Angiogenesis and apoptosis

Penta- O -galloyl-beta- d -glucose suppresses tumor growth via inhibition of angiogenesis and stimulation of apoptosis: roles of cyclooxygenase-2 and mitogen-activated protein kinase pathways

Recent studies have revealed that 1,2,3,4,6-penta-O-galloyl-beta-d-glucose (PGG) has anti-tumorigenic activity in vitro. In the present work, we evaluated the in vitro and in vivo antiangiogenic and antitumor activities of PGG and examined its molecular mechanisms. PGG significantly inhibited the proliferation and tube formation in basic fibroblast growth factor (bFGF)-treated human umbilical vein endothelial cells (HUVECs) at non-cytotoxic concentrations. PGG effectively disrupted the bFGF-induced neo-vascularization in chick chorioallantoic membrane (CAM) and in Matrigel plugs in the mice. When mice were intraperitoneally injected, PGG also significantly inhibited tumor angiogenesis induced by Lewis lung carcinoma (LLC) and the growth of LLC by 57 and 91% of control tumor weight at 4 and 20 mg/kg, respectively. Immunohistochemical analysis revealed decreased microvessel density, decreased expression of cyclooxygenase-2 (COX-2) and vascular endothelial growth factor (VEGF), reduced tumor cell proliferation and increased tumor cell apoptosis. Similarly, PGG significantly attenuated the expression of COX-2 and VEGF and reduced the secretion of VEGF and prostaglandin E2 in bFGF-treated HUVECs. Furthermore, the COX-2 inhibitor NS398 significantly inhibited tube formation and neo-vascularization in CAM, supporting the role of COX-2 in PGG inhibition of angiogenesis. PGG diminished the phosphorylation of extracellular signal regulated kinase 1/2, Jun NH2-terminal kinase and activated phospho-p38 mitogen-activated protein kinase (MAPK) in a dose-dependent manner in bFGF-treated HUVECs. In addition, p38 inhibitor SB203580 abolished the downregulation of COX-2, VEGF and the antiproliferative activity by PGG. Taken together, our data demonstrate that PGG exerts antitumor activity primarily via inhibition of angiogenesis through COX-2 and MAPK- dependent pathways.

c-myc-induced hepatocarcinogenesis in the absence of IGF-I receptor

Numerous tumours, including hepatocarcinomas, produce IGFs, and some depend on these growth factors in a paracrine or autocrine fashion. We have shown that c-myc-induced experimental hepatocarcinogenesis is associated with enhanced production of IGF-II. To assess the role of the IGF-I receptor (IGF-IR) in hepatocarcinogenesis, we generated conditional mutant mice that overexpressed c-myc and were knocked out for IGF-IR specifically in the liver. We compared these mice with littermate controls that also overexpressed c-myc but had wild-type IGF-IR alleles. We found that the pretumoral phase, induced by early c-myc expression and characterised by increased cell proliferation, was largely unaffected by the lack of IGF-IR. To our further surprise, hepatocellular carcinomas (HCCs) lacking IGF-IR readily developed and progressed at the same rate as control HCCs. At 9 months, all c-myc transgenic mice displayed well-differentiated multifocal tumours, regardless of whether their livers-and their tumours-were able to produce IGF-IR. Levels of IRS-1 and IRS-2 were elevated in all tumours in the presence or absence of IGF-IR, suggesting that the signalling pathway downstream of IGF-IR is activated via IGF-IR-independent mechanisms in HCC. In conclusion, the deregulation of IGF signalling pathways, which often occurs during liver tumorigenesis, does not necessarily require IGF-IRs, and hepatic IGF-IR alone may not play a determinant role in c-myc-induced hepatocarcinogenesis.

Matrix-bound sixth Ig-like domain of cell adhesion molecule L1 acts as an angiogenic factor by ligating alphavbeta3-integrin and activating VEGF-R2

Angiogenic signals can be matrix attached or freely diffusible. Here, the sixth Ig-like domain of L1 (L1Ig6), a ligand for alphavbeta3-integrin, was investigated. This domain was expressed as a fusion protein having a substrate sequence for factor XIII to enable covalent binding into three-dimensional fibrin matrices. Matrix-bound L1Ig6 induced endothelial cell (EC) process extension in vitro, which was associated with ligation and phosphorylation of alphavbeta3-integrin. VEGF-R2 and alphavbeta3 were observed to co-associate after stimulation with either L1Ig6 or VEGF-A165, whereas no co-association with bFGF-R was observed. Furthermore, VEGF-R2 was tyrosine phosphorylated after stimulation with L1Ig6, even in the absence of exogenous VEGF-A165, indicating close cooperation between VEGF-R2 and alphavbeta3. Angiogenesis was investigated in vivo by stimulating chicken chorioallantoic membranes (CAMs) with L1Ig6-modified matrices with or without co-incorporation of VEGF-A165 or bFGF. Matrix-immobilized L1Ig6 induced angiogenesis to a similar degree as VEGF-A165; co-stimulation with bFGF increased vascular branching, whereas VEGF-A165 did not. Matrix-immobilized L1Ig6 induced up-regulation of alphav in CAMs by a similar degree as stimulation with VEGF-A165, and this up-regulation was increased further by co-stimulation with matrix-bound L1Ig6 and VEGF-A165. alpha5 and beta1 levels were not increased. The similarity of action of matrix-bound L1Ig6 and soluble VEGF-A165 indicate a close link between specific ligation of alphavbeta3-integrin and VEGF-R2 and suggest the possible use of matrix-bound L1Ig6 in local therapeutic angiogenesis.

