Overexpression of Akt converts radial growth melanoma to vertical growth melanoma

Melanoma is the cancer with the highest increase in incidence, and transformation of radial growth to vertical growth (i.e., noninvasive to invasive) melanoma is required for invasive disease and metastasis. We have previously shown that p42/p44 MAP kinase is activated in radial growth melanoma, suggesting that further signaling events are required for vertical growth melanoma. The molecular events that accompany this transformation are not well understood. Akt, a signaling molecule downstream of PI3K, was introduced into the radial growth WM35 melanoma in order to test whether Akt overexpression is sufficient to accomplish this transformation. Overexpression of Akt led to upregulation of VEGF, increased production of superoxide ROS, and the switch to a more pronounced glycolytic metabolism. Subcutaneous implantation of WM35 cells overexpressing Akt led to rapidly growing tumors in vivo, while vector control cells did not form tumors. We demonstrated that Akt was associated with malignant transformation of melanoma through at least 2 mechanisms. First, Akt may stabilize cells with extensive mitochondrial DNA mutation, which can generate ROS. Second, Akt can induce expression of the ROS-generating enzyme NOX4. Akt thus serves as a molecular switch that increases angiogenesis and the generation of superoxide, fostering more aggressive tumor behavior. Targeting Akt and ROS may be of therapeutic importance in treatment of advanced melanoma.

Presence of p16 hypermethylation and Epstein–Barr virus infection in transplant-associated hematolymphoid neoplasm of the skin

BACKGROUND

Epstein-Barr virus (EBV) is associated with the malignant transformation of B, T, and NK lymphocytes in humans, especially in immunosuppressed individuals.

OBJECTIVE

We describe an unusual case confined to the skin in a 39-year-old African American female following a renal transplant.

METHODS

Morphologically and immunophenotypically, the tumor was best classified as a plasmablastic lymphoma; however, the neoplastic population revealed rearrangements of both immunoglobulin heavy chain (IgG) and T cell receptor gamma (TCR-gamma). In situ hybridization demonstrated the presence of Epstein-Barr early RNA species (EBER) in the lymphoma cells, consistent with EBV infection.

RESULTS

We have previously demonstrated that EBV-induced reactive oxygen is associated with hypermethylation of the tumor suppressor gene p16 in Burkitt lymphoma, and that p16 hypermethylation is nearly always associated with EBV infection in Burkitt lymphoma.

LIMITATIONS

Further studies are needed to determine whether p16 is widely suppressed in immunosuppression-induced lymphoma.

CONCLUSION

In this study, we demonstrated high levels of hypermethylation of the tumor suppressor gene p16, thus supporting the role of EBV as a carcinogen in post-transplant lymphoproliferative disease.

The duality of angiogenesis: implications for therapy of human disease

Angiogenesis, the development of a microvasculature to a neoplastic, inflammatory, or infectious disease process, is a promising therapeutic target for disease therapy that has not been fully exploited. To further understand angiogenesis and its potential for therapy of dermatologic disorders, one must understand the many dualities of pathologic angiogenesis. These dualities are direct versus indirect angiogenesis inhibition, the differing origins of endothelial cells, which may arise either locally or through bone marrow stem cells, and regulation of vascular endothelial growth factor (VEGF) by hypoxia-dependent and/or independent pathways. The future development of therapy directed at pathologic angiogenesis is dependent upon an understanding of the factors that regulate angiogenesis. The presence of both direct and indirect inhibition of angiogenesis, the multiple sources of endothelial cells, and the regulation of VEGF by hypoxia-independent and/or-dependent pathways must taken into consideration if the promise of effective therapy of human disease is to be realized.

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.

Honokiol Potentiates Apoptosis, Suppresses Osteoclastogenesis, and Inhibits Invasion through Modulation of Nuclear Factor-κB Activation Pathway

Recent reports have indicated that honokiol can induce apoptosis, suppress tumor growth, and inhibit angiogenesis. In this report, we found that honokiol potentiated the apoptosis induced by tumor necrosis factor (TNF) and chemotherapeutic agents, suppressed TNF-induced tumor cell invasion, and inhibited RANKL-induced osteoclastogenesis, all of which are known to require nuclear factor-kappaB (NF-kappaB) activation. Honokiol suppressed NF-kappaB activation induced by a variety of inflammatory stimuli, and this suppression was not cell type specific. Further studies showed that honokiol blocked TNF-induced phosphorylation, ubiquitination, and degradation of IkappaBalpha through the inhibition of activation of IkappaBalpha kinase and of Akt. This led to suppression of the phosphorylation and nuclear translocation of p65 and NF-kappaB-dependent reporter gene expression. Magnolol, a honokiol isomer, was equally active. The expression of NF-kappaB-regulated gene products involved in antiapoptosis (IAP1, IAP2, Bcl-x(L), Bcl-2, cFLIP, TRAF1, and survivin), proliferation (cyclin D1, cyclooxygenase-2, and c-myc), invasion (matrix metalloproteinase-9 and intercellular adhesion molecule-1), and angiogenesis (vascular endothelial growth factor) were also down-regulated by honokiol. Honokiol also down-regulated NF-kappaB activation in in vivo mouse dorsal skin model. Thus, overall, our results indicate that NF-kappaB and NF-kappaB-regulated gene expression inhibited by honokiol enhances apoptosis and suppresses osteoclastogenesis and invasion.

