play a well-defined role in later stages of tumor progression. However, there has been evidence that they also contribute to earlier stages of malignant transformation. The Wnt signaling transduction pathway plays a critical role in development and in the pathogenesis of many epithelial cancers. Here we have used Wnt1-induced epithelial-mesenchymal transition (EMT) in C57MG murine mammary epithelial cells to study the role of MMPs in this early step of malignant progression. Overexpression of Wnt1 in C57MG cells promoted EMT, the translocation of β-catenin from the cell membrane to the nucleus and its transcriptional activity, cell proliferation and cell motility. Simultaneously, we observed an increased expression of stromelysin-1 (MMP-3) and a 5.5-fold increase in MMP-3 promoter activity in C57MG cells expressing Wnt1 compared with C57MG cells. Treatment of Wnt-overexpressing cells with MMP inhibitor AG3340 decreased MMP-3 expression. We also found evidence that MMP-3 and Wnt3a cooperate in enhancing the transcriptional activity of β-catenin in C57MG cells. Consistently, the effects of Wnt1 on EMT, proliferation and migration were inhibited by MMP inhibitors, or upon downregulation of MMP-3 by siRNA. These results suggest that MMP-3 is both a direct transcriptional target and a necessary contributor of the Wnt/β-catenin signaling pathway.

Down-regulation of connective tissue growth factor by inhibition of transforming growth factor beta blocks the tumor-stroma cross-talk and tumor progression in hepatocellular carcinoma

Tumor-stroma interactions in hepatocellular carcinoma (HCC) are of key importance to tumor progression. In this study, we show that HCC invasive cells produce high levels of connective tissue growth factor (CTGF) and generate tumors with a high stromal component in a xenograft model. A transforming growth factor beta (TGF-beta) receptor inhibitor, LY2109761, inhibited the synthesis and release of CTGF, as well as reducing the stromal component of the tumors. In addition, the TGF-beta-dependent down-regulation of CTGF diminished tumor growth, intravasation, and metastatic dissemination of HCC cells by inhibiting cancer-associated fibroblast proliferation. By contrast, noninvasive HCC cells were found to produce low levels of CTGF. Upon TGF-beta1 stimulation, noninvasive HCC cells form tumors with a high stromal content and CTGF expression, which is inhibited by treatment with LY2109761. In addition, the acquired intravasation and metastatic spread of noninvasive HCC cells after TGF-beta1 stimulation was blocked by LY2109761. LY2109761 interrupts the cross-talk between cancer cells and cancer-associated fibroblasts, leading to a significant reduction of HCC growth and dissemination. Interestingly, patients with high CTGF expression had poor prognosis, suggesting that treatment aimed at reducing TGF-beta-dependent CTGF expression may offer clinical benefits.

CONCLUSION

Taken together, our preclinical results indicate that LY2109761 targets the cross-talk between HCC and the stroma and provide a rationale for future clinical trials.

Navigating ECM barriers at the invasive front: the cancer cell-stroma interface

A seminal event in cancer progression is the ability of the neoplastic cell to mobilize the necessary machinery to breach surrounding extracellular matrix barriers while orchestrating a host stromal response that ultimately supports tissue-invasive and metastatic processes. With over 500 proteolytic enzymes identified in the human genome, interconnecting webs of protease-dependent and protease-independent processes have been postulated to drive the cancer cell invasion program via schemes of daunting complexity. Increasingly, however, a body of evidence has begun to emerge that supports a unifying model wherein a small group of membrane-tethered enzymes, termed the membrane-type matrix metalloproteinases (MT-MMPs), plays a dominant role in regulating cancer cell, as well as stromal cell, traffic through the extracellular matrix barriers assembled by host tissues in vivo. Understanding the mechanisms that underlie the regulation and function of these metalloenzymes as host cell populations traverse the dynamic extracellular matrix assembled during neoplastic states should provide new and testable theories regarding cancer invasion and metastasis.