Prolactin-induced expression of vascular endothelial growth factor via Egr-1

Angiogenesis is a dynamic process regulated by both local and systemic factors. Among these is vascular endothelial growth factor (VEGF), a potent effector of angiogenesis and vascular permeability. Previously we showed that VEGF is temporally and spatially regulated in the mouse mammary gland during development and lactation. Given the functions of prolactin (PRL) during these stages and the supporting role of the vasculature, we investigated the regulation of VEGF by PRL. Treatment of HC11 mouse mammary epithelial and Nb2 rat lymphoma cells with PRL induced VEGF expression. Deletion and mutation analysis identified a GC-rich region in the proximal region of the VEGF promoter that constitutively bound Sp1 and PRL-induced Egr-1. These sites conferred PRL-responsiveness leading to increased VEGF transcription. The induction of VEGF by PRL was PRL receptor-, Jak2- and MAP kinase kinase-dependent. Our results indicate that PRL induces VEGF expression through Egr-1, and implicates VEGF as an intermediary of PRL-regulated angiogenesis.

Tumour-selective drug delivery via folate receptor-targeted liposomes

Tumour cell-targeted liposomal delivery has the potential to enhance the therapeutic efficacy and reduce the toxicity of anticancer agents. Folate receptor (FR) expression is frequently amplified among human malignancies. FR is, therefore, potentially useful as a tumour marker for targeted drug delivery. FR-mediated liposomal delivery has been shown to enhance the antitumour efficacy of doxorubicin both in vitro and in vivo, and to overcome P-glycoprotein-mediated multi-drug resistance. In addition, FR-targeted liposomes have shown utility as effective delivery vehicles of genes and antisense oligodeoxyribonucleotides to FR(+) tumour cells. Both solid tumours and leukaemias can potentially benefit from FR-targeted drug delivery. Multiple mechanisms might contribute to greater therapeutic efficacy for FR-targeted liposomes, such as FR-dependent cytotoxicity and antiangiogenic activity. Further investigation of this promising drug delivery strategy is clearly warranted.

GPR4 plays a critical role in endothelial cell function and mediates the effects of sphingosylphosphorylcholine

Angiogenesis is critical for many physiological and pathological processes. We show here that the lipid sphingosylphosphorylcholine (SPC) induces angiogenesis in vivo and GPR4 is required for the biological effects of SPC on endothelial cells (EC). In human umbilical vein EC, down-regulation of GPR4 specifically inhibits SPC-, but not sphingosine-1-phosphate-, or vascular endothelial growth factor (VEGF)-induced tube formation. Re-introduction of GPR4 fully restores the activity of SPC. In microvascular EC, GPR4 plays a pivotal role in cell survival, growth, migration, and tube formation through both SPC-dependent and -independent pathways. The biological effects resulting from SPC/GPR4 interactions involve the activation of both phosphatidylinositol-3 kinase and Akt. Moreover, the effects of SPC on EC require SPC induced trans-phosphorylation and activation of the VEGF receptor 2. These results identify SPC and its receptor, GPR4, as critical regulators of the angiogenic potential of EC.

Fumagillin treatment of hepatocellular carcinoma in rats: An in vivo study of antiangiogenesis

AIM: To investigate the effect and possible mechanisms of antiangiogenesis therapy for HCC in rats.

METHODS: Adult male LEW/SsN rats were divided into 3 groups, 25 animals each. Group A was the control group. Groups B and C were given diethylnitrosamine, 5 mg/kg/d. In addition, group C rats received an intraperitoneal injection of fumagillin, 30 mg/(kg·d). Five animals in each group were killed at 6^th, 12^th, 18^th, 20^th and 24^th wk to evaluate the development of HCC and metastasis. Weight of the rats, liver tumors, and number of organs involved by HCC were measured at each stage. We compared methionine aminopeptidase-2 (MetAP-2) mRNA, Bcl-2 mRNA, telomerase mRNA, and telomerase activity at 24^th wk in the liver tissue of group A rats and tumor tissue of HCC from group B and C rats.

RESULTS: No HCC developed in group A, but tumors were present in group B and C rats by the 18^th wk. At wk 20 and 24, the median liver weight in group B was 0.64 g (range: 0.58-0.70 g) and 0.79 g (range: 0.70-0.90 g) (P = 0.04), and that in group C was 0.37 g (range: 0.35-0.42 g) and 0.39 g (range: 0.35-0.47 g) (P = 0.67). The liver weight in group C rats was significantly lower than that in group B rats (P = 0.009). At the same time, the median metastasis score (number of organ systems involved) was 3 (range 2-3) in group B, and 1 (range 1-2) in group C, a significant difference between the groups (P = 0.007, 0.004). The levels of MetAP-2 mRNA were significantly higher in groups B and C than in group A (P = 0.025), and significantly higher in group C than in group B (P = 0.047). The level of Bcl-2 mRNA was significantly higher in group B than in group A (P = 0.024), but lower in group C than in group B, although not significantly (P = 0.072). Telomerase mRNA was significantly higher in group B than in group A (P = 0.025), but significantly lower in group C than in group B (P = 0.016). The same inter-group relationship was also true for telomerase activity (P = 0.025 and 0.046).

CONCLUSION: Fumagillin effectively inhibits both liver tumor growth and metastasis in rats in vivo. A possible mechanism is fumagillin-induced inhibition of MetAP-2, which plays an essential role in endothelial cell proliferation. Inhibition of MetAP-2 also results in inhibition of Bcl-2 and telomerase activity.

