Dual mechanisms for lysophosphatidic acid stimulation of human ovarian carcinoma cells

Platelet-activating factor acetyl hydrolase IB2 dysregulated cell proliferation in ovarian cancer

Background

Ovarian cancer is the leading cause of death from gynaecologic illnessed worldwide. Platelet-activating factor acetyl hydrolase IB2 (PAF-AH IB2) is an intracellular serine esterase that hydrolyzes platelet-activating factor, a G-protein-like trimer with two catalytic subunits and one regulatory subunit. The regulatory role of PAF-AH IB2 in the oncogenesis of ovarian cancer is not well understood.

Methods

In this study, the TCGA dataset and clinical cancer tissue microarray were utilized to investigate abnormal overexpression of PAF-AH IB2 in ovarian cancer. To investigate the impact on the cell proliferation, migration, and tumorigenicity in vitro, PAF-AH IB2 stable knocking down (KD) ovarian cancer cells were established by ShRNA. The whole transcription profiling, tyrosine kinase profiling and standard cell functional assays were integrated to explore the biological importance and mechanism of PAF-AH IB2 modulated in ovarian cancer.

Results

PAF-AH IB2 was identified significantly overexpression in four subtypes of ovarian cancer. In vitro, PAF-AH IB2 KD significantly inhibited cancer cell proliferation, migration, and tumorigenicity, activated caspases and caused cell cycle arrest, and made the cells more sensitive to PAF. PAF-AH 1B2 KD cells down-regulated several key regulators of the multiple tyrosine kinases-mediated signaling pathway, suggesting a novel interaction network between the growth factor receptors pathway and PAF-AH 1B2 mediated PAF signalling.

Conclusions

These findings revealed a previously undiscovered role for PAF-AH IB2 as a potenial therapy target and essential signaling mediators in ovarian cancer pathogenesis, as well as new possible preventive and therapeutic strategies to inhibit this enzyme in clinical treatment for ovarian cancer.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-021-02406-9.

Deregulation of Lipid Metabolism: The Critical Factors in Ovarian Cancer

Ovarian cancer is one of the most malignant gynecological cancers around the world. In spite of multiple treatment options, the five-year survival rate is still very low. Several metabolism alterations are described as a hallmark in cancers, but alterations of lipid metabolism in ovarian cancer have been paid less attention. To explore new markers/targets for accurate diagnosis, prognosis, and therapeutic treatments based on metabolic enzyme inhibitors, here, we reviewed available literature and summarized several key metabolic enzymes in lipid metabolism of ovarian cancer. In this review, the rate limiting enzymes associated with fatty acid synthesis (FASN, ACC, ACLY, SCD), the lipid degradation related enzymes (MAGL, CPT, 5-LO, COX2), and the receptors related to lipid uptake (FABP4, CD36, LDLR), which promote the development of ovarian cancer, were analyzed and evaluated. We also focused on the review of application of current metabolic enzyme inhibitors for the treatment of ovarian cancer through which the potential therapeutic agents may be developed for ovarian cancer therapy.

Interfering Human Papillomavirus E6/E7 Oncogenes in Cervical Cancer Cells Inhibits the Angiogenesis of Vascular Endothelial Cells via Increasing miR-377 in Cervical Cancer Cell-Derived Microvesicles

Background

The dysregulation of the human papillomavirus 18 E6 and E7 oncogenes plays a critical role in the angiogenesis of cervical cancer (CC), including the proliferation, migration, and tube formation of vascular endothelial cells. Interfering E6/E7 increases the number of CC cell-derived microvesicles (CC-MVs). Additionally, microRNAs (miRNAs) can modulate CC angiogenesis and can be encapsulated in MVs.

Objective

We aim to investigate whether E6/E7 affects CC angiogenesis via regulating miRNAs in CC-MVs.

Methods

CC-MVs were isolated from a CC cell line (HeLa) which were transfected with small interfering RNAs (siRNAs) against E6/E7 or co-transfected with miR-377 mimics/inhibitors. The expression of several miRNAs in CC-MVs was detected using quantitative real-time PCR. After co-incubating CC-MVs with human umbilical vein endothelial cells (HUVECs), cell proliferation, migration, and tube formation of HUVECs were determined using cell counting kit-8, transwell, and tube formation assays, respectively.

Results

MiR-377 was increased in E6/E7-interfering CC-MVs. Overexpressing miR-377 in CC-MVs suppressed HUVEC proliferation, migration, and tube formation. LPAR2, the cell surface G protein-coupled receptor, was the downstream target of miR-377 in HUVECs. The co-transfection of E6/E7 siRNAs and miR-377 inhibitors in CCs negated the effect of E6/E7 siRNAs on the elevation of miR-377 in CC-MVs. In HUVECs, the co-transfection of E6/E7 siRNAs and miR-377 inhibitors restored the LPAR2 expression which was reduced by the E6/E7 siRNA transfection. Meanwhile, miR-377 mimic reduced LPAR2 expression and inhibited HUVEC proliferation, migration, and tube formation, while such response was negated by LPAR2 overexpression.

Conclusion

Interfering E6/E7 increased miR-377 in CC-MVs, and overexpressing miR-377 in CC-MVs inhibited angiogenesis of HUVECs via reducing LPAR2.

Lysophosphatidic Acid Receptors: Biochemical and Clinical Implications in Different Diseases

Lysophosphatidic acid (LPA, 1-acyl-2-hemolytic-sn-glycerol-3-phosphate) extracted from membrane phospholipid is a kind of simple bioactive glycophospholipid, which has many biological functions such as stimulating cell multiplication, cytoskeleton recombination, cell survival, drug-fast, synthesis of DNA and ion transport. Current studies have shown that six G-coupled protein receptors (LPAR1-6) can be activated by LPA. They stimulate a variety of signal transduction pathways through heterotrimeric G-proteins (such as Gα12/13, Gαq/11, Gαi/o and GαS). LPA and its receptors play vital roles in cancers, nervous system diseases, cardiovascular diseases, liver diseases, metabolic diseases, etc. In this article, we discussed the structure of LPA receptors and elucidated their functions in various diseases, in order to better understand them and point out new therapeutic schemes for them.

The role of AP-1 in self-sufficient proliferation and migration of cancer cells and its potential impact on an autocrine/paracrine loop

Activating protein-1 (AP-1) family members, especially Fra-1 and c-Jun, are highly expressed in invasive cancers and can mediate enhanced migration and proliferation. The aim of this study was to explore the significance of elevated levels of AP-1 family members under conditions that restrict growth. We observed that invasive MDA-MB-231 cells express high levels of Fra-1, c-Jun, and Jun-D during serum starvation and throughout the cell cycle compared to non-tumorigenic and non-invasive cell lines. We then analyzed Fra-1 levels in additional breast and other cancer cell lines. We found breast and lung cancer cells with higher levels of Fra-1 during serum starvation had relatively higher ability to proliferate and migrate under these conditions. Utilizing a dominant negative construct of AP-1, we demonstrated that proliferation and migration of MDA-MB-231 in the absence of serum requires AP-1 activity. Finally, we observed that MDA-MB-231 cells secrete factors(s) that induce Fra-1 expression and migration in non-tumorigenic and non-metastatic cells and that both the expression of and response to these factors require AP-1 activity. These results suggest the presence of an autocrine/paracrine loop that maintains high Fra-1 levels in aggressive cancer cells, enhancing their proliferative and metastatic ability and affecting neighbors to alter the tumor environment.