Wnt signaling activation and mammary gland hyperplasia in MMTV-LRP6 transgenic mice: implication for breast cancer tumorigenesis

Although Wnt signaling activation is frequently observed in human breast cancer, mutations in the genes encoding intracellular components of the Wnt signaling pathway are rare. We found that expression of Wnt signaling co-receptor LRP6 is up-regulated in a subset of human breast cancer tissues and cell lines. To examine whether overexpression of LRP6 in mammary epithelial cells is sufficient to activate Wnt signaling and promote cell proliferation, we generated transgenic mice overexpressing LRP6 in mammary epithelial cells driven by the mouse mammary tumor virus (MMTV) promoter. We found that mammary glands from MMTV-LRP6 mice exhibit significant Wnt activation evidenced by the translocation of β-catenin from membrane to cytoplasmic/nuclear fractions. Expression of several Wnt-target genes including Axin2, Cyclin D1 and c-Myc was also increased in MMTV-LRP6 mice. More importantly, mammary glands from virgin MMTV-LRP6 mice exhibit significant hyperplasia, a precursor to breast cancer, when compared to wild-type littermate controls. Several matrix metalloproteinases are up-regulated in MMTV-LRP6 mice that could contribute to the hyperplasia phenotype. Our results suggest that Wnt signaling activation at the cell surface receptor level can contribute to breast cancer tumorigenesis.

Downregulation of SFRP5 expression and its inverse correlation with those of MMP-7 and MT1-MMP in gastric cancer

Background

As negative regulators in Wnt signaling, Secreted Frizzled-Related Proteins (SFRPs) are downregulated in a series of human cancers; and specifically, some matrix metalloproteinases (MMPs), including MMP-2, MMP-7, MMP-9 and MT1-MMP, are frequently overexpressed in gastric cancer. The aim of this study is to determine the expression status of SFRP5 in gastric cancer and explore the correlation between both the expression of SFRP5 and that of these MMPs in this cancer.

Methods

Expression of SFRP5, MMP-2, MMP-7, MMP-9 and MT1-MMP was determined by real-time PCR, RT-PCR or Western blotting. The methylation status of SFRP5 was detected by Methylation-specific PCR (MSP). Cell lines with SFRP5 methylation were demethylated by a DNA methyltransferase inhibitor 5-Aza-2'-deoxycytidine (DAC). KatoIII cells were transfected with pcDNA3.1 SFRP5 vector to strengthen SFRP5 expression. To abrogate SFRP5 expression in MKN1 cells, SFRP5 RNAi plamid was used to transfect them.

Results

SFRP5 expression was remarkably downregulated in 24 of 32 primary gastric cancer specimens, and even was not detectable in 5 of 8 gastric cancer cell lines. MMP-7 and MT1-MMP mRNA showed a stronger expression in these 24 specimens compared to the other 8 specimens. They also showed higher levels in gastric cancer cell lines AGS and NCI-N87 which had no SFRP5 expression, compared to MKN1 with strong SFRP5 expression. However, they were significantly downregulated, with SFRP5 expression restored in AGS and NCI-N87; and were considerably upregulated with it abrogated in MKN1.

Conclusion

The results indicate there are frequent occurrences of downregualtion of SFRP5 expression in gastric cancer, primarily due to SFRP5 methylation. It seems to be responsible for the upregulation of MMP-7 expression and MT1-MMP expression on the ground that they are inversely correlated with SFRP5 expression.

The tumour microenvironment: a novel target for cancer therapy

Cancer therapy is in the midst of a major paradigm shift. Traditionally, cancer treatments have focused on tumour cells. However, studies over the past few decades have demonstrated that cancer is a vastly complex entity with multiple components affecting a tumour's growth, invasion and metastasis. These components, collectively termed the 'tumour microenvironment', include endothelial cells, pericytes, fibroblasts, inflammatory cells, leucocytes and elements of the extracellular matrix (ECM). Biological agents that target components of the tumour microenvironment may provide an interesting alternative to traditional tumour cell-directed therapy. Because of the complexity of the tumour milieu, the most beneficial therapy will likely involve the combination of one or more agents directed at this new target. This review highlights recent preclinical and clinical studies involving agents that target tumour vasculature, leucocytes, pericytes, cancer-associated fibroblasts and ECM components. We pay particular attention to combination therapies targeting multiple components of the tumour microenvironment, and aim to demonstrate that this strategy holds promise for the future of cancer treatment.