CXCR4 regulates growth of both primary and metastatic breast cancer

The chemokine receptor CXCR4 and its cognate ligand CXCL12 recently have been proposed to regulate the directional trafficking and invasion of breast cancer cells to sites of metastases. However, effects of CXCR4 on the growth of primary breast cancer tumors and established metastases and survival have not been determined. We used stable RNAi to reduce expression of CXCR4 in murine 4T1 cells, a highly metastatic mammary cancer cell line that is a model for stage IV human breast cancer. Using noninvasive bioluminescence and magnetic resonance imaging, we showed that knockdown of CXCR4 significantly limited the growth of orthotopically transplanted breast cancer cells. Mice in which parental 4T1 cells were implanted had progressively enlarging tumors that spontaneously metastasized, and these animals all died from metastatic disease. Remarkably, RNAi of CXCR4 prevented primary tumor formation in some mice, and all mice transplanted with CXCR RNAi cells survived without developing macroscopic metastases. To analyze effects of CXCR4 on metastases to the lung, an organ commonly affected by metastatic breast cancer, we injected tumor cells intravenously and monitored cell growth with bioluminescence imaging. Inhibiting CXCR4 with RNAi, or the specific antagonist AMD3100, substantially delayed the growth of 4T1 cells in the lung, although neither RNAi nor AMD3100 prolonged overall survival in mice with experimental lung metastases. These data indicate that CXCR4 is required to initiate proliferation and/or promote survival of breast cancer cells in vivo and suggest that CXCR4 inhibitors will improve treatment of patients with primary and metastatic breast cancer.

A DNA Vaccine Targeting Survivin Combines Apoptosis with Suppression of Angiogenesis in Lung Tumor Eradication

A novel strategy achieved the eradication of lung tumor metastases by joint suppression of angiogenesis in the tumor neovasculature and induction of tumor cell apoptosis. This was accomplished by CTLs induced by a DNA vaccine encoding secretory chemokine CCL21 and the inhibitor of apoptosis protein survivin, overexpressed by both proliferating endothelial cells in the tumor vasculature and tumor cells. Oral delivery of this DNA vaccine by doubly attenuated Salmonella typhimurium (dam− and AroA−) to such secondary lymphoid organs as Peyer's patches in the small intestine, elicited marked activation of antigen-presenting dendritic cells, and an effective CD8+T cell immune response against the survivin self-antigen. This resulted in eradication or suppression of pulmonary metastases of non–small cell lung carcinoma in both prophylactic and therapeutic settings in C57BL/6J mice. Moreover, the suppression of angiogenesis induced by the vaccine did not impair wound healing or fertility of treated mice. It is anticipated that such novel DNA vaccines will aid in the rational design of future strategies for the prevention and treatment of cancer.

Transgenic nude mouse with ubiquitous green fluorescent protein expression as a host for human tumors

We report here the development of the transgenic green fluorescent protein (GFP) nude mouse with ubiquitous GFP expression. The GFP nude mouse was obtained by crossing nontransgenic nude mice with the transgenic C57/B6 mouse in which the beta-actin promoter drives GFP expression in essentially all tissues. In crosses between nu/nu GFP male mice and nu/+ GFP female mice, the embryos fluoresced green. Approximately 50% of the offspring of these mice were GFP nude mice. Newborn mice and adult mice fluoresced very bright green and could be detected with a simple blue-light-emitting diode flashlight with a central peak of 470 nm and a bypass emission filter. In the adult mice, the organs all brightly expressed GFP, including the heart, lungs, spleen, pancreas, esophagus, stomach, and duodenum. The following systems were dissected out and shown to have brilliant GFP fluorescence: the entire digestive system from tongue to anus; the male and female reproductive systems; brain and spinal cord; and the circulatory system, including the heart and major arteries and veins. The skinned skeleton highly expressed GFP. Pancreatic islets showed GFP fluorescence. The spleen cells were also GFP positive. Red fluorescent protein (RFP)-expressing human cancer cell lines, including PC-3-RFP prostate cancer, HCT-116-RFP colon cancer, MDA-MB-435-RFP breast cancer, and HT1080-RFP fibrosarcoma were transplanted to the transgenic GFP nude mice. All of these human tumors grew extensively in the transgenic GFP nude mouse. Dual-color fluorescence imaging enabled visualization of human tumor-host interaction by whole-body imaging and at the cellular level in fresh and frozen tissues. The GFP mouse model should greatly expand our knowledge of human tumor-host interaction.

Serum levels of angiogenic cytokines decrease after antineoplastic radiotherapy

Serum levels of angiogenic cytokines decrease after radiotherapy in patients with cancer and their may have an impact on response to treatment and progression-free survival. Here, we have evaluated sera of patients before and after radiotherapy for various tumour types for levels of soluble fibroblast growth factor-2 (FGF-2), vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF) to assess whether these factors decrease after radiotherapy, and whether their diminution is related to the radiation dose, tumour type, age and haemoglobin level. We demonstrate that levels of FGF-2 and VEGF, but not HGF, decrease significantly, and that the extent of their diminution is related to the radiation dose and response.

Adenovirus-mediated FLT1-targeted proapoptotic gene therapy of human prostate cancer

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL/Apo2L) is of particular interest in the development of prostate carcinoma therapeutics as it preferentially induces apoptosis of tumor cells. To employ adenoviral vectors for highly efficient and specific TRAIL gene transfer into cancer cells could overcome some potential problems for recombinant TRAIL. The vascular endothelial growth factor receptor FLT-1 is involved in regulation of angiogenesis and tumor growth, invasion, and metastasis of prostate carcinoma. FLT-1 expression is observed in both tumor endothelial cells and prostate cancer cells. We developed an adenoviral vector encoding the TRAIL gene under control of the FLT1 promoter (AdFlt-TRAIL), which produced endothelial and prostate cancer cell death. The combination of ionizing radiation and adenovirus-driven TRAIL expression overcame human prostate cancer cell resistance to TRAIL. Furthermore, in vivo administration of AdFlt-TRAIL at the site of tumor growth in combination with radiation treatment produced significant suppression of the growth of DU145 human prostate tumor xenografts in athymic nude mice. Our results suggest that specific TRAIL delivery employing the FLT1 promoter can effectively inhibit tumor growth and demonstrate the advantage of combination radiotherapy and gene therapy for the treatment of prostate cancer.