Wilms Tumor 1 Expression Present in Most Melanomas but Nearly Absent in Nevi

BACKGROUND

Pigmented lesions are common, yet they present diagnostic and therapeutic challenges. They range from nevi, which are clinically stable, to melanomas, which are notorious for distant metastasis and death. Both nevi and melanomas arise from melanocytes, which are neural crest derivatives, and melanocyte precursors migrate from the paraspinal area to their eventual location at the dermoepidermal junction. Atypical nevi have been clinically considered to be precursors of melanoma, and recently, biochemical abnormalities have been found that are present in both nevi and melanomas, including inactivation of the p16INK4a tumor suppressor gene and mutations in B-raf. These mutations suggest not only that nevi and melanomas share a common origin but also that additional events are required for transformation to malignant melanoma.

OBSERVATIONS

We performed a Panomics protein array comparing a radial growth melanoma cell line with a vertical growth melanoma cell line and found that the transcription factor Wilms tumor 1 is highly expressed in the vertical growth cell line compared with the radial growth cell line. Using immunohistochemical analysis, we compared expression of archival nevi and melanomas in a tissue microarray.

CONCLUSION

We found that Wilms tumor 1 is expressed in most melanomas but is nearly absent in nevi. Immunohistochemical analysis for Wilms tumor 1 may be clinically useful in distinguishing nevi from melanoma.

Facile purification of honokiol and its antiviral and cytotoxic properties

A separation of honokiol 1 from the closely structurally related magnolol 2 was developed. Honokiol demonstrated weak activity against HIV-1 in human lymphocytes.

Carbazole Is a Naturally Occurring Inhibitor of Angiogenesis and Inflammation Isolated from Antipsoriatic Coal Tar

Coal tar is one of the oldest and an effective treatment for psoriasis. Coal tar has been directly applied to the skin, or used in combination with UV light as part of the Goeckerman treatment. The use of coal tar has caused long-term remissions in psoriasis, but has fallen out of favor because the treatment requires hospitalization and coal tar is poorly acceptable aesthetically to patients. Thus, determining the active antipsoriatic component of coal tar is of considerable therapeutic interest. We fractionated coal tar into its components, and tested them using the SVR angiogenesis inhibitor assay. Treatment of SVR endothelial cells with coal tar fractions resulted in the isolation of a single fraction with antiangiogenic activity. The active antiangiogenic compound in coal tar is carbazole. In addition to antiangiogenic activity, carbazole inhibited the production of inflammatory IL-15 by human mononuclear cells. IL-15 is elevated in psoriasis and is thought to contribute to psoriatic inflammation. Carbazole treatment also reduced activity of inducible nitric oxide synthase (iNOS), which is proinflammatory and elevated in psoriasis. The effect of carbazole on upstream pathways in human psoriasis was determined, and carbazole was shown to inhibit signal transducer and activator of transcription (stat)3-mediated transcription, which has been shown to be relevant in human psoriasis. IL-15, iNOS, and stat3 activation require the activation of the small GTPase rac for optimal activity. Carbazole was found to inhibit rac activation as a mechanism for its inhibition of downstream inflammatory and angiogenic pathways. Given its antiangiogenic and anti-inflammatory activities, carbazole is likely a major component of the antipsoriatic activity of coal tar. Carbazole and derivatives may be useful in the therapy of human psoriasis.

Pharmacologic blockade of angiopoietin-2 is efficacious against model hemangiomas in mice

Hemangioma of infancy is the most common neoplasm of childhood. While hemangiomas are classic examples of angiogenesis, the angiogenic factors responsible for hemangiomas are not fully understood. Previously, we demonstrated that malignant endothelial tumors arise in the setting of autocrine loops involving vascular endothelial growth factor (VEGF) and its major mitogenic receptor vascular endothelial growth factor receptor 2. Hemangiomas of infancy differ from malignant endothelial tumors in that they usually regress, or can be induced to regress by pharmacologic means, suggesting that angiogenesis in hemangiomas differs fundamentally from that of malignant endothelial tumors. Here, we demonstrate constitutive activation of the endothelial tie-2 receptor in human hemangioma of infancy and, using a murine model of hemangioma, bEnd.3 cells; we show that bEnd.3 hemangiomas produce both angiopoietin-2 (ang-2) and its receptor, tie-2, in vivo. We also demonstrate that inhibition of tie-2 signaling with a soluble tie-2 receptor decreases bEnd.3 hemangioma growth in vivo. The efficacy of tie-2 blockade suggests that either tie-2 activation or ang-2 may be required for in vivo growth. To address this issue, we used tie-2-deficient bEnd.3 hemangioma cells, which, surprisingly, were fully proficient in in vivo growth. Previous studies from our laboratory and others have implicated reactive oxygen-generating nox enzymes in the angiogenic switch, so we examined the effect of nox inhibitors on ang-2 production in vitro and on bEnd.3 tumor growth in vivo. We then inhibited ang-2 production pharmacologically using novel inhibitors of nox enzymes and found that this treatment nearly abolished bEnd.3 hemangioma growth in vivo. Signal-transduction blockade targeting ang-2 production may be useful in the treatment of human hemangiomas in vivo.