Metastasis is strongly reduced by the matrix metalloproteinase inhibitor Galardin in the MMTV-PymT transgenic breast cancer model

Matrix metalloproteinases (MMP) have several roles that influence cancer progression and dissemination. However, low molecular weight metalloproteinase inhibitors (MPI) have not yet been tested in transgenic/spontaneous metastasis models. We have tested Galardin/GM6001, a potent MPI that reacts with most MMPs, in the MMTV-PymT transgenic breast cancer model. We followed a cohort of 81 MMTV-PymT transgenic mice that received Galardin, placebo, or no treatment. Galardin treatment was started at age 6 weeks with 100 mg/kg/d, and all mice were killed at age 13.5 weeks. Galardin treatment significantly reduced primary tumor growth. Final tumor burden in Galardin-treated mice was 1.69 cm3 compared with 3.29 cm3 in placebo-treated mice (t test, P = 0.0014). We quantified the total lung metastasis volume in the same cohort of mice. The median metastasis volume was 0.003 mm(3) in Galardin-treated mice compared with 0.56 mm(3) in placebo-treated mice (t test, P < 0.0001). Thus, metastasis burden was reduced more than 100-fold, whereas primary tumor size was reduced only 2-fold. We also found that primary tumors from Galardin-treated mice exhibited a lower histopathologic tumor grade, increased collagen deposition, and increased MMP-2 activity. MMPs are known to have tumor-promoting and tumor-inhibitory effects, and several clinical trials of broad-spectrum MPIs have failed to show promising effects. The very potent antimetastatic effect of Galardin in the MMTV-PymT model does, however, show that it may be possible to find broad-spectrum MPIs with favorable inhibition profiles, or perhaps combinations of monospecific MPIs, for future clinical application.

The activated stroma index is a novel and independent prognostic marker in pancreatic ductal adenocarcinoma

BACKGROUND AND AIMS

Pancreatic ductal adenocarcinoma (PDAC) is a highly desmoplastic tumor with an innate resistance to therapy. Pancreatic stellate cells (PSCs) produce this excessively desmoplastic microenvironment. The impact of PSC activity on PDAC behavior in vivo is analyzed.

METHODS

233 patients who underwent surgery for PDAC were evaluated by immunohistochemistry using antibodies against alpha-smooth muscle actin as a marker of PSC activity. Aniline was used to stain collagen deposition. The ratio of alpha-smooth muscle actin-stained area to collagen-stained area was defined as the activated stroma index (ASI). Survival analysis was performed using the Kaplan-Meier method. Prognostic factors were determined in a multivariable analysis using a Cox proportional hazards model.

RESULTS

Four major patterns of collagen deposition were defined with regard to PSC activity. The combination of high stromal activity and low collagen deposition was associated with a worse prognosis, whereas the combination of high collagen deposition and low stromal activity indicated a better prognosis. Patients with the lowest ASI had the best median survival rate (25.7 mo). The highest ASI was found in patients with the worst median survival rate (16.1 mo; P = .007; lowest vs highest ASI: hazard ratio, 1.61; 95% confidence interval, 1.014-2.562). ASI was an independent prognostic marker in multivariable survival analysis comparable with the nodal status of cancer.

CONCLUSIONS

The activated stroma index is a novel independent prognostic marker in PDAC in cases undergoing surgery. This finding highlights the impact of the microenvironment in cancer progression and on patient survival.

Hypermethylation and aberrant expression of secreted fizzled-related protein genes in pancreatic cancer

AIM: To determine the methylation status and aberrant expression of some secreted frizzled-related protein (SFRP) genes in pancreatic cancer and explore their role in pancreatic carcinogenesis.

METHODS: Methylation status and expression of SFRP genes were detected by methylation-specific PCR (MSPCR) and reverse-transcription PCR (RT-PCR) respectively.

