UV radiation promotes melanoma dissemination mediated by the sequential reaction axis of cathepsins-TGF-ß1-FAP-α.

BACKGROUND: Ultraviolet radiation (UVR) is the major risk factor for development of malignant melanoma. Fibroblast activation protein (FAP)-α is a serine protease expressed on the surface of activated fibroblasts, promoting tumour invasion through extracellular matrix (ECM) degradation. The signalling mechanism behind the upregulation of FAP-α is not yet completely revealed. METHODS: Expression of FAP-α was analysed after UVR exposure in in vitro co-culture systems, gene expression arrays and artificial skin constructs. Cell migration and invasion was studied in relation to cathepsin activity and secretion of transforming growth factor (TGF)-ß1. RESULTS: Fibroblast activation protein-α expression was induced by UVR in melanocytes of human skin. The FAP-α expression was regulated by UVR-induced release of TGF-ß1 and cathepsin inhibitors prevented such secretion. In melanoma cell culture models and in a xenograft tumour model of zebrafish embryos, FAP-α mediated ECM degradation and facilitated tumour cell dissemination. CONCLUSIONS: Our results provide evidence for a sequential reaction axis from UVR via cathepsins, TGF-ß1 and FAP-α expression, promoting cancer cell dissemination and melanoma metastatic spread.

Evaluation of tubulin ß-3 as a novel senescence-associated gene in melanocytic malignant transformation.

Malignant melanoma might develop from melanocytic nevi in which the growth-arrested state has been broken. We analyzed the gene expression of young and senescent human melanocytes in culture and compared the gene expression data with a dataset from nevi and melanomas. A concordant altered gene expression was identified in 84 genes when comparing the growth-arrested samples with proliferating samples. TUBB3, which encodes the microtubule protein tubulin ß-3, showed a decreased expression in senescent melanocytes and nevi and was selected for further studies. Depletion of tubulin ß-3 caused accumulation of cells in the G2/M phase and decreased proliferation and migration. Immunohistochemical assessment of tubulin ß-3 in benign lesions revealed strong staining in the superficial part of the intradermal components, which faded with depth. In contrast, primary melanomas exhibited staining without gradient in a disordered pattern and strong staining of the invasive front. Our results describe an approach to find clinically useful diagnostic biomarkers to more precisely identify cutaneous malignant melanoma and present tubulin ß-3 as a candidate marker.

Extracellular vesicles are transferred from melanocytes to keratinocytes after UVA irradiation.

Ultraviolet (UV) irradiation induces skin pigmentation, which relies on the intercellular crosstalk of melanin between melanocytes to keratinocytes. However, studying the separate effects of UVA and UVB irradiation reveals differences in cellular response. Herein, we show an immediate shedding of extracellular vesicles (EVs) from the plasma membrane when exposing human melanocytes to UVA, but not UVB. The EV-shedding is preceded by UVA-induced plasma membrane damage, which is rapidly repaired by Ca(2+)-dependent lysosomal exocytosis. Using co-cultures of melanocytes and keratinocytes, we show that EVs are preferably endocytosed by keratinocytes. Importantly, EV-formation is prevented by the inhibition of exocytosis and increased lysosomal pH but is not affected by actin and microtubule inhibitors. Melanosome transfer from melanocytes to keratinocytes is equally stimulated by UVA and UVB and depends on a functional cytoskeleton. In conclusion, we show a novel cell response after UVA irradiation, resulting in transfer of lysosome-derived EVs from melanocytes to keratinocytes.

Melanoma growth and progression after ultraviolet a irradiation: impact of lysosomal exocytosis and cathepsin proteases.

