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BInduced Matrix Metalloproteinase-9 Promoter Activation: Implications for Soft Tissue Sarcoma Growth and Metastasis
Departments of 1 Surgical Oncology, 2 Cancer Biology, and 3 Pathology, The University of Texas M.D. Anderson Cancer Center, Houston, Texas
Requests for reprints: Dina Lev, Department of Cancer Biology, Unit 173, The University of Texas M.D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030. Phone: 713-792-1637; Fax: 713-794-0722. E-mail: dlev{at}mdanderson.org
| Abstract |
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B (NF-
B) site. Mutating this NF-
B binding site eliminated the wtp53-repressive effect. Electrophoretic mobility shift assays confirmed decreased NF-
B binding in STS cells in the presence of wtp53. Our findings suggest a role for MMP-9 in STS progression and expand the role of p53 in molecular control of STS growth and metastasis. Therapeutic interventions in human STS targeting MMP-9 activity directly or via reintroduction of wtp53 merit further investigation. (Mol Cancer Res 2006;4(11):80310) | Introduction |
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A potential target is the matrix metalloproteinase (MMP) family, consisting of numerous proteases separable by substrate specificity, inhibitor, and extracellular membrane binding efficiency. MMPs are implicated in invasion and angiogenesis (3). MMP-9 (gelatinase B), the focus of this study, preferentially degrades denatured collagens and native collagen type IV, a major component of extracellular matrix and basement membranes whose disruption is central to tumor invasion and metastasis. Tumor MMP-9 also exerts early control of the angiogenic switch necessary in primary tumor progression (4). Degradation of extracellular matrix facilitates endothelial cell migration and subsequent proliferation. Experimentally, overexpression of MMP-9 contributes to pulmonary metastasis (5-7), whereas inhibiting MMP-9 expression blocks metastasis (8-10).
Given invasive and pulmonary metastatic STS propensities, it is surprising that MMP-9 in STS has received scant attention. Increased STS expression of MMP-2 and MMP-9 (with concomitant decreased expression of their cognate inhibitors tissue inhibitor of metalloproteinase-2 and tissue inhibitor of metalloproteinase-1) correlates with overall survival (11). Abrogating MMP-9 activity by transfecting anti-MMP-9 small interfering RNA resulted in decreased Ewing's sarcoma spread on extracellular matrixcoated surfaces (12).
Regulation of MMP-9 expression and activity is multifactorial yet incompletely understood (7); MMP-9 regulation in STS has apparently not been examined. Because p53 mutations are prevalent in STS and other malignancies, it is intriguing that possible p53 regulation of MMP-9 activity has also received little consideration.
Our studies show that MMP-9 expression levels in human STS correlate with both metastasis and p53 mutational status. Reintroduction of wild-type p53 (wtp53) into mutant p53 (mutp53) STS favorably alters MMP-9 tumor biology by down-regulation of the MMP-9 promoter, mediated via decreased nuclear factor-
B (NF-
B) activity, a potentially effective anti-MMP-9 therapeutic strategy. To have an impact, such approaches should target early-stage STS patients in whom MMP-9 activity has an evolving role in facilitating primary tumor angiogenesis and subsequent metastasis.
| Results |
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We considered possible regulatory relationships between mutp53 status and MMP-9 expression/function. SKLMS1 human leiomyosarcoma cells have p53 core-binding point mutation at codon 245. Previously, we stably transfected SKLMS1 cells with wtp53 (designated SK-p53) and temperature-sensitive 143Ala-p53 (SKAla-10, SKAla-14, and SKAla-21), demonstrating that restoration of wtp53 suppresses the malignant phenotype in vitro and in vivo (14). Immunohistochemistry of severe combined immunodeficient mouse xenografts generated from these cell lines showed strongly decreased MMP-9 expression and induction of p21 in wtp53 cells compared with controls (Fig. 2A ). Immunohistochemistry done on severe combined immunodeficient mouse SKLMS1 xenografts intratumorally injected with either Adp53 or AdLacZ showed increased p21 expression as well as much lower MMP-9 expression with Adp53 compared with AdLacZ treatment (Fig. 2B). These in vivo results collectively suggest that wtp53 might help regulate MMP-9 expression in human STS.