RESULTS: The frequencies of methylation for SFRP genes 1, 2, 4, 5 were 70%, 48.3%, 60% and 76.7% in pancreatic cancer samples, and 21.7%, 20%, 10% and 36.7% in matched cancer adjacent normal tissue samples, respectively (χ² = 28.23, P < 0.0001 for SFRP gene 1; χ² = 10.71, P = 0.001 for SFRP gene 2; χ² = 32.97, P < 0.0001 for SFRP gene 4; χ² = 19.55, P < 0.0001 for SFRP gene 5). Expression loss of SFRP genes 1, 2, 4 and 5 was found in 65%, 40%, 55% and 71.7% of 60 pancreatic cancer samples, and 25%, 15%, 18.3% and 31.7% of matched cancer adjacent normal tissue samples, respectively (χ² = 19.39, P < 0.0001 for SFRP gene 1; χ² = 9.40, P = 0.002 for SFRP gene 2; χ² = 17.37, P < 0.0001 for SFRP gene 4; χ² = 19.22, P < 0.0001 for SFRP gene 5). SFRP gene 1 was methylated but not expressed in PC-3 and PANC-1, SFRP gene 2 was methylated but not expressed in PANC-1 and CFPAC-1, SFRP gene 4 was methylated but not expressed in PC-3, and SFRP gene 5 was methylated but not expressed in CFPAC-1.

CONCLUSION: Hypermethylation and aberrant expression of SFRP genes are common in pancreatic cancer, which may be involved in pancreatic carcinogenesis.

The tumor microenvironment: regulation by MMP-independent effects of tissue inhibitor of metalloproteinases-2

Proteolytic remodeling of the extracellular matrix is an important component of disease progression in many chronic disease states and is the initiating event in the formation of the tumor microenvironment in cancer. It is the balance of extracellular matrix degrading enzymes, the matrix metalloproteinases (MMPs) and their endogenous inhibitors that determine the extent of tissue remodeling. Unchecked MMP activity can result in significant tissue damage, facilitate disease progression and is associated with host responses to pathologic injury such as angiogenesis and inflammation. The tissue inhibitors of metalloproteinases (TIMPs) have been shown to regulate MMP activity. However, recent findings demonstrate that the tissue inhibitor of metalloproteinases-2 (TIMP-2) inhibits the mitogenic response of human microvascular endothelial cells to growth factors, such as VEGF-A and FGF-2 in vitro and angiogenesis in vivo. The mechanism of this effect is independent of metalloproteinase inhibition. Our lab is the first to demonstrate a cell-surface signaling receptor for a member of the TIMP family and suggest that TIMP-2 functions to regulate cellular responses to growth factors. These new findings are discussed in terms of a model of TIMP-2 regulation of cellular functions in the tumor microenvironment.

Inflammation and breast cancer: metalloproteinases as common effectors of inflammation and extracellular matrix breakdown in breast cancer

Two rapidly evolving fields are converging to impact breast cancer: one has identified novel substrates of metalloproteinases that alter immune cell function, and the other has revealed a role for inflammation in human cancers. Evidence now shows that the mechanisms underlying these two fields interact in the context of breast cancer, providing new opportunities to understand this disease and uncover novel therapeutic strategies. The metalloproteinase class of enzymes is well studied in mammary gland development and physiology, but mostly in the context of extracellular matrix modification. Aberrant metalloproteinase expression has also been implicated in breast cancer progression, where these genes act as tumor modifiers. Here, we review how the metalloproteinase axis impacts mammary physiology and tumorigenesis and is associated with inflammatory cell influx in human breast cancer, and evaluate its potential as a regulator of inflammation in the mammary gland.

Intrinsic genetic characteristics determine tumor-modifying capacity of fibroblasts: matrix metalloproteinase-3 5A/5A genotype enhances breast cancer cell invasion

BACKGROUND

Stromal fibroblasts can contribute to tumor invasion through the release of matrix metalloproteinases (MMPs). Population studies have suggested that single nucleotide polymorphisms (SNPs) in MMP genes influence levels of expression and may be associated with breast cancer risk and with disease progression. This study directly examined the impact of MMP SNP genotype on the ability of host fibroblasts to promote tumor cell invasion.

METHODS

Primary breast fibroblasts were isolated from patients with (n = 13) or without (n = 19) breast cancer, and their ability to promote breast cancer cell invasion was measured in in vitro invasion assays. Fibroblast invasion-promoting capacity (IPC) was analyzed in relation to donor type (tumor or non-tumor patient), MMP-1, MMP-3, and MMP-9 SNP genotype and MMP activity using independent samples t test and analysis of variance. All statistical tests were two-sided.