Expression of Wilms tumor 1 gene distinguishes vascular malformations from proliferative endothelial lesions

BACKGROUND

Vascular malformations and hemangiomas, which are endothelial lesions of childhood, may result in considerable morbidity because they can cause discomfort and functional impairment and have a negative affect on the patient's appearance. Although vascular malformations may initially appear very similar to hemangiomas, they have distinct clinical courses. Infantile hemangiomas progress through 3 stages: proliferative, involuting, and involuted. The proliferative phase is characterized by clinical growth. Once hemangiomas reach their maximum size, they begin to regress or involute. Histologically, this stage is characterized by endothelial apoptosis. Finally, the involuted stage of the hemangioma occurs when the original lesion is replaced by a connective tissue remnant. In contrast to hemangiomas, vascular malformations do not involute but continue to enlarge as the patient grows.

OBSERVATIONS

The biochemical differences between hemangiomas, which involute, and vascular malformations, which do not involute, are not well understood. We found that the transcription factor encoded by the Wilms tumor 1 (WT1) gene is expressed in the endothelium of hemangiomas but not in vascular malformations.

CONCLUSIONS

Defects in WT1 signaling may underlie the inability of malformation endothelial cells to undergo physiologic apoptosis and remodeling. The availability of WT1 staining in hospital laboratories may allow the clinician to distinguish hemangiomas from vascular malformations and thus to give appropriate therapy to the patient.

Synthesis and biological evaluation of aromatic enones related to curcumin

Curcumin, a natural product isolated from the spice turmeric, has been shown to exhibit a wide range of pharmacological activities including certain anti-cancer properties. It has been specifically shown to be an effective inhibitor of angiogenesis both in vitro and in vivo. Using curcumin as a lead compound for anti-angiogenic analog design, a series of structurally related compounds utilizing a substituted chalcone backbone have been synthesized and tested via an established SVR cell proliferation assay. The results have yielded a wide range of compounds that equal or exceed curcumin's ability to inhibit endothelial cell growth in vitro. Due to both their commercial availability and their fairly straightforward synthetic preparation, these low molecular weight compounds are attractive leads for developing future angiogenic inhibitors.

Apolipoprotein D is down-regulated during malignant transformation of neurofibromas

Apolipoprotein D (apoD) expression was studied in nonneoplastic peripheral nerve, neurofibromas (NFs), and malignant peripheral nerve sheath tumors (MPNSTs) by quantitative polymerase chain reaction, in situ hybridization, and immunohistochemistry. Multiplex quantitative polymerase chain reaction for messenger RNA was performed on a series of formalin-fixed and paraffin-embedded specimens that included 9 MPNSTs, 12 NFs, and 4 normal peripheral nerves. The average apoD expression was 108-fold decreased (DeltaCt = -7.3) in the MPNSTs compared with the NFs (P < .05). ApoD expression levels were 3.0-fold elevated (DeltaCt = 1.7) in the NFs compared with nonneoplastic peripheral nerve (P < .05). In situ hybridization for apoD RNA was performed on a separate series of 10 cases in which each microscopic section included both MPNST and the NF from which it arose. These studies confirmed elevated apoD expression in NFs compared with MPNSTs and demonstrated that this expression was variable among individual cells within the NFs. Differential expression by immunohistochemistry could only be demonstrated in selected areas, most likely because apoD protein is a small molecule that is secreted out of the cell into the extracellular space and plasma. ApoD expression initially increases a small amount with the formation of NFs from nonneoplastic peripheral nerve and subsequently decreases markedly as NFs transform into MPNSTs. This expression pattern may serve as a marker for cell cycle inhibition during peripheral nerve tumorigenesis.

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.

gli-1 Oncogene is highly expressed in granulomatous skin disorders, including sarcoidosis, granuloma annulare, and necrobiosis lipoidica diabeticorum

BACKGROUND

Sarcoidosis, which occurs most commonly in African American women, is a granulomatous multisystem disorder affecting the skin, lungs, and central nervous system. In a previous immunohistochemistry study of keloids, a scar granuloma stained highly positive for glioma-associated oncogene homologue (gli)-1.

OBSERVATION

This observation led us to study whether gli-1, one of the vertebrate zinc finger transcription factor genes of the gli superfamily, is expressed in granulomatous skin disorders such as cutaneous sarcoidosis, granuloma annulare (GA), and necrobiosis lipoidica diabeticorum (NLD). Immunohistochemistry studies for gli-1 were performed on biopsy specimens from patients with cutaneous sarcoidosis, GA, and NLD. All sarcoid lesions were highly positive for gli-1 expression, and 75% of the cells demonstrated positivity with a stain intensity of 3 on a scale of 1 to 3. The gli-1 expression was confined to cutaneous granulomas. CD68 staining was highly positive in the sarcoid lesions as well. Similarly, GA and NLD lesions were uniformly positive for gli-1 expression.

CONCLUSIONS

We found that gli-1 is inappropriately expressed in granulomatous lesions of the skin such as cutaneous sarcoidosis, GA, and NLD. These findings provide a rationale for clinical trials of inhibitors of gli-1 signaling, including tacrolimus and sizolimus, for the treatment of cutaneous sarcoidosis and other granulomatous disorders of the skin.