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The decreased MMP-9 mRNA observed in 32°C SKAla cells suggested that wtp53 might exert at least partial transcriptional repression of MMP-9 gene expression. To test this hypothesis, we first examined the effect of wtp53 on MMP-9 promoter activity. The 674 to +3 bp MMP-9 promoter fragment (relative to the transcription start site) was subcloned into the firefly luciferase reporter gene plasmid pGL3 to generate pMMP-9-674Luc. SKLMS1 cells preinfected with incremental doses of Adp53 or AdLacZ were transiently transfected with the pMMP-9-674Luc reporter construct, and luciferase expression was assayed 48 hours later. Compared with control SKLMS1 and AdLacZ-infected cells, Adp53-infected SKLMS1 showed significant inhibition of MMP-9 promoter activity, up to 40% (±6) promoter inhibition at 500 plaque-forming units of Adp53 (two-tailed Student's t test; P < 0.05; Fig. 5A ). An increased p21 promoter-driven luciferase expression in the presence of wtp53 verified the activity of the wtp53 plasmid used for transfection (Fig. 5B). These results suggest that wtp53 transcriptionally regulates MMP-9 expression. Although not further explored in the present study, the relatively modest differences in luciferase activity observed point to the possibility that additional wtp53 regulatory mechanisms might be affecting MMP-9 level and activity in our cells.
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Sequence analysis revealed that the identified wtp53-responsive region contains a consensus NF-
B binding site (5'-ggaattcccc-3') at positions 604 to 595. To further explore the role of this site in wtp53-mediated MMP-9 transcriptional repression, the putative NF-
B site was mutated to AAaaAATTTc, and the full-length MMP-9 promoter (674/+3) containing this mutation was subcloned into pGL3 and transfected into STS cells. Reporter assays using this NF-
Bmutated construct showed that the difference in MMP-9 promoterdriven luciferase expression observed after reintroduction of wtp53 was now abolished (Fig. 5B). NF-
B binding at this site was previously shown to be critical for both basal MMP-9 promoter activation and also induction of MMP-9 by growth factors and cytokines (15, 16). Taken together, our data suggests that NF-
Binduced basal MMP-9 promoter activity is inhibited by wtp53. Although not previously shown in the context of the STS MMP-9 promoter, an inverse relationship between wtp53 and NF-
B activity has been identified in other tumor systems (17). We further investigated whether the wtp53-induced decrease in NF-
Bmediated MMP-9 promoter activity could be due to decreased NF-
B expression and/or DNA binding. Western blotting did not show decreased NF-
B (p50 and p65) protein levels in nuclear protein extracts after Adp53 transfection of SKLMS1 cells compared with parental SKLMS1 or AdLacZ transfectants (data not shown). Electrophoretic mobility shift assays (EMSA) using 32P-labeled NF-
B consensus site oligonucleotides confirmed NF-
B DNA binding in SKLMS1 nuclear extracts (Fig. 5C and data not shown). Anti-NF-
B antibodies "supershifted" the protein-oligonucleotide complex, and radiolabeled probe signal was competitively abolished by excess unlabeled oligonucleotides. EMSA signal intensity was decreased in nuclear extracts from Adp53-treated SKLMS1 cells but not in extracts from AdLacZ-treated cells (Fig. 5C). EMSAs done with probes specific for the MMP-9 NF-
B 604 to 595 region showed similar findings (data not shown). Taken together, these data indicate that wtp53 represses MMP-9 transcription via inhibition of NF-
B activation of the MMP-9 promoter.
| Discussion |
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Multiple genetic mutations underlie STS proliferation and dissemination. p53 alterations are the most frequently identified derangement in STS, and contribute to metastasis-promoting behaviors, including loss of cell cycle control (14), enhanced angiogenesis (18), and STS chemoresistance (19). p53 may regulate some MMPs (20); mutp53 activates synovial cell MMP-1 and MMP-13, processes inhibited by wtp53 (21). wtp53 inhibits MMP-2 in melanoma cells (22). In contrast, wtp53 has been shown to activate the MMP-2 promoter (23). Before our study, a regulatory wtp53 inhibition of MMP-9 expression has apparently not been shown.