RESULTS

Tumor-derived fibroblasts promoted higher levels of invasion than normal fibroblasts (p = 0.041). When IPC was related to genotype, higher levels of IPC were generated by tumor fibroblasts with the high-expressing MMP-3 5A/5A genotype compared with the 5A/6A and 6A/6A genotypes (p = 0.05 and 0.07, respectively), and this was associated with enhanced MMP-3 release. The functional importance of MMP-3 was demonstrated by enhanced invasion in the presence of recombinant MMP-3, whereas reduction occurred in the presence of a specific MMP-3 inhibitor. An inverse relationship was demonstrated between fibroblast IPC and the high-expressing MMP-1 genotype (p = 0.031), but no relationship was seen with MMP-9 SNP status. In contrast, normal fibroblasts showed no variation in IPC in relation to MMP genotype, with MMP-3 5A/5A fibroblasts exhibiting significantly lower levels of IPC than their tumor-derived counterparts (p = 0.04).

CONCLUSION

This study has shown that tumor-derived fibroblasts exhibit higher levels of IPC than normal fibroblasts and that the MMP-3 5A/5A genotype contributes to this through enhanced MMP-3 release. Despite a high-expressing genotype, normal fibroblasts do not exhibit higher IPC or enhanced MMP release. This suggests that more complex changes occur in tumor-derived fibroblasts, enabling full expression of the MMP SNP genotype and these possibly are epigenetic in nature. The results do suggest that, in women with breast cancer, a high-expressing MMP-3 genotype may promote tumor progression more effectively.

Nucleolin binds specifically to an AP-1 DNA sequence and represses AP1-dependent transactivation of the matrix metalloproteinase-13 gene

Transcriptional regulation via activator protein-1 (AP-1) protein binding to AP-1 binding sites within gene promoter regions of AP-1 target genes plays a key role in controlling cellular invasion, proliferation, and oncogenesis, and is important to pathogenesis of arthritis and cardiovascular disease. To identify new proteins that interact with the AP-1 DNA binding site, we performed the DNA affinity chromatography-based Nucleotide Affinity Preincubation Specificity TEst of Recognition (NAPSTER) assay, and discovered a 97 kDa protein that binds in vitro to a minimal AP-1 DNA sequence element. Mass spectrometric fragmentation sequencing determined that p97 is nucleolin. Immunoblotting of DNA affinity-purified material with anti-nucleolin antibodies confirmed this identification. Nucleolin also binds the AP-1 site in gel shift assays. Nucleolin interacts in NAPSTER with the AP-1 site within the promoter sequence of the metalloproteinase-13 gene (MMP-13), and binds in vivo in chromatin immunoprecipitation assays in the vicinity of the AP-1 site in the MMP-13 promoter. Overexpression of nucleolin in human HeLa cervical carcinoma cells significantly represses AP-1 dependent gene transactivation of a minimal AP-1 reporter construct and of an MMP-13 promoter reporter sequence. This is the first report of nucleolin binding and transregulation at the AP-1 site.

Retinoic acid inhibits beta-catenin through suppression of Cox-2: a role for truncated adenomatous polyposis coli

Mutations in adenomatous polyposis coli (APC) underlie the earliest stages of colorectal carcinogenesis. Consequences of APC mutation include stabilization of beta-catenin, dysregulation of cyclooxygenase-2 (COX-2) expression, and loss of retinoic acid production, events with poorly defined interactions. Here we showed that treatment of zebrafish expressing a truncated form of Apc with either retinoic acid or a selective COX-2 inhibitor decreased beta-catenin protein levels and downstream signaling events. Interestingly, the destruction of beta-catenin in apc mutant embryos following Cox-2 inhibition required the presence of truncated Apc. These findings support roles for retinoic acid and Cox-2 in regulating the stability of beta-catenin following Apc loss. Furthermore, truncated Apc appears to retain the ability to target beta-catenin for destruction, but only in the absence of Cox-2 activity. This novel function of truncated Apc may provide a molecular basis for the efficacy of COX-2 inhibitors in the treatment of colon cancer.