PSK and Trx80 inhibit B-cell growth in EBV-infected cord blood mononuclear cells through T cells activated by the monocyte products IL-15 and IL-12

Epstein-Barr virus (EBV)–specific immunologic memory is not transferred from mother to child. In vitro infection of cord blood cells can therefore readily lead to the outgrowth of transformed B lymphocytes. We found that the immunomodulator polysaccharide K (PSK) or the mitogenic cytokine truncated thioredoxin (Trx80) inhibited the EBV-induced B-cell proliferation. Using signaling lymphocytic activation molecule (SLAM)–associated protein (SAP) induction as a sign for T- and natural killer (NK) cell activation, we could follow it without any need for cell separation because neither macrophages nor B lymphocytes express SAP. The results suggest the following scenario: EBV infected and activated B lymphocytes. Upon interacting with these cells, T cells became posed for responding to cytokines produced by monocytes. Both PSK and Trx80, which is a secreted C-terminally truncated thioredoxin, activated the monocytes, which then produced cytokines in the presence of the primed T cells. PSK induced interleukin-15 (IL-15), while Trx80 induced IL-12 production. Both cytokines activated the T cells for function. Phosphatidylinositol 3–(PI 3)–kinase and reactive oxygen species (ROSs) were involved in the PSK-induced activation of monocytes. Restimulation of the cultures with EBV-transformed B cells generated specific cytotoxic activity.

Malignant transformation of human cells by constitutive expression of platelet-derived growth factor-BB

Platelet-derived growth factors (PDGFs) comprise a family of growth factors strongly implicated in human oncogenesis. A number of human tumors overexpress PDGF family members or have translocations activating PDGF receptors. Whereas the epidemiologic evidence implicating PDGF in human tumors is strong, malignant transformation of human cells by overexpression of PDGF has not been demonstrated. We have previously developed a human cell line by the sequential introduction of large T cells and telomerase, and we have demonstrated that these cells express functionally active PDGF receptor (PDGFR) beta. In order to determine whether growth factor-mediated transformation of human cells could occur, these cells were transduced with a retrovirus encoding PDGF-BB. Constitutive expression of PDGF-BB led to malignant transformation in nude mice. This is the first demonstration of constitutive signaling causing malignant transformation of human cells. Some of the changes that occur because of constitutive growth factor expression can be reversed by the clinically approved tyrosine kinase inhibitor Glivec, whereas other changes are not reversible by tyrosine kinase inhibitors. Our model allows the assessment of epigenetic changes that occur during human carcinogenesis. In addition, these studies provide insight into the clinical failure of tyrosine kinase inhibitors as monotherapy for advanced malignancy.

Transgenic Expression of Dominant Negative Tuberin through a Strong Constitutive Promoter Results in a Tissue-specific Tuberous Sclerosis Phenotype in the Skin and Brain

Tuberous sclerosis (TS) is a common autosomal dominant disorder caused by loss or malfunction of hamartin (tsc1) or tuberin (tsc2). Many lesions in TS do not demonstrate loss of heterozygosity for these genes, implying that dominant negative forms of these genes may account for some hamartomas and neoplasms in TS. To test this hypothesis, we expressed a dominant negative allele of tuberin (DeltaRG) behind the cytomegalovirus promoter in NIH3T3 cells and transgenic mice. This allele binds hamartin but has a deletion in the C terminus of tuberin, leading to constitutive activation of rap1 and rab5/rabaptin. Expression of DeltaRG in NIH3T3 cells led to a strong induction of reactive oxygen species, induction of vascular endothelial growth factor, and malignant transformation in vivo. Expression of DeltaRG driven by the constitutive cytomegalovirus promoter led to high level expression in all murine tissues examined, including skin, kidney, liver, and brain. Surprisingly, mice expressing the DeltaRG transgene developed a fibrovascular collagenoma in the dermis, which closely resembles the Shagreen patch observed in human patients with TS. In addition, numerous small subpial collections of external granule cells in the cerebellum were observed, which may be the murine equivalent of subependymal giant cell astrocytomas or tubers commonly seen in TS patients. Thus, expression of a dominant negative tuberin in multiple tissues can lead to a tissue-specific phenotype resembling some of the findings in human TS. Our data are the first to demonstrate that specific signaling abnormalities underlie specific hamartomas in a model of a human genetic disorder.

Antiangiogenic Agents: Studies on Fumagillin and Curcumin Analogs

Cancer is a general term used to describe many disease states, each of which are characterized by abnormal cell proliferation. The causes which bring about this abnormal cellular behavior are specific to each type of cancer. The success of tumor-targeted therapy is limited by this diversity. One common denominator for all types of cancer is the requirement of a suitable blood supply. Therefore, tumor vasculature has emerged as a potential target for therapeutic intervention. New blood vessel growth from preexisting vasculature stimulated by biochemical signals is termed angiogenesis. Tumor masses require a constant supply of oxygen and nutrients, and a means of efficient waste removal to ensure sustained development. Diffusion from nearby capillaries can supply adequate nutrition for tumors less than 2 mm in size, but for continued growth the tumors must develop their own blood supply. Alteration of the delicate balance of angiogenic stimulating factors and angiogenic inhibitors results in the phenotypic change from quiescence to active endothelial proliferation. To date, this angiogenic switch is not completely understood. The goal of antiangiogenic therapy is to interfere with these mechanisms and prevent tumor cells from developing a viable blood supply. Fumagillin is a naturally occurring antifungal agent. Curcumin is a natural product isolated from the spice turmeric. Both compounds have been shown to have antiangiogenic properties in vitro and in vivo. This paper describes efforts to design and prepare fumagillin and curcumin analogs and evaluate their corresponding antiangiogenic activities.