Ultraviolet (UV) irradiation is a risk factor for development of malignant melanoma. UVA-induced lysosomal exocytosis and subsequent cell growth enhancement was studied in malignant melanoma cell lines and human skin melanocytes. UVA irradiation caused plasma membrane damage that was rapidly repaired by calcium-dependent lysosomal exocytosis. Lysosomal content was released into the culture medium directly after irradiation and such conditioned media stimulated the growth of non-irradiated cell cultures. By comparing melanocytes and melanoma cells, it was found that only the melanoma cells spontaneously secreted cathepsins into the surrounding medium. Melanoma cells from a primary tumour showed pronounced invasion ability, which was prevented by addition of inhibitors of cathepsins B, D and L. Proliferation was reduced by cathepsin L inhibition in all melanoma cell lines, but did not affect melano-cyte growth. In conclusion, UVA-induced release of cathepsins outside cells may be an important factor that promotes melanoma growth and progression.

MDM2 SNP309 promoter polymorphism confers risk for hereditary melanoma.

The p53 pathway regulates stress response, and variations in p53, MDM2, and MDM4 may predispose an individual to tumor development. The aim of this study was to study the impact of genetic variation on sporadic and hereditary melanoma. We have analyzed a combination of three functionally relevant variants of the p53 pathway in 258 individuals with sporadic malignant melanomas, 50 with hereditary malignant melanomas, and 799 healthy controls. Genotyping was performed by PCR-restriction fragment length polymorphism, pyrosequencing, and allelic discrimination. We found an increased risk for hereditary melanoma in MDM2 GG homozygotes, which was more pronounced among women (P=0.035). In the event of pairwise combinations of the single nucleotide polymorphisms, a risk elevation was shown for MDM2 GG homozygotes/p53 wild-type Arg in hereditary melanoma (P=0.01). Individuals with sporadic melanomas of the superficial spreading type, including melanoma in situ, showed a slightly higher frequency of the MDM2 GG genotype compared with those with nodular melanomas (P=0.04). The dysplastic nevus phenotype, present in the majority of our hereditary melanoma cases and also in some sporadic cases, further enhanced the effect of the MDM2 GG genotype on melanoma risk (P=0.005). In conclusion, the results show an association between MDM2 SNP309 and an increased risk for hereditary melanoma, especially among women. Analysis of sporadic melanoma also shows an association between MDM2 and the superficial spreading melanoma subtype, as well as an association with the presence of dysplastic nevi in sporadic melanoma.

Lysosomal exocytosis and caspase-8-mediated apoptosis in UVA-irradiated keratinocytes.

Ultraviolet (UV) irradiation is a major environmental carcinogen involved in the development of skin cancer. To elucidate the initial signaling during UV-induced damage in human keratinocytes, we investigated lysosomal exocytosis and apoptosis induction. UVA, but not UVB, induced plasma membrane damage, which was repaired by Ca(2+)-dependent lysosomal exocytosis. The lysosomal exocytosis resulted in extracellular release of cathepsin D and acid sphingomyelinase (aSMase). Two hours after UVA irradiation, we detected activation of caspase-8, which was reduced by addition of anti-aSMAse. Furthermore, caspase-8 activation and apoptosis was reduced by prevention of endocytosis and by the use of cathepsin inhibitors. We conclude that lysosomal exocytosis is part of the keratinocyte response to UVA and is followed by cathepsin-dependent activation of caspase-8. The findings have implications for the understanding of UV-induced skin damage and emphasize that UVA and UVB initiate apoptosis through different signaling pathways in keratinocytes.

Inflammasome polymorphisms confer susceptibility to sporadic malignant melanoma.

