Inhibition of MAP kinase kinase causes morphological reversion and dissociation between soft agar growth and in vivo tumorigenesis in angiosarcoma cells

Hemangiosarcoma in dogs as a potential non-rodent animal model for drug discovery research of angiosarcoma in humans

Since the domestication of dogs 10,000 years ago, they have shared their living environment with humans and have co-evolved. The breeding process that dogs have undergone in only a few centuries has led to a significant accumulation of specific genetic alterations that could induce particular diseases in certain breeds. These canine diseases are similar to what is found in humans with several differences; therefore, comparing such diseases occurring in humans and dogs can help discover novel disease mechanisms, pathways, and causal genetic factors. Human angiosarcoma (AS) and canine hemangiosarcoma (HSA), which are sarcomas originating from endothelium, are examples of diseases shared between humans and dogs. They exhibit similar characteristics and clinical behaviors, although with some critical differences resulting from evolution. In this review, we will describe the similarities and differences in terms of clinical and molecular characteristics between human AS and canine HSA, and discuss how these similarities and differences can be applied to advance the treatment of these diseases.

Inhibition of Endoglin Exerts Antitumor Effects through the Regulation of Non-Smad TGF-β Signaling in Angiosarcoma

Angiosarcoma is a rare malignant tumor derived from endothelial cells, and its prognosis is poor because advanced angiosarcoma is often resistant to taxane therapy. Endoglin (CD105) acts as a coreceptor for TGF-β signaling and is overexpressed in tumor-associated endothelial cells and enhances tumor angiogenesis. Numerous clinical trials are testing the effectiveness of anti-endoglin antibodies in various types of malignancies. Here, we investigated the role of endoglin in the pathogenesis of angiosarcoma and whether endoglin inhibition results in antitumor activity. Endoglin was overexpressed in angiosarcoma, and its inhibition was effective in promoting apoptosis and the suppression of migration, invasion, tube formation, and Warburg effect in angiosarcoma cells. Knockdown of endoglin activated caspase 3/7 that is essential for apoptosis, reduced survivin levels, and decreased paxillin and vascular endothelial cadherin phosphorylation and matrix metalloproteinase 2 and matrix metalloproteinase 9 activities in angiosarcoma cells. Although endoglin is a coreceptor that regulates TGF-β signaling, the antitumor effect of endoglin in angiosarcoma was not based on Smad signaling regulation but on non-Smad TGF-β signaling. Taken together, these results indicated that endoglin could be a novel therapeutic target for angiosarcoma.

Rho kinase proteins display aberrant upregulation in vascular tumors and contribute to vascular tumor growth

BACKGROUND

The serine/threonine protein kinases ROCK1 and 2 are key RhoA-mediated regulators of cell shape and cytoskeletal dynamics. These proteins perform multiple functions in vascular endothelial cell physiology and are attractive targets for cancer therapy based on their roles as oncogenes and metastatic promoters. Given their critical functions in both of these processes, we hypothesized that molecular targeting of ROCK proteins would be exceedingly effective against vascular tumors such as hemangiomas and angiosarcomas, which are neoplasms composed of aberrant endothelial cells.

METHODS

In this study, we compared ROCK1 and 2 protein expression in a large panel of benign and malignant vascular tumors to that of normal vasculature. We then utilized shRNA technology to knockdown the expression of ROCK1 and 2 in SVR tumor-forming vascular cells, and evaluated tumor size and proliferation rate in a xenograft model. Finally, we employed proteomics and metabolomics to assess how knockdown of the ROCK paralogs induced alterations in protein expression/phosphorylation and metabolite concentrations in the xenograft tumors.

RESULTS

Our findings revealed that ROCK1 was overexpressed in malignant vascular tumors such as hemangioendotheliomas and angiosarcomas, and ROCK2 was overexpressed in both benign and malignant vascular tumors including hemangiomas, hemangioendotheliomas, hemangiopericytomas, and angiosarcomas. shRNA-mediated knockdown of ROCK2, but not ROCK1, in xenograft vascular tumors significantly reduced tumor size and proliferative index compared to control tumors. Proteomics and metabolomics analysis of the xenograft tumors revealed both overlapping as well as unique roles for the ROCK paralogs in regulating signal transduction and metabolite concentrations.

CONCLUSIONS

Collectively, these data indicate that ROCK proteins are overexpressed in diverse vascular tumors and suggest that specific targeting of ROCK2 proteins may show efficacy against malignant vascular tumors.