Which cis-DNA element is responsible for the wtp53 inhibition of MMP-9 promoter activity? Sequence analysis of the MMP-9 promoter revealed that there is no conservative p53 DNA-binding sequence therein; however, recent studies show that wtp53 can transcriptionally regulate downstream target genes through conservative binding siteindependent pathways, such as Sp1 (19). The 5' flanking sequence of the MMP-9 promoter contains putative binding sites within the first 670 bp for activator protein-1, NF-
B, Sp1, and Ets transcription factors, which have been implicated in the induction of MMP-9 gene expression by tumor necrosis factor, Src, and Ras (15, 24). Our experiments identified the NF-
B binding site as the cis-element responsible for the repression of the MMP-9 promoter by wtp53. NF-
B transcription factor is a dimer of proteins (p50/p105 or NF-
B1, p52/p100 or NF-
B2, p65 or RelA, and c-Rel and RelB) that is retained in the cytoplasm by I
B family inhibitors until cells receive an appropriate stimulus. In response to growth factors, cytokines, hormones, or other agents, I
B phosphorylation and degradation is induced, resulting in liberation and nuclear translocation of NF-
B. In cell nuclei, NF-
B regulates expression of genes controlling differentiation, apoptosis, cell growth, migration, and inflammation. NF-
B participate in the basal activity of the MMP-9 promoter as well as its induction by growth factors and cytokines (16, 25). Tumor-suppressor genes, such as PTEN, have been shown to decrease MMP-9 expression by inhibiting NF-
B promoter binding activity in vascular smooth muscle (26). wtp53 plays a role in NF-
B expression and activity: wtp53 transfection into human colon cancer cells resulted in suppressed NF-
B protein levels and decreased constitutive NF-
B activity, resulting in enhanced apoptosis (27). Our results concur with these findings, showing decreased NF-
B promoter-binding activity in mutp53 STS cells with wtp53 reintroduction, and are apparently the first demonstration of an interaction between wtp53 and NF-
B in regulating MMP-9 activity in STS or any other malignancy. The recent demonstration that transcriptionally active mutp53 expressed in H1299 lung carcinoma cell lines induces expression of
100 cell growth and survival genes, including NF-
B, suggests a gain of function for p53 mutations in NF-
B regulation (28). Treatment of these cells with small interfering RNA specific for NF-
B caused enhanced chemosensitivity to etoposide. However, the complexity of p53/NF-
B interplay is suggested because contradictory findings have also been reported. Induction of wtp53 in Saos2 osteosarcoma cells has been observed to cause activation of NF-
B that correlated with wtp53 apoptosis-inducing abilities, whereas loss of NF-
B activity decreased wtp53-induced apoptosis (28); further study is needed.
Our findings suggest that increased MMP-9 expression/activity is associated with decreased survival in STS, suggesting a rationale for anti-MMP-9targeted therapy in STS patient subsets. Although MMP inhibitors have yet to be tested in STS, several have been evaluated as antiangiogenic or antimetastatic agents in clinical trials for advanced pancreatic, gastric, prostate, and lung cancer (29-32). Collectively, the results of these trials have been disappointing with no apparent efficacy but increased concomitant morbidity. It is possible that MMP inhibitors have little effect on advanced-stage tumors, but might have impact if administered in earlier-stage tumors before their deployment of multiple metastasis-facilitating molecular derangements. The results of the present study also suggest that wtp53 restorative therapy might help inhibit MMP-9 function in human STS. Adding p53/MMP-9 abrogating therapies to standard chemotherapy might possibly facilitate control of STS metastasis, thereby improving outcomes in this devastating malignancy.
| Materials and Methods |
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Cell Lines and Constructs
SKLMS1 cells (human leiomyosarcoma; p53 codon 245 mutation) were obtained from American Type Culture Collection (Rockville, MD) and cultured in DMEM/Ham's F-12 with 10% fetal bovine serum (complete culture medium; Life Technologies, Inc., Grand Island, NY). SKp53; SKAla-10, SKAla-14, and SKAla-21 temperature-sensitive p53; and SKneo control cell lines were generated as previously reported (14). Adp53 and AdLacZ adenoviruses were produced and titered by the Vector Core Laboratory at M.D. Anderson Cancer Center.
Antibodies
Anti-MMP-9: Ab-3 monoclonal antibody (Oncogene Research Products, Boston, MA); anti-p21: C-19 polyclonal; anti-p50: C-19 polyclonal; and anti-p65: C-20 polyclonal (Santa Cruz Biotechnology, Inc., Santa Cruz, CA). Anti-ß-actin: monoclonal (Sigma-Aldrich, St. Louis, MO). Anti-p53: DO1 monoclonal (Santa Cruz Biotechnology Inc., CA). Anti-Jagged-1 (Santa Cruz Biotechnology). Horseradish peroxidaseconjugated secondary antibodies were detected by ECL chemiluminesence (Amersham Biosciences, Plc., United Kingdom). IRdye680- and IRdye800-conjugated secondary antibodies (Molecular Probes, Eugene, OR) were detected using Odyssey Imaging (LICOR Biosciences, Lincoln, NE).
Tissue Specimens
Human STS samples were randomly selected from M.D. Anderson Sarcoma Tissue Bank and formalin fixed before paraffin block sectioning at 5 µmol/L for immunohistochemical staining. Genomic DNA was extracted from tumor and autologous normal tissue using a QIAamp DNA minikit according to instructions of the manufacturer (QIAGEN Sciences, Germantown, MA). Mock-, AdLacZ-, and Adp53-treated SKLMS1 severe combined immunodeficient mouse xenografts were harvested as previously published (33).
