Melanocyte expression of survivin promotes development and metastasis of UV-induced melanoma in HGF-transgenic mice.

We previously found the apoptosis inhibitor Survivin to be expressed in melanocytic nevi and melanoma but not in normal melanocytes. To investigate the role of Survivin in melanoma development and progression, we examined the consequences of forced Survivin expression in melanocytes in vivo. Transgenic (Tg) mouse lines (Dct-Survivin) were generated with melanocyte-specific expression of Survivin, and melanocytes grown from Dct-Survivin mice expressed Survivin. Dct-Survivin melanocytes exhibited decreased susceptibility to UV-induced apoptosis but no difference in proliferative capacity compared with melanocytes derived from non-Tg littermates. Induction of nevi in Dct-Survivin and non-Tg mice by topical application of 7,12-dimethylbenz(a)anthracene did not reveal significant differences in lesion onset (median, 10 weeks) or density (4 lesions per mouse after 15 weeks). Dct-Survivin mice were bred with melanoma-prone MH19/HGF-B6 Tg mice, and all progeny expressing either individual, neither, or both (Survivin/HGF) transgenes were UV-treated as neonates and then monitored for 43 weeks. Melanocytes in neonatal Survivin+/HGF+ mouse skin were less susceptible to UV-induced apoptosis than those from Survivin-/HGF+ mice. Onset of melanocytic tumors was earlier (median, 18 versus 24 weeks; P = 0.01, log-rank test), and overall tumor density was greater (7.7 versus 5.2 tumors per mouse; P = 0.04) in Survivin+/HGF+ compared with Survivin-/HGF+ mice. Strikingly, melanomas arising in Survivin+/HGF+ mice showed a greater tendency for lymph node (35% versus 0%; P = 0.04) and lung (53% versus 22%) metastasis and lower rates of spontaneous apoptosis than those in Survivin-/HGF+ mice. These studies show a role for Survivin in promoting both early and late events of UV-induced melanoma development in vivo.

N-acetylcysteine protects melanocytes against oxidative stress/damage and delays onset of ultraviolet-induced melanoma in mice.

PURPOSE: UV radiation is the major environmental risk factor for melanoma and a potent inducer of oxidative stress, which is implicated in the pathogenesis of several malignancies. We evaluated whether the thiol antioxidant N-acetylcysteine (NAC) could protect melanocytes from UV-induced oxidative stress/damage in vitro and from UV-induced melanoma in vivo. EXPERIMENTAL DESIGN: In vitro experiments used the mouse melanocyte line melan-a. For in vivo experiments, mice transgenic for hepatocyte growth factor and survivin, shown previously to develop melanoma following a single neonatal dose of UV irradiation, were given NAC (7 mg/mL; mother's drinking water) transplacentally and through nursing until 2 weeks after birth. RESULTS: NAC (1-10 mmol/L) protected melan-a cells from several UV-induced oxidative sequelae, including production of intracellular peroxide, formation of the signature oxidative DNA lesion 8-oxoguanine, and depletion of free reduced thiols (primarily glutathione). Delivery of NAC reduced thiol depletion and blocked formation of 8-oxoguanine in mouse skin following neonatal UV treatment. Mean onset of UV-induced melanocytic tumors was significantly delayed in NAC-treated compared with control mice (21 versus 14 weeks; P = 0.0003). CONCLUSIONS: Our data highlight the potential importance of oxidative stress in the pathogenesis of melanoma and suggest that NAC may be useful as a chemopreventive agent.

Treatment of lentigo maligna with imiquimod before staged excision.

BACKGROUND: Imiquimod 5% cream has demonstrated effectiveness in the treatment of lentigo maligna (LM) in several small studies. None of the studies to date have included posttreatment surgical removal to confirm negative histologic margins. OBJECTIVE: The aim of this retrospective analysis was to assess the efficacy of topical imiquimod in LM by circumferentially examining vertically oriented sections from a geometrically designed "picture frame" margin as well as bread-loafed sections of the central portion after staged excisions of imiquimod-treated lesions of LM. METHODS: Forty patients with biopsy-confirmed LM were treated five times a week for 3 months with 5% imiquimod cream before staged excision. Tazarotene 0.1% gel was added when no clinical signs of erythema developed with imiquimod alone after 1 month (10 patients). After the course of topical therapy, patients were assessed for clinical and complete histologic clearance after staged excision. RESULTS: A total of 33 of 40 patients had a complete clinical response as determined by the absence of remaining clinical lesion on physical examination. Upon histologic review, 30 of 40 patients had no evidence of LM whereas 10 of 40 harbored residual disease. One patient was found to have histologic evidence of invasion after completing the topical protocol. After a mean follow-up of 18 months (range, 12-34 months) and after complete surgical excision of the treatment site, none of the imiquimod-treated patients had evidence of recurrence. CONCLUSIONS: Imiquimod appears to be an effective adjunctive treatment for LM but does not qualify as a replacement therapy for surgery.

Unsuitability of organ donation from a patient with a history of melanoma?