Rapamycin (sirolimus) as a steroid-sparing agent in dermatomyositis

Dermatomyositis is an autoimmune condition that results in significant morbidity and mortality through effects on muscle and skin. Corticosteroids are the mainstay of therapy of dermatomyositis, and severe morbidity and mortality occurs in part through the known long-term side effects of chronic steroid use. In addition, dermatomyositis is commonly associated with underlying malignancy, and high-dose steroids may adversely impair treatment of these malignancies. We describe the first use of rapamycin in a young patient with dermatomyositis.

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.

Involvement of p53 and p16 Tumor Suppressor Genes in Recessive Dystrophic Epidermolysis Bullosa-Associated Squamous Cell Carcinoma

Recessive dystrophic epidermolysis bullosa (RDEB) is an autosomal recessive disorder characterized by the loss of collagen type VII, an intrinsic component of the anchoring fibrils, which attach the epidermis to the dermis. Of the genetic blistering disorders, RDEB has the highest rate of morbidity and mortality, with morbidity arising from fusion of digits in a mitten-glove deformity and growth retardation associated with anemia. The leading cause of death in RDEB is cutaneous squamous cell carcinoma, which causes death through invasion and metastasis. In order to better understand the pathogenesis of these rare but aggressive squamous cell carcinoma (SCC), we analyzed them for mutations in p53 and loss of p16ink4a. Three tumors demonstrated mutations in the p53 tumor suppressor gene. We also analyzed SCC from patients with RDEB for the presence of p16ink4a hypermethylation, and found two tumors that have loss of p16ink4a through hypermethylation. This is the first description of specific abnormalities in tumor suppressor genes in RDEB associated SCC, and demonstrates that alterations in both p53 and p16ink4a can contribute to RDEB associated SCC.

Keloids demonstrate high-level epidermal expression of vascular endothelial growth factor

BACKGROUND

Keloids are a major cause of morbidity, and arise after operation, injury, or cutaneous infection. Clinically, keloids differ from hypertrophic scars in that they grow beyond the original borders of the injury. Keloids occur most commonly for patients of African and Asian descent, and treatment options are multiple, indicating that there is no entirely satisfactory treatment for keloids. Angiogenesis inhibition has been shown to be effective in treatment of malignancy in both animal models and human beings.

OBJECTIVE

We sought to determine whether keloids produce the potent angiogenic factor vascular endothelial growth factor (VEGF).

METHODS

We performed in situ hybridization for VEGF on keloid tissue and normal skin.

RESULTS

Our study demonstrated abundant production of VEGF in keloids and, surprisingly, the major source of VEGF was the overlying epidermis.

CONCLUSIONS

Our results suggest that the overlying epidermis is the major source of keloid angiogenesis. These findings demonstrate that keloids are angiogenic lesions. Topical antiangiogenic therapy, directed at either down-regulating epidermal VEGF or inhibiting keratinocyte-derived VEGF activity on its endothelial receptors, may be useful in the treatment of keloids.

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.

Weight loss-induced calciphylaxis: potential role of matrix metalloproteinases

Calciphylaxis is an uncommon and often devastating syndrome of calcification of small vessels, leading to tissue infarction. The mechanism of how calcium deposits on small vessels is unknown. Recently, metalloproteinase digestion of elastin has been shown to enhance deposition of calcium, suggesting a possible mechanism of calciphylaxis. We describe a case of a patient who developed calciphylaxis after rapid weight loss, but had normocalcemia and normal renal function. She was found to have high levels of matrix metalloproteinases, which may have chemically altered elastin, allowing deposition of calcium on small vessels. Inhibitors of matrix metalloproteinases may be useful in the prevention and treatment of calciphylaxis.

Angiomotin expression promotes hemangioendothelioma invasion

Angiomotin was identified by its ability to bind angiostatin and has been shown to mediate its activity in vitro. The family of angiomotin-like protein consists of three members that have coiled-coil domains and conserved c-terminal PDZ-binding motifs. We show here that expression of angiomotin in mouse aortic endothelial (MAE) cells results in stabilization of tubes in the Matrigel assay. Control tubes start to regress after 72 h, whereas MAE-angiomotin (MAE Amot) tubes were stable for over 30 days. In contrast, cells expressing a functional mutant lacking the PDZ protein interaction motif did not migrate and form tubes. Cells from the established tubes invaded into the solidified matrigel. We therefore tested whether angiomotin promotes endothelial invasion. In microcarrier-based invasion in vitro assay, angiomotin-expressing cells invaded collagen matrix and formed tube-like branches. This was confirmed in vivo as injection of MAE-Amot cells promoted tumor growth and invasion into surrounding muscle tissue. Injection of cells transfected with the functional mutant resulted in establishment of noninvasive tumors surrounded by a capsule of fibrous tissue. These tumors remained in constant size or dormant over 3 weeks. Zymogel analysis of the transfected cells did not reveal any differences in proteolytic activity. However, time-lapse photography showed a significant increase in random motility in MAE-Amot cells. We conclude that angiomotin may promote angiogenesis by both stimulating invasion as well as stabilizing established tubes.

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.