Phase 1 study of 28-day, low-dose temozolomide and BCNU in the treatment of malignant gliomas after radiation therapy

We conducted a study to determine the dose-limiting toxicity of an extended dosing schedule of temozolomide (TMZ) when used with a fixed dose of BCNU, or 1,3-bis(2-chloroethyl)-1-nitrosourea (carmustine), taking advantage of TMZ's ability to deplete O6-alkylguanine-DNA-alkyltransferase and the synergistic activity of these two agents. Patients with malignant gliomas who had undergone radiation therapy were eligible. Patients were treated with TMZ for 28 days, followed by a 28-day rest (1 cycle). The TMZ was started at 50 mg/m2 and increased in 10-mg/m2 increments; a fixed dose of BCNU (150 mg/m2) was given within 72 h of starting TMZ. A standard phase 1 dose-escalation scheme was used with 3 patients per cohort. Fourteen glioblastoma patients and 10 anaplastic astrocytoma patients were treated. The dose-limiting toxicity was myelosuppression at 90 mg/m2 of TMZ. The total number of cycles given was 73 (median number was 2). Six patients (25%) required a dose reduction in BCNU, and six were removed from study for hematologic toxicity after cycle 1; three patients overlapped. The median time to progression and overall survival were, respectively, 82 and 132 weeks for anaplastic astrocytomas and 14 and 69 weeks for glioblastomas. We conclude that the combination of BCNU and the extended dosing schedule of TMZ is feasible and that the maximal tolerated dose of a 28-day course of TMZ is 80 mg/m2 when combined with a fixed dose of BCNU at 150 mg/m2. This is the recommended dose for phase 2, but myelosuppression after cycle 1 suggests that long-term treatment may be difficult.

Nuclear factor of activated T cells balances angiogenesis activation and inhibition

It has been demonstrated that vascular endothelial cell growth factor (VEGF) induction of angiogenesis requires activation of the nuclear factor of activated T cells (NFAT). We show that NFATc2 is also activated by basic fibroblast growth factor and blocked by the inhibitor of angiogenesis pigment epithelial–derived factor (PEDF). This suggests a pivotal role for this transcription factor as a convergence point between stimulatory and inhibitory signals in the regulation of angiogenesis.

We identified c-Jun NH₂-terminal kinases (JNKs) as essential upstream regulators of NFAT activity in angiogenesis. We distinguished JNK-2 as responsible for NFATc2 cytoplasmic retention by PEDF and JNK-1 and JNK-2 as mediators of PEDF-driven NFAT nuclear export.

We identified a novel NFAT target, caspase-8 inhibitor cellular Fas-associated death domain–like interleukin 1β–converting enzyme inhibitory protein (c-FLIP), whose expression was coregulated by VEGF and PEDF. Chromatin immunoprecipitation showed VEGF-dependent increase of NFATc2 binding to the c-FLIP promoter in vivo, which was attenuated by PEDF. We propose that one possible mechanism of concerted angiogenesis regulation by activators and inhibitors may be modulation of the endothelial cell apoptosis via c-FLIP controlled by NFAT and its upstream regulator JNK.

Hedgehog-interacting protein is highly expressed in endothelial cells but down-regulated during angiogenesis and in several human tumors

BACKGROUND

The Hedgehog (Hh) signaling pathway regulates a variety of developmental processes, including vasculogenesis, and can also induce the expression of pro-angiogenic factors in fibroblasts postnatally. Misregulation of the Hh pathway has been implicated in a variety of different types of cancer, including pancreatic and small-cell lung cancer. Recently a putative antagonist of the pathway, Hedgehog-interacting protein (HIP), was identified as a Hh binding protein that is also a target of Hh signaling. We sought to clarify possible roles for HIP in angiogenesis and cancer.

METHODS

Inhibition of Hh signaling by HIP was assayed by measuring the induction of Ptc-1 mRNA in TM3 cells treated with conditioned medium containing Sonic hedgehog (Shh). Angiogenesis was assayed in vitro by EC tube formation on Matrigel. Expression of HIP mRNA was assayed in cells and tissues by Q-RT-PCR and Western blot. HIP expression in human tumors or mouse xenograft tumors compared to normal tissues was assayed by Q-RT-PCR or hybridization of RNA probes to a cancer profiling array.

RESULTS

We show that Hedgehog-interacting protein (HIP) is abundantly expressed in vascular endothelial cells (EC) but at low or undetectable levels in other cell types. Expression of HIP in mouse epithelial cells attenuated their response to Shh, demonstrating that HIP can antagonize Hh signaling when expressed in the responding cell, and supporting the hypothesis that HIP blocks Hh signaling in EC. HIP expression was significantly reduced in tissues undergoing angiogenesis, including PC3 human prostate cancer and A549 human lung cancer xenograft tumors, as well as in EC undergoing tube formation on Matrigel. HIP expression was also decreased in several human tumors of the liver, lung, stomach, colon and rectum when compared to the corresponding normal tissue.

CONCLUSION

These results suggest that reduced expression of HIP, a naturally occurring Hh pathway antagonist, in tumor neo-vasculature may contribute to increased Hh signaling within the tumor and possibly promote angiogenesis.