Genetic variants of NLRP3 and NLRP1 are known to modulate levels of pro-inflammatory cytokine interleukin (IL)-1ß. The purpose of this study was to investigate the association of NLRP3/NLRP1 polymorphisms with susceptibility and clinical features of malignant melanoma in a Swedish case-control study. Common variants in NLRP3/NLRP1 were investigated in sporadic malignant melanoma patients and healthy controls followed by analysis using logistic regression. NLRP3 variant (rs35829419) was significantly more common in male patients than in controls (OR, 2.22; CI, 1.27-3.86). Upon stratification, significant association with nodular melanoma was observed (OR, 2.89; CI, 1.33-6.30), which intensified in male patients (OR 4.03, CI 1.40-11.59). The NLRP1 variant (rs12150220) was significantly more common in fair-skinned female patients (OR, 1.85; CI, 1.04-3.33) and showed strong associations with nodular melanoma (OR, 6.03; CI, 1.33-25). Our data suggest that NLRP3/NLRP1 polymorphisms are associated with melanoma susceptibility; these findings warrant validation in other independent populations.

Ultraviolet exposure of melanoma cells induces fibroblast activation protein-α in fibroblasts: Implications for melanoma invasion.

Fibroblast activation protein-α (FAP-α) promotes tumor growth and cell invasiveness through extracellular matrix degradation. How ultraviolet radiation (UVR), the major risk factor for malignant melanoma, influences the expression of FAP-α is unknown. We examined the effect of UVR on FAP-α expression in melanocytes, keratinocytes and fibroblasts from the skin and in melanoma cells. UVR induces upregulation of FAP-α in fibroblasts, melanocytes and primary melanoma cells (PM) whereas keratinocytes and metastatic melanoma cells remained FAP-α negative. UVA and UVB stimulated FAP-α-driven migration and invasion in fibroblasts, melanocytes and PM. In co-culture systems UVR of melanocytes, PM and cells from regional metastases upregulated FAP-α in fibroblasts but only supernatants from non-irradiated PM were able to induce FAP-α in fibroblasts. Further, UV-radiated melanocytes and PM significantly increased FAP-α expression in fibroblasts through secretory crosstalk via Wnt5a, PDGF-BB and TGF-ß1. Moreover, UV radiated melanocytes and PM increased collagen I invasion and migration of fibroblasts. The FAP-α/DPPIV inhibitor Gly-ProP(OPh)2 significantly decreased this response implicating FAP-α/DPPIV as an important protein complex in cell migration and invasion. These experiments suggest a functional association between UVR and FAP-α expression in fibroblasts, melanocytes and melanoma cells implicating that UVR of malignant melanoma converts fibroblasts into FAP-α expressing and ECM degrading fibroblasts thus facilitating invasion and migration. The secretory crosstalk between melanoma and tumor surrounding fibroblasts is mediated via PDGF-BB, TGF-ß1 and Wnt5a and these factors should be evaluated as targets to reduce FAP-α activity and prevent early melanoma dissemination.

Societal cost of skin cancer in Sweden in 2005.

Skin cancer is one of the most rapidly increasing cancers among the Swedish population and a significant cause of illness and death. This study aims to estimate the total societal cost of skin cancer in Sweden for 2005, using a prevalence-based cost-of-illness approach. The total cost of skin cancer was estimated at euro 142.4 million (euro 15/inhabitant), of which euro 79.6 million (euro 8/inhabitant) was spent on health services and euro 62.8 million (euro 7/inhabitant) was due to loss of production. The main cost driver was resource utilization in outpatient care, amounting to 42.2% of the total cost. Melanoma was the most costly skin cancer diagnosis. Non-melanoma skin cancer was, however, the main cost driver for health services alone. For the future it is important to establish effective preventive measures to avoid increasing costs and suffering caused by skin cancer.

The Gln/Gln genotype of XPD codon 751 as a genetic marker for melanoma risk and Lys/Gln as an important predictor for melanoma progression: a case control study in the Swedish population.