Conjugated linoleic acid alters matrix metalloproteinases of metastatic mouse mammary tumor cells

Conjugated linoleic acid (CLA) is a group of linoleic acid derivatives that has been implicated in animal studies to reduce a number of components of mammary tumorigenesis. Previously, we showed that CLA could alter the latency and metastasis of the highly metastatic transplantable line 4526 mouse mammary tumor. Several possible mechanisms have been proposed for the actions of CLA, but here we assessed how CLA may act to alter the expression and activity of matrix-modifying proteins within tumors from line 4526. In vitro, highly metastatic mouse mammary tumor cells had significantly decreased invasiveness after treatment with CLA, an indication that matrix-modifying proteins may have been altered. Using these same highly metastatic cells, primary tumors were grown in mice of separate groups fed 0, 0.1, 0.5, and 1% CLA (wt:wt) and evaluated for their levels and activities of matrix-modifying enzymes, enzyme inhibitors, and enzyme activators. The addition of CLA to the diet increased steady-state levels of messenger RNA (mRNA) of the matrix metalloproteinases (MMP) -2 and -9 in primary tumors removed from mice. However, western analysis revealed that although relative levels of the proform of MMP-9 were consistent with the mRNA observations, MMP-2 proform levels were actually decreased by dietary CLA. The activity of MMP-2 was barely detectable, but gelatin zymography and an in vitro activity assay showed that MMP-9 activity was significantly decreased by CLA. The steady-state mRNA and protein levels of tissue inhibitors of metalloproteinase-1 (TIMP-1) and TIMP-2, natural inhibitors of MMP, were increased at higher dietary CLA levels relative to low or no CLA. Suppression of MMP activity, therefore, may be 1 pathway through which CLA reduces tumor invasion and spread.

Morphogens, morphostats, microarchitecture and malignancy

Morphogenetic fields organize tissue morphology in the embryo. By analogy, morphostatic fields maintain normal cell behaviour and normal tissue microarchitecture in the adult. The most prominent feature of cancer is the disruption of tissue microarchitecture. Cancer occurs much more frequently when morphostatic influences fail (metaplasia) or at the junction of two different morphostatic fields. This Review will describe what we know about morphostats and morphostasis, discuss the evidence for the role of disruption of morphostasis in malignancy, and address some testable hypotheses.

Hypermethylation and aberrant expression of Wnt antagonist secreted frizzled-related protein 1 in gastric cancer

AIM: To identify the methylation of secreted frizzled-related protein 1 (SFRP1) in gastric cancer and to investigate the aberrant expression of SFRP1 and its correlation with the clinical pathological features of patients.

METHODS: We determined SFRP1 methylation and SFRP1 mRNA expression in 3 gastric cancer cell lines SGC-7901, BGC-823, HGC-27, from 52 primary gastric cancer specimens and matched tumor adjacent tissue specimens by methylation-specific (MSP) PCR and RT-PCR respectively. Fisher’s exact test was used to analyze the statistical association between clinical pathological data and aberrant expression of SFRP1.

RESULTS: In 3 cancer cell lines, BGC-823 and HGC-27 had methylated SFRP1 and lost SFRP1 mRNA expression. After treatment of BGC-823 and HGC-27 with the demethylating agent, 5-aza-2’-deoxycytidine, SFRP1 was re-expressed. In 52 primary gastric cancer specimens and matched tumor adjacent tissue specimens, hypermethylation of SFRP1 was detected in 23 (44%) and 8 (15%) specimens respectively (χ² = 10.34, P < 0.01). Loss of SFRP1 expression was detected in 17(33%) and 6 (12%) specimens respectively (χ² = 6.75, P < 0.01). There was a significant correlation between SFRP1 hypermethylation and SFRP1 expression loss. SFRP1 expression was also correlated significantly with tumor stage and lymph node status, but not with patient sex, age and histological type.

CONCLUSION: SFRP1 inactivation is a common and early event caused mainly by hypermethylation in gastric cancer. SFRP1 expression loss may be correlated with tumor metastasis in primary gastric cancer.