Targeting the duality of cancer

Cancer is the second leading cause of death in the United States, and is an increasing cause of death in the developing world. While there is great heterogeneity in the anatomic site and mutations involved in human cancer, there are common features, including immortal growth, angiogenesis, apoptosis evasion, and other features, that are common to most if not all cancers. However, new features of human cancers have been found as a result of clinical use of novel “targeted therapies,” angiogenesis inhibitors, and immunotherapies, including checkpoint inhibitors. These findings indicate that cancer is a moving target, which can change signaling and metabolic features based upon the therapies offered. It is well-known that there is significant heterogeneity within a tumor and it is possible that treatment might reduce the heterogeneity as a tumor adapts to therapy and, thus, a tumor might be synchronized, even if there is no major clinical response. Understanding this concept is important, as concurrent and sequential therapies might lead to improved tumor responses and cures. We posit that the repertoire of tumor responses is both predictable and limited, thus giving hope that eventually we can be more effective against solid tumors. Currently, among solid tumors, we observe a response of 1/3 of tumors to immunotherapy, perhaps less to angiogenesis inhibition, a varied response to targeted therapies, with relapse and resistance being the rule, and a large fraction being insensitive to all of these therapies, thus requiring the older therapies of chemotherapy, surgery, and radiation. Tumor phenotypes can be seen as a continuum between binary extremes, which will be discussed further. The biology of cancer is undoubtedly more complex than duality, but thinking of cancer as a duality may help scientists and oncologists discover optimal treatments that can be given either simultaneously or sequentially.

The antioxidant paradox: what are antioxidants and how should they be used in a therapeutic context for cancer

So-called antioxidants have yet to make a clinical impact on the treatment of human cancer. The reasons for this failure are several. First, many agents that are called antioxidants are truly antioxidants at a given dose, but this dose may not have been given in clinical trials. Second, many agents are not antioxidants at all. Third, not all tumors use reactive oxygen as a signaling mechanism. Finally, reactive oxygen inhibition is often insufficient to kill or regress a tumor cell by itself, but requires sequential introduction of a therapeutic agent for maximal effect. We hope to provide a framework for the logical use of these agents in cancer.

Low level of baseline circulating VEGF-A is associated with better outcome in patients with vascular sarcomas receiving sorafenib: an ancillary study from a phase II trial

We have carried out a stratified phase II study of sorafenib (So) in patients with advanced angiosarcoma (n = 32) and epithelioid hemangioendothelioma (n = 13). This report concerns the correlative analysis of the predictive values of circulating pro/anti-angiogenetic biomarkers. Using the ELISA method (R&D Systems), circulating biomarkers (VEGF-A, in picograms per milliliter), thrombospondin-1 (TSP1, in micrograms per milliliter), stem cell factor (SCF, in picograms per milliliter), placental growth factor (PlGF, in picograms per milliliter), VEGF-C (in picograms per milliliter), and E-selectin (in nanograms per milliliter) were measured before So treatment and after 7 days. VEGF-A (mean value 475 vs. 541, p = 0.002), TSP1 (16 vs. 24, p = 0.0002), and PlGF (20.9 vs. 40.7, p = 0.0001) significantly increased during the treatment. Treatment did not affect the levels of SCF, VEGF-C, and E-selectin. Only two biomarkers were associated with better outcome as follows: VEGF-A and PlGF. Best objective response and non-progression at 180 days were associated with low level of VEGF-A at baseline (p = 0.04 and 0.03, respectively). There was a correlation between the circulating level of VEGF-A and time to progression (TTP) (r = -0.47, p = 0.001). Best objective response and non-progression at 180 days were not associated with baseline level of PIGF, but there was a correlation between the circulating level of PIGF at baseline and TTP. Low level of VEGF-A at baseline (<500) was significantly associated with better outcome.

Alterations of the p53 and PIK3CA/AKT/mTOR pathways in angiosarcomas: a pattern distinct from other sarcomas with complex genomics

BACKGROUND

The p53 and phosphoinositide-3-kinase, catalytic, alpha polypeptide/v-akt murine thymoma viral oncogene homolog/mechanistic target of rapamycin (PIK3CA/AKT/mTOR) pathways frequently are altered in sarcoma with complex genomics, such as leiomyosarcoma (LMS) or undifferentiated pleomorphic sarcoma (UPS). The scale of genetic abnormalities in these pathways remains unknown in angiosarcoma (AS).

METHODS

The authors investigated the status of critical genes involved in the p53 and PIK3CA/AKT/mTOR pathways in a series of 62 AS.

RESULTS

The mutation and deletion rates of tumor protein 53 (TP53) were 4% and 0%, respectively. Overexpression of p53 was detected by immunohistochemistry in 49% of patients and was associated with inferior disease-free survival. Although p14 inactivation or overexpression of the human murine double minute homolog (HDM2) were frequent in LMS and UPS and could substitute for TP53 mutation or deletion, such alterations were rare in angiosarcomas. Phosphorylated ribosomal protein S6 kinase (p-S6K) and/or phosphorylated eukaryotic translation initiation factor 4E binding protein 1 (p-4eBP1) overexpression was observed in 42% of patients, suggesting frequent activation of the PIK3CA/AKT/mTOR pathway in angiosarcomas. Activation was not related to intragenic deletion of phosphatase and tensin homolog (PTEN), an aberration that is frequent in LMS and UPS but absent in angiosarcomas.

CONCLUSIONS

The current results indicated that angiosarcomas constitute a distinct subgroup among sarcomas with complex genomics. Although TP53 mutation and PTEN deletion are frequent in LMS and UPS, these aberrations are rarely involved in the pathogenesis of angiosarcoma.

