Douglas Grossman

Transgenic expression of survivin in keratinocytes counteracts UVB-induced apoptosis and cooperates with loss of p53

The inhibitor of apoptosis protein survivin has been implicated in both cell cycle control and apoptosis resistance. To discriminate between these different roles, we used transgenic expression of survivin in the skin as a model for cell proliferation, differentiation, and apoptosis. Transgenic mice expressing survivin under the control of a keratin-14 promoter developed normally, without histologic abnormalities of the skin or hair, epidermal hyperplasia, or developmental abnormalities of basal or suprabasal epidermis. Keratinocyte proliferation assessed under basal conditions, or after ultraviolet-B (UVB) irradiation, or phorbol ester stimulation was unchanged in survivin transgenic mice. In contrast, survivin expression inhibited UVB-induced apoptosis in vitro and in vivo (i.e., sunburn cell formation), whereas it did not affect Fas-induced cell death. When crossed with p53 knockout mice, transgenic expression of survivin in a p53(+/-) background substituted for the loss of a second p53 allele and further inhibited UVB-induced apoptosis. These data provide the first in vivo evidence that survivin inhibits apoptosis and suggest that this pathway may oppose the elimination of cancerous cells by p53.

Metastatic Melanoma in Pregnancy: Risk of Transplacental Metastases in the Infant

PURPOSE Although metastases to the fetus via the placenta are rare, melanoma is the most common culprit. When it occurs, maternally derived melanoma metastasis in the infant is almost invariably fatal. PATIENTS AND METHODS This article reviews current guidelines for placental evaluation in pregnant women with metastatic melanoma and presents surveillance recommendations for their infants. Comprehensive literature reviews were performed on melanoma in pregnancy and melanoma metastasis to the placenta and fetus. The use of interferon alfa in the pediatric population was also reviewed. A comprehensive search of the MEDLINE database (1966 to 2002) was performed. Articles were reviewed and additional references were obtained from the bibliographies. Translation of non-English articles was performed, and authors of previous publications were contacted. RESULTS Eighty-seven patients with placental or fetal metastasis were identified. Twenty-seven occurrences were attributed to melanoma (31%). The fetus was affected in six of 27 melanoma patients (22%), with five of six infants dying of disease. The use of high-dose interferon alfa adjuvant therapy in pediatric patients has not been reported. CONCLUSION The placentas of women with known or suspected metastatic melanoma should be carefully examined grossly and histologically by pathologists. With placental involvement, fetal risk of melanoma metastasis is approximately 22%. Neonates delivered with concomitant placental involvement should be considered a high-risk population. The risk-benefit ratio of adjuvant treatment for a potentially affected infant should be carefully weighed.

Drug resistance in melanoma: Mechanisms, apoptosis, and new potential therapeutic targets

Melanoma is the most aggressive form of skin cancer. Patients with advanced disease, such as lymph node involvement and distant metastases, have 5-year survival rates of 50% and 10–20%, respectively. This poor prognosis largely results from resistance to conventional chemotherapy, namely cytotoxic drugs. The basis for drug resistance in melanoma is most likely dysregulation of apoptosis, although other mechanisms including drug transport, detoxification, and enhanced DNA repair may also play a role. Defects at multiple levels and in both major apoptotic pathways have been described in melanoma. Our laboratory has identified an inhibitor of apoptosis, termed survivin, that is expressed in melanoma and required for maintenance of melanoma cell viability. Targeting of survivin and other apoptotic regulators increases the sensitivity of melanoma cells to cytotoxic drugs, and may provide a promising new therapeutic approach to cancer.