Primary administration of Lactobacillus johnsonii NCC533 in weaning period suppresses the elevation of proinflammatory cytokines and CD86 gene expressions in skin lesions in NC/Nga mice

The administration of probiotic lactic acid bacteria (LAB) has been studied for its potential to prevent atopic dermatitis (AD). The objective of this study was to assess the inhibitory mechanism of a skin lesion by LAB using an experimental model that we previously demonstrated in NC/Nga mice. Lactobacillus johnsonii NCC533 (La1) was administered orally to the La1 group from 20 to 22 days after birth, while phosphate-buffered saline was given to the control group. After the induction of skin lesions in 6-week-old mice, the expression of genes supposedly involved in AD was evaluated. Gene expression of the proinflammatory cytokines [interleukin-8 (IL-8), IL-12 and IL-23] was significantly enhanced in the lesional skin of the control group by the induction of the lesion, whereas gene expression of those in the La1 group was not elevated. Interestingly, expression of the costimulatory molecule CD86 showed a pattern similar to the expression of the cytokines in the lesional skin. Moreover, the La1 group showed a significantly lower gene expression of CD86 in Peyer's patches and mesenteric lymph nodes than the control group. The suppression of proinflammatory cytokines and CD86 by primary administration of La1 may significantly contribute to the inhibitory effect on the skin lesion.

Extracellular proteolysis in transgenic mouse models of breast cancer

Growth and invasion of breast cancer require extracellular proteolysis in order to physically restructure the tissue microenvironment of the mammary gland. This pathological tissue remodeling process depends on a collaboration of epithelial and stromal cells. In fact, the majority of extracellular proteases are provided by stromal cells rather than cancer cells. This distinct expression pattern is seen in human breast cancers and also in transgenic mouse models of breast cancer. The similar expression patterns suggest that transgenic mouse models are ideally suited to study the role of extracellular proteases in cancer progression. Here we give a status report on protease intervention studies in transgenic models. These studies demonstrate that proteases are involved in all stages of breast cancer progression from carcinogenesis to metastasis. Transgenic models are now beginning to provide vital mechanistic insight that will allow us to combat breast cancer invasion and metastasis with new protease-targeted drugs.

[The role of matrix metalloproteinases and tissue inhibitors of metalloproteinases in invasion of tumours of neuroepithelial tissue]

Tumour invasion requires degradation of extracellular matrix components and migration of cells through degraded structures into surrounding tissues. Matrix metalloproteinases (MMP) constitute a family of zinc and calcium-dependent endopeptidases that play a key role in the breakdown of extracellular matrix, and in processing of cytokines, growth factors, chemokines and cell surface receptors. Their activity is regulated at the levels of transcription, activation and inhibition by tissue inhibitors of metalloproteinases (TIMP). Changes in expression of MMP and TIMP are implicated in tumour invasion, because they may contribute to both migration of tumour cells and angiogenesis. Alterations of MMP expression observed in brain tumours arouse interest in the development and evaluation of synthetic matrix metalloproteinase inhibitors as antitumour agents.

MUC1 alters oncogenic events and transcription in human breast cancer cells

Introduction

MUC1 is an oncoprotein whose overexpression correlates with aggressiveness of tumors and poor survival of cancer patients. Many of the oncogenic effects of MUC1 are believed to occur through interaction of its cytoplasmic tail with signaling molecules. As expected for a protein with oncogenic functions, MUC1 is linked to regulation of proliferation, apoptosis, invasion, and transcription.

Methods

To clarify the role of MUC1 in cancer, we transfected two breast cancer cell lines (MDA-MB-468 and BT-20) with small interfering (si)RNA directed against MUC1 and analyzed transcriptional responses and oncogenic events (proliferation, apoptosis and invasion).

Results

Transcription of several genes was altered after transfection of MUC1 siRNA, including decreased MAP2K1 (MEK1), JUN, PDGFA, CDC25A, VEGF and ITGAV (integrin α_v), and increased TNF, RAF1, and MMP2. Additional changes were seen at the protein level, such as increased expression of c-Myc, heightened phosphorylation of AKT, and decreased activation of MEK1/2 and ERK1/2. These were correlated with cellular events, as MUC1 siRNA in the MDA-MB-468 line decreased proliferation and invasion, and increased stress-induced apoptosis. Intriguingly, BT-20 cells displayed similar levels of apoptosis regardless of siRNA, and actually increased proliferation after MUC1 siRNA.

Conclusion

These results further the growing knowledge of the role of MUC1 in transcription, and suggest that the regulation of MUC1 in breast cancer may be more complex than previously appreciated. The differences between these two cell lines emphasize the importance of understanding the context of cell-specific signaling events when analyzing the oncogenic functions of MUC1, and caution against generalizing the results of individual cell lines without adequate confirmation in intact biological systems.