The Xeroderma pigmentosum complementation group D (XPD) is a critical protein in the nucleotide excision repair system for DNA damage. Genetic variations in XPD exert an important effect on the capacity of DNA repair. In this study, we examined Lys751Gln polymorphism at the XPD gene in 244 melanoma patients and 251 healthy individuals (as controls) from the south-eastern region of Sweden. The associations of polymorphism with melanoma risk, as well as with melanoma features and pigment phenotypes of the melanoma patients were analysed. DNA was extracted from the mononuclear cells of venous blood of the melanoma patients and controls. XPD codon 751 was genotyped by the PCR restriction fragment length polymorphism technique. Results showed that there was no difference in the distribution of the XPD codon 751 genotypes between the melanoma patients and healthy controls. However, the Gln/Gln genotype was found to be associated with melanoma risk in the male population. Furthermore, the frequency of the Gln/Gln genotype was significantly higher in the early stages of melanomas, whereas Lys/Gln was more frequent in the later stages and in the patients with melanoma located on intermittently UV-exposed areas. No correlations between the polymorphisms and phenotypes of the patients were found. In conclusion, Gln/Gln was a useful genetic marker for melanoma risk in the males, while Lys/Gln was an important predictor for melanoma progression.

Importance of FAS-1377, FAS-670, and FASL-844 polymorphisms in tumor onset, progression, and pigment phenotypes of Swedish patients with melanoma: a case-control analysis.

PURPOSE: Human skin melanoma at later stages usually has an extremely poor prognosis. It is of importance to search for biologic markers to identify and monitor individuals at risk for melanoma for early diagnosis and to avoid tumor progression. The FAS gene and its natural ligand (FASL) gene initiate the death signal cascade, playing a central role in the apoptotic signaling pathway and tumor growth and metastasis. PATIENTS AND METHODS: In this study, we analyzed polymorphisms in 229 patients with melanoma and 351 age- and gender-matched tumor-free individuals. Genomic DNAs were isolated from mononuclear cells in peripheral vein blood, and the polymorphisms were examined with polymerase chain reaction-restriction fragment length polymorphism techniques. Frequency in distribution of the polymorphisms was compared between the patients with melanoma and the healthy control subjects, and associations with patients' pigment phenotypes, age at diagnosis, and melanoma characteristics were analyzed. RESULTS AND CONCLUSIONS: The FAS-1377, FAS-670, and FASL-844 polymorphisms were not found to be markers of melanoma risk (P > 0.05). In patients with melanoma, frequencies of the FAS-1377, FAS-670, and FASL-844 polymorphisms were different between the patients aged <50 and > or =50 years (P < or = 0.025, P < or = 0.025, and P < or = 0.01). Moreover, the FAS-670 polymorphism correlated with tumor Breslow thickness (P < or = 0.01) and Clark level (P < or = 0.001) and was associated with tumors developing in sun-exposed locations (P < or = 0.001). FAS and FASL were not markers for melanoma risk but might be important in the development and progression of sun-induced melanoma independently of skin type.

Monitoring of kindreds with hereditary predisposition for cutaneous melanoma and dysplastic nevus syndrome: results of a Swedish preventive program.

PURPOSE: To evaluate a program initiated in 1987 by the Swedish Melanoma Study Group aiming to provide preventive surveillance to kindreds with hereditary cutaneous melanoma and dysplastic nevus syndrome. PATIENTS AND METHODS: Overall, 2,080 individuals belonging to 280 melanoma families were followed for 14 years between 1987 and 2001 at 12 participating centers. Data were registered in a central database. RESULTS: Among 1,912 skin lesions excised during follow-up, 41 melanomas were removed in 32 individuals. Of these, 15 (37%) were in situ melanomas and 26 (63%) invasive melanomas. The median tumor thickness of invasive melanomas was 0.5 mm. Ulceration was absent in 24 of 26 invasive melanomas (92%) and 12 (46%) lacked vertical growth phase. Compared with melanomas in the general Swedish population, the melanomas identified in these kindreds during follow-up had better prognostic characteristics. All melanomas except one were diagnosed in families with two or more first-degree relatives with melanoma. Diagnosis of melanoma occurred in three of eight kindreds with germline CDKN2A mutations, supporting that families with such mutations are at increased risk for melanoma development. Of the 32 individuals who developed melanoma during follow-up, 21 (66%) had had at least one previously diagnosed melanoma. CONCLUSION: This study shows that a coordinated program aimed at detecting and offering skin surveillance in kindreds with hereditary cutaneous melanoma results in a low incidence of melanomas during the follow-up period and that the tumors that do arise have favorable prognostic characteristics.