Targeting NADPH oxidases for the treatment of cancer and inflammation

NADPH oxidases are a family of oxidases that utilize molecular oxygen to generate hydrogen peroxide and superoxide, thus indicating physiological functions of these highly reactive and short-lived species. The regulation of these NADPH oxidases (nox) enzymes is complex, with many members of this family exhibiting complexity in terms of subunit composition, cellular location, and tissue-specific expression. While the complexity of the nox family (Nox1-5, Duox1, 2) is daunting, the complexity also allows for targeting of NADPH oxidases in disease states. In this review, we discuss which inflammatory and malignant disorders can be targeted by nox inhibitors, as well as clinical experience in the use of such inhibitors.

Dual Roles of METCAM in the Progression of Different Cancers

METCAM, an integral membrane cell adhesion molecule (CAM) in the Ig-like gene superfamily, is capable of performing typical functions of CAMs, such as mediating cell-cell and cell-extracellular interactions, crosstalk with intracellular signaling pathways, and modulating social behaviors of cells. METCAM is expressed in about nine normal cells/tissues. Aberrant expression of METCAM has been associated with the progression of several epithelial tumors. Further in vitro and in vivo studies show that METCAM plays a dual role in the progression of different tumors. It can promote the malignant progression of several tumors. On the other hand, it can suppress the malignant progression of other tumors. We suggest that the role of METCAM in the progression of different cancer types may be modulated by different intrinsic factors present in different cancer cells and also in different stromal microenvironment. Many possible mechanisms mediated by this CAM during early tumor development and metastasis are suggested.

Sorafenib for patients with advanced angiosarcoma: a phase II Trial from the French Sarcoma Group (GSF/GETO)

BACKGROUND

Angiosarcomas account for <2% of all soft tissue sarcomas. This subtype is one of the most aggressive forms of soft tissue sarcoma. The prognosis for angiosarcoma patients in the advanced phase remains poor with current cytotoxic agents (progression-free survival [PFS] time of ∼4 months and overall survival [OS] time of ∼8 months). We investigated the antitumor activity of sorafenib in patients with metastatic or advanced angiosarcomas in a phase II trial.

METHODS

We conducted a stratified phase II trial. The primary endpoint was the progression-free rate (PFR) at 9 months according to the Response Evaluation Criteria in Solid Tumors. A two-stage design (optimal Simon design) was used. Patients received sorafenib (400 mg twice daily) for 9 months until unacceptable toxicity or tumor progression. Central pathological and radiological reviews were performed. Data on stratum A (superficial angiosarcoma) and stratum B (visceral angiosarcoma) are currently available. This trial is registered with ClinicalTrials.gov (identifier, NCT00874874).

FINDINGS

Strata A and B recruited 26 and 15 patients, respectively. The median age was 63 years (range, 31-82 years), with 17 male and 24 female patients. Fourteen cases arose in irradiated fields. Thirty patients (73.0%) had been pretreated with conventional chemotherapy. No unexpected toxicity occurred. The PFR at 9 months was 3.8% in stratum A and 0.0% in stratum B. The median PFS times were 1.8 months and 3.8 months, respectively, whereas the median OS times were 12.0 months and 9.0 months, respectively. No responses were observed in chemotherapy-naïve patients, whereas a 40% tumor control rate and 23% response rate were observed in the pretreated population. In this cohort, no activating mutation of the KDR gene (exons 15, 16, 24) was detected.

INTERPRETATION

Sorafenib showed limited antitumor activity in pretreated patients only, for both visceral and superficial angiosarcoma, but tumor control was of short duration.

Resveratrol inhibits pathologic retinal neovascularization in Vldlr(-/-) mice

PURPOSE

Macular telangiectasia (MacTel) is a vision-threatening retinal disease with unknown pathogenesis and no approved treatment. Very low-density lipoprotein receptor mutant mice (Vldlr(-/-)) exhibit critical features of MacTel such as retinal neovascularization and photoreceptor degeneration. In this study, the authors evaluate the therapeutic potential of resveratrol, a plant polyphenol, in Vldlr(-/-) mice as a model for MacTel.

METHODS

Vldlr(-/-) and wild-type mice at postnatal day (P) 21 to P60 or P10 to P30 were treated orally with resveratrol. The number of neovascular lesions was evaluated on retinal flatmounts, and resveratrol effects on endothelial cells were assessed by Western blot for phosphorylated ERK1/2, aortic ring, and migration assays. Vegf and Gfap expression was evaluated in laser-capture microdissected retinal layers of angiogenic lesions and nonlesion areas from Vldlr(-/-) and wild-type retinas.

RESULTS

From P15 onward, Vldlr(-/-) retinas develop vascular lesions associated with the local upregulation of Vegf in photoreceptors and Gfap in the inner retina. Oral resveratrol reduces lesion formation when administered either before or after disease onset. The reduction of vascular lesions in resveratrol-treated Vldlr(-/-) mice is associated with the suppression of retinal Vegf transcription. Resveratrol also reduces endothelial ERK1/2 signaling as well as the migration and proliferation of endothelial cells. Furthermore, a trend toward increased rhodopsin mRNA in Vldlr(-/-) retinas is observed.

CONCLUSIONS

Oral administration of resveratrol is protective against retinal neovascular lesions in Vldlr(-/-) mice by inhibiting Vegf expression and angiogenic activation of retinal endothelial cells. These results suggest that resveratrol might be a safe and effective intervention for treating patients with MacTel.