Lysophosphatidic acid increases in vitro maturation efficiency via uPA-uPAR signaling pathway in cumulus cells

Lysophosphatidic acid (LPA) is a phospholipid-derived signaling molecule with biological activities, such as stimulating cell proliferation, differentiation and migration. In the present study, we examined the effect of LPA on porcine oocytes during in vitro maturation (IVM) and subsequent embryonic development following parthenogenetic activation (PA) and in vitro fertilization (IVF). During IVM, the maturation medium was supplemented with various concentrations of LPA (0, 10, 30, and 60 μM). After 42 h of IVM, the 30 μM LPA-treated group showed a significant (P <0.05) increase in nuclear maturation and intracellular glutathione (GSH) levels compared with the other groups. The 30 μM LPA-treated group exhibited a significant decrease in intracellular reactive oxygen species (ROS) levels compared with the other groups. In PA, the 30 μM LPA-treated group had significantly higher cleavage (CL) and blastocyst (BL) rates compared with those of the other LPA-treated groups. In IVF, the 30 μM LPA-treated group had significantly higher CL and BL rates than the other LPA-treated groups. The expression of the developmental competence gene (proliferating cell nuclear antigen, PCNA) in the oocytes and cumulus cells of the individuals in the 30 μM LPA-treated group was significantly increased compared with the control group. In addition, the specific expression of urokinase Plasminogen Activator (uPA) and uPA Receptor (uPAR) in cumulus cells was significantly increased in the 30 μM LPA-treated group. The western blotting results revealed that LPA improves the activities of p38 mitogen-activated protein kinase (MAPK) and epidermal growth factor (EGF) by enhanced phosphorylation. In conclusion, treatment with 30 μM LPA during IVM promotes enhances the EGF-EGFR signaling pathway, resulting in cumulus cell expansion. And then, this treatment improves the developmental potential of PA and IVF porcine embryos by enhancing nuclear and cytoplasmic maturation and reducing ROS.

TRIP6 antagonizes the recruitment of A20 and CYLD to TRAF6 to promote the LPA2 receptor-mediated TRAF6 activation

The elevated lysophosphatidic acid signaling has been causally linked to cancer-associated inflammation and tumorigenesis through upregulation of nuclear factor-κB signaling. However, how this signaling event is regulated has not yet been fully understood. Here we demonstrate that TRIP6, an LPA2 receptor-interacting adaptor protein, functions as a positive regulator of nuclear factor-κB and JNK signaling through direct binding to and activation of the E3 ligase TRAF6. Upon lysophosphatidic acid stimulation, TRIP6 recruits TRAF6 to the LPA2 receptor and promotes lysophosphatidic acid-induced JNK and nuclear factor-κB activation in a TRAF6-dependent manner. TRIP6 antagonizes the recruitment of deubiquitinases A20 and CYLD to TRAF6, thus sustaining the E3 ligase activity of TRAF6 and augmenting lysophosphatidic acid-activated nuclear factor-κB signaling. In contrast, depletion of TRIP6 by TRIP6-specific shRNA or Cas9/sgRNA greatly enhances the association of TRAF6 with A20 and CYLD, and attenuates lysophosphatidic acid-induced muclear factor-κB and JNK/p38 activation in ovarian cancer cells. On the other hand, TRAF6 also regulates TRIP6 by facilitating its binding to nuclear factor-κB p65 and phosphorylation by c-Src. Together, TRIP6 cooperates with TRAF6 to regulate the LPA2 receptor signaling, which may ultimately contribute to chronic inflammation, apoptotic resistance and cell invasion.

Lysophosphatidic acid signaling in ovarian cancer

Lysophosphatidic acid (LPA) is a bioactive phospholipid that is involved in signal transduction between cells. Plasma and ascites levels of LPA are increased in ovarian cancer patients even in the early stages and thus LPA is considered as a potential diagnostic marker for this disease. This review presents the current knowledge regarding LPA signaling in epithelial ovarian cancer. LPA stimulates proliferation, migration and invasion of ovarian cancer cells through regulation of vascular endothelial growth factor, matrix metalloproteinases, urokinase plasminogen activator, interleukin-6, interleukin-8, CXC motif chemokine ligand 12/CXC receptor 4, COX2, cyclin D1, Hippo-Yap and growth-regulated oncogene α concentrations. In this article, all of these targets and signal pathways involved in LPA influence are described.

Plasma levels of lysophosphatidic acid in ovarian cancer versus controls: a meta-analysis

Background

In this study, using a meta-analysis approach, we examined the correlation between serum levels of lysophosphastidic acid (LPA) and ovarian cancer (OC).

Methods

Relevant published studies were identified from multiple scientific literature databases by using a pre-determined electronic and manual search strategy. The search results were screened through a multi-step process to select high-quality case–control studies suitable for the present meta-analysis. Mean values and standardized mean differences (SMD) were calculated for plasma LPA levels. Two investigators independently extracted the data from the studies and performed data analysis using STATA software version 12.0 (Stata Corp, College Station, TX, USA).

Results

Nineteen case–control studies met our selection criteria and contained a total of 980 OC patients, 872 benign controls and 668 healthy controls. Our meta-analysis results revealed that the plasma levels of LPA in OC patients were significantly higher than benign controls (SMD = 2.36, 95 % CI: 1.61–3.10, P <0.001) and healthy controls (SMD = 2.32, 95 % CI: 1.77–2.87, P <0.001). Subgroup analysis by ethnicity showed that the plasma LPA levels in OC patients were significantly higher than the benign controls only in Asian populations (SMD = 2.52, 95 % CI: 1.79–3.25, P <0.001). However, a comparison between healthy controls and OC patients revealed that, in both Asians and Caucasians, the OC patients displayed significantly higher plasma LPA levels compared to healthy controls (all P <0.05).

Conclusion

Our meta-analysis showed strong evidence that a significantly higher plasma LPA levels are present in OC patients, compared to benign controls and healthy controls, and plasma LPA levels may be used as a biomarker or target of OC.

Effect of the LPA-mediated CXCL12-CXCR4 axis in the tumor proliferation, migration and invasion of ovarian cancer cell lines

Ovarian cancer is the most fatal gynecological cancer, with a 5-year survival rate of only 30%. Lysophosphatidic acid (LPA), which possesses growth factor-like functions, is a major regulatory factor in the peritoneal metastasis of ovarian cancer. LPA stimulates the expression of numerous genes that are associated with angiogenesis and metastasis. Ovarian epithelial carcinoma specifically expresses chemotactic factor C-X-C motif chemokine ligand 12 (CXCL12) and its receptor, CXC receptor 4 (CXCR4). The CXCL12-CXCR4 axis directly contributes to ovarian cancer cell proliferation, migration and invasion. The present study investigated the regulation of LPA on the CXCL12-CXCR4 axis and the effect of the LPA-mediated CXCL12-CXCR4 axis on the tumor proliferation, migration and invasion of ovarian cancer cell lines. The CXCR4 proteins expressed in the cell membrane and the cytoplasm of ovarian cancer cells, CAOV3 and SKOV3, were detected by immunocytochemistry. The expression of CXCR4 and CXCL12 was increased in the ovarian cancer cells in a dose- and time-dependent manner when treated with LPA compared with the control groups (P<0.05), as determined by reverse transcription polymerase chain reaction and flow cytometry. LPA (20 μM) and CXCL12 (100 ng/ml) enhanced the proliferation, migration and invasion of the ovarian cancer cells, CAOV3 and SKOV3, as identified by MTT, Transwell and Matrigel assays following co-treatment for 24 h. LPA promoted invasiveness of ovarian cancer by upregulating CXCL12-CXCR4 axis expression.