Regulation of endothelial cell differentiation and transformation by H-Ras

Angiogenesis is regulated by growth factors which activate tyrosine kinase receptors leading to the activation of a number of intracellular signaling pathways. The specific function of H-Ras during FGF-2 stimulated endothelial cell differentiation, defined as invasive growth and formation of branching networks in fibrin gels, was investigated by using conditionally immortalized endothelial cell lines induced to express H-Ras mutants. Expression of inhibitory N17Ras did not impair differentiation in response to FGF-2 and TNF-alpha. The farnesyltransferase inhibitor FTI-277 inhibited farnesylation of Ras but did not inhibit differentiation of human microvascular endothelial cells or mouse brain endothelial cells. In contrast, activated V12Ras inhibited endothelial cell differentiation and cells displayed a transformed phenotype with an increased rate of proliferation and loss of contact inhibited growth. Furthermore, V12Ras expressing endothelial cells grew as solid tumors when injected subcutaneously into mice. Our data suggest that, in endothelial cells, H-Ras activity is not required for differentiation. However, this activity must be tightly regulated as aberrant activity can disturb the ability of endothelial cells to undergo differentiation.

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.

Tuberous sclerosis-associated neoplasms express activated p42/44 mitogen-activated protein (MAP) kinase, and inhibition of MAP kinase signaling results in decreased in vivo tumor growth

PURPOSE

Tuberous sclerosis (TS) is a common autosomal disorder attributable to inactivation of the tumor suppressor genes tuberin and hamartin. To determine whether mitogen-activated protein (MAP) kinase signaling plays a role in the pathogenesis of TS, we stained human TS-associated neoplasms with antibodies directed against activated MAP kinase, and observed high-level expression.

EXPERIMENTAL DESIGN

To determine whether MAP kinase is functionally important for the development of neoplasia in TS, we established a murine model of TS-associated neoplasia (Tsc2Ang1 cells) from a tumor arising in a mouse heterozygous for tuberin. Tsc2Ang1 cells demonstrate tumorigenesis in vivo and high-level expression of activated MAP kinase in vitro. The functionality of MAP kinase signaling was assessed by inactivating MAP kinase using a dominant-negative MAP kinase kinase in tsc2ang1 cells and assessing the effect of this intervention on in vivo tumorigenicity and production of the potent angiogenic factor vascular endothelial growth factor (VEGF).

RESULTS

Human TS-related neoplasms demonstrate high-level expression of activated MAP kinase, as does a tumor arising in a mouse heterozygous for tuberin. The inhibition of MAP kinase signaling by the introduction of a dominant-negative MAP kinase kinase leads to the inhibition of tumor growth in vivo and decreased production of VEGF.

CONCLUSIONS

MAP kinase is activated in TS-related neoplasia in mice and humans. Inhibition of MAP kinase leads to decreased tumor growth in vivo. Pharmacological inhibition of MAP kinase may be a therapeutic target in the prevention and treatment of TS-related tumors.

Cutaneous lesions of secondary syphilis are highly angiogenic

BACKGROUND

The role of angiogenesis in infectious processes is poorly studied. Some viruses have been linked to angiogenesis, but the role of bacteria and protozoa in inducing angiogenesis in chronic infections is poorly understood.

OBJECTIVES

We examined the role of angiogenesis in syphilis, a common and often difficult-to-treat infectious disease, especially in the setting of HIV/AIDS.

METHOD

Microvessel counts were performed on 27 paraffin-fixed sections of secondary syphilis by staining with monoclonal antibodies against CD31. In addition, immunohistochemistry was performed using antibodies against vascular endothelial growth factor (VEGF) to determine whether increased angiogenesis may be mediated, in part, through increased production of VEGF.

RESULTS

The CD31 mean microvessel count in secondary syphilis sections was significantly higher than in normal control sections. VEGF intensity appeared increased in the patients with secondary syphilis.

CONCLUSIONS

Infection with Treponema pallidum results in increased angiogenesis in secondary syphilis. The mechanism for increased angiogenesis may involve elaboration of angiogenic cytokines, such as VEGF and epidermal growth factor.

High-level expression of vascular endothelial growth factor and its receptors in an aphthous ulcer

BACKGROUND

Aphthous ulcers are an extremely common disorder of unknown etiology. These ulcers cause significant morbidity through pain and interference with eating. Thalidomide, an angiogenesis inhibitor, is efficacious for the treatment of aphthous ulcers.

METHODS

In situ hybridization was performed on an idiopathic aphthous ulcer using probes specific for the angiogenesis factor vascular endothelial growth factor, and its receptors, in order to determine whether these ulcers are highly angiogenic.

CONCLUSIONS

Aphthous ulcers are highly angiogenic. Thalidomide may act to heal aphthous ulcers by inhibiting angiogenesis and promoting reepithelialization. Excess angiogenesis may inhibit reepithelialization in certain types of ulcers, and angiogenesis inhibitors may actually promote wound healing if ulcers are caused by excess angiogenesis.

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.

Design, synthesis, and biological evaluation of angiogenesis inhibitors: aromatic enone and dienone analogues of curcumin

The quest to find new antitumor compounds is an ongoing research endeavor in many laboratories around the world. The use of small-molecule angiogenesis inhibitors promises to be a potentially effective method for cancer treatment and possible prevention. Many antiangiogenic compounds are in various stages of laboratory evaluations and clinical trials. Curcumin is a natural product that has exhibited potent antiangiogenic properties. Based on a simple pharmacophore model, using standard drug design concepts, aromatic enone and aromatic dienone analogues of curcumin were prepared and/or obtained commercially. These compounds were screened for antiangiogenic properties via an in vitro SVR assay and were found to inhibit cell proliferation.