Angiosarcoma: state of the art and perspectives

We propose a literature review of available data on angiosarcoma (AS). AS account for 1% of adult soft tissue sarcoma. Two risk factors are well-establish chronic lymhoedema, previous radiotherapy. Clinical presentations of AS are heterogeneous. Large resection followed, if possible, by adjuvant radiotherapy is the cornerstone of curative intent treatment of localized forms. There are no convincing data supporting the administration of adjuvant chemotherapy. For metastatic or locally advanced AS, doxorubicin and weekly paclitaxel seem to provide the longer progression-free survival. Three phase II or parts of phase II trials have been published in the last 2 years, investigating weekly paclitaxel, sorafenib and imatinib, demonstrating that clinical trials are feasible for such rare diseases. Biological evidences for the key role of angiogentic factors have been accumulated during the last years and support the further investigation of anti-angiogenetic agents alone and almost combination with chemotherapy in such disease.

Angiosarcoma

Angiosarcomas are rare soft-tissue sarcomas of endothelial cell origin that have a poor prognosis. They can arise anywhere in the body, most commonly presenting as cutaneous disease in elderly white men, involving the head and neck and particularly the scalp. They can be caused by therapeutic radiation or chronic lymphoedema and hence secondary breast angiosarcomas are an important subgroup. Recent work has sought to establish the molecular biology of angiosarcomas and identify specific targets for treatment. Interest is now focused on trials of vascular-targeted drugs, which are showing promise in the control of angiosarcomas. In this review we discuss angiosarcoma and its current management, with a focus on clinical trials investigating the treatment of advanced disease.

Unexpected autocrine role of vascular endothelial growth factor in squamous cell carcinoma

Mirones et al. demonstrate that keratinocytes deficient in VEGF are capable of forming tumors but use a distinct form of aneuploidy and signaling to form tumors. This knowledge is important because inhibitors of VEGF, including bevacizumab (anti-VEGF antibodies) and sorafenib (Braf/VEGFR2 kinase inhibitor), have already entered the clinic. These agents may "remodel" tumor signaling.

Identification of an aberrant cell line among human adipose tissue-derived stem cell isolates

Adipose tissue-derived stem cells (ADSC) are isolated from the stromal vascular fraction (SVF) of adipose tissue and considered an excellent cell source for regenerative medicine. During the isolation and propagation of several human ADSC cell lines, we observed the emergence of an unusual cell line designated HADSC-6. Although initially fibroblast-like as typical ADSC are, HADSC-6 cells became homogeneously cuboid in shape, had very little cytoplasm, and formed aggregates with capsule-like boundary. Proliferation assay showed that HADSC-6 grew much faster than typical HADSC cell lines, such as HADSC-20. Immunocytochemistry showed that HADSC-6 did not express endothelial markers CD31 and vWF, and matrigel tube formation assay showed that it was unable to form endothelial-like tube structures. However, LDL uptake, a reliable endothelial marker, was positively identified. Chromosomal analysis showed that HADSC-6 cells were hypertriploid, and soft agar colony formation assay showed that they were able to proliferate and form large colonies in an anchorage-independent manner. However, tumorigenicity test showed that HADSC-6 was unable to form tumors in athymic mice. RT-PCR analysis showed that both HADSC-6 and HADSC-20 expressed VEGF-A, VEGF-B, VEGF-D, and VEGFR1 but not VEGFR2 or VEGFR3. VEGF-C, however, was expressed at a high level in HADSC-20 but undetectable in HADSC-6. In the IGF system, IGF-1 was abundantly expressed in HADSC-20 but marginally detectable in HADSC-6, and IGF-1R was abundantly expressed in HADSC-6 but not detectable in HADSC-20. In the FGF system, bFGF was abundantly expressed in HADSC-20 but marginally detectable in HADSC-6, and FGFR1 was abundantly expressed in both. Taken together, these results suggested that HADSC-6 cells were spontaneously transformed from the endothelium; therefore, they were further compared to previously published data of four naturally occurring human angiosarcoma cell lines. The results showed that the established angiosarcoma cell lines exhibit considerable variations among themselves and HADSC-6 displayed most of these variable characteristics.

The reactive oxygen-driven tumor: relevance to melanoma

In melanoma, at least four major signaling abnormalities have been described. They include beta-catenin deregulation (mutation/mislocalization), p16 loss, MAP kinase activation, and Akt activation. In this review, we discuss the role of the fourth pathway, known as the reactive oxygen driven tumor. The role of reactive oxygen in tumorigenesis is likely to relate to virtually all forms of cancer, and lends itself to specific therapies. These include blockade of reactive oxygen, resulting in decreased activation of NF-kappaB, which should sensitize tumors to chemotherapy and radiation. The phenotype of the reactive oxygen driven tumor can be monitored using available markers already in use in most hospital laboratories.

Synthesis, cytotoxicity, and antiviral activities of new neolignans related to honokiol and magnolol

A series of new bisphenol derivatives bearing allylic moieties were synthesized as potential analogs of honokiol and/or magnolol. Certain compounds exhibited specific anti-proliferation activity against SVR cells and moderate anti-HIV-1 activity in primary human lymphocytes. Compound 5h was the most potent compound and its anti-tumor activity was evaluated in vivo.