Lysophosphatidic Acid Stimulates the Proliferation of Ovarian Cancer Cells via the gep Proto-Oncogene Gα(12)

Lysophosphatidic acid (LPA), an agonist that activates specific G protein-coupled receptors, is present at an elevated concentration in the serum and ascitic fluid of ovarian cancer patients. Although the increased levels of LPA have been linked to the genesis and progression of different cancers including ovarian carcinomas, the specific signaling conduit utilized by LPA in promoting different aspects of oncogenic growth has not been identified. Here, we show that LPA stimulates both migration and proliferation of ovarian cancer cells. Using multiple approaches, we demonstrate that the stimulation of ovarian cancer cells with LPA results in a robust and statistically significant proliferative response. Our results also indicate that Gα(12), the gep proto-oncogene, which can be stimulated by LPA via specific LPA receptors, is overtly activated in a large array of ovarian cancer cells. We further establish that LPA stimulates the rapid activation of Gα(12) in SKOV-3 cells and the expression of CT12, an inhibitory minigene of Gα(12) that disrupts LPAR-Gα(12) interaction and potently inhibits such activation. Using this inhibitory molecule as well as the shRNA approach, we show that the inhibition of Gα(12) or silencing of its expression drastically and significantly attenuates LPA-mediated proliferation of ovarian cancer cell lines such as SKOV3, Hey, and OVCAR-3. Together with our findings that the silencing of Gα(12) does not have any significant effect on LPA-mediated migratory response of SKOV3 cells, our results point to a critical role for LPA-LPAR-Gα(12) signaling in ovarian cancer cell proliferation and not in migration. Thus, results presented here for the first time demonstrate that the gep proto-oncogene forms a specific node in LPA-LPAR-mediated mitogenic signaling in ovarian cancer cells.

Lysophosphatidic acid receptor 2/3-mediated IL-8-dependent angiogenesis in cervical cancer cells

The expression of lysophosphatidic acid (LPA)-specific receptors in cervical cancer has not been clearly defined. In this study, we identified LPA1, LPA2 and LPA3 receptors' mRNA in SiHa, HeLa and CaSki cell lines by RT-PCR. These receptors were not associated with tumor cell proliferation in vitro. We then used a xenograph animal model to evaluate the effects of these receptors on in vivo cervical cancer tumorigenicity. When SiHa cells with different receptor expression patterns were seeded on the backs of SCID mice, the resulting knockout of both LPA2 and LPA3 significantly attenuated tumor growth; this decrease in tumor growth was found to be linked with decreased angiogenesis (microvessel density), suggesting that LPA2 and LPA3 are crucial for in vivo tumor growth through an angiogenic mechanism. We further investigated this mechanism of LPA receptor 2/3-mediated angiogenic capability by analyzing angiogenic factors in protein lysates from receptor knockout tumors, by detecting interleukin (IL-8) mRNA expression after treating with siRNA, by evaluating the biological role of LPA-enhanced IL-8 via endothelial cell tube formation, monolayer permeability, migration and cell growth assays, and by IL-8 knockout xenograft mice modeling. We found that the angiogenesis is mediated through IL-8. Finally, we evaluated the regulation pathways involved in LPA-induced IL-8 expression. We found that LPA receptor 2/3-mediated IL-8 expression occurs through Gi/PI3K/AKT, Gi/PKC and IκB/NF-κB signaling. In conclusion, we propose that LPA2 and LPA3 might play an important role in cervical cancer tumor growth through IL-8-dependent angiogenesis.

Lysophosphatidic acid is a lipid mediator with wide range of biological activities. Biosynthetic pathways and mechanism of action

Lysophosphatidic acid (LPA) is a lipid mediator required for maintaining homeostasis of numerous physiological functions and also involved in development of some pathological processes through interactions with G protein-coupled receptors. Recently many data have appeared about the role of this phospholipid in humans, but pathways of LPA biosynthesis and mechanisms of its action remain unclear. This review presents modern concepts about biosynthesis, reception, and biological activity of LPA in humans. Natural and synthetic LPA analogs are considered in the view of their possible use in pharmacology as agonists and/or antagonists of G protein-coupled receptors of LPA.

Genomics of the NF-κB signaling pathway: hypothesized role in ovarian cancer

OBJECTIVE

We sought to review evidence linking nuclear factor-kappa B (NF-κB) to ovarian cancer and to identify genetic variants involved in NF-κB signaling.

METHODS

PubMed was reviewed to inform on ovarian cancer biology and NF-κB signaling and to identify key genes. Public linkage disequilibrium (LD) data were analyzed to identify informative inherited variants (tagSNPs) using ldSelect.

RESULTS

We identified 319 key NF-κB genes including five NF-κB subunits, 167 activating genes, and 55 inhibiting genes. We found that the 1000 Genomes Project was the most informative LD source for most genes (92.8%), and we identified 13,027 LD bins (r (2) ≥ 0.9, minor allele frequency ≥ 0.05) and 1,018 putative-functional variants worthy of investigation. We also report that reliance on a commonly used genome-wide SNP array and genotype imputation with HapMap Phase II data provides data on only 74% of the common inherited NF-κB SNPs of interest.

CONCLUSIONS

Compelling evidence suggests that NF-κB plays a critical role in ovarian cancer, yet inherited variation in these genes has not been thoroughly assessed in relation to disease risk or outcome. We present a collection of variants in key genes and suggest creation of a custom genotyping array as an optimal approach.

CARMA3: A novel scaffold protein in regulation of NF-κB activation and diseases

CARD recruited membrane associated protein 3 (CARMA3) is a novel scaffold protein. It belongs to the CARMA protein family, and is known to activate nuclear factor (NF)-κB. However, it is still unknown which receptor functions upstream of CARMA3 to trigger NF-κB activation. Recently, several studies have demonstrated that CARMA3 serves as an indispensable adaptor protein in NF-κB signaling under some G protein-coupled receptors (GPCRs), such as lysophosphatidic acid (LPA) receptor and angiotensin (Ang) II receptor. Mechanistically, CARMA3 recruits its essential downstream molecules Bcl10 and MALT1 to form the CBM (CARMA3-Bcl10-MALT1) signalosome whereby it triggers NF-κB activation. GPCRs and NF-κB play pivotal roles in the regulation of various cellular functions, therefore, aberrant regulation of the GPCR/NF-κB signaling axis leads to the development of many types of diseases, such as cancer and atherogenesis. Recently, the GPCR/CARMA3/NF-κB signaling axis has been confirmed in these specific diseases and it plays crucial roles in the pathogenesis of disease progression. In ovarian cancer cell lines, knockdown of CARMA3 abolishes LPA receptor-induced NF-κB activation, and reduces LPA-induced ovarian cancer invasion. In vascular smooth cells, downregulation of CARMA3 substantially impairs Ang-II-receptor-induced NF-κB activation, and in vivo studies have confirmed that Bcl10-deficient mice are protected from developing Ang-II-receptor-induced atherosclerosis and aortic aneurysms. In this review, we summarize the biology of CARMA3, describe the role of the GPCR/CARMA3/NF-κB signaling axis in ovarian cancer and atherogenesis, and speculate about the potential roles of this signaling axis in other types of cancer and diseases. With a significant increase in the identification of LPA- and Ang-II-like ligands, such as endothelin-1, which also activates NF-κB via CARMA3 and contributes to the development of many diseases, CARMA3 is emerging as a novel therapeutic target for various types of cancer and other diseases.