Mitogen-actived protein kinase activation is an early event in melanoma progression

PURPOSE

Melanoma is the most common cause of death from cutaneous malignancy, and is the cancer that is most rapidly rising in incidence. Because current therapeutic methods for metastatic melanoma are poorly efficacious, enhanced understanding of signal transduction in melanoma progression is warranted. Prior experimental studies in murine models and human tissues have shown a correlation among activation of mitogen activated protein kinase (MAPK) signaling, angiogenesis, and tumorigenesis. Because of these findings, we wanted to assess the role of MAPK signaling in melanoma progression and angiogenesis.

EXPERIMENTAL DESIGN

We studied expression of phosphorylated (active) MAPK and two target genes known to be induced by MAPK signaling, tissue factor and vascular endothelial growth factor, in 131 melanocytic lesions, ranging from atypical nevi to metastatic melanoma.

RESULTS

We observed little staining for activated (phosphorylated) MAPK and low amounts of angiogenesis in atypical nevi, but angiogenesis and MAPK activation were activated in radial growth melanoma and in later stage lesions.

CONCLUSIONS

Our findings implicate MAPK activation as an early event in melanoma progression, and MAPK may be a potential target for pharmacologic intervention.

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.

SVR angiosarcomas can be rejected by CD4 costimulation dependent and CD8 costimulation independent pathways

PURPOSE

We wished to determine whether virally- induced endothelial tumors are rejected by CD4 and CD8 lymphocytes, and whether there are differences in requirements for costimulation in the rejection of these tumors by lymphocyte subsets.

EXPERIMENTAL DESIGN

We have developed a model of endothelial tumorigenesis through the sequential introduction of SV40 large T antigen and oncogenic H-ras into endothelial cells. These cells (SVR cells) form highly aggressive angiosarcomas in immunocompromised mice, but do not grow in syngeneic C57BL/6 mice. Using both acute blockade with systemic administration of antibodies and mice genetically deficient in the costimulatory molecules CD28, CD40, and CD40L, we have delineated the requirements of costimulation required to reject this virally-induced endothelial tumor.

RESULTS

Control of SVR angiosarcoma is mediated through T lymphocytes, and both CD4 and CD8 lymphocytes are capable of controlling SVR angiosarcoma growth in vivo. Mice genetically deficient in CD28, CD40, and CD40L were able to reject SVR tumors, but depletion of these mice of CD8, but not CD4 cells led to rapid tumor growth. This data suggests that CD4 mediated rejection has a greater dependence of costimulation than CD8 mediated rejection. Surprisingly, acute depletion of costimulatory molecules in immunocompetent C57BL/6 mice led to rapid tumor growth.

CONCLUSIONS

Significant differences exist in the immune status of mice acutely depleted of costimulatory molecules versus genetically deficient mice. Our results suggest that acute depletion is more immunosuppressive than genetic depletion. Humans who undergo costimulatory blockade may require periodic surveillance for virally-induced tumors.

Phosphorylation by mitogen-activated protein kinase mediates the hypoxia-induced turnover of the TAL1/SCL transcription factor in endothelial cells

The basic helix-loop-helix transcription factor TAL1 (or SCL), originally identified from its involvement by a chromosomal rearrangement in T-cell acute lymphoblastic leukemia, is required for hematopoietic development. TAL1 also has a critical role in embryonic vascular remodeling and is expressed in endothelial cells postnatally, although little is known about its function or regulation in this cell type. We report here that the important proangiogenic stimulus hypoxia stimulates phosphorylation, ubiquitination, and proteasomal breakdown of TAL1 in endothelial cells. Tryptic phosphopeptide mapping and chemical inhibitor studies showed that hypoxia induced the mitogen-activated protein kinase-mediated phosphorylation of a single serine residue, Ser(122), in the protein, and site-directed mutagenesis demonstrated that Ser(122) phosphorylation was necessary for hypoxic acceleration of TAL1 turnover in an immortalized murine endothelial cell line. Finally, whereas TAL1 expression was detected in endothelial cells from both large and small vessels, hypoxia-induced TAL1 turnover was observed only in microvascular endothelial cells. Besides their implications for TAL1 function in angiogenic processes, these results demonstrate that a protein kinase(s) important for mitogenic signaling is also utilized in hypoxic endothelial cells to target a transcription factor for destruction.

Tuberous sclerosis-associated lesions of the kidney, brain, and skin are angiogenic neoplasms

BACKGROUND

Tuberous sclerosis is an autosomal dominant condition characterized by the development of benign neoplasms of the brain, kidney, and skin. Progressive growth and malignant transformation of brain and kidney lesions constitute the major cause of morbidity and mortality in adults with tuberous sclerosis. In addition, growth of skin lesions may be disfiguring to patients.

OBJECTIVE

The purpose of this study was to determine whether benign tumors in patients with tuberous sclerosis are angiogenic.

METHODS

Brain, kidney, and skin tumors from patients with tuberous sclerosis were stained with CD31, a specific marker of vascular endothelium. In addition, we used Northern blot analysis to demonstrate that renal angiomyolipoma cells express the potent angiogenesis stimulator vascular endothelial growth factor (VEGF).