Basis for dosing time-dependent change in the anti-tumor effect of imatinib in mice

Because a variety of receptor tyrosine kinases are involved in the mechanism of tumor progression, the development of a clinically useful tyrosine kinase inhibitor is expected as a therapeutic agent for the treatment of malignant cancers. Imatinib mesylate, known as Gleevec or STI-571, is a molecule that inhibits the function of various receptors with tyrosine kinase activity, such as Abl, the bcr-abl chimeric product, KIT, and platelet-derived growth factor (PDGF) receptors. In this study, we investigated the influence of dosing time on the ability of imatinib to inhibit tumor growth in mice. Tumor-bearing mice were housed under standardized light/dark cycle conditions (lights on at 07:00 h, off at 19:00 h) with food and water ad libitum. The growth of tumor cells implanted in mice was more severely inhibited by the administration of imatinib (50 mg/kg, i.p.) in the early light phase than when it was administered in the early dark phase. The dosing time-dependency of anti-tumor effects was parallel to that of imatinib-induced anti-angiogenic effect. The inhibitory effect of imatinib on tyrosine kinase activity of PDGF receptors, but not of KIT and Abl, varied according to its administration time. The dosing time-dependency of imatinib-induced inhibition of PDGF receptor activity was closely related to that of its anti-tumor effects. Our results suggest that the anti-tumor efficacy of imatinib is enhanced by administering the drug when PDGF receptor activity was increased. The potent therapeutic efficacy of the drug could be expected by optimizing the dosing schedule.

Solenopsin, the alkaloidal component of the fire ant (Solenopsis invicta), is a naturally occurring inhibitor of phosphatidylinositol-3-kinase signaling and angiogenesis

Phosphatidylinositol-3-kinase (PI3K), and its downstream effector Akt, or protein kinase Balpha (PKBalpha), play a major regulatory role in control of apoptosis, proliferation, and angiogenesis. PI3K and Akt are amplified or overexpressed in a number of malignancies, including sarcomas, ovarian cancer, multiple myeloma, and melanoma. This pathway regulates production of the potent angiogenic factor vascular endothelial growth factor (VEGF), and protects tumor cells against both chemotherapy and reactive oxygen-induced apoptosis through phosphorylation of substrates such as apoptotic peptidase-activating factor-1 (APAF-1), forkhead proteins, and caspase 9. Given its diverse actions, compounds that suppress the PI3K/Akt pathway have potential pharmacologic utility as angiogenesis inhibitors and antineoplastic agents. Using the SVR angiogenesis assay, a screen of natural products, we isolated the alkaloid solenopsin, and found that it is a potent angiogenesis inhibitor. We also found that solenopsin inhibits the PI3K signaling pathway in cells upstream of PI3K, which may underlie its affects on angiogenesis. Consistent with inhibition of the activation of PI3K, solenopsin prevented the phosphorylation of Akt and the phosphorylation of its substrate forkhead box 01a (FOXO1a), a member of the forkhead family of transcription factors. Interestingly, solenopsin also inhibited Akt-1 activity in an ATP-competitive manner in vitro without affecting 27 of 28 other protein kinases tested.

Confirmation of a linkage between H-Ras and MMP-13 expression as well as MMP-9 by chemical genomic approach

As farnesylation of the Ras protein by farnesyl transferase is a critical step for the Ras functional activity, the farnesyl transferase inhibitor could affect H-Ras functions and the inhibitors such as arteminolide, SCH66336 and LB42908 completely inhibited Ras-farnesylation. However, they did not induce apoptosis of H-Ras-transformed cells with concentration for blocking H-Ras farnesylation. To determine the antitumor effects of the inhibitors, it was analyzed through the expression profile of genes, regulated by activated H-Ras or FTIs by using cDNA microarray. On the basis of the results, the relationship between H-Ras and MMPs expression was confirmed by RT-PCR, Western bolt, zymographic analysis and angiogenesis assay. Our results suggested that activation of MMP-13 as well as MMP-9 induced by H-Ras is involved in angiogenesis and with farnesyl transferase inhibitors, in part, exerts their anticancer effects. We confirmed that MMP-13 is a critical H-Ras target gene through chemical genomic approaches with farnesyl transferase inhibitors.

Angiosarcoma after conservation treatment for breast carcinoma: Our experience and a review of the literature