Fasudil inhibits lysophosphatidic acid-induced invasiveness of human ovarian cancer cells

Ovarian cancer is known to be highly invasive. The poor prognosis of advanced ovarian cancer comes from increased invasiveness of human ovarian cancer cells. The lysophosphatidic acid (LPA)/Rho/Rho-associated kinase (ROCK) pathway is intimately involved in the course of ovarian cancer progression, and the inhibition of this pathway attenuates ovarian cancer invasiveness. Fasudil (1-[5-isoquinolinesulfonyl]-homopiperazine; HA-1077) is a drug that has been in clinical use in Japan for the prevention of vasospasm after subarachnoid hemorrhage and is known to be a potent ROCK-specific inhibitor. In this study, we examined the effect of fasudil on LPA-induced invasiveness of human ovarian cancer cells to explore the potential of fasudil as an anticancer agent against ovarian cancer. Fasudil induced changes in cell morphology but not in cell viability. Fasudil significantly inhibited LPA-induced invasion and motility of human ovarian cancer cells in a dose-dependent manner. Furthermore, fasudil caused the loss of intracellular cytoskeletal rearrangement, which is necessary for cell motility, such as stress fiber formation and focal adhesion assembly. Fasudil suppressed LPA-induced tyrosine phosphorylation of paxillin, a representative focal adhesion protein, and serine phosphorylation of myosin light chain, which are essential for the process for cell migration. These findings showed that fasudil attenuated the invasiveness of human ovarian cancer cells via inhibition of the LPA/Rho/ROCK pathway. In SKOV-3ip1 ovarian cancer xenografts, intraperitoneal treatment with fasudil significantly reduced tumor burden and ascites formation. Our findings suggest that fasudil might be useful to prevent the progression of ovarian cancer in clinical settings.

Sphingosine 1-phosphate induces vascular endothelial growth factor expression in endothelial cells

Angiogenesis is essential for tumor growth and vascular endothelial cell growth factor (VEGF) plays a key role in this process. Conversely, sphingosine 1-phosphate (S1P) is a biologically active sphingolipid known to play a key role in cancer progression by regulating endothelial cell proliferation and migration. In this study, the authors found that S1P increases the level of VEGF mRNA in human umbilical vein endothelial cells (HUVECs) and immortalized HUVECs (iHUVECs). Additionally, S1P was found to increase VEGF promoter activity in MS-1 mouse pancreatic islet endothelial cells. Furthermore, a pharmacological inhibitory study revealed that G(alpha i/o)-mediated phospholipase C, Akt, Erk, and p38 MAPK signaling are involved in this S1P-induced expression of VEGF. A component of AP1 transcription factor is important for S1P-induced VEGF expression. Taken together, these findings suggest that S1P enhances endothelial cell proliferation and migration by upregulating the expression of VEGF mRNA.

Effects of lysophosphatidic acid on human colon cancer cells and its mechanisms of action

AIM: To study the effects of lysophosphatidic acid (LPA) on proliferation, adhesion, migration, and apoptosis in the human colon cancer cell line, SW480, and its mechanisms of action.

METHODS: Methyl tetrazolium assay was used to assess cell proliferation. Flow cytometry was employed to detect cell apoptosis. Cell migration was measured by using a Boyden transwell migration chamber. Cell adhesion assay was performed in 96-well plates according to protocol.

RESULTS: LPA significantly stimulated SW480 cell proliferation in a dose-dependent and time-dependent manner compared with the control group (P < 0.05) while the mitogen-activated protein kinase (MAPK) inhibitor, PD98059, significantly blocked the LPA stimulation effect on proliferation. LPA also significantly stimulated adhesion and migration of SW480 cells in a dose-dependent manner (P < 0.05). Rho kinase inhibitor, Y-27632, significantly inhibited the up-regulatory effect of LPA on adhesion and migration (P < 0.05). LPA significantly protected cells from apoptosis induced by the chemotherapeutic drugs, cisplatin and 5-FU (P < 0.05), but the phosphoinositide 3-kinase (PI3K) inhibitor, LY294002, significantly blocked the protective effect of LPA on apoptosis.

CONCLUSION: LPA stimulated proliferation, adhesion, migration of SW480 cells, and protected from apoptosis. The Ras/Raf-MAPK, G12/13-Rho-RhoA and PI3K-AKT/PKB signal pathways may be involved.

Phosphorylation of CREB, a cyclic AMP responsive element binding protein, contributes partially to lysophosphatidic acid-induced fibroblast cell proliferation

Lysophospholipids regulate a wide array of biological processes including cell survival and proliferation. In our previous studies, we found that in addition to SRE, CRE is required for maximal c-fos promoter activation triggered by lysophosphatidic acid (LPA). c-fos is an early indicator of various cells into the cell cycle after mitogenic stimulation. However, role of CREB activation in LPA-stimulated proliferation has not been elucidated yet. Here, we investigate how LPA induces proliferation in Rat-2 fibroblast cell via CREB activation. We found that total cell number and BrdU-positive cells were increased by LPA. Moreover, levels of c-fos mRNA and cyclin D1 protein were increased via LPA-induced CREB phosphorylation. Furthermore, LPA-induced Rat-2 cell proliferation was decreased markedly by ERK inhibitor (U0126) and partially by MSK inhibitor (H89). Taken together, these results suggest that CREB activation could partially up-regulate accumulation of cyclin D1 protein level and proliferation of LPA-stimulated Rat-2 fibroblast cells.

Inhibition of cell proliferation, vascular endothelial growth factor and tumor growth by albendazole

Vascular endothelial growth factor (VEGF) is the key molecule mediating tumor growth and malignant ascites formation. We recently reported that, in an end stage OVCAR-3 xenograft model, albendazole (ABZ) suppresses ascites formation, but not tumor growth. Hence, in the present study, we assessed the effect of ABZ on in vitro OVCAR-3 cell proliferation plus in vivo tumor growth, however, initiating ABZ treatment at mid stage (3 weeks post cell inoculation) rather than end stage disease. Here, ABZ treatment led to potent inhibition of cell proliferation, VEGF suppression, complete inhibition of ascites formation and most strikingly arrest of tumor growth.

National Academy of Clinical Biochemistry Laboratory Medicine Practice Guidelines for Use of Tumor Markers in Testicular, Prostate, Colorectal, Breast, and Ovarian Cancers

Background: Updated National Academy of Clinical Biochemistry (NACB) Laboratory Medicine Practice Guidelines for the use of tumor markers in the clinic have been developed.

Methods: Published reports relevant to use of tumor markers for 5 cancer sites—testicular, prostate, colorectal, breast, and ovarian—were critically reviewed.

Results: For testicular cancer, α-fetoprotein, human chorionic gonadotropin, and lactate dehydrogenase are recommended for diagnosis/case finding, staging, prognosis determination, recurrence detection, and therapy monitoring. α-Fetoprotein is also recommended for differential diagnosis of nonseminomatous and seminomatous germ cell tumors. Prostate-specific antigen (PSA) is not recommended for prostate cancer screening, but may be used for detecting disease recurrence and monitoring therapy. Free PSA measurement data are useful for distinguishing malignant from benign prostatic disease when total PSA is &lt;10 μg/L. In colorectal cancer, carcinoembryonic antigen is recommended (with some caveats) for prognosis determination, postoperative surveillance, and therapy monitoring in advanced disease. Fecal occult blood testing may be used for screening asymptomatic adults 50 years or older. For breast cancer, estrogen and progesterone receptors are mandatory for predicting response to hormone therapy, human epidermal growth factor receptor-2 measurement is mandatory for predicting response to trastuzumab, and urokinase plasminogen activator/plasminogen activator inhibitor 1 may be used for determining prognosis in lymph node–negative patients. CA15-3/BR27–29 or carcinoembryonic antigen may be used for therapy monitoring in advanced disease. CA125 is recommended (with transvaginal ultrasound) for early detection of ovarian cancer in women at high risk for this disease. CA125 is also recommended for differential diagnosis of suspicious pelvic masses in postmenopausal women, as well as for detection of recurrence, monitoring of therapy, and determination of prognosis in women with ovarian cancer.

