Lysophosphatidic acid (LPA) effects on endometrial carcinoma in vitro proliferation, invasion, and matrix metalloproteinase activity.

OBJECTIVES: Lysophosphatidic acid (LPA) has potent growth-regulatory effect in many cell types and has been linked to the in vivo tumor growth and metastasis in several malignancies. The goal of this study was to assess the regulation of (EC) microenvironment by LPA through the examination of its effect on cell proliferation, migration, invasion, uPA activity, and matrix metalloproteinase (MMP) secretion/activation. METHODS: All experiments were performed in vitro using an EC cell line, HEC-1A. Cell proliferation was determined using the Promega MTS proliferation assay following 48 h of exposures to different concentrations of LPA (0.1, 1.0 and 10.0 microM). Cell invasion was assessed using a modified Boyden chamber assay with collagen I coated on the membrane. HEC-1A motility was examined by Boyden chamber migration assay as well as the scratch wound closure assay on type I collagen. MMP secretion/activation in HEC-1A conditioned medium was detected by gelatin zymography. MMP-7 mRNA expression was determined using real-time PCR. uPA activity was measured using a coupled colorimetric assay. RESULTS: LPA, at the concentrations of 0.1 and 1.0 microM, significantly induced the proliferation of HEC-1A cells (p<0.01). At 10 microM, LPA- induced HEC-1A proliferation to a less extent and showed no significant effect on HEC-1A invasion and migration (p>0.05). Gelatin zymogram showed that HEC-1A cells secreted high levels of MMP-7, while MMP-2 and MMP-9 are barely detectable. In addition, LPA significantly enhanced uPA activity in HEC-1A conditioned medium in a concentration-dependent manner. CONCLUSIONS: LPA is a potent modulator of cellular proliferation and invasion for EC cells. It also has the capacity to stimulate the secretion/activity of uPA and MMP-7. Those results suggest that LPA is a bioactive modulator of EC microenvironment and may have a distinct regulation mechanism as observed in epithelial ovarian cancer.

S1P induced changes in epithelial ovarian cancer proteolysis, invasion, and attachment are mediated by Gi and Rac.

OBJECTIVES: We previously demonstrated that sphingosine 1-phosphate (S1P) bimodally regulates epithelial ovarian cancer (EOC) cell invasiveness: low-concentration S1P stimulates invasion similar to lysophophatidic acid (LPA), while high-concentration S1P inhibits invasion. In this study, we investigated the mechanisms through which S1P affects EOC cell proteolysis, invasion, and adhesion in two cultured epithelial ovarian cancer cell lines. METHODS: G-protein Gi was inhibited by pertussis toxin (PTX) and GTP binding protein Rac by NSC23766. S1P conditioned media of DOV13 and OVCA429 cells were evaluated via gel zymography, fluorometric gelatinase assay, urokinase plasminogen activator (uPA) activity assay, and Western Blot for MT1-MMP. Cell invasion was analyzed in Matrigel chambers. Membrane-N-cadherin was localized via fluorescence microscopy. RESULTS: Zymography revealed pro-MMP2 in conditioned media of EOC cells regardless of treatment. Gelatinase activity was increased by low-concentration S1P. In DOV13 cells this effect was Gi and Rac dependent. In all OVCA429 and control DOV13 cells, PTX enhanced gelatinolysis, suggesting an MMP2-inhibitory pathway via Gi. MT1-MMP was decreased Gi-dependently by high-concentration S1P. Rac inhibition significantly counteracted low-S1P enhancement and high-S1P reduction of DOV13 invasiveness; and uPA activity in conditioned media of invading cells correlated significantly. Immunohistochemistry revealed Gi-dependent clustering of membrane-N-cadherin in DOV13 cells treated with 0.5 microM S1P or 10 microM LPA. CONCLUSIONS: S1P influences EOC invasion by regulating ECM-proteolysis and cell-cell attachment via MMP2, uPA, and membrane-N-cadherin. Furthermore, this study illustrates that the net effect of S1P on each of these processes reflects a complex interplay of multiple GPCR pathways involving Gi and downstream Rac.

Inhibition of matrilysin expression by antisense or RNA interference decreases lysophosphatidic acid-induced epithelial ovarian cancer invasion.

