Knuth Rass

UV Damage and DNA Repair in Malignant Melanoma and Nonmelanoma Skin Cancer

Exposition of the skin with solar ultraviolet radiation (UV) is the main cause of skin cancer development. The consistently increasing incidences of melanocytic and nonmelanocytic skin tumors are believed to be at least in part associated with recreational sun exposure. Epidemiological data indicate that excessive or cumulative sunlight exposition takes place years and decades before the resulting malignancies arise. The most important defense mechanisms that protect human skin against UV radiation involve melanin synthesis and active repair mechanisms. DNA is the major target of direct or indirect UV-induced cellular damage. Low pigmentation capacity in white Caucasians and rare congenital defects in DNA repair are mainly responsible for protection failures. The important function of nucleotide excision DNA repair (NER) to protect against skin cancer becomes obvious by the rare genetic disease xeroderma pigmentosum, in which diverse NER genes are mutated. In animal models, it has been demonstrated that UVB is more effective to induce skin cancer than UVA. UV-induced DNA photoproducts are able to cause specific mutations (UV-signature) in susceptible genes for squamous cell carcinoma (SCC) and basal cell carcinoma (BCC). In SCC development, UV-signature mutations in the p513 tumor suppressor gene are the most common event, as precancerous lesions reveal approximately 80% and SCCs > 90% UV-specific p53 mutations. Mutations in Hedgehog pathway related genes, especially PTCH1, are well known to represent the most significant pathogenic event in BCC. However, specific UV-induced mutations can be found only in approximately 50% of sporadic BCCs. Thus, cumulative UVB radiation can not be considered to be the single etiologic risk factor for BCC development. During the last decades, experimental animal models, including genetically engineered mice, the Xiphophorus hybrid fish, the south american oppossum and human skin xenografts, have further elucidated the important role of the DNA repair system in the multi-step process of UV-induced melanomagenesis. An increasing body of evidence now indicates that nucleotide excision repair is not the only DNA repair pathway that is involved in UV-induced tumorigenesis of melanoma and nonmelanoma skin cancer. An interesting new perspective in DNA damage and repair research lies in the participation of mammalian mismatch repair (MMR) in UV damage correction. As MMR enzyme hMSH2 displays a p53 target gene, is induced by UVB radiation and is involved in NER pathways, studies have now been initiated to elucidate the physiological and pathophysiological role of MMR in malignant melanoma and nonmelanoma skin cancer development.

High-throughput miRNA profiling of human melanoma blood samples

BackgroundMicroRNA (miRNA) signatures are not only found in cancer tissue but also in blood of cancer patients. Specifically, miRNA detection in blood offers the prospect of a non-invasive analysis tool.MethodsUsing a microarray based approach we screened almost 900 human miRNAs to detect miRNAs that are deregulated in their expression in blood cells of melanoma patients. We analyzed 55 blood samples, including 20 samples of healthy individuals, 24 samples of melanoma patients as test set, and 11 samples of melanoma patients as independent validation set.ResultsA hypothesis test based approch detected 51 differentially regulated miRNAs, including 21 miRNAs that were downregulated in blood cells of melanoma patients and 30 miRNAs that were upregulated in blood cells of melanoma patients as compared to blood cells of healthy controls. The tets set and the independent validation set of the melanoma samples showed a high correlation of fold changes (0.81). Applying hierarchical clustering and principal component analysis we found that blood samples of melanoma patients and healthy individuals can be well differentiated from each other based on miRNA expression analysis. Using a subset of 16 significant deregulated miRNAs, we were able to reach a classification accuracy of 97.4%, a specificity of 95% and a sensitivity of 98.9% by supervised analysis. MiRNA microarray data were validated by qRT-PCR.ConclusionsOur study provides strong evidence for miRNA expression signatures of blood cells as useful biomarkers for melanoma.

Efficacy of Low-Dose Interferon α2a 18 Versus 60 Months of Treatment in Patients With Primary Melanoma of ≥ 1.5 mm Tumor Thickness: Results of a Randomized Phase III DeCOG Trial

PURPOSE Low-dose (LD) interferon (IFN) alfa (LDI) has demonstrated a consistent disease-free survival benefit for patients with clinically lymph node-negative melanoma in clinical trials. However, the optimal duration of treatment is still under discussion, and no previous trial has evaluated this question specifically. A prolongation of LDI from 18 months to 60 months might be of clinical benefit for patients with intermediate or high-risk melanoma. PATIENTS AND METHODS Eight hundred fifty patients with resected cutaneous melanoma of at least 1.5 mm tumor thickness were included in this prospective randomized, multicenter trial in Germany and Austria. Patients had to be clinically lymph node-negative, and sentinel node biopsy (SLNB) was performed in a majority of cases. They were randomly assigned to receive 3 MU IFNalpha2a three times a week subcutaneously for either 18 months (arm A) or 60 months (arm B). Results Of 850 randomly assigned patients, 840 were eligible for evaluation after a median follow-up of 4.3 years. Tumor thickness and other relevant prognostic factors were well balanced between both groups. SLNB was performed in 635 patients (75.6%), with a positivity rate of 18.0% in arm A and 17.5% in arm B. Neither relapse-free survival (arm A, 75.6% v arm B, 72.6%; P = .72; hazard ratio, 1.05; 95% CI, 0.80 to 1.39) nor distant-metastasis-free survival (81.9% v 79.7%; P = .56; HR, 1.10; 95% CI, 0.80 to 1.52) or overall survival (85.9% v 84.9%; P = .86; HR, 1.03; 95% CI, 0.71 to 1.50) showed significant differences. CONCLUSION A prolongation of conventional LDI therapy from 18 to 60 months showed no clinical benefit in patients with intermediate and high-risk primary melanoma.