Conclusions: Implementation of these recommendations should encourage optimal use of tumor markers.

LPA receptor 2 mediates LPA-induced endometrial cancer invasion

OBJECTIVE

We have previously shown that lysophosphatidic acid (LPA) promotes the ovarian cancer metastatic cascade. In this study, we evaluated the role of LPA on endometrial cancer invasion.

METHODS

Transient mRNA knockdown was accomplished using pre-designed siRNA duplexes against LPA receptor 2 (LPA2) and human matrix metalloproteinase-7 (MMP-7). RT-PCR was used to characterize LPA receptor and MMP-7 expression. Analysis of in vitro invasion was performed with rat-tail collagen type I coated Boyden chambers. Gelatin zymography was used to evaluate the MMP activity in cell culture conditioned media. Cell-cell and cell-matrix attachment was also assessed upon LPA2 knockdown to further illuminate the LPA2 cascade.

RESULTS

LPA increases HEC1A cellular invasion at physiologic concentrations (0.1-1 muM). Of the four principle LPA receptors, LPA2 is predominantly expressed by HEC1A cells. Transient transfection of LPA2 siRNA reduced LPA2 mRNA expression in HEC1A cells by 93% (P<0.01). Silencing LPA2 eliminated the LPA-stimulated increase in invasion (P<0.05) and reduced LPA-induced MMP-7 secretion/activation, without significantly affecting cell-cell or cell-matrix adhesion. Silencing MMP-7 reduced overall invasion but did not eliminate LPA's pro-invasive effect on HEC1A cells, as compared to negative control (P<0.05). Gelatin zymography confirmed that LPA2 and MMP-7 knockdown reduced MMP-7 activation in HEC1A conditioned media.

CONCLUSION

LPA2 mediates LPA-stimulated HEC1A invasion and the subsequent activation of MMP-7.

Inhibition of lysophosphatidic acid receptor-2 expression by RNA interference decreases lysophosphatidic acid-induced urokinase plasminogen activator activation, cell invasion, and migration in ovarian cancer SKOV-3 cells

AIM

To explore the role of lysophosphatidic acid receptor-2 (LPA2) in regulating lysophosphatidic acid (LPA)-induced urokinase plasminogen activator (uPA) activation, cell invasion, and migration in human ovarian cancer cell line SKOV-3.

METHODS

SKOV-3 cells were stimulated with LPA. Cell supernatant uPA level and activity were measured using enzyme-linked immunosorbent assay. LPA2 mRNA expression was inhibited with LPA2-specific small interfering RNA (siRNA) and examined using semiquantitative reverse transcriptase-polymerase chain reaction. LPA-induced cell invasion and migration in transfected cells were evaluated by a Matrigel invasion chamber and a Transwell chemotaxis chamber, respectively.

RESULTS

LPA stimulation significantly enhanced in vitro uPA activity in time- and dose-dependent manner. The levels of LPA-induced uPA protein decreased by 55% in LPA2 siRNA-transfected cells compared with negatively transfected cells at 24 hours after being treated with 80 micromol/L LPA (0.75+/-0.03 vs 0.34+/-0.04, P=0.004). In the LPA2 specific siRNA-transfected SKOV-3 cells, LPA treatment at 80 micromol/L induced considerably less invasion and migration compared with negative control siRNA-transfected SKOV-3 cells (invasion: 178+/-17.2 vs 36.2+/-3.3, P=0.009; migration: 220.4+/-25.5 vs 57+/-7.6, P=0.009).

CONCLUSION

LPA2 has an essential role in LPA-induced uPA activation and tumor cell invasion in ovarian cancer SKOV-3 cells.

Critical molecular abnormalities in high-grade serous carcinoma of the ovary

Ovarian carcinomas show more morphological heterogeneity than adenocarcinomas of any other body site. It has recently become clear that the morphologically defined subtypes of ovarian carcinoma are distinct diseases, with different risk factors, molecular events during oncogenesis, likelihood of spread, responses to chemotherapy, and outcomes. This review focuses on molecular abnormalities (in genes expressing BRCA1/2, TP53 and RB1/CCND1/CDKN2A/E2F) found in high-grade serous carcinomas of the ovary, which account for most ovarian cancer deaths. These highly aggressive but chemosensitive tumours are associated with perturbation of molecular pathways leading to genomic instability and extreme mutability and present unique challenges in oncological research and practice.

Gene-expression profiling in epithelial ovarian cancer

DNA-microarray technology has made it possible to simultaneously analyze the expression of thousands of genes in a small sample of tumor tissue. In epithelial ovarian cancer, gene-expression profiling has been used to provide prognostic information, to predict response to first-line platinum-based chemotherapy, and to discriminate between different histologic subtypes. Furthermore, DNA-microarray technology might permit identification of novel markers for early detection of disease and provide insights into the mechanisms of cancer growth and chemotherapy resistance. In this Review, we summarize the contributions of gene-expression profiling to the diagnosis and management of epithelial ovarian cancer and discuss ways in which this technique could become a useful tool in clinical management.

Lysophosphatidic acid decreases the nuclear localization and cellular abundance of the p53 tumor suppressor in A549 lung carcinoma cells

Lysophosphatidic acid (LPA) is a bioactive lipid that promotes cancer cell proliferation and motility through activation of cell surface G protein-coupled receptors. Here, we provide the first evidence that LPA reduces the cellular abundance of the tumor suppressor p53 in A549 lung carcinoma cells, which express endogenous LPA receptors. The LPA effect depends on increased proteasomal degradation of p53 and it results in a corresponding decrease in p53-mediated transcription. Inhibition of phosphatidylinositol 3-kinase protected cells from the LPA-induced reduction of p53, which implicates this signaling pathway in the mechanism of LPA-induced loss of p53. LPA partially protected A549 cells from actinomycin D induction of both apoptosis and increased p53 abundance. Expression of LPA(1), LPA(2), and LPA(3) receptors in HepG2 hepatoma cells, which normally do not respond to LPA, also decreased p53 expression and p53-dependent transcription. In contrast, neither inactive LPA(1) (R124A) nor another G(i)-coupled receptor, the M(2) muscarinic acetylcholine receptor, reduced p53-dependent transcription in HepG2 cells. These results identify p53 as a target of LPA action and provide a new dimension for understanding how LPA stimulates cancer cell division, protects against apoptosis, and thereby promotes tumor progression.

Endogenous RGS proteins attenuate Galpha(i)-mediated lysophosphatidic acid signaling pathways in ovarian cancer cells

Lysophosphatidic acid is a bioactive phospholipid that is produced by and stimulates ovarian cancer cells, promoting proliferation, migration, invasion, and survival. Effects of LPA are mediated by cell surface G-protein coupled receptors (GPCRs) that activate multiple heterotrimeric G-proteins. G-proteins are deactivated by Regulator of G-protein Signaling (RGS) proteins. This led us to hypothesize that RGS proteins may regulate G-protein signaling pathways initiated by LPA in ovarian cancer cells. To determine the effect of endogenous RGS proteins on LPA signaling in ovarian cancer cells, we compared LPA activity in SKOV-3 ovarian cancer cells expressing G(i) subunit constructs that are either insensitive to RGS protein regulation (RGSi) or their RGS wild-type (RGSwt) counterparts. Both forms of the G-protein contained a point mutation rendering them insensitive to inhibition with pertussis toxin, and cells were treated with pertussis toxin prior to experiments to eliminate endogenous G(i/o) signaling. The potency and efficacy of LPA-mediated inhibition of forskolin-stimulated adenylyl cyclase activity was enhanced in cells expressing RGSi G(i) proteins as compared to RGSwt G(i). We further showed that LPA signaling that is subject to RGS regulation terminates much faster than signaling thru RGS insensitive G-proteins. Finally, LPA-stimulated SKOV-3 cell migration, as measured in a wound-induced migration assay, was enhanced in cells expressing Galpha(i2) RGSi as compared to cells expressing Galpha(i2) RGSwt, suggesting that endogenous RGS proteins in ovarian cancer cells normally attenuate this LPA effect. These data establish RGS proteins as novel regulators of LPA signaling in ovarian cancer cells.