Importance of polymorphisms in NF-kappaB1 and NF-kappaBIalpha genes for melanoma risk, clinicopathological features and tumor progression in Swedish melanoma patients.

PURPOSE: Importance of polymorphisms in NF-kappaB1 and NF-kappaBIalpha genes for melanoma risk, clinicopathological features and tumor progression is analyzed in Swedish melanoma patients. PATIENTS AND METHODS: Functional polymorphisms of NF-kappaB1 and NF-kappaBIalpha genes were examined in 185 melanoma patients and 438 tumor-free individuals. Associations of the polymorphisms with melanoma risk, age and pigment phenotypes of the patients and clinicopathological tumor characteristics were analyzed. DNAs were isolated from mononuclear cells of venous blood. Polymorphisms of the genes were genotyped by a PCR-RFLP technique, and transcription level of NF-kappaBIalpha was examined by a quantitative real-time reverse transcription PCR. RESULTS: Both ATTG insertion polymorphism of NF-kappaB1 and A to G polymorphism of NF-kappaBIalpha genes were correlated with melanoma risk, especially, in a combination of ATTG( 2 )/ATTGT(2) and GG. NF-kappaB1 ATTG(2)/ATTG(2) and NF-kappaBIalpha GG genotypes were associated with male gender and age >65 years (at diagnosis). Patients with ATTG(1)/ATTG(1 )genotype had thinner tumors and lower Clark levels at diagnosis. Frequency of ATTG(1)/ATTG(1) genotype was higher in patients with melanomas on intermittently sun-exposed pattern of the body and NF-kappaBIalpha GG was more frequent in the patients with melanomas at rarely exposed sites. There were no differences in the gene transcription level between patients with different NF-kappaBIalpha genotypes. CONCLUSION: NF-kappaB1 and NF-kappaBIalpha genes might be susceptible genes for melanoma risk and functional polymorphisms of these genes might be biological predictors for melanoma progression.

Spectrophotometric analysis of melanocytic naevi during pregnancy.

Malignant melanoma is the most common cancer during pregnancy, but it is unknown whether melanocytic naevi in general are activated. A total of 381 melanocytic naevi in 34 Caucasian primigravidae were examined using spectrophotometric intracutaneous analysis (SIAscopy) technology in early pregnancy and prior to delivery. The Siagraphs of each naevus were then compared in order to evaluate changes over time. A total of 163 melanocytic naevi in 21 nulliparous women served as an additional control group. At the first visit none of the Siagraphs examined for the case or control groups aroused suspicion of dysplastic naevus or melanoma and no significant structural changes were noted during the observation period. However, 2.1% of the melanocytic naevi in the pregnant group increased and 1.3% decreased in size. Corresponding figures in the non-pregnant group were 1.8% and 0%, respectively. Only one naevus in a pregnant woman increased slightly in epidermal pigmentation, and a decrease in pigmentation was noted in 3.7% of the melanocytic naevi in the cases and 1.8% in the controls. None of the differences within or between the groups was statistically significant. We conclude that pregnancy does not influence the appearance of pigmented naevi. A changing naevus during pregnancy should be examined carefully and considered for excision and histopathology.

Hsp70 protects against UVB induced apoptosis by preventing release of cathepsins and cytochrome c in human melanocytes.