Our previous reports show that matrilysin [matrix metalloproteinase (MMP)-7] is overexpressed in epithelial ovarian cancer (EOC) and recombinant MMP-7 promotes EOC invasion in vitro. In the present study, we further evaluated the correlation of MMP-7 expression to EOC invasiveness and examined its role in lysophosphatidic acid (LPA)-induced invasion. By sense and antisense gene transfection in vitro, we show that overexpression of MMP-7 in all MMP-7 stably transfected DOV13 clones significantly enhanced their invasiveness, although MMP-7 antisense transfection caused a 91% decrease of MMP-7 expression (P < 0.01) and 87% decrease of invasion (P < 0.05) in geneticin (G418)-selected DOV13 clone P47-M7As-3 compared with vector-transfected control. As assessed by MMP-7 ELISA, LPA treatment at 10 to 80 micromol/L significantly stimulated the secretion of total MMP-7 in DOV13 conditioned medium (P < 0.01). In addition, LPA apparently induced the activation of MMP-7 in DOV13 cells as detected by gelatin zymography. In the antisense MMP-7-transfected DOV13 clone (P47-M7As-3), LPA-increased invasion was significantly decreased compared with vector control. Moreover, knocking down of MMP-7 by small interfering RNA also suppressed LPA-induced invasion in two EOC cell lines (DOV13 and R182). Altogether, our results show that MMP-7 expression is correlated with EOC invasiveness and LPA-induced MMP-7 secretion/activation may represent a new mechanism that facilitates ovarian cancer invasion besides the well-known induction of MT1-MMP-mediated proMMP-2 activation by LPA.

S1P and LPA have an attachment-dependent regulatory effect on invasion of epithelial ovarian cancer cells.

OBJECTIVES: We previously demonstrated the regulation of epithelial ovarian cancer (EOC) cell invasiveness by the bioactive phospholipid sphingosine 1-phosphate (S1P). Low-dose S1P stimulated invasion like lysophosphatidic acid (LPA), while high-dose S1P inhibited invasion. Here we investigate how cell attachment status affects response to S1P and examine the effects of S1P and LPA on cell-cell and cell-extracellular matrix (ECM) adhesion. METHODS: EOC Dov13 cell invasion, ECM attachment and cell adhesion were tested through in vitro assays of Matrigel invasion and attachment to Matrigel, collagen or cell monolayer. Fractionated membrane and cytoplasmic proteins and biotin-labeled surface proteins were analyzed by western analysis. Actin cytoskeleton and FAK were visualized by immunofluorescence. RESULTS: S1P (20 muM) inhibited invasion of sustained, attached cells but enhanced that of invading cells. Membrane N-cadherin was depleted upon reattachment to ECM. S1P pretreatment (20 muM) accelerated N-cadherin recovery, while 40 muM LPA or 0.5 muM S1P delayed recovery. Cell-cell adhesion and stress fibers were decreased by LPA and by 0.5 muM S1P but increased by 20 muM S1P. While S1P increased cellular attachment to Matrigel and collagen-I, LPA inhibited attachment to Matrigel. Surface N-cadherin, gamma- and beta-catenins, FAK and integrinbeta1 were altered by both reattachment and treatment with S1P or LPA. CONCLUSIONS: S1P inversely affects invasion of attached and invading cells, switching from inhibition to stimulation. This switch is associated with depletion of N-cadherin and membrane FAK. The recovery of membrane N-cadherin, change in cell-cell adhesion and actin stress fibers intensity in response to LPA and S1P inversely correlate with their effects on cellular invasiveness.

Selective induction of cyclooxygenase-2 plays a role in lysophosphatidic acid regulated Fas ligand cell surface presentation.

Previous studies found that lysophosphatidic acid (LPA) upregulated Fas ligand (FasL) presentation on the ovarian cancer cell surface and lead to apoptosis of activated lymphocytes. In this report, we investigated the role of selective induction of cyclooxygenase-2 (Cox-2) in FasL cell surface presentation stimulated by LPA. Ovarian cancer cells pretreated with general aspirin derivative acetylsalicylic acid and specific Cox-2 inhibitor (NS-398) before stimulation with LPA, FasL cell surface presentation was significantly blocked, so was the apoptosis of activated lymphocytes mediated by increasing FasL on the ovarian cancer cell surface. Using the specific inhibitors PD98059, AG1478 or dominant-negative epidermal-growth-factor receptor (EGFR-DN) plasmid, we found that the activation of ERK1/2 played a role in Cox-2 induction, and the transactivation of EGFR worked as an upstream signaling pathway in ERK1/2 phosphorylation. This study first revealed the selective induction of Cox-2 by LPA led to FasL presentation on ovarian cancer cell surface and provide cancer cell immune privilege, and might provide important information of Cox-2 in cancer progression and Cox-2 inhibitors' application in cancer chemoprevention.