Overexpression of GD3 synthase induces apoptosis of vascular endothelial ECV304 cells through downregulation of Bcl-2

The disialoganglioside GD3 plays a major role in proliferation, differentiation, and apoptosis. It has been reported that ganglioside GD3 can induce apoptosis through bcl-2 mediated mitochondrial pathway. However, the relationship between ganglioside GD3 and B-cell/CLL lymphoma 2 (Bcl-2) is not fully understood. In this study, we have demonstrated that the downregulation of Bcl-2 by overexpression of CMP-NeuAc:GM3 alpha-2,8-sialyltransferase (GD3 synthase) results in an accelerated apoptosis in vascular endothelial cells (ECV304), as evidenced by DNA fragmentation and caspase-3 activation. In addition, phosphorylation of AKT and cyclic-AMP responsive element binding protein (CREB) was reduced by GD3 synthase overexpression. Moreover, the activation of CREB as a transcriptional factor was also inhibited, as evidenced by electrophoretic mobility shift assay. Therefore, we conclude that GD3 synthase has an apoptotic effect on ECV304 cells through downregulation of Bcl-2 expression via dephosphorylation of AKT and CREB.

The role of Fas ligand and transforming growth factor beta in tumor progression: molecular mechanisms of immune privilege via Fas-mediated apoptosis and potential targets for cancer therapy

Despite the fact that expression of Fas ligand (FasL) in cytotoxic T lymphocytes (CTLs) and in natural killer (NK) cells plays an important role in Fas-mediated tumor killing, During tumor progression FasL-expressing tumor cells are involved in counterattacking to kill tumor-infiltrating lymphocytes (TILs). Soluble FasL levels also increase with tumor progression in solid tumors, and this increase inhibits Fas-mediated tumor killing by CTLs and NK cells. The increased expression of FasL in tumor cells is associated with decreased expression of Fas; and the promoter region of the FASL gene is regulated by transcription factors, such as neuronal factor kappaB (NF-kappaB) and AP-1, in the tumor microenvironment. Although the ratio of FasL expression to Fas expression in tumor cells is not strongly related to the induction of apoptosis in TILs, increased expression of FasL is associated with decreased Fas levels in tumor cells that can escape immune surveillance and facilitate tumor progression and metastasis. Transforming growth factor beta (TGF-beta) is a potent growth inhibitor and has tumor-suppressing activity in the early phases of carcinogenesis. During subsequent tumor progression, the increased secretion of TGF-beta by both tumor cells and, in a paracrine fashion, stromal cells, is involved in the enhancement of tumor invasion and metastasis accompanied by immunosuppression. Herein, the authors review the clinical significance of FasL and TGF-beta expression patterns as features of immune privilege accompanying tumor progression in the tumor microenvironment. Potential strategies for identifying which molecules can serve as targets for effective antitumor therapy also are discussed.

Dual effects of IGFBP-3 on endothelial cell apoptosis and survival: involvement of the sphingolipid signaling pathways

Insulin-like growth factor binding protein (IGFBP)-3 has both growth-inhibiting and growth-promoting effects at the cellular level. The cytotoxic action of several anticancer drugs is linked to increased ceramide generation through sphingomyelin hydrolysis or de novo biosynthesis. Herein, we investigated the role of IGFBP-3 on apoptosis of human umbilical vein endothelial cells (HUVEC) and its relationship with ceramide levels. We report that IGFBP-3 exerts dual effects on HUVEC, potentiating doxorubicin-induced apoptosis but enhancing survival in serum-starved conditions. Ceramide was increased by IGFBP-3 in the presence of doxorubicin and decreased when IGFBP-3 was added alone to cells cultured in serum-free medium. The protection exerted by the ceramide synthase inhibitor fumonisin B1 over doxorubicin-induced apoptosis was enhanced by IGFBP-3 with concomitant reduction of ceramide levels. IGFBP-3 alone activated sphingosine kinase (SK) and increased SK1 mRNA; the SK inhibitor N,N-dimethylsphingosine (DMS) blocked IGFBP-3 antiapoptotic effect. Moreover, IGFBP-3 increased IGF-I mRNA and dramatically enhanced IGF-I release. IGF-I receptor (IGF-IR) and its downstream signaling pathways Akt and ERK were phosphorylated by IGFBP-3, whereas inhibition of IGF-IR phosphorylation with tyrphostin AG1024 suppressed the antiapopoptic effect of IGFBP-3. Finally, IGFBP-3 increased endothelial cell motility in all experimental conditions. These findings provide evidence that IGFBP-3 differentially regulates endothelial cell apoptosis by involvement of the sphingolipid signaling pathways. Moreover, the survival effect of IGFBP-3 seems to be mediated by the IGF-IR.

Apoptosis of human umbilical vein endothelial cells induced by artesunate

Artesunate (ART), a semi-synthetic derivative of artemisinin isolated from the traditional Chinese herb Artemisia annua, is an effective novel antimalarial drug. The present study investigated the apoptotic activity of artesunate in cultured human umbilical vein endothelial cell (HUVEC) by means of nuclear staining, DNA agarose gel electrophoresis, and flow cytometry. The observations also indicated that artesunate induced apoptosis of HUVEC in a concentration-dependent and time-dependent manner. A Western immunoblot analysis showed down-regulation of the bcl-2 protein and up-regulation of the bax protein in the artesunate-treated HUVEC. Ca2+ in cells was evaluated by fluorescent spectrophotometer using Fura 2-AM as probe. These results suggest that artesunate may be a potential apoptosis-inducing agent for endothelial cells.