Immunohistochemistry
Immunohistochemistry was done as previously described (33). Briefly, paraffin sections were dewaxed and rehydrated before antigen retrieval in 0.01 mol/L sodium citrate buffer (pH 6). Endogenous peroxidase activity was quenched with 0.6% hydrogen peroxide before blocking with horse serum. Immunohistochemistry was done with MMP-9, and p21 was diluted 1:200 in PBS containing 0.1% sodium azide and 0.5% bovine serum albumin. Biotinylated secondary antibodies were applied at 1:200 before ABC peroxidase system application (Vectastain ABComplex; Vector Laboratories, Inc., Burlingame, CA), 3,3'-diaminobenzidine color development (Sigma Chemical Co., St. Louis, MO), and Mayer's hematoxylin counterstaining. MMP-9 expression was evaluated by two independent reviewers counting 20 representative fields.
Sequencing of p53 in STS Samples
Genomic DNA was isolated from pathologist-confirmed tumor tissue. PCR amplification of all coding exons and intron-exon boundaries (exons 2-11) was done with primers and conditions as previously described (34). DNA sequencing was done in the DNA core facility at M.D. Anderson Cancer Center.
In vitro Chemoinvasion and Migration Assays
In vitro invasiveness was assayed as previously described (35). Chemoinvasion was measured using 24-well BioCoat Matrigel invasion chambers with 8 µmol/L pore size polycarbonate filters coated with Matrigel (Becton Dickinson Labware, Bedford, MA). Lower compartments contained 0.6 mL laminin (Becton Dickinson Labware) as a chemoattractant. Cells were seeded in the upper compartments and incubated for 72 hours at 38°C or 32°C in a humidified atmosphere of 95% air and 5% CO2. After incubation, filters were fixed and stained with Giemsa (Fisher Scientific, Orangeburg, NY). Cells on the upper surface of the filters were removed by wiping with a cotton swab, and chemoinvasive activity was determined by counting the number of cells per high-power field (x200) that had migrated to the lower side of the filter. Migrant cells were counted in at least three high-power fields per filter. Each sample was assayed in triplicate, and the assays were done twice. The chemotaxis assay was done essentially as described previously (36) using BioCoat cell culture inserts and polycarbonate filters with 8 µmol/L pores (Becton Dickinson Labware). Lower compartments of the insert contained 0.6 mL laminin at 30 µg/mL in DMEM/Ham's F-12 as a chemoattractant or DMEM/Ham's F-12 alone as a negative control. Cells were seeded in the upper compartment and incubated for 6 hours at 37°C in a humidified atmosphere of 95% air and 5% CO2 before fixation, staining, and counting as described above for the chemoinvasion assay. All of the assays were done in duplicate and repeated thrice. Both assays were repeated using SKAla-14 incubated at 38°C with or without 20 nmol/L of a selective MMP-9 inhibitor (Calbiochem, San Diego, CA; a kind gift from Dr. Dougles Boyd, M.D. Anderson Cancer Center).
Zymography Assay
This assay was done as previously described (36). Cells (5 x 105) were seeded onto 100-mm tissue culture plates in serum-containing medium and cultured overnight. Monolayers were then washed and incubated in serum-free medium for 30 hours. Conditioned medium supernatant was concentrated (10-fold) using Amicon spin columns (Amicon, Beverly, MA) before protein quantitation, and subjected to 10% SDS-PAGE (with gel containing 1.5% gelatin) without reducing agents. After electrophoresis, the gel was washed thrice with wash buffer; incubated at 37°C for 16 to 24 hours in 0.2% Triton X-100, 50 mmol/L NaCl, 10 mmol/L CaCl, 50 mmol/L Tris-HCl (pH 7.5), and 1 µmol/L ZnCl containing 0.05% sodium azide; and then stained by Coomassie brilliant blue and destained with 10% acetic acid.
Western Blot Analysis
Western blotting was done by standard methods. Briefly, the conditioned medium (as used in the zymography assay) or equimolar amounts of nuclear extract proteins were separated by SDS-PAGE and transferred onto nitrocellulose membranes. Membranes were then blocked and blotted with anti-MMP-9, or anti-p50 and anti-p65 (antibodies as above), and visualized with ECL or IR-conjugated secondary antibodies.