Rapid induction of mitochondrial events and caspase-independent apoptosis in Survivin-targeted melanoma cells

The inhibitor of apoptosis (IAP) protein Survivin is expressed in most cancers and is a key factor in maintaining apoptosis resistance. Although several IAPs have been shown to act as direct inhibitors of caspases, the precise antiapoptotic function of Survivin remains controversial. To clarify the mechanism by which Survivin protects cells, we investigated the kinetics of apoptosis and apoptotic events following Survivin inhibition utilizing a melanoma cell line harboring a tetracycline-regulated Survivin dominant-negative mutant (Survivin-T34A). Blocking Survivin resulted in both caspase activation and apoptosis; however, the level of apoptosis was only partially reduced by caspase inhibition. Survivin blockade also resulted in mitochondrial events that preceded caspase activation, including depolarization and release of cytochrome c and Smac/DIABLO. Levels of other IAPs were not altered in Survivin-targeted cells, although modest cleavage of XIAP and Livin was observed. The earliest proapoptotic event observed in Survivin-targeted cells was nuclear translocation of mitochondrial apoptosis-inducing factor (AIF), known to trigger both apoptotic mitochondrial events and caspase-independent DNA fragmentation. These findings suggest that a key antiapoptotic function of Survivin relates to inhibition of mitochondrial and AIF-dependent apoptotic pathways, and its expression in melanoma and other cancers likely protects against both caspase-independent and -dependent apoptosis.

Melanoma genetics: A review of genetic factors and clinical phenotypes in familial melanoma

Purpose of review The clinical phenotypes of familial melanoma syndromes and genetic and environmental interactions are reviewed to summarize the current status of the field and to identify gaps in molecular and clinical investigations. Recent findings The familial melanoma syndromes are associated with germline mutations in three highly penetrant gene products: p16, alternate reading frame, and cyclin-dependent kinase 4. Certain variants in a low-penetrance gene, MC1R, the melanocortin 1 receptor gene, increase melanoma risk to a lesser extent and act as a genetic modifier when cosegregating with a deleterious p16 gene. The penetrance of these melanoma-predisposing genes is largely influenced by ultraviolet exposure across geographic latitude. Yet cumulative studies are conflicting on whether ultraviolet radiation, including sunburns, early childhood and adolescent sun exposure, and chronic exposure, increases melanoma risk in familial melanoma. To date, the clinical phenotypes of increased number of atypical nevi and nevi body distribution are independent risk factors for melanoma risk, regardless of family history. The atypical mole syndrome cannot reliably predict melanoma germline mutations but increases melanoma risk in p16 mutation carriers. Familial melanoma patients develop melanomas earlier and are prone to developing multiple primary melanomas. Other than these two differences, familial and sporadic melanoma share similar histopathology, prognostic factors, and survival rates. Summary Familial melanoma is an excellent human model system for the investigation of melanoma. Understanding genotype–phenotype and environmental relationships in familial melanoma will likely lead to improved understanding of pathogenesis for all melanoma patients.

Proliferation, Apoptosis, and Survivin Expression in Keratinocytic Neoplasms and Hyperplasias

The dysregulation of apoptosis occurs in many cutaneous disease states. Several apoptosis inhibitors have been shown elevated in neoplasms and in some inflammatory conditions, but their relation to proliferative and apoptotic states has not been defined. We examined the expression of the apoptosis inhibitor survivin in a panel of keratinocytic neoplasms and hyperproliferative skin lesions using both immunohistochemistry and a newly developed in situ hybridization technique. Proliferation and apoptotic indices were also assessed by immunohistochemical staining for proliferating cell nuclear antigen and TUNEL, respectively. We found the highest rate of proliferation in verrucae and psoriasis followed by actinic keratosis, squamous and basal cell carcinoma, lichen simplex chronicus, and seborrheic keratosis; all were significantly (P < 0.05) higher than normal skin. Apoptotic rate was increased in squamous (P = 0.05) and basal cell carcinoma (P = 0.03), but not significantly different from normal skin in the other lesions tested. Survivin expression was seen in most neoplasms and hyperproliferative lesions, but not normal skin. Survivin expression was often restricted to the upper third of the epidermis in psoriasis and lichen simplex chronicus, whereas all the other lesions stained diffusely. Survivin expression appears to be a consistent feature of keratinocytic neoplasms and hyperproliferative lesions and may contribute to the formation of epidermal hyperplasia seen in all of these disease states.