Antiangiogenic gene therapy of cancer: recent developments

With the role of angiogenesis in tumor growth and progression firmly established, considerable effort has been directed to antiangiogenic therapy as a new modality to treat human cancers. Antiangiogenic agents have recently received much widespread attention but strategies for their optimal use are still being developed. Gene therapy represents an attractive alternative to recombinant protein administration for several reasons. This review evaluates the potential advantages of gene transfer for antiangiogenic cancer therapy and describes preclinical gene transfer work with endogenous angiogenesis inhibitors demonstrating the feasibility of effectively suppressing and even eradicating tumors in animal models. Additionally, we describe the advantages and disadvantages of currently available gene transfer vectors and update novel developments in this field. In conclusion, gene therapy holds great promise in advancing antiangiogenesis as an effective cancer therapy and will undoubtedly be evaluated in human clinical trials in the near future.

GW112, a novel antiapoptotic protein that promotes tumor growth

GW112 is a novel gene that has little homology to other known genes. It is overexpressed in a number of human tumor types, especially in those of the digestive system. We show here that GW112 is associated with GRIM-19, a protein known to be involved in regulating cellular apoptosis. Functionally, GW112 could significantly attenuate the ability of GRIM19 to mediate retinoic acid-IFN-beta-mediated cellular apoptosis and apoptosis-related gene expression. In addition, GW112 demonstrated strong antiapoptotic effects in tumor cells treated with other stress exposures such as hydrogen peroxide. Finally, forced overexpression of GW112 in murine prostate tumor cells led to more rapid tumor formation in a syngeneic host. Taken together, our data suggest that GW112 is an important regulator of cell death that plays important roles in tumor cell survival and tumor growth.

Critical overview and outlook: pathogenesis, prevention, and treatment of hepatitis and hepatocarcinoma caused by hepatitis B virus

Viral hepatitis B is an enigmatic disease in which the host's own immune response to persistent viral infection may bring about host destruction through antiviral inflammatory responses which might otherwise present as a benign or inapparent disease. The simple solution to the hepatitis B problem is by immunoprophylaxis using the vaccine licensed in 1981, which prevents both infection and the late sequelae of liver cirrhosis and hepatocarcinoma. Immunotherapeutic vaccines against persistent hepatitis B infection have not been successful and new explorations are being directed to therapies which include antisense, ribozymes, gene silencing by RNA interference (RNAi) and aptamer approaches. Limited benefits from nucleoside therapy and limitations in opportunity for liver transplantation have left a large void of curative treatments. Findings with respect to e antigen tolerance provide a basis for exploration to determine whether passively administered e antigen might suppress cell-mediated immunity, creating a commensal state in which virus persists but without pathologic damage to the host. Therapy of hepatocarcinoma by conventional chemotherapy, radiation, or surgical resection and ablation gives little hope for restoration of health unless the tumor is detected very early. The large engagement of the world medical science community to develop therapeutic vaccines against cancer is now in major clinical trials to determine the hope and credibility for the immunization approach. Vaccines based on tumor peptides which are linked to heat shock proteins and directed to host dendritic cells give reason for excitement and may be the "best show in town". A new era of tumor therapy will need to be based on new discoveries in immune function which are required to pursue immunotherapy on a more rational basis. The many facets of current hepatitis B virology, pathogenesis, immunoprophylaxis, immunotherapeusis, chemotherapy, and tumor pathogenesis and therapy are discussed here, in depth, but in keeping with needed brevity.

Cell type-specific expression of LINE-1 open reading frames 1 and 2 in fetal and adult human tissues

The LINE-1 (L1) family of non-long terminal repeat retrotransposons is a major force shaping mammalian genomes, and its members can alter the genome in many ways. Mutational analyses have shown that coexpression of functional proteins encoded by the two L1-specific open reading frames, ORF1 and ORF2, is an essential prerequisite for the propagation of L1 elements in the genome. However, all efforts to identify ORF2-encoded proteins have failed so far. Here, applying a novel antibody we report the presence of proteins encoded by ORF2 in a subset of cellular components of human male gonads. Immunohistochemical analyses revealed coexpression of ORF1 and ORF2 in prespermatogonia of fetal testis, in germ cells of adult testis, and in distinct somatic cell types, such as Leydig, Sertoli, and vascular endothelial cells. Coexpression of both proteins in male germ cells is necessary for the observed genomic expansion of the number of L1 elements. Peptide mass fingerprinting analysis of a approximately 130-kDa polypeptide isolated from cultured human dermal microvascular endothelial cells led to the identification of ORF2-encoded peptides. An isolated approximately 45-kDa polypeptide was shown to derive from nonfunctional copies of ORF2 coding regions. The presence of both ORF1- and ORF2-encoded proteins in vascular endothelial cells and its apparent association with certain stages of differentiation and maturation of blood vessels may have functional relevance for vasculogenesis and/or angiogenesis.

Heparanase induces endothelial cell migration via protein kinase B/Akt activation

Heparanase is a mammalian endoglycosidase that degrades heparan sulfate (HS) at specific intra-chain sites. Blood-borne neutrophils, macrophages, mast cells, and platelets exhibit heparanase activity that is thought to be stored in specific granules. The degranulated heparanase is implicated in extravasation of metastatic tumor cells and activated cells of the immune system. Degranulation and heparanase release in response to an inflammatory stimulus or platelet activation would facilitate cellular extravasation directly, by altering the composition and structural integrity of the extracellular matrix, or indirectly, by releasing HS-bound proinflammatory cytokines and chemokines. We hypothesized that in addition to such indirect effect, the released heparanase may also locally affect and activate neighboring cells such as endothelial cells. Here, we provide evidence that addition of the 65-kDa latent heparanase to endothelial cells enhances Akt signaling. Heparanase-mediated Akt phosphorylation was independent of its enzymatic activity or the presence of cell membrane HS proteoglycans and was augmented by heparin. Moreover, addition of heparanase stimulated phosphatidylinositol 3-kinase-dependent endothelial cell migration and invasion. These results suggest, for the first time, that heparanase activates endothelial cells and elicits angiogenic responses directly. This effect appears to be mediated by as yet unidentified heparanase receptor.