Stress-induced heat shock protein 70 (Hsp70) effectively protects cells against apoptosis, although the anti-apoptotic mechanism is still undefined. Exposure of human melanocytes to heat and subsequent UVB irradiation increased the level of Hsp70 and pre-heating reduced UVB induced apoptosis. Immunofluorescence staining of Hsp70 in combination with staining of lysosomes (Lamp2) or mitochondria (Mitotracker) in pre-heated UVB exposed cells showed co-localization of Hsp70 with both lysosomes and mitochondria in the surviving cell population. Furthermore, UVB induced apoptosis was accompanied by lysosomal and mitochondrial membrane permeabilization, detected as release of cathepsin D and cytochrome c, respectively, which were prevented by heat pre-treatment. In purified fractions of lysosomes and mitochondria, recombinant Hsp70 attached to both lysosomal and mitochondrial membranes. Moreover, in apoptotic cells Bax was translocated from a diffuse cytosolic location into punctate mitochondrial-like structures, which was inhibited by Hsp70 induction. Such inhibition of Bax translocation was abolished by transfection with Hsp70 siRNA. Furthermore, Hsp70 siRNA eliminated the apoptosis preventive effect observed after pre-heating. These findings show Hsp70 to rescue melanocytes from UVB induced apoptosis by preventing release of cathepsins from lysosomes, Bax translocation and cytochrome c release from mitochondria.

Important factors for pain during photodynamic therapy for actinic keratosis.

Photodynamic therapy (PDT) is an efficient treatment for actinic keratosis. A common problem, however, is pain. The aim of this study was to investigate pain during PDT for actinic keratosis. The possibility of using capsaicin cream for pain relief was also assessed. Pain was investigated during aminolaevulinic acid PDT in 91 patients. Size, redness, scaling and induration of the lesions were recorded. Maximum pain during treatment was registered, using a visual analogue scale (0-10). The pain-reducing efficacy of capsaicin was tested in a pilot study in six patients (10 lesions). These patients were pre-treated with capsaicin cream for one week before commencing PDT. Pain was found to be normally distributed around a mean value of visual analogue scale 4.6. Larger lesions gave more pain (p=0.001). The redness of the actinic lesions was found to be related to PDT-induced pain (p=0.01), the reduction of actinic area (p=0.007), and the cure rate (p=0.01). The redder the actinic area, the better the treatment outcome and the more pain experienced. Patients with the largest reduction in the actinic area experienced more pain (p=0.053). The most important factors for presence of pain seem to be the size and the redness of the lesion. No significant pain relief was experienced after pre-treatment with capsaicin.

UVA/B-induced apoptosis in human melanocytes involves translocation of cathepsins and Bcl-2 family members.

We demonstrate UVA/B to induce apoptosis in human melanocytes through the mitochondrial pathway, displaying cytochrome c release, caspase-3 activation, and fragmentation of nuclei. The outcome of a death signal depends on the balance between positive and negative apoptotic regulators, such as members of the Bcl-2 protein family. Apoptotic melanocytes, containing fragmented nucleus, show translocation of the proapoptotic proteins Bax and Bid from the cytosol to punctate mitochondrial-like structures. Bcl-2, generally thought to be attached only to membranes, was in melanocytes localized in the cytosol as well. In the fraction of surviving melanocytes, that is, cells with morphologically unchanged nucleus, the antiapoptotic proteins Bcl-2 and Bcl-X(L) were translocated to mitochondria following UVA/B. The lysosomal proteases, cathepsin B and D, which may act as proapoptotic mediators, were released from lysosomes to the cytosol after UVA/B exposure. Proapoptotic action of the cytosolic cathepsins was confirmed by microinjection of cathepsin B, which induced nuclear fragmentation. Bax translocation and apoptosis were markedly reduced in melanocytes after pretreatment with either cysteine or aspartic cathepsin inhibitors. No initial caspase-8 activity was detected, excluding involvement of the death receptor pathway. Altogether, our results emphasize translocation of Bcl-2 family proteins to have central regulatory functions of UV-induced apoptosis in melanocytes and suggest cathepsins to be proapoptotic mediators operating upstream of Bax.