| 1. |
- Bivik, Cecilia, 1978-
(författare)
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Regulation of UV induced apoptosis in human melanocytes
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Malignant melanoma arises from the pigment producing melanocytes in epidermis and is the most aggressive type of skin cancer. The incidence of malignant melanoma is increasing faster than any other type of cancer in white population worldwide, with a doubling rate every 10-20 years. So far, the only identified external risk factor for malignant melanoma is UV exposure. Elimination of photodamaged cells by apoptosis (programmed cell death) is essential to prevent tumor formation. Melanocytes are considered relatively resistant to apoptosis, however, the regulation of apoptosis in melanocytes is still unknown.The aim of this thesis was to investigate the apoptotic process following ultraviolet (UV) irradiation in primary cultures of human melanocytes. Focus was on regulation of mitochondrial stability by Bcl-2 family proteins and the possible participation of lysosomal proteases, cathepsins. UV irradiation activated the mitochondrial pathway of apoptosis, leading to cytochrome c release, caspase activation, and nuclear fragmentation. No change in protein expression of Bax and Bcl-2 was observed in response to UV. Instead, translocation of the Bcl-2 family proteins from cytosol to mitochondia was important in the regulation of survival and death of melanocytes. The findings further demonstrated permeabilization of the lysosomal membrane to occur early in the apoptotic process, resulting in cathepsin release into the cytosol. The cathepsins were potent pro-apoptotic mediators and triggered apoptosis upstream of Bax translocation and mitochondrial membrane permeabilization. In response to both heat and UV irradiation, there was a marked increase in expression of stress-induced heat shock protein 70 (Hsp70), which inhibited apoptosis by binding lysosomal and mitochondrial membranes and counteracting the release of cathepsins and cytochrome c. Furthermore, UV irradiation activated c-jun N-terminal kinase (JNK), which triggered apoptosis upstream of cathepsins release from the lysosomes. In addition, JNK mediated apoptosis through phosphorylation of pro-apoptotic Bim, which was released from anti-apoptotic Mcl-1, by UV induced Mcl-1 depletion.This thesis illustrates that permeabilization of mitochondria and lysosomes and release of their constituents to the cytosol participates in UV induced apoptosis signaling in human melanocytes in vitro. The process is regulated by a complex network of pro- and anti-apoptotic proteins, exerting their effects through intracellular translocation and alteration of protein expression.
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| 2. |
- Karlsson, Pia, 1965-
(författare)
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Cutaneous melanoma in children and adolescents and aspects of naevus phenotype in melanoma risk assessment
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Cutaneous malignant melanoma (CMM) is one of the most rapidly increasing cancers in the Swedish population. The aetiology of melanoma is a complex interplay between genetics, host characteristics and environmental factors. The host characteristic with the strongest association with CMM is a phenotype with high numbers of common naevi and with dysplastic naevi. The principal environmental factor is sun exposure.Melanoma risk assessment (paper I)In a multi-national study including 986 subjects from Sweden, Denmark, the UK, Germany and the Netherlands, the ability of primary care physicians and nurses to identify individuals at increased melanoma risk was assessed. The atypical mole syndrome (AMS) scoring system for melanoma risk was used. The AMS scoring system consists of a five point check list incorporating total body naevus counts, clinically dysplastic naevi and body distribution of naevi. After brief training, the overall agreement in diagnosis between the trained personnel and experienced dermatologists was 94.5% (kappa value 0.70, p<0.05). The study showed that the scoring system successfully can be taught to personnel in primary care.The naevus phenotype in a population in northern Sweden (paper II)The naevus phenotype was investigated in a population living in the inland of northern Sweden with a low melanoma incidence. Two hundred and one participants from the community of Storuman were included. The median naevus count was15 common naevi/individual, and the prevalence of dysplastic naevi was 11%. The median naevus count and prevalence of dysplastic naevi were significantly lower than previously described in populations with higher melanoma incidence and higher ambient ultraviolet exposure in southern Sweden. This geographical variation in naevus phenotype might be explained by differences in levels of sun exposure and in genotype.Cutaneous malignant melanoma in children and adolescents (papers III–V)During the years 1973 to 2002, 250 cases of primary CMM in individuals aged 0-19 years were reported to the Swedish Cancer Registry. Histological material was available for review in 87% of the cases registered during the two first decades (1973–1992). The diagnostic accuracy in the reviewed material was 88%.The melanoma incidence doubled in teenagers between the first decade (1973–1982) and the second (1983–1992). During the third decade (1993–2002) the increasing trend was broken. A decrease in incidence was noted in boys during 1993–1997, and in girls during 1998–2002. In younger children the incidence remained extremely low, only 4 cases in children aged 0–9 years were reported during the studied 30-year period. The trunk was the most common melanoma site in boys, and legs and trunk were the most common sites in girls. Superficial spreading melanoma was the most frequent subtype, followed by nodular melanoma. During the two first decades (1973–1992), the median melanoma thickness decreased from 1.5 to 0.9 mm. The melanoma-specific 5-year survival rate was 93%. The most important prognostic factor was melanoma thickness. The prognosis for thin lesions was excellent, during a median follow up time of 12 years, no tumour less than 0.8 mm was lethal according to the Registry.The results indicate that CMM in teenagers has many features in common with adult onset melanoma. The tudy also underlines the importance of not neglecting lesions suspected for malignant change in children and adolescents, as early detection and removal is crucial for the prognosis also in this young age group.