The p16 INK4A tumor suppressor regulates cellular oxidative stress

Mutations or deletions in the cyclin-dependent kinase inhibitor p16INK4A are associated with multiple cancer types, but are more commonly found in melanoma tumors and associated with familial melanoma predisposition. Although p16 is thought to function as a tumor suppressor by negatively regulating the cell cycle, it remains unclear why the genetic compromise of p16 predisposes to melanoma over other cancers. Here we describe a novel role for p16 in regulating oxidative stress in several cell types, including melanocytes. Expression of p16 was rapidly upregulated following ultraviolet-irradiation and in response to H2O2-induced oxidative stress in a p38 stress-activated protein kinase-dependent manner. Knockdown of p16 using small interfering RNA increased intracellular reactive oxygen species (ROS) and oxidative (8-oxoguanine) DNA damage, which was further enhanced by H2O2 treatment. Elevated ROS levels were also observed in p16-depleted human keratinocytes and in whole skin and dermal fibroblasts from Cdkn2a-deficient mice. Aberrant ROS and p38 signaling in Cdkn2a-deficient fibroblasts was normalized by expression of exogenous p16. The effect of p16 depletion on ROS was not recapitulated by the knockdown of retinoblastoma protein (Rb) and did not require Rb. Finally, p16-mediated suppression of ROS could not be attributed to the potential effects of p16 on cell cycle phase. These findings suggest a potential alternate Rb-independent tumor-suppressor function of p16 as an endogenous regulator of carcinogenic intracellular oxidative stress. Compared with keratinocytes and fibroblasts, we also found increased susceptibility of melanocytes to oxidative stress in the context of p16 depletion, which may explain why the compromise of p16 predisposes to melanoma over other cancers.

Survivin Enhances Motility of Melanoma Cells by Supporting Akt Activation and α5 Integrin Upregulation

Survivin expression in melanoma is inversely correlated with patient survival. Transgenic mice harboring melanocyte-specific overexpression of survivin exhibit increased susceptibility to UV-induced melanoma and metastatic progression. To understand the mechanistic basis for metastatic progression, we investigated the effects of survivin on the motility of human melanocytes and melanoma cells. We found that survivin overexpression enhanced migration on fibronectin and invasion through Matrigel, whereas survivin knockdown under subapoptotic conditions blocked migration and invasion. In melanocytes, survivin overexpression activated the Akt and mitogen-activated protein kinase pathways. Akt phosphorylation was required for survivin-enhanced migration and invasion, whereas Erk phosphorylation was required only for enhanced invasion. In both melanocytes and melanoma cells, survivin overexpression was associated with upregulation of α5 integrin (fibronectin receptor component), the antibody-mediated blockade or RNA interference-mediated knockdown of which blocked survivin-enhanced migration. Knockdown of α5 integrin did not affect Akt activation, but inhibition of Akt phosphorylation prevented α5 integrin upregulation elicited by survivin overexpression. Together, our results showed that survivin enhanced the migration and invasion of melanocytic cells and suggested that survivin may promote melanoma metastasis by supporting Akt-dependent upregulation of α5 integrin.

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; mothers 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.

Comparative Analysis of Total Body and Dermatoscopic Photographic Monitoring of Nevi in Similar Patient Populations at Risk for Cutaneous Melanoma

BACKGROUND Our previous experience monitoring nevi in high‐risk patients using serial digital epiluminescence microscopy (DELM) photography achieved low biopsy rates but was limited by melanomas presenting as new lesions or arising from nevi that had not been photographed. OBJECTIVE To determine whether biopsy rates, efficiency of melanoma detection, and melanoma origin (de novo vs nevus derived) differed in a similar patient population monitored using total body (TB) photography. METHODS One thousand seventy‐six patients (including 187 from a prior cohort) underwent TB photography and were monitored using photographs obtained at the initial visit. Risk factors and median monitoring periods for these patients were comparable with those of patients previously monitored using DELM photography. RESULTS Two hundred seventy‐five biopsies were performed in 467 patients on follow‐up visits. Of 12 melanomas detected on follow‐up, five were invasive, five presented as changing lesions and two as new lesions, nine arose de novo, and the remainder were nevus derived. CONCLUSIONS In our experience with both approaches, monitoring patients at risk for melanoma using TB photography was associated with lower biopsy rates and lower nevus‐to‐melanoma ratios than using DELM and facilitated detection of new and changing lesions. In both cohorts, the majority of melanomas detected on follow‐up arose de novo. The authors have indicated no significant interest with commercial supporters.