Recognition of linear stress fibers based on Hough transform.

OBJECTIVE: To present an algorithm based on Hough transform for recognition and extraction of linear stress fibers formed on exposure to lysophosphatidic acid (LPA). STUDY DESIGN: A ridge set of head points with lower shoulders is calculated, followed by a thinning process shrinking long, narrow regions to regions of single pixel thickness, then converted into a rectangular map whose value is the number of regional points in the path of a straight line at the angle and intercept determined by two coordinates. The location of the maximum in the map is sought, and the corresponding line with an unlimited length is constructed from the paired coordinates. We removed the line before repeating the process for the next longest straight line, continuing until all lines with reasonable lengths are extracted. RESULTS: Application of the algorithm to the stress fiber images of DOV13 cells stained with Texas red-phalloidin on LPA and AG1478 demonstrates close matches between stress fibers in the original images and linear lines. CONCLUSION: An algorithm for recognition of linear stress fibers formed on exposure to LPA is described and applications to stress fiber images using DOV13 cells with Texas red-phalloidin staining are demonstrated.

S1P regulation of ovarian carcinoma invasiveness.

OBJECTIVES: Within the tumor microenvironment the invasiveness of epithelial ovarian carcinoma (EOC) cells is stimulated by biologically active lipids such as lysophosphatidic acid (LPA). We tested the in vitro effect of another bioactive lysophospholipid, sphingosine-1-phosphate (S1P), on the invasiveness of EOC cells. METHODS: Dov13 EOC cells were tested for invasion through matrigel-coated chambers and for gelatinase activity using a fluorogenic assay. cDNA was analyzed through real-time PCR. Cell surface proteins, isolated through biotinylation and affinity purification, were analyzed by Western blots. RESULTS: Invasion of Dov13 cells was enhanced by low (0.5 microM) and inhibited by high (20 microM) concentrations of S1P, which correlated with increased and reduced gelatinase activity in conditioned media. Low and high S1P dose also differently affected the presentation of surface S1P receptors; low S1P dose increased S1P1 and decreased S1P2, while high S1P increased S1P3. LPA and S1P differently altered transcript levels of their respective and reciprocal receptors; receptors that were upregulated by one lysophospholipid (S1P2,3 and LPA1 by LPA, LPA3,4 and S1P1,4,5 by S1P) were downregulated or unchanged by the other. CONCLUSIONS: The dual effect of high and low S1P concentration on invasion was probably caused by the diverse changes to the presentation of surface S1P receptors. The opposite effect of S1P and LPA on expression of each receptor suggests a homeostatic transcriptional mechanism that abrogates the effects of LPA and S1P on EOC cells. Altogether this study demonstrates a complex role of S1P in EOC cell invasion, a process highly balanced and regulated by LPA and S1P within the tumor microenvironment.

Endogenously expressed multimeric self-cleaving hammerhead ribozymes ablate mutant collagen in cellulo.

Hammerhead ribozymes are small catalytic RNA molecules that can be targeted to any RNA molecule containing a putative cleavage site. We developed a vector (pCOLZ) that uses the COL1A1 promoter to drive expression of a self-cleaving multimeric ribozyme (M8Rz547) and its monomeric counterpart (Rz547). The ribozymes were stably coexpressed in MC3T3-E1 osteoblasts expressing a truncated COL1A1 target transcript. The multimeric ribozyme exhibited self-cleavage to derivative fragments, including monomers. Increased expression of ribozymes was found in cells expressing the multimeric ribozyme. A modest reduction of truncated target transcript and protein was seen in cells expressing the ribozyme monomer, while nearly complete ablation of target transcript and protein occurred in cells expressing the ribozyme multimer. A reversion to a more normal collagen phenotype, measured as an increase in fibril diameter and restored fibrillar architecture, and a decreased rate of collagen turnover were seen in cells expressing the ribozyme multimer.