MGMT gene promoter methylation correlates with tolerance of temozolomide treatment in melanoma but not with clinical outcome

Background:Despite limited clinical efficacy, treatment with dacarbazine or temozolomide (TMZ) remains the standard therapy for metastatic melanoma. In glioblastoma, promoter methylation of the counteracting DNA repair enzyme O6-methylguanine-DNA-methyltransferase (MGMT) correlates with survival of patients exposed to TMZ in combination with radiotherapy. For melanoma, data are limited and controversial.Methods:Biopsy samples from 122 patients with metastatic melanoma being treated with TMZ in two multicenter studies of the Dermatologic Cooperative Oncology Group were investigated for MGMT promoter methylation. We used the COBRA (combined bisulphite restriction analysis) technique to determine aberrant methylation of CpG islands in small amounts of genomic DNA isolated from paraffin-embedded tissue sections. To detect aberrant methylation, bisulphite-treated DNA was amplified by PCR, enzyme restricted, and visualised by gel electrophoresis.Results:Correlation with clinical data from 117 evaluable patients in a best-response evaluation indicated no statistically significant association between MGMT promoter methylation status and response. A methylated MGMT promoter was observed in 34.8% of responders and 23.4% of non-responders (P=0.29). In addition, no survival advantage for patients with a methylated MGMT promoter was detectable (P=0.79). Interestingly, we found a significant correlation between MGMT methylation and tolerance of therapy. Patients with a methylated MGMT promoter had more severe adverse events, requiring more TMZ dose reductions or discontinuations (P=0.007; OR 2.7 (95% CI: 1.32–5.7)). Analysis of MGMT promoter methylation comparing primaries and different metastases over the clinical course revealed no statistical difference (P=0.49).Conclusions:In advanced melanoma MGMT promoter, methylation correlates with tolerance of therapy, but not with clinical outcome.

Prospective Randomized Multicenter Adjuvant Dermatologic Cooperative Oncology Group Trial of Low-Dose Interferon Alfa-2b With or Without a Modified High-Dose Interferon Alfa-2b Induction Phase in Patients With Lymph Node–Negative Melanoma

PURPOSE Interferon alfa (IFN-alpha) has shown clinical efficacy in the adjuvant treatment of patients with high-risk melanoma in several clinical trials, but optimal dosing and duration of treatment are still under discussion. It has been argued that in high-dose IFN-alpha (HDI), the intravenous (IV) induction phase might be critical for the clinical benefit of the regimen. PATIENTS AND METHODS In an attempt to investigate the potential role of a modified high-dose induction phase, lymph node-negative patients with resected primary malignant melanoma of more than 1.5-mm tumor thickness were included in this prospective randomized multicenter Dermatologic Cooperative Oncology Group trial. Six hundred seventy-four patients were randomly assigned to receive 4 weeks of a modified HDI scheme. This schedule consisted of 5 times weekly 10 MU/m(2) IFN-alpha-2b IV for 2 weeks and 5 times weekly 10 MU/m(2) IFN-alpha-2b administered subcutaneously (SC) for another 2 weeks followed by 23 months of low-dose IFN-alpha-2b (LDI) 3 MU SC three times a week (arm A). LDI 3 MU three times a week was given for 24 months in arm B. Results Of 650 assessable patients, there were 92 relapses among the 321 patients receiving high-dose induction as compared with 95 relapses among the 329 patients receiving LDI only. Five-year relapse-free survival rates were 68.0% (arm A) and 67.1% (arm B), respectively. Likewise, melanoma-related fatalities were similar between both groups, resulting in 5-year overall survival rates of 80.2% (arm A) and 82.9% (arm B). CONCLUSION The addition of a 4-week modified HDI induction phase to a 2-year low-dose adjuvant IFN-alpha-2b treatment schedule did not improve the clinical outcome.