The development of angiosarcoma of the breast is a recognized complication of breast conservation therapy (BCT), but the evolution, prevalence, and outcome have not been accurately established. We sought to evaluate and review the clinicopathologic, prognostic, and treatment attributes of angiosarcoma arising in the irradiated breast after BCT. We conducted a retrospective chart and slide review of 8 patients seen between 1996 and 2004 with a diagnosis of secondary angiosarcoma. All were treated with mastectomy. Clinical and histopathologic findings were studied and previously reported cases were reviewed. Primary surgery-related breast edema and cellulitis was observed in 7 and 5 patients of the 8 patients studied, respectively. Postirradiation breast edema and grade 2/3 fibrosis occurred in 5 and 8 patients, respectively. The mean age of the patients at onset of the breast cancer and angiosarcoma was 65 and 72 years, respectively. The mean latency period between the treatment of the breast cancer and the diagnosis of angiosarcoma was 75 months. The actuarial rate of 2-year survival for patients presented with single (n = 4) compared with multiple (n = 4) skin lesions was 50% and 0%, respectively (P = .0233). The estimated incidence of angiosarcoma after BCT was found to be 0.14 %. BCT-associated angiosarcoma arises after a relatively brief interval, and breast edema-fibrosis can possibly contribute to its development. Special attention should be paid to skin changes occurring after BCT. The extent of skin lesions is predictive of survival. As shown by a review of the literature, angiosarcomas are often resistant to surgery, chemotherapy, and radiotherapy, and targeted therapy against tumor biological properties may be a new approach to angiosarcoma treatment.

Naturally Occurring Proteasome Inhibitors from Mate Tea (Ilex paraguayensis) Serve as Models for Topical Proteasome Inhibitors

Proteasome inhibitors have emerged as a clinically important therapy for neoplastic disease, with velcade, an organoboron compound used extensively in multiple myeloma. Recently, (-)-epigallocatechin gallate has been found to be a potent inhibitor of the proteasomal chymotrypsin-like activity. Other compounds that inhibit angiogenesis and are active as chemopreventive agents, such as curcumin, also inhibit proteasome activity. We have screened natural product extracts using ras-transformed endothelial cells (SVR cells) as a bioassay, and found that extracts of mate tea (Ilex paraguayensis) inhibit the growth of these endothelial cells. The extract was fractionated and found to have novel cinnamate esters that inhibit proteasome activity. Based upon the structures of the compounds isolated from mate tea, we examined synthetic analogs of these compounds for proteasome activity. Cinnamic acid amides had no inhibitory activity against proteasomes, whereas cinnamate esters displayed the activity. Based upon these findings, preclinical and clinical trials of topical cinnamate esters as proteasome inhibitors are warranted for psoriasis and other inflammatory disorders.

Reactive oxygen signaling and MAPK activation distinguish Epstein-Barr Virus (EBV)-positive versus EBV-negative Burkitt's lymphoma

Burkitt's lymphoma (BL) is an aggressive B cell neoplasm, which is one of the most common neoplasms of childhood. It is highly widespread in East Africa, where it appears in endemic form associated with Epstein-Barr virus (EBV) infection, and around the world in a sporadic form in which EBV infection is much less common. In addition to being the first human neoplasm to be associated with EBV, BL is associated with a characteristic translocation, in which the Ig promoter is translocated to constitutively activate the c-myc oncogene. Although many BLs respond well to chemotherapy, a significant fraction fails to respond to therapy, leading to death. In this article, we demonstrate that EBV-positive BL expresses high levels of activated mitogen-activated protein kinase and reactive oxygen species (ROS), and that ROS directly regulate NF-kappaB activation. EBV-negative BLs exhibit activation of phosphoinositol 3-kinase, but do not have elevated levels of ROS. Elevated reactive oxygen may play a role in diverse forms of viral carcinogenesis in humans, including cancers caused by EBV, hepatitis B, C, and human T cell lymphotropic virus. Our findings imply that inhibition of ROS may be useful in the treatment of EBV-induced neoplasia.

Tumor necrosis factor-related apoptosis-inducing ligand can induce apoptosis in subsets of premalignant cells

During the transformation from a normal to a malignant cell, several mutations are required to bypass the pathways responsible for controlling proliferation. Premalignant cells have acquired some, but not all of these mutations and consequently have not yet attained a malignant phenotype characterized by tumor formation in vivo. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) can induce apoptosis in malignant cells while sparing normal ones and is currently being considered as adjuvant therapy for various human malignancies. Whether TRAIL is effective in inducing apoptosis in premalignant cells is unclear, however. We studied the effect of TRAIL on two human premalignant cell lines the SV7tert and HA1E cells. Both cell lines had been immortalized by the addition of simian virus 40 large T antigen and the telomerase subunit hTERT, but had not been transformed into malignant cells. TRAIL initiated apoptosis by activating both the mitochondrial-independent and -dependent apoptotic pathways in both cell lines at relatively low doses whereas it had no effect on normal human pulmonary artery smooth muscle cells even at high doses. These results suggest that TRAIL can induce apoptosis in premalignant cells and suggests a novel therapy for the treatment of premalignant lesions in vivo.

Honokiol: A potent chemotherapy candidate for human colorectal carcinoma

AIM: To investigate the anticancer activity of Honokiol on RKO, a human colorectal carcinoma cell line in vitro and in vivo, and to evaluate its possible use in clinic.

METHODS: in vitro anticancer activity of honokiol was demonstrated by its induction of apoptosis in tumor cells. We analyzed cell proliferation with MTT assay, cell cycle with flow cytosmeter, DNA fragment with electrophoresis on agarose gels. To test the mechanism of honokiol-induced apoptosis, Western blotting was used to investigate the factors involved in this process. The pharmacokinetics study of honokiol was tested by high phase liquid chromatography. In in vivo study, Balb/c nude mice were incubated with RKO cells. Honokiol was injected intraperitoneally every other day into tumor bearing Balb/c nude mice.