RESULTS

Brain, kidney, and skin neoplasms from patients with tuberous sclerosis are highly angiogenic. Renal angiomyolipoma cells produce the potent angiogenic factor VEGF.

CONCLUSION

Benign neoplasms of patients with tuberous sclerosis are highly vascular. Our results provide a rationale for antiangiogenic therapy in the treatment and prevention of tuberous sclerosis-associated neoplasms.

Reactive oxygen generated by Nox1 triggers the angiogenic switch

The reactive oxygen-generating enzyme Nox1 transforms NIH 3T3 cells, rendering them highly tumorigenic and, as shown herein, also increases tumorigenicity of DU-145 prostate epithelial cells. Although Nox1 modestly stimulates cell division in both fibroblasts and epithelial cells, an increased mitogenic rate alone did not account fully for the marked tumorigenicity. Herein, we show that Nox1 is a potent trigger of the angiogenic switch, increasing the vascularity of tumors and inducing molecular markers of angiogenesis. Vascular endothelial growth factor (VEGF) mRNA becomes markedly up-regulated by Nox1 both in cultured cells and in tumors, and VEGF receptors (VEGFR1 and VEGFR2) are highly induced in vascular cells in Nox1-expressing tumors. Matrix metalloproteinase activity, another marker of the angiogenic switch, also is induced by Nox1. Nox1 induction of VEGF is eliminated by coexpression of catalase, indicating that hydrogen peroxide signals part of the switch to the angiogenic phenotype.

Reactive oxygen-induced carcinogenesis causes hypermethylation of p16(Ink4a) and activation of MAP kinase

BACKGROUND

Implantation of foreign materials into mice and humans has been noted to result in the appearance of soft tissue sarcomas at the site of implantation. These materials include metal replacement joints and Dacron vascular grafts. In addition, occupational exposure to nickel has been shown to result in an increased risk of carcinogenesis. The molecular mechanisms of foreign body-induced carcinogenesis are not fully understood.

MATERIALS AND METHODS

In order to gain insight into these mechanisms, we implanted nickel sulfide into wild type C57BL/6 mice as well as a mouse heterozygous for the tumor suppressor gene, p53. Malignant fibrous histiocytomas arose in all mice, and we have characterized the profile of tumor suppressor genes and signal transduction pathways altered in these cells.

RESULTS

All tumors demonstrated hypermethylation of the tumor suppressor gene p16, as well as activation of the mitogen activated protein kinase (MAP kinase) signaling pathway. This knowledge may be beneficial in the prevention and treatment of tumors caused by foreign body implantation.

CONCLUSIONS

Oxidative stress induced by nickel sulfide appears to cause loss of p16 and activation of MAP kinase signaling. These findings support the hypothesis of synergistic interactions between MAP kinase activation and p16 loss in carcinogenesis.

Neuroendocrine lung tumors: grade correlates with proliferation but not angiogenesis

Angiogenesis has been implicated in the progression of human neoplasia from benign precursor to invasive and metastatic phenotypes. The acquisition of dominant oncogenes in preneoplastic cells in vitro and in vivo has been associated with the increased ability of tumor cells to secrete angiogenic mediators and recruit blood vessels. However, in a subset of benign lesions, high levels of angiogenesis have been found before the conversion to invasive and metastatic phenotypes. In many of these benign lesions, dominant oncogenic pathways are activated first; then as malignant potential is acquired, there is a loss of nuclear tumor suppressor genes, such as p53 and p16. We studied neuroendocrine lung tumors (NLT) ranging from typical and atypical carcinoid tumors to large cell neuroendocrine and small cell carcinomas in order to determine whether angiogenesis (as assessed by mean vessel density) and proliferation rates (as assessed by MIB-1 nuclear immunohistochemical staining) correlate with tumor type. We found that increased rates of proliferation, but not angiogenesis, correlate with tumor type. The association of increased proliferation and tumor type may prove to be clinically useful and shed light on the role of sequential oncogenic alterations in NLT.

Are keloids really "gli-loids"?: High-level expression of gli-1 oncogene in keloids

BACKGROUND

Keloids are a common lesion arising from sites of previous trauma and are a considerable source of morbidity because of continued growth of lesions, pruritus, and physical appearance. They consist of mesenchymal cells embedded in a stroma of disordered collagen matrix. Clinically, keloids are distinguished from scars in that keloids demonstrate continued growth over the borders of the original injury. Keloids appear with increased frequency in patients of African and Asian descent. Currently, no entirely satisfactory method of treatment exists for these lesions. Recently, a patient who was enrolled in a clinical trial of topical tacrolimus for atopic dermatitis applied this drug to a keloid and noted clearing.

OBJECTIVE

Based on this clinical observation and the observation that rapamycin, a chemically similar compound to tacrolimus, is known to inhibit signaling from the gli-1 oncogene, we examined keloids and scars for expression of Gli-1 protein.

METHODS

Skin sections from keloids and scars were examined by immunohistochemical staining for gli-1. To further confirm the presence of gli-1 expression in keloids, reverse transcriptase-polymerase chain reaction was carried out.

RESULTS

Expression of gli-1 was strongly elevated in keloids compared with scars.

CONCLUSION

These results provide a rationale for the treatment of keloids with topical rapamycin analogs, including tacrolimus. Clinical trials of topical tacrolimus are warranted.