Profiling studies in ovarian cancer: a review

Ovarian cancer is a heterogeneous disease with respect to histopathology, molecular biology, and clinical outcome. In advanced stages, surgery and chemotherapy result in an approximately 25% overall 5-year survival rate, pointing to a strong need to identify subgroups of patients that may benefit from targeted innovative molecular therapy. This review summarizes: (a) microarray research identifying gene-expression profiles in ovarian cancer; (b) the methodological flaws in the available microarray studies; and (c) applications of pathway analysis to define new molecular subgroups. Microarray technology now permits the analysis of expression levels of thousands of genes. So far seven studies have aimed to identify a genetic profile that can predict survival/clinical outcome and/or response to platinum-based therapy. To date, the clinical evidence of prognostic microarray studies has only reached the level of small retrospective studies, and there are other issues that may explain the nonreproducibility among the reported prognostic profiles, such as overfitting, technical platform differences, and accuracy of measurements. We consider pathway analysis a promising new strategy. The accumulation of small differential expressions within a meaningful molecular regulatory network might lead to a critical threshold level, resulting in ovarian cancer. Microarray technologies have already provided valuable expression data for classifying ovarian cancer and the first clues about which molecular changes in ovarian cancer could be exploited in new treatment strategies. Further improvements in technology as well as in study design, combined with pathway analysis, will allow us to detect even more subtle tumor expression differences among subgroups of ovarian cancer patients. Disclosure of potential conflicts of interest is found at the end of this article.

Antiangiogenic therapy for ovarian cancer

PURPOSE OF REVIEW

To highlight the current antiangiogenic compounds being evaluated as single agents or in association with chemotherapy in the treatment of ovarian cancer, as well as the rationale for their development.

RECENT FINDINGS

Several proangiogenic factors may be potential targets for antiangiogenic therapy in ovarian cancer. Bevacizumab, a monoclonal antibody against vascular endothelial growth factor, has been evaluated as a single agent in two phase II clinical trials and in combination with chemotherapy in three phase II studies, with promising results. This agent is also being evaluated in association with chemotherapy in two phase III clinical trials, both in the treatment and in the maintenance settings. Heparanase inhibitors and inhibitors of platelet-derived growth factor signalling remain as potential agents to be investigated in phase II trials. The development of biomarkers to define appropriate dosing regimens and predict which patients may benefit from antiangiogenic therapies is of great importance.

SUMMARY

Data from preclinical and clinical studies reported in the last 2 years demonstrate the importance of several proangiogenic factors in the prognosis of ovarian cancer, suggesting possible new targets for antiangiogenic therapy. The agents that are currently being investigated in phase II and III clinical trials include bevacizumab, erlotinib, sunitinib, sorafenib and vascular endothelial growth factor Trap, and the results of these trials will have significant implications in the future management of ovarian cancer.

Lysophospholipid receptors in cell signaling

There is increasing evidence that different phospholipids are involved in regulation of various cell processes and cell-cell interactions. Lysophospholipids (lysophosphatidic acid, lysophosphatidylcholine) and a number of lysosphingolipids play particular roles in these regulations. Their effects are mediated by specific G-protein-coupled receptors. G-Protein coupled signal transduction to the cell nucleus involving a chain of intracellular protein kinases induces the main effects in cells--growth, proliferation, survival, or apoptosis. This review summarizes recent data on various groups of lysophospholipid receptors and their cell signal transduction pathways.

The lysophosphatidic acid (LPA) receptors their expression and significance in epithelial ovarian neoplasms

OBJECTIVE

To investigate the lysophosphatidic acid (LPA) receptors expression situation and their biological significance in human ovarian cancer cell lines and in human epithelial ovarian neoplasms.

METHODS

The reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting were employed to measure the expression levels of LPA(1), LPA(2) and LPA(3) mRNA, LPA(2) and LPA(3) protein expression in cultured human ovarian cancer cell lines (3AO, SKOV3 and OVCAR3) and in human epithelial ovarian neoplasms. The immunocytochemical method was used to detect LPA(2) and LPA(3) protein expression in cultured human ovarian cancer cell lines.

RESULTS

RT-PCR revealed that all ovarian cancer cell lines expressed LPA(1), LPA(2) and LPA(3) mRNA. The positive rates (100%; 86.4%; 88.2%) of LPA(1) mRNA in normal ovarian tissue, benign tumor and ovarian cancer were no significant difference (p>0.05). The expression level of LPA(1) mRNA was significantly higher in normal ovarian tissue compared with that in benign tumor and in ovarian cancer tissue (p<0.01). LPA(1) expression level was no significant difference in both benign tumor and ovarian cancer tissue (p>0.05). LPA(2) mRNA-positive rates (92.6%) and expression level were significantly higher in ovarian cancer compared with that in benign tumor (31.8%) and in normal ovarian tissue (31.3%) (p<0.01); LPA(2) mRNA-positive rates and expression level were no significant difference in both benign tumor and normal ovarian tissue (p>0.05). LPA(3) mRNA-positive rates (92.6%) and expression level were significantly higher in ovarian cancer compared with that in benign tumor (31.8%) and in normal ovarian tissue (31.3%) (p<0.01), LPA(3) mRNA-positive rates and expression level were no significant difference in both benign tumor and normal ovarian tissue (p>0.05). LPA(1) mRNA expression level was significantly decreased compared with that of LPA(2) and LPA(3) in ovarian cancer (p<0.01); Western blotting clearly revealed that all ovarian cancer cell lines showed LPA(2) and LPA(3) protein. The positive rates and expression level of LPA(2) and LPA(3) protein were significantly increased in ovarian cancer (92.6%; 92.6%) compared with that in benign tumor (45.5%; 45.5%) and that in normal ovarian tissue (43.8%; 43.8%) (p<0.01); LPA(2) and LPA(3) protein-positive rates and expression level were no significant difference in both benign tumor and normal ovarian tissue (p>0.05). Correlation of clinicopathological parameters showed that LPA receptors mRNA and protein expression were associated with FIGO stage and histological grade, except pathologic types and age. The mRNA and protein expression of LPA(2) and LPA(3) in stages III and IV was significantly higher than that in stages I and II epithelial ovarian cancer (p<0.05). The mRNA and protein expression of pathologic grade G(3) was significantly higher compared with grade G(1) (p<0.05).

CONCLUSION

LPA(1), LPA(2) and LPA(3) mRNA and protein expressed widely in human epithelial ovarian neoplasms. LPA(2) and LPA(3) may be involved in the development and progression of human ovarian cancer. There was a significant correlation between LPA(2), LPA(3) and invasion and metastasis of epithelial ovarian cancer. LPA(2) and LPA(3) may be a prognostic indicator in patients with epithelial ovarian cancer.