RESULTS: Our results showed that honokiol induced apoptosis of RKO cells in a time- and dose-dependent manner. At 5-10 ug/mL for 48 h, honokiol induced apoptosis through activating Caspase cascades. Pharmacokinetics study demonstrated that, honokiol could be absorbed quickly by intraperitoneal injection, and maintained in plasma for more than 10 h. In nude mice bearing RKO-incubated tumor, honokiol displayed anticancer activity by inhibiting tumor growth and prolonging the lifespan of tumor bearing mice.

CONCLUSION: With its few toxicity to normal cells and potent anticancer activity in vitro and in vivo, honokiol might be a potential chemotherapy candidate in treating human colorectal carcinoma.

Molecular regulation of angiogenesis and tumorigenesis by signal transduction pathways: evidence of predictable and reproducible patterns of synergy in diverse neoplasms

A large number of oncogenes, tumor suppressor genes, and signal transduction pathways have been described. Currently, a framework that allows prediction of tumor behavior based upon oncogenes, tumor suppressors, and signal transduction pathways is lacking. In 1869, Mendeleev published a periodic table of elements which allowed prediction of properties of elements based upon atomic weights that allowed prediction of chemical and physical properties of elements yet to be discovered. In this paper, I will discuss recurrent patterns of synergy found in the literature and our laboratory between tumor suppressor genes, oncogenes, and signaling pathways that allows one to predict the signaling pathway in a given tumor based upon the inactivation of a tumor suppressor gene. These patterns can be found in multiple different human neoplasms. Conversely, one can predict the inactivation of a tumor suppressor based upon the activation status of a signaling pathway. This knowledge can be used by a clinician or pathologist with access to immunohistochemistry to make predictions based upon simple technologies and determine the signaling pathways involved in a patient's tumor. These strategies may be useful in the design of prevention and treatment strategies for cancer.

Molecular Pathogenesis of Vascular Anomalies: Classification into Three Categories Based upon Clinical and Biochemical Characteristics

Vascular tumors and malformations can be challenging to diagnose. Although they can resemble one another, their classification into tumors, such as hemangiomas of infancy, and malformations, such as venous or arteriovenous malformations, is based not only on their divergent biological behavior, but also on their pathogenesis. This review examines the molecular pathobiology of the processes involved in the development of these vascular birthmarks as they are currently understood. The terms hemangioma, hemangiosarcoma, and vascular proliferation are often used interchangeably, even though these entities are clinically and biochemically distinct. A more precise classification is necessary to facilitate communication between basic scientists and clinicians. Vasculogenesis, the in situ differentiation of blood vessels, occurs very early in the developing embryo. In vivo and in vitro studies, as well as knockout models, seem to indicate that this mechanism is unlikely to be involved in the development of either vascular malformations or hemangiomas of infancy. Recent advances in embryonic angiogenesis, especially explorations of mechanisms of vascular remodeling, have brought new understanding of the pathogenesis of vascular malformations. Vascular remodeling, an integral part of angiogenesis that centers upon the interactions between pericytes and endothelial cells, has been shown to be defective in certain experimental models and in some familial cases of vascular malformation. The occurrences of arteriovenous malformations in territories susceptible to increased remodeling also point towards epigenetic events in the development of vascular malformations.

Infectious angiogenesis: Bartonella bacilliformis infection results in endothelial production of angiopoetin-2 and epidermal production of vascular endothelial growth factor

Pathological angiogenesis, the development of a microvasculature by neoplastic processes, is a critical component of the development of tumors. The role of oncogenes in the induction of angiogenesis has been extensively studied in benign and malignant tumors. However, the role of infection in inducing angiogenesis is not well understood. Verruga peruana is a clinical syndrome caused by the bacterium Bartonella bacilliformis, and is characterized by the development of hemangioma-like lesions, in which bacteria colonize endothelial cells. To gain insight into how this bacteria induces angiogenesis in vivo, we performed in situ hybridization of clinical specimens of verruga peruana for the angiogenesis factors vascular endothelial growth factor (VEGF), its receptors VEGFR1 and VEGFR2, and angiopoietin-2. High-level expression of angiopoietin-2 and VEGF receptors was observed in the endothelium of verruga peruana. Surprisingly, the major source of VEGF production in verruga peruana is the overlying epidermis. Infection of cultured endothelium with B. bacilliformis also resulted in induction of angiopoetin-2 in vitro. These findings imply a collaboration between infected endothelium and overlying epidermis to induce angiogenesis.

Honokiol, a small molecular weight natural product, inhibits angiogenesis in vitro and tumor growth in vivo

Natural products comprise a major source of small molecular weight angiogenesis inhibitors. We have used the transformed endothelial cell line SVR as an effective screen of natural product extracts to isolate anti-angiogenesis and anti-tumor compounds. Aqueous extracts of Magnolia grandiflora exhibit potent activity in our SVR proliferation assays. We found that the small molecular weight compound honokiol is the active principle of magnolia extract. Honokiol exhibited potent anti-proliferative activity against SVR cells in vitro. In addition, honokiol demonstrated preferential inhibition of primary human endothelial cells compared with fibroblasts and this inhibition was antagonized by antibodies against TNF alpha-related apoptosis-inducing ligand. In vivo, honokiol was highly effective against angiosarcoma in nude mice. Our preclinical data suggests that honokiol is a systemically available and non-toxic inhibitor of angiogenesis and should be further evaluated as a potential chemotherapeutic agent.