Reverse Transcription-PCR
Reverse transcription-PCR was done as previously described (37). Briefly, total RNA was isolated from cultured cells using TRIzol reagent (Life Technologies) per instructions of the manufacturer. After denaturation at 65°C for 5 minutes, 2 µg RNA was added to 20 µL reverse transcriptase mixture [10 µg/mL oligo(dT), 1x reverse transcriptase buffer; Promega, Madison, WI], four deoxynucleosides (each 0.5 mmol/L), 1 unit/µL RNasein (Promega), and 10 units of avian myeloblastosis virus reverse transcriptase (Promega). RNA was reverse transcribed at 42°C for 60 minutes, and 2 µL of the products were used as templates for multiplex PCR containing both target MMP-9 and ß-actin primers for normalization. Primers used were MMP-9 (PCR product size, 120 bp), 5'-GAGGTTCGACGTGAAGGCGCAGATG-3' and 5'-CATAGGTCACGTAGCCCACTTGGTC-3'; ß-actin (product size, 621 bp), 5'-ACACTGTGCCCATCTACGAGG-3' and 5'-AGGGGCCGGACTCGTCATACT-3'. The PCR reaction mixture contained 50 ng genomic DNA; 1.5 mmol/L MgCl2; 0.2 mmol/L dATP, dTTP, dGTP, and dCTP; primers (each 0.5 µmol/L); and 1x Q solution (Qiagen, Valencia, CA). PCR consisted of 30 cycles of denaturation for 1 minute at 95°C, annealing for 1 minute at 62°C, and an extension for 40 seconds at 72°C. PCR cycles were terminated by an extension at 72°C for 7 minutes and products were resolved on a 2% agarose gel.
MMP-9 Promoter Deletion and Mutation Constructs
MMP-9 proximal promoter sequences (from 674 and 328, to +3 bp of the transcription start sitenumbered according to Genbank locus NT_011362.9, GI:51475129) were kindly provided by Dr. Douglas Boyd (M.D. Anderson Cancer Center) and cloned into pGL3. PCR-based substitution mutations (capitalized) were incorporated into the 604 to 595 bp NF-
B consensus site to generate sequence 5'-AAaaAATTTc-3'.
Reporter Gene Assays
Transfections were done in six-well cluster plates using Fugene 6 transfection reagent (Roche Diagnostics GmbH, Denzburg, Germany) per instructions of the manufacturer, with 100 ng of the MMP-9-Lucbased luciferase reporter per well and 20 ng pRL/cytomegalovirus control per well for normalization. SKLMS1 cells were pretreated with wtp53- or lacZ-expressing adenoviruses (500 plaque-forming units per cell) or mock-infected for 48 hours before transfection. The total amount of DNA transfected per well was 120 ng. Lysates were prepared 48 hours posttransfection and luciferase activity was measured using Promega dual luciferase assay kit per instructions of the manufacturer (Promega). The p53 response elementcontaining region of the p21 promoter was subcloned from WWP-LUC (38) into pGL3 and used as a positive control for wtp53 activity. All of the reporter assays were done in duplicates and repeated thrice.
EMSA
Nuclear extracts were prepared from SKLMS1 cells in cold nuclear extraction buffer. Binding reaction was initiated by adding 5 µg nuclear extract to binding buffer and 1 µg poly(deoxyinosinic-deoxycytidylic acid) from Amersham Biosciences (Piscataway, NJ), 3 x 105 cpm 32P-labeled target double-stranded oligonucleotide, and 1% NP40 (total volume 20 µL), and incubated for 30 minutes at 37°C. The reaction was terminated by adding 4 µL of 6x DNA loading dye and then placing samples on ice before 5% native PAGE. The dried gel was autoradiographed. For supershifts, 1 µg antibody was added to the nuclear extract and incubated at room temperature for 30 minutes before being added to the binding reaction. NF-
B consensus site probe sequence: 5'-AGTTGAGGGGACTTTCCCAGGC-3'; MMP-9 NF-
B 604 to 595 containing probe sequence: 5'-GACAGGGGTTGCCCCAGTGGAATTCCCCAGCCTTGCCTAGCA-3'. EMSA was repeated thrice.
Statistical Analysis
The correlations of MMP-9, p53 mutation, and clinicopathologic variables were assessed using Fisher's exact test. Differences in invasion rate were analyzed using a two-tailed Student's t test. Significance was P
0.05.
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The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
Received 7/ 7/06; revised 9/21/06; accepted 9/25/06.
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B and AP-1 in vascular smooth muscle cells. Arch Biochem Biophys 2004;421:26776.[CrossRef][Medline]
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B binding to the promoter as a consequence of I
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-induced block of p65/p50 nuclear translocation. J Biol Chem 2001;276:116472.This article has been cited by other articles:
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