Evidence that the Pim1 kinase gene is a direct target of HOXA9

The HOXA9 homeoprotein exerts dramatic effects in hematopoiesis. Enforced expression of HOXA9 enhances proliferation of primitive blood cells, expands hematopoietic stem cells (HSCs), and leads to myeloid leukemia. Conversely, loss of HOXA9 inhibits proliferation and impairs HSC function. The pathways by which HOXA9 acts are largely unknown, and although HOXA9 is a transcription factor, few direct target genes have been identified. Our previous study suggested that HOXA9 positively regulates Pim1, an oncogenic kinase. The hematologic phenotypes of Hoxa9- and Pim1-deficient animals are strikingly similar. Here we show that HOXA9 protein binds to the Pim1 promoter and induces Pim1 mRNA and protein in hematopoietic cells. Pim1 protein is diminished in Hoxa9(-/-) cells, and Hoxa9 and Pim1 mRNA levels track together in early hematopoietic compartments. Induction of Pim1 protein by HOXA9 increases the phosphorylation and inactivation of the proapoptotic BAD protein, a target of Pim1. Hoxa9(-/-) cells show increased apoptosis and decreased proliferation, defects that are ameliorated by reintroduction of Pim1. Thus Pim1 appears to be a direct transcriptional target of HOXA9 and a mediator of its antiapoptotic and proproliferative effects in early cells. Since HOXA9 is frequently up-regulated in acute myeloid leukemia, Pim1 may be a therapeutic target in human disease.

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.

Transactivation of platelet-derived growth factor receptor alpha by the GTPase-deficient activated mutant of Galpha12

The GTPase-deficient, activated mutant of Galpha12 (Galpha12Q229L, or Galpha12QL) induces neoplastic growth and oncogenic transformation of NIH 3T3 cells. Using microarray analysis, we have previously identified a role for platelet-derived growth factor receptor alpha (PDGFRalpha) in Galpha12-mediated cell growth (R. N. Kumar et al., Cell Biochem. Biophys. 41:63-73, 2004). In the present study, we report that Galpha12QL stimulates the functional expression of PDGFRalpha and demonstrate that the expression of PDGFRalpha by Galpha12QL is dependent on the small GTPase Rho. Our results indicate that it is cell type independent as the transient expression of Galpha12QL or the activation of Galpha12-coupled receptors stimulates the expression of PDGFRalpha in NIH 3T3 as well as in human astrocytoma 1321N1 cells. Furthermore, we demonstrate the presence of an autocrine loop involving PDGF-A and PDGFRalpha in Galpha12QL-transformed cells. Analysis of the functional consequences of the Galpha12-PDGFRalpha signaling axis indicates that Galpha12 stimulates the phosphatidylinositol 3-kinase (PI3K)-AKT signaling pathway through PDGFR. In addition, we show that Galpha12QL stimulates the phosphorylation of forkhead transcription factor FKHRL1 via AKT in a PDGFRalpha- and PI3K-dependent manner. Since AKT promotes cell growth by blocking the transcription of antiproliferative genes through the inhibitory phosphorylation of forkhead transcription factors, our results describe for the first time a PDGFRalpha-dependent signaling pathway involving PI3K-AKT-FKHRL1, regulated by Galpha12QL in promoting cell growth. Consistent with this view, we demonstrate that the expression of a dominant negative mutant of PDGFRalpha attenuated Galpha12-mediated neoplastic transformation of NIH 3T3 cells.

c-Src regulates constitutive and EGF-mediated VEGF expression in pancreatic tumor cells through activation of phosphatidyl inositol-3 kinase and p38 MAPK

OBJECTIVES

Multiple signaling proteins may be aberrantly activated and/or overexpressed in pancreatic tumors, including the nonreceptor protein tyrosine kinase Src. The goal of this study was to determine the role of Src in regulating VEGF expression and angiogenic potential in pancreatic cancer cell lines.

METHODS

Src activity was inhibited using the Src family kinase selective inhibitor PP2, and c-Src expression was down-regulated via siRNA. The activities of downstream signaling molecules phosphatidyl inositol 3'-kinase (PI3K) and p38 mitogen-activated protein kinase (MAPK) were disrupted via selective inhibitors. In vivo angiogenesis was assessed through the use of a gel-foam assay.

RESULTS

Inhibition of Src activity or expression decreases both constitutive and EGF-induced VEGF production. Both the PI3K/Akt and p38 MAPK pathways are activated in a Src family kinase-dependent fashion on EGF-R activation and are important for EGF-mediated VEGF production in pancreatic cancer cells. Additionally, media from Src-inhibited L3.6pl cells fail to promote angiogenesis into gel foams implanted subcutaneously into mice, whereas media from control cells promote a robust angiogenic response.

CONCLUSIONS

Src activity contributes to constitutive and EGF-induced VEGF expression and angiogenic potential in pancreatic cancer cells. Therefore, Src may be a viable target for antiangiogenesis therapy in pancreatic cancer.

Expression of the endothelial cell differentiation gene 7 (EDG-7), a lysophosphatidic acid receptor, in ovarian tumor

AIM

Lysophosphatidic acid (LPA) has received attention as a mitogen because the physiologically active lipid stimulates ovarian cancer cell growth by interacting with specific receptors, the endothelial cell differentiation gene (EDG) family. In the present study, we have investigated the expression of EDG-7 mRNA, part of the EDG family, in both human ovarian cancers and established human ovarian cancer cell lines.

METHODS

RNA was extracted from six ovarian cancer cell lines and multiple cancerous and normal ovarian tissues. The expression of EDG-7 mRNA was measured using reverse transcription-polymerase chain reaction and northern blotting, using reduced glyceraldehyde-phosphate dehydrogenase and S26 as internal controls.

RESULTS

Of the cell lines tested, EDG-7 mRNA was expressed most intensely in CRL-11731 and CRL-1572 and at a lesser but still substantial level in CRL-11732. The expression of EDG-7 mRNA was limited in MCAS, CRL-11730 and TYKnu. In the ovarian cancer tissues, EDG-7 mRNA was expressed most highly in endometrioid adenocarcinoma and serous cystadenocarcinoma. The expression of EDG-7 mRNA was limited in clear cell adenocarcinoma and undetectable in mucinous cystadenocarcinoma.

CONCLUSIONS

The intense EDG-7 expression in ovarian cancers suggests that the relation between LPA and EDG-7 (an LPA receptor) is involved in cancer cell growth and proliferation in some histologic subtypes of ovarian cancer.

Patterns of gene expression that characterize long-term survival in advanced stage serous ovarian cancers

PURPOSE

A better understanding of the underlying biology of invasive serous ovarian cancer is critical for the development of early detection strategies and new therapeutics. The objective of this study was to define gene expression patterns associated with favorable survival.

EXPERIMENTAL DESIGN

RNA from 65 serous ovarian cancers was analyzed using Affymetrix U133A microarrays. This included 54 stage III/IV cases (30 short-term survivors who lived <3 years and 24 long-term survivors who lived >7 years) and 11 stage I/II cases. Genes were screened on the basis of their level of and variability in expression, leaving 7,821 for use in developing a predictive model for survival. A composite predictive model was developed that combines Bayesian classification tree and multivariate discriminant models. Leave-one-out cross-validation was used to select and evaluate models.

RESULTS

Patterns of genes were identified that distinguish short-term and long-term ovarian cancer survivors. The expression model developed for advanced stage disease classified all 11 early-stage ovarian cancers as long-term survivors. The MAL gene, which has been shown to confer resistance to cancer therapy, was most highly overexpressed in short-term survivors (3-fold compared with long-term survivors, and 29-fold compared with early-stage cases). These results suggest that gene expression patterns underlie differences in outcome, and an examination of the genes that provide this discrimination reveals that many are implicated in processes that define the malignant phenotype.