A 52-year-old man with a history of melanoma presented to the emergency department with a massive intracranial hemorrhage. The patient deteriorated rapidly and was being considered as a potential organ donor. Three years before presentation, the patient had undergone wide excision of a 3.75-mm melanoma from his back with sentinel lymph node biopsy, which yielded negative findings. He had been well until the day of presentation. Although there are no specific guidelines for candidacy of organ donation from patients with a history of melanoma, there are several reports of donor-derived melanoma in organ transplant recipients, most with grave consequences. The literature relevant to this case is reviewed and discussed.

Molecular biology of Kaposi's sarcoma-associated herpesvirus.

Over the past twenty odd years, kaposi's sarcoma has launched from being a rare pathological curiosity to a significant public health concern. This massive increase in incidence, concurrent with the aids epidemic, has sparked a tremendous amount of interest in uncovering the etiopathogenesis of this disease. Due to its striking association with hiv infection, researchers have focused on identifying a possible infectious agent as the cause of this disease. Such an agent, termed kaposi's sarcoma-associated herpes virus (kshv) was identified in 1994. In the following years, virologists have employed all of their molecular tools to characterize this new agent and its role in the pathogenesis of human disease. Indeed, these efforts have been quite fruitful. It is now known that kshv is a gammaherpesvirus, which like its relatives establishes a latent form of infection that appears to be a prerequisite for expression of a disease phenotype. The relevant disease states and the basic virology are discussed.

Use of oral N-acetylcysteine for protection of melanocytic nevi against UV-induced oxidative stress: towards a novel paradigm for melanoma chemoprevention.

PURPOSE: Induction of oxidative stress has been implicated in UV-induced melanoma. We sought to determine whether the antioxidant N-acetylcysteine (NAC) could be safely administered to protect melanocytic nevi from the oxidative stress resulting from acute UV exposure. EXPERIMENTAL DESIGN: Patients at increased risk for melanoma were recruited from a screening clinic. Induction and detection of oxidative stress (reactive oxygen species and glutathione depletion) was optimized in nevi following ex vivo UV irradiation. Nevi were removed from patients before, and following, oral ingestion of a single (1,200 mg) dose of NAC, and then these nevi were UV irradiated (4,000 J/m(2)). RESULTS: Oxidative stress was induced in nevi 24 to 48 hours following ex vivo UV irradiation. A single oral dose of NAC was well tolerated in all patients (n = 72). Basal levels of reduced glutathione and the NAC metabolite cysteine were well correlated between similar-appearing nevi from the same patient and were significantly increased in nevi removed 3 hours after NAC ingestion compared with nevi removed before drug ingestion. In approximately half (9 of 19) of patients tested, UV-induced glutathione depletion was attenuated in the postdrug (compared with predrug) nevus. CONCLUSIONS: NAC can be safely administered to patients for the purpose of modulating UV-induced oxidative stress in nevi. This study suggests the feasibility of patients taking NAC prophylactically before acute UV exposure, to prevent pro-oncogenic oxidative stress in nevi and ultimately reduce long-term melanoma risk.

An autonomous replicating element within the KSHV genome.

Members of the herpesviridae family including Kaposi's sarcoma-associated herpesvirus (KSHV) persist latently in their hosts and harbor their genomes as closed circular episomes. Propagation of the KSHV genome into new daughter cells requires replication of the episome once every cell division and is considered critically dependent on expression of the virus encoded latency-associated nuclear antigen (LANA). This study demonstrates a LANA-independent mechanism of KSHV latent DNA replication. A cis-acting DNA element within a discreet KSHV genomic region termed the long unique region (LUR) can initiate and support replication of plasmids lacking LANA-binding sequences or a eukaryotic replication origin. The human cellular replication machinery proteins ORC2 and MCM3 associated with the LUR element and depletion of cellular ORC2 abolished replication of the plasmids indicating that recruitment of the host cellular replication machinery is important for LUR-dependent replication. Thus, KSHV can initiate replication of its genome independent of any trans-acting viral factors.

KSHV encoded LANA upregulates Pim-1 and is a substrate for its kinase activity.

Pim kinases are proto-oncogenes that are upregulated in a number of B cell cancers, including Epstein-Barr Virus (EBV) associated Burkitt's lymphoma. They have also been shown to be upregulated in Kaposi sarcoma-associated herpes virus (KSHV) infected primary B cells. Most cells in KSHV-associated tumors are latently infected and express only a small subset of viral genes, with KSHV latency associated nuclear antigen (LANA) being constitutively expressed. LANA regulates the transcription of a large number of cellular and viral genes. Here, we show that LANA upregulates transcription from the Pim-1 promoter (pPim-1) and map this activation to a region in the promoter located within the sequence (-681 to +37). We show that LANA expressing cells can proliferate faster and are better protected from drug induced apoptosis. Since transition through cell cycle check points and anti-apoptosis are functions associated with Pim-1, it is likely that higher Pim-1 expression in cells expressing LANA is responsible, at least in part, for this effect. A Pim-1 phosphorylation site was also identified within the amino-terminal domain of LANA. Using in vitro kinase assays, we confirmed that LANA was indeed a Pim-1 substrate, and the failure of Pim-1 to phosphorylate LANA mutated at SS205/6RR identified this site as the specific serine residues phosphorylated by Pim-1. This report provides valuable insight into yet another cellular signaling pathway subverted by KSHV LANA and suggests a contribution to KSHV related oncogenesis.