VEGF receptor phosphorylation status and apoptosis is modulated by a green tea component, epigallocatechin-3-gallate (EGCG), in B-cell chronic lymphocytic leukemia

We recently reported that chronic lymphocytic leukemia (CLL) cells synthesize and release vascular endothelial growth factor (VEGF) under normoxic and hypoxic conditions. CLL B cells also express VEGF membrane receptors (VEGF-R1 and VEGF-R2), suggesting that they use VEGF as a survival factor. To assess the mechanism of apoptosis resistance related to VEGF, we determined the impact of VEGF on CLL B cells, and we studied the impact of epigallocatechin-3-gallate (EGCG), a known receptor tyrosine kinase (RTK) inhibitor, on VEGF receptor status and viability of CLL B cells. VEGF165 significantly increased apoptotic resistance of CLL B cells, and immunoblotting revealed that VEGF-R1 and VEGF-R2 are spontaneously phosphorylated on CLL B cells. EGCG significantly increased apoptosis/cell death in 8 of 10 CLL samples measured by annexin V/propidium iodide (PI) staining. The increase in annexin V/PI staining was accompanied by caspase-3 activation and poly-adenosine diphosphate ribose polymerase (PARP) cleavage at low concentrations of EGCG (3 microg/mL). Moreover, EGCG suppressed the proteins B-cell leukemia/lymphoma-2 protein (Bcl-2), X-linked inhibitor of apoptosis protein (XIAP), and myeloid cell leukemia-1 (Mcl-1) in CLL B cells. Finally, EGCG (3-25 microg/mL) suppressed VEGF-R1 and VEGF-R2 phosphorylation, albeit incompletely. Thus, these results suggest that VEGF signaling regulates survival signals in CLL cells and that interruption of this autocrine pathway results in caspase activation and subsequent leukemic cell death.

Endostatin-mediated concomitant resistance in neuroblastoma

PURPOSE

Concomitant resistance, the phenomenon whereby a primary malignancy inhibits the growth of metastatic lesions, is likely caused by the production of endogenous anti-angiogenic factors. The purpose of this study was to evaluate the influence of the angiogenesis inhibitor, endostatin, expressed by primary sites of neuroblastoma, on synchronous disease.

METHODS

Two neuroblastoma models were used. In one, the growth of a second primary tumor in mice with an already established primary tumor was compared with tumor growth in nave mice. In the other, the growth of liver metastases arising spontaneously from a subcutaneous tumor was compared in mice in which the primary tumor was either excised or left in place. Systemic endostatin levels and endothelial cell density, vascularity, and degree of apoptosis in the secondary tumors and liver metastasis were evaluated.

RESULTS

Subcutaneous tumors in mice with preexisting neuroblastoma were significantly smaller than in mice without an established primary tumor; systemic endostatin levels at the time of tumor implantation in mice with preexisting tumors were nearly 3 times that of nave mice. Decreased angiogenesis and increased apoptosis were seen in the secondary tumors of mice with preexisting tumors. Similarly, the weight of liver metastases was significantly less in mice in which the primary tumor was left in place as compared with those in which the primary tumor had been excised. Systemic endostatin levels in this model paralleled the status of the primary tumor; levels decreased with primary tumor excision but increased when the primary tumor was retained and allowed to grow. Although no difference in microvessel density was seen between groups in the liver metastasis, more tumor cell apoptosis was seen in liver metastasis when the primary tumor was retained. Thus, the presence of an established primary neuroblastoma had a significant inhibitory effect on the growth of secondary disease in both models and was associated with elevated systemic endostatin levels.

CONCLUSIONS

Concomitant antitumoral resistance occurred in these experimental murine models of neuroblastoma and appears to be caused, at least in part, by angiogenesis inhibition mediated by endostatin elaborated from primary tumors.

Anti-neoplastic efficacy of Haimiding on gastric carcinoma and its mechanisms

AIM

To study the anti-neoplastic effect of Haimiding and its mechanisms of action.

METHODS

Experiments using MTT and colony formation were carried out to study the in vitro anti-neoplastic action of Haimiding, its in vivo anti-neoplastic action was studied by observing its effect on the weight of tumors in FC mice and S(180), H(22) tumor bearing mice, as well as their life spans. The effect of Haimiding on cell apoptosis and different stages of cell cycles in human gastric carcinoma cells were studied by flow cytometry. Its effect on [Ca(2+)](i) of human gastric carcinoma cells and the source of Ca(2+) during the change of [Ca(2+)](i) were observed by confocal laser scanning technique.

RESULTS

Haimiding showed a definite cytotoxicity to 8 human tumor cell lines, which was most prominent against BGC-823, E(ca-109) and HCT-8 tumor cells. It also exhibited an obvious inhibition on colony formation of the above tumor cell lines, which was most prominent in E(ca-109) tumor cells. It showed obvious inhibition on the growth of tumor in FC mice and S(180) bearing mice as well as prolonged the life span of H(22) bearing mice. It was able to induce apoptosis and elevate intracellular [Ca(2+)](i) concentration of tumor cells. The source of Ca(2+) came from both extracellular Ca(2+) influx and intracellular Ca(2+) release.