CONCLUSIONS

Differences in survival of advanced ovarian cancers are reflected by distinct patterns of gene expression. This biological distinction is further emphasized by the finding that early-stage cancers share expression patterns with the advanced stage long-term survivors, suggesting a shared favorable biology.

Gene signatures of progression and metastasis in renal cell cancer

PURPOSE

To address the progression, metastasis, and clinical heterogeneity of renal cell cancer (RCC).

EXPERIMENTAL DESIGN

Transcriptional profiling with oligonucleotide microarrays (22,283 genes) was done on 49 RCC tumors, 20 non-RCC renal tumors, and 23 normal kidney samples. Samples were clustered based on gene expression profiles and specific gene sets for each renal tumor type were identified. Gene expression was correlated to disease progression and a metastasis gene signature was derived.

RESULTS

Gene signatures were identified for each tumor type with 100% accuracy. Differentially expressed genes during early tumor formation and tumor progression to metastatic RCC were found. Subsets of these genes code for secreted proteins and membrane receptors and are both potential therapeutic or diagnostic targets. A gene pattern ("metastatic signature") derived from primary tumor was very accurate in classifying tumors with and without metastases at the time of surgery. A previously described "global" metastatic signature derived by another group from various non-RCC tumors was validated in RCC.

CONCLUSION

Unlike previous studies, we describe highly accurate and externally validated gene signatures for RCC subtypes and other renal tumors. Interestingly, the gene expression of primary tumors provides us information about the metastatic status in the respective patients and has the potential, if prospectively validated, to enrich the armamentarium of diagnostic tests in RCC. We validated in RCC, for the first time, a previously described metastatic signature and further showed the feasibility of applying a gene signature across different microarray platforms. Transcriptional profiling allows a better appreciation of the molecular and clinical heterogeneity in RCC.

Inter-patient variation in efficacy of five oncolytic adenovirus candidates for ovarian cancer therapy

BACKGROUND

Gene therapy offers a new strategy for cancer treatment. Adenoviruses represent the most widely used gene therapy vector and feature an excellent safety record. Conditionally replicative adenoviruses (CRAds) effect solid tumor penetration and tumor selective oncolysis and consequently offer potential efficacy for metastatic disease treatment. We evaluated five CRAds as candidate clinical agents for ovarian cancer therapy: RGDCRADcox-2R, Ad5VEGFE1, Ad5/3VEGFE1, Ad5-Delta24RGD, and Ad5/3-Delta24.

METHODS

DNA replication by these five CRAds, wild-type adenovirus, and an E1-deleted control was measured in purified primary ovarian cancer cell spheroids by quantitative PCR. CRAd-mediated oncolysis was quantified in ovarian cancer cell monolayers and three-dimensional spheroids by cellular viability assays. The therapeutic efficacy of each CRAd was tested by intraperitoneal administration in mice with peritoneally disseminated human ovarian cancer.

RESULTS

An increase in viral DNA was noted in primary tumor cell spheroids for all replicative viruses tested. Variation was noted in viral DNA replication between patient samples. All five CRAds induced remarkable oncolysis. They also prolonged survival in vivo compared with the wild-type control group.

CONCLUSIONS

All five CRAds tested showed robust DNA replication, oncolysis, and in vivo therapeutic efficacy. Each virus has potential for clinical testing, and such further testing will ultimately determine its safety and relative usefulness. Variation of CRAd DNA replication between different patient samples suggests that target tissue features, such as surface receptors and endogenous transcription factors, may affect CRAd infectivity and replicativity. Evaluation of such factors may become important to optimize cancer therapy for individual patients.

Lysophospholipids in development: Miles apart and edging in

Sphingosine-1-phosphate (S1P) and lysophosphatidic acid (LPA) are endogenous bioactive lipids that participate in the regulation of mammalian cell proliferation, apoptosis, migration, and angiogenesis. These processes are each critical for successful embryogenesis, raising the possibility that lysophospholipid signaling may contribute to normal animal development. In fact, recent studies in developmental model systems have established that S1P and LPA are necessary for diverse developmental programs including those required for morphogenesis of vertebrate reproductive, cardiovascular and central and peripheral nervous systems (PNS), as well as the establishment of maternal-fetal circulation and the immune system. Genetic, morphological, and biochemical characterization of developmental model systems offer powerful approaches to elucidating the molecular mechanisms of lysophospholipid signaling and its contributions to animal development and postnatal physiology. In this review, the routes of S1P and LPA metabolism and our current understanding of lysophospholipid-mediated signal transduction in mammalian cells will be summarized. The evidence implicating lysophospholipid signaling in the development of specific vertebrate systems will then be reviewed, with an emphasis on signals mediated through G protein-coupled receptors of the Edg family. Lastly, recent insights derived from the study of simple metazoan models and implications regarding lysophospholipid signaling in organisms in which Edg receptors are not conserved will be explored.

Minireview: Cyclin D1: normal and abnormal functions

Cyclin D1 encodes the regulatory subunit of a holoenzyme that phosphorylates and inactivates the retinoblastoma protein and promotes progression through the G1-S phase of the cell cycle. Amplification or overexpression of cyclin D1 plays pivotal roles in the development of a subset of human cancers including parathyroid adenoma, breast cancer, colon cancer, lymphoma, melanoma, and prostate cancer. Of the three D-type cyclins, each of which binds cyclin-dependent kinase (CDK), it is cyclin D1 overexpression that is predominantly associated with human tumorigenesis and cellular metastases. In recent years accumulating evidence suggests that in addition to its original description as a CDK-dependent regulator of the cell cycle, cyclin D1 also conveys cell cycle or CDK-independent functions. Cyclin D1 associates with, and regulates activity of, transcription factors, coactivators and corepressors that govern histone acetylation and chromatin remodeling proteins. The recent findings that cyclin D1 regulates cellular metabolism, fat cell differentiation and cellular migration have refocused attention on novel functions of cyclin D1 and their possible role in tumorigenesis. In this review, both the classic and novel functions of cyclin D1 are discussed with emphasis on the CDK-independent functions of cyclin D1.

Mechanisms for Lysophosphatidic Acid-induced Cytokine Production in Ovarian Cancer Cells

A potential role for lysophosphatidic acid (LPA) in human oncogenesis was first suggested by the observation that LPA is present at elevated levels in ascites of ovarian cancer patients. In the current study, we demonstrated that LPA is a potent inducer of interleukin-6 (IL-6) and interleukin-8 (IL-8) production in ovarian cancer cells. Both IL-6 and IL-8 have been implicated in ovarian cancer progression. We characterized the IL-8 gene promoter to ascertain the transcriptional mechanism underlying LPA -induced expression of these cytokines. LPA stimulated the transcriptional activity of the IL-8 gene with little effect on IL-8 mRNA stability. The optimal response of the IL-8 gene promoter to LPA relied on binding sites for NF-kappaB and AP-1, two transcription factors that were strongly activated by LPA in ovarian cancer cell lines. Positive regulators of the NF-kappaB and AP-1 pathways synergistically activated the IL-8 gene promoter. Further, the effect of LPA on IL-6 and IL-8 generation is mediated by the Edg LPA receptors as enforced expression of LPA receptors restored LPA-induced IL-6 and IL-8 production in non-responsive cells and enhanced the sensitivity to LPA in responsive cell lines. The LPA(2) receptor was identified to be the most efficient in linking LPA to IL-6 and IL-8 production although LPA(1) and LPA(3) were also capable of increasing the response to a certain degree. These studies elucidate the transcriptional mechanism and the Edg LPA receptors involved in LPA-induced IL-6 and IL-8 production and suggest potential strategies to restrain the expression of these cytokines in ovarian cancer.