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| 3. |
- Seifert (Bock), Oliver, 1971-
(författare)
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Keloids - A fibroproliferative disease
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Keloids are a fibroproliferative disorder of unknown etiology developing in the skin after injury or spontaneously. The aim of this thesis is to gain deeper insight into the role of TGF-β and its signaling pathway proteins, SMADs, in the pathogenesis of keloids and describe the gene expression profile in different keloid sites in the search for potential target genes for future treatment. Further aim is to develop an instrument to describe the quality of life of patients with keloids.We find cultured keloid fibroblasts to express an increased level of TGF-β1 mRNA and a decreased level of TGF-β3 mRNA compared to control skin. Keloid derived fibroblasts exhibit significantly decreased mRNA levels of TGF-β receptor type II (TβRII) and the ratio of TβRI/TβRII mRNA expression is increased. This suggests that a certain expression pattern of TGF-β subtypes and receptors may be important in keloid pathogenesis.Analysis of keloid derived fibroblasts reveal decreased SMAD3 mRNA expression and decreased ratio of SMAD2/SMAD3 mRNA implicating a disturbed SMAD signaling. Keloid fibroblasts up-regulate SMAD4 protein after stimulation with TGF-β1 and display diminished levels of the inhibitory proteins SMAD6 and 7. This may contribute to unlimited and deregulated TGF-β signaling leading to increased extracellular matrix production (ECM).The gene expression pattern is described in fibroblasts from different keloid sites using microarrays covering the whole human genome. This study reveals 105 regulated genes (79 genes are up- and 26 down-regulated) resulting in a unique gene expression profile in different sites of keloids, where progression or regression of the keloid process took place. In cells from the central part of keloids with clinical signs of regression, an up-regulation of apoptosis inducing genes as ADAM12 and ECM degrading genes as MMP19 is found. These genes may contribute to regression of keloids and might be possible future target genes for treatment. Overexpression of apoptosis inhibitors as AVEN and down-regulation of angiogenesis inhibiting genes as PTX3 found at the active margin of keloids may be responsible for the invasive character of the keloid margin.We develop a disease specific questionnaire to measure the quality of life of patients with keloids. We find two scales, psychological and physical impairment, describing the dimensions of quality of life in patients with scars. These two scales are independent of each other and show a high test-retest reliability. Single items which clinically characterize the disease show correlations to these scales. The results of this study demonstrate for the first time a severe impairment of quality of life of patients suffering from keloids and hypertrophic scars.In conclusion the described alteration in TGF-β expression and its receptors, the disrupted SMAD signaling pathway and the unique gene expression patterns in different keloid sites provide new knowledge on ECM formation and degradation in keloids. Regulatory genes in ECM homeostasis may be future target genes for keloid prevention, regression and treatment. The disease specific quality of life instrument of patients with keloids and scars is a useful tool to estimate success in future therapeutic efforts over time.
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| 4. |
- Wäster Larsson, Petra, 1977-
(författare)
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UVA/B induced redox alterations and apoptosis in human melanocytes
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Malignant melanoma is one of the most rapidly increasing cancers and accounts for about three-quarter of all skin cancer deaths worldwide. Despite compelling evidence that ultraviolet (UV) irradiation causes melanoma the knowledge how various wavelength spectra affect the balance between proliferation and apoptosis controlling the homeostasis of the melanocyte population is still limited. The aim of this thesis was to elucidate the regulation of UVA/B induced apoptotic signaling in human epidermal melanocytes in vitro in relation to redox alterations and antioxidant photoprotection.UVA irradiation induced changes in plasma membrane stability, decreased cell proliferation and increased apoptosis. In comparison, melanocyte plasma membrane was markedly resistant to UVB irradiation although apoptosis was triggered. Thus, UVA irradiation should not be overlooked as an etiologic factor in melanoma development. Further, after irradiation with UVA/B we found alterations in redox state manifested by a reduction of intracellular GSH levels, translocation of nuclear factor-κB from the cytosol to the nucleus, an increase of γ-glutamylcysteine synthetase, the rate-limiting enzyme in GSH synthesis, and an increased apoptosis frequency. α-Tocopherol provided photoprotection through several modes of action affecting redox alterations and signaling, stabilizing the plasma membrane, and decreased proliferation and apoptosis rate, while β-carotene did not show the same protective capacity. Altogether, α-tocopherol might be a useful substance in protecting melanocytes from UV induced damage.We demonstrate UVA/B irradiation to activate the intrinsic pathway of apoptosis in melanocytes where translocation of Bcl-2 family proteins to the mitochondria modulates the apoptosis signal. Interestingly, the anti-apoptotic Bcl-2 family proteins generally thought to be attached to membranes, were localized in the cytosol before UV irradiation and translocated to the mitochondria in the surviving population, which might be a critical event in preventing apoptotic cell death. Lysosomal cathepsins were released to the cytosol acting as pro-apoptotic mediators upstream of activation and translocation of Bax to the mitochondria. When melanocytes were exposed to UVA, p53 participated in apoptosis regulation through interaction with Bcl-2 family proteins, while UVB induced p53-transcriptional activity and apoptosis involving lysosomal membrane permeabilization. Thus, depending on the UV wavelength p53 mediated apoptosis in melanocytes by transcriptional dependent or independent activity. These results emphasize p53 as an important pro-apoptotic component in the regulation of apoptosis.This thesis gives new insight in the harmful and various effects of different wavelengths within the UV spectrum on human melanocytes in vitro. Improved knowledge of the apoptosis regulatory systems in melanocytes might lead to a better understanding of the formation of pigment nevi and malignant melanoma and, in the future, provide better strategies to prevent and eliminate tumor development and progression.
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