CONCLUSION

Haimiding is composed of a TCM preparation and 5-flurouracil. Its anti-neoplastic potency is highly enhanced by synergism as compared with either one of its components. Its mechanisms of anti-neoplastic action can be attributed to its action to initiate apoptosis of tumor cells by opening the membrane calcium channel and inducing intracellular Ca(2+) release to elevate [Ca(2+)](i) of the tumor cells.

Prognostic and predictive factors in oral squamous cell cancer: important tools for planning individual therapy?

An escalation in the incidence of oral cancer and its attributable mortality has been observed in recent decades in Europe; oral cancer is expected to become a public health problem in the foreseeable future. However, survival rates have remained at a disappointingly stable level despite significant development in the multimodality treatment of the disease. Additionally, due to the limited prognostic value of conventional prognostic factors and the uniformity of treatment strategies, several patients are still over- or under-treated with significant personal and socio-economical impact. Here we review some promising prognostic and predictive markers that can help the clinician to improve prognostic accuracy and define the most appropriate management for the individual patient with oral cancer.

Do the signalling proteins for angiogenesis exist as a modular complex? The case for the angosome

The vasculature remains quiescent during much of adult life, but new blood vessels can be rapidly produced when required by a process referred to as angiogenesis. Angiogenesis involves a complex series of events including the proliferation, migration, differentiation and apoptosis of capillary endothelial cells, as well as changes in vascular permeability. This hypothesis argues that in the quiescent vasculature the many factors that regulate angiogenesis are normally held together as part of an inactive modular unit, and that when angiogenesis is stimulated the modular unit dissociates thus enabling angiogenic regulators to become active. I have termed this modular unit the "angosome". It is proposed that the angosome is present in the caveolae of capillary endothelial cells. Caveolae are flask-shaped invaginations in the plasmalemma that compartmentalise signalling molecules. Endothelial cells are particularly rich in caveolae. Many of the structural and functional aspects of caveolae are controlled by the protein caveolin, one form of which, caveolin-1, interacts directly or indirectly with most of the regulatory molecules involved in angiogenesis. Caveolin-1 forms oligomers of 14-16 sub-units and I propose that oligomers of caveolin-1 form the scaffold that holds together the angosome. There is evidence that caveolin-1 is up-regulated in the differentiated, quiescent vasculature and down-regulated in proliferating endothelial cells. Since the presence of caveolin-1 can inhibit pro-angiogenic factors, it may act as a "master-switch" co-ordinating events during angiogenesis. Thus when the vasculature is quiescent the angosome may hold angiogenic factors in an inactive state and when angiogenesis is required, the angosome must disassociate to enable angiogenic factors to become active.

Chorionic gonadotropin regulates the transcript level of VHL, p53, and HIF-2? in human granulosa lutein cells

The ovarian corpus luteum plays a critical role in reproduction being the primary source of circulating progesterone. After ovulation the corpus luteum is build by avascular granulosa lutein cells through rapid vascularization regulated by gonadotropic hormones. The present study was performed to investigate whether this process might be influenced by the human chorionic gonadotropin (hCG)-dependent expression of different tumor suppressor genes and hypoxia dependent transcription factors. RNA was isolated from cultured granulosa lutein cells, transcribed into cDNA, and the transcript level of following genes were determined: RB-1, VHL, NF-1, NF-2, Wt-1, p53, APC, and hypoxia inducible factor-1 (HIF-1), -2, and -3alpha. Additionally, the influence of hCG on the expression of VHL, p53, and HIf2alpha were investigated. We demonstrate that in human granulosa lutein cells the tumor suppressor genes RB-1, VHL, NF-1, NF-2, Wt-1, p53, and APC and the hypoxia dependent transcription factors HIF-1alpha, -2alpha, and -3alpha are expressed. In addition, we showed that hCG regulates the expression of p53, VHL, and HIF-2alpha. Our results indicate that hCG may determine the growth and development of the corpus luteum by mediating hypoxic and apoptotic pathways in human granulosa lutein cells.

Antiangiogenic therapy and tumor progression

Angiogenesis is necessary for tumor growth (a rationale for antiangiogenic therapy), but hypoxia caused by such a therapy will, in theory, drive tumor progression and metastasis. To reconcile conflicting notions, we discuss that, first, although a shift from normoxia (21% O2) to hypoxia indeed activates cancer cells for aggressive behavior, this may not occur during therapy, because most cancers are not normoxic to start with. Second, only successful antiangiogenic therapy, which is capable of controlling cancer, will select for resistance and progression. After all, in order to occur, therapy-induced tumor progression must be preceded by tumor regression.

Dual-color fluorescence imaging distinguishes tumor cells from induced host angiogenic vessels and stromal cells

We have developed a simple yet powerful technique for delineating the morphological events of tumor-induced angiogenesis and other tumor-induced host processes with dual-color fluorescence. The method clearly images implanted tumors and adjacent stroma, distinguishing unambiguously the host and tumor-specific components of the malignancy. The dual-color fluorescence imaging is effected by using red fluorescent protein (RFP)-expressing tumors growing in GFP-expressing transgenic mice. This model shows with great clarity the details of the tumor-stroma interaction, especially tumor-induced angiogenesis and tumor-infiltrating lymphocytes. The GFP-expressing tumor vasculature, both nascent and mature, could be readily distinguished interacting with the RFP-expressing tumor cells. GFP-expressing dendritic cells were observed contacting RFP-expressing tumor cells with their dendrites. GFP-expressing macrophages were observed engulfing RFP-expressing cancer cells. GFP lymphocytes were seen surrounding cells of the RFP tumor, which eventually regressed. Dual-color fluorescence imaging visualizes the tumor-host interaction by whole-body imaging and at the cellular level in fresh tissues, dramatically expanding previous studies in fixed and stained preparations.