Malignant transformation of melanocytes to melanoma by constitutive activation of mitogen-activated protein kinase kinase (MAPKK) signaling

Malignant melanoma is the cancer with the most rapid increase in incidence in the United States. Ultraviolet light and deficiency of the p16ink4a gene are known factors that predispose one to the development of malignant melanoma. The signal transduction pathways that underlie the progression of melanoma from their precursors, atypical nevi, are not well understood. We examined activation of the MAP kinase pathway in atypical nevi and melanoma cells and found that this pathway is activated in melanomas. To determine the functional significance of this activation, we introduced constitutively active MAP kinase kinase (MAPKK) into immortalized melanocytes. The introduction of this gene into melanocytes leads to tumorigenesis in nude mice, activation of the angiogenic switch, and increased production of the proangiogenic factor, vascular endothelial growth factor (VEGF), and matrix metalloproteinases (MMPs). Activation of MAP kinase signaling may be an important pathway involved in melanoma transformation. Inhibition of MAP kinase signaling may be useful in the prevention and treatment of melanoma.

Functional tyrosine kinase inhibitor profiling: a generally applicable method points to a novel role of platelet-derived growth factor receptor-beta in tuberous sclerosis

Tumors often exhibit activation of specific tyrosine kinases, which may allow targeting of therapy through inhibition of tyrosine kinase signaling. This strategy has been used successfully in the development of STI571 (gleevec), an inhibitor of bcr-abl tyrosine kinase that has been used successfully in the treatment of chronic myelogenous leukemia. STI571 also shows activity against c-kit and platelet-derived growth factor receptor-beta (PDGFRbeta) tyrosine kinase signaling, thus potentially expanding the number of tumors that may respond to it. We describe a simple and rapid method to assess functional activity of tyrosine kinase signaling that is broadly applicable to tumor types. As proof of principle, we have applied it to cells that serve as models of the autosomal-dominant tumor syndrome tuberous sclerosis (TS). We found that TS model cells derived from tuberin heterozygous mice and from a human renal angiomyolipoma are highly sensitive to PDGFR antagonists and that these cells express PDGFRbeta. Given that PDGFRbeta signaling is inhibited by STI571, we found that SV7tert human angiomyolipoma cells are sensitive to STI571. Thus, we describe a novel but simple method of determining the functional tyrosine kinase profile of a neoplastic cell and our results suggest that STI571 might be useful in the treatment of neoplasms commonly seen in patients with TS.

High expression of Met/hepatocyte growth factor receptor suppresses tumorigenicity in NCI-H1264 lung carcinoma cells

The protein product of c-met proto-oncogene, Met, is a tyrosine kinase receptor for the hepatocyte growth factor (HGF). Met receptor is expressed in normal human bronchial epithelium. In comparison, its expression in squamous cell carcinoma (SQCC) of the lung is markedly decreased in a great majority of cases. To understand further the role of Met receptor overexpression in non-small-cell lung carcinoma, we forced-expressed the full-length met cDNA in the NCI-H1264 (H1264) lung carcinoma cell line with low constitutive expression of this receptor. In vitro studies demonstrated that increased Met expression in H1264 cells resulted in strong inhibition of their ability to form soft agar colonies and in marked suppression of tumorigenicity in the subcutaneous tissue of immune-deficient mice. This is despite inconsistent alteration in the proliferation rate on plastic surfaces. Tumor cells explanted from occasional xenograft tumors formed by the Met-overexpressing H1264 cells also demonstrated marked down-regulation of the receptor protein levels as compared to the transplanted cells. The results suggest that constitutive overexpression of Met receptor may negatively regulate the malignancy of certain human lung cancer cells.

Suppression of ras-mediated transformation and inhibition of tumor growth and angiogenesis by anthrax lethal factor, a proteolytic inhibitor of multiple MEK pathways

Lethal factor is a protease, one component of Bacillus anthracis exotoxin, which cleaves many of the mitogen-activated protein kinase kinases (MEKs). Given the importance of MEK signaling in tumorigenesis, we assessed the effects of anthrax lethal toxin (LeTx) on tumor cells. LeTx was very effective in inhibiting mitogen-activated protein kinase activation in V12 H-ras-transformed NIH 3T3 cells. In vitro, treatment of transformed cells with LeTx caused them to revert to a nontransformed morphology, and inhibited their abilities to form colonies in soft agar and to invade Matrigel without markedly affecting cell proliferation. In vivo, LeTx inhibited growth of ras-transformed cells implanted in athymic nude mice (in some cases causing tumor regression) at concentrations that caused no apparent animal toxicity. Unexpectedly, LeTx also greatly decreased tumor neovascularization. These results demonstrate that LeTx potently inhibits ras-mediated tumor growth and is a potential antitumor therapeutic.