Ultraviolet Damage, DNA Repair and Vitamin D in Nonmelanoma Skin Cancer and in Malignant Melanoma

Skin exposure with UV radiation (UV) is the main cause of skin cancer development. Epidemiological data indicate that excessive or cumulative UV exposure takes place years and decades before the resulting malignancies arise. The most important defense mechanisms that protect human skin against UV radiation involve melanin synthesis and active repair mechanisms. DNA is the major target of direct or indirect UV-induced cellular damage. Low pigmentation capacity in white Caucasians and rare congenital defects in DNA repair are mainly responsible for protection failures. The important function of nucleotide excision DNA repair (NER) to protect against skin cancer becomes obvious by the rare genetic disease xeroderma pigmentosum, in which diverse NER genes are mutated. In animal models, it has been demonstrated that UVB is more effective to induce skin cancer than UVA. UV-induced DNA photoproducts are able to cause specific mutations (UV-signature) in susceptible genes for squamous cell carcinoma (SCC) and basal cell carcinoma (BCC). In SCC development, UV-signature mutations in the p53 tumor suppressor gene are the most common event, as precancerous lesions reveal -80% and SCCs > 90% UV-specific p53 mutations. Mutations in Hedgehog pathway related genes, especially PTCH1, are well known to represent the most significant pathogenic event in BCC. However, specific UV-induced mutations can be found only in -50% of sporadic BCCs. Thus, cumulative UVB radiation cannot be considered to represent the only etiologic risk factor for BCC development. During the last decades, experimental animal models, including genetically engineered mice, the Xiphophorus hybrid fish, the South American oppossum and human skin xenografts, have further elucidated the important role of the DNA repair system in the multi-step process of UV-induced melanomagenesis. An increasing body of evidence now indicates that nucleotide excision repair is not the only DNA repair pathway that is involved in UV-induced tumorigenesis of melanoma and nonmelanoma skin cancer. An interesting new perspective in DNA damage and repair research lies in the participation of mammalian mismatch repair (MMR) in UV damage correction. As MMR enzyme hMSH2 displays a p53 target gene, is induced by UVB radiation and is involved in NER pathways, studies have now been initiated to elucidate the physiological and pathophysiological role of MMR in malignant melanoma and nonmelanoma skin cancer development. Interestingly, increasing evidence now demonstrates an important function of the vitamin D endocrine system (VDES) for prevention of BCC, SCC and melanoma, identifying the vitamin D receptor as a tumor suppressor in the skin.

DNA Mismatch Repair Enzyme hMSH2 in Malignant Melanoma: Increased Immunoreactivity as Compared to Acquired Melanocytic Nevi and Strong MRNA Expression in Melanoma Cell Lines

Mutations in the mismatch DNA repair gene human MutS homologen 2 (hMSH2) are causative for microsatellite instability and carcinogenesis in various human tumours, including hereditary nonpolyposis colorectal cancer. Because microsatellite instability has been detected in malignant melanoma, we have investigated hMSH2 in melanocytic tumours. We found strong nuclear immunoreactivity for hMSH2 that was elevated in malignant melanoma and melanoma metastases as compared to acquired nevi. These findings suggest that increased genomic instability in malignant melanoma is associated with elevated protein levels of this DNA repair enzyme. hMSH2 is not exclusively regulated by proliferative activity in melanocytes, because there was no correlation between staining patterns of hMSH2 and the proliferation marker Ki-67. In contrast, immunoreactivity scores for hMSH2 and p53 were both upregulated in malignant melanocytic tumours. These findings support the concept that hMSH2 gene expression may be regulated in melanocytes by the p53 protein, as has been reported previously in other tissues. Using the reverse transcription-polymerase chain reaction, we detected strong hMSH2 mRNA expression in each of 8 melanoma cell lines analysed (highest amounts in SK-MEL-25 cells, lowest amounts in MML-I cells). In conclusion, our findings indicate that hMSH-2 may be of importance for genetic stability, tumorigenesis and progression of malignant melanoma.

Sorafenib and pegylated interferon-α2b in advanced metastatic melanoma: a multicenter phase II DeCOG trial

BACKGROUND The combination of sorafenib, a multikinase inhibitor, and pegylated interferon-α2b (Peg-IFN-α2b) could potentially lead to an improved antitumoral response. Previously, combinations of interferon and sorafenib have been used in renal cell cancer. PATIENTS AND METHODS Patients with stage IV metastatic melanoma and no previous systemic therapies apart from adjuvant immunotherapy received Peg-IFN-α2b 3 μg/kg once per week, and sorafenib 400-mg b.i.d. for a minimum of 8 weeks. The primary study end point was disease control rate (DCR). RESULTS Between February 2008 and February 2009, 55 patients were enrolled with a median age of 64 years (20-85). At 8 weeks, 2 patients (3.6%) had a partial response (PR) and 14 patients a stable disease (25.5%), for a DCR of 29.1% in the intention-to-treat (ITT) population. The median progression-free survival in the ITT population was 2.47 months (95% confidence interval 1.22-3.72 months). The toxicity of sorafenib and Peg-IFN-α2b combination was characterized by mainly hematological side-effects, including one treatment-related bleeding complication with a fatal outcome. Other grade 3/4 toxic effects were fatigue and flu-like symptoms. CONCLUSION The combination of sorafenib and Peg-IFN-α2b showed modest clinical activity and some serious side-effects including fatal bleeding complications.

Immunohistochemical analysis of DNA mismatch repair enzyme hMSH-2 in normal human skin and basal cell carcinomas.

We have analysed the expression and distribution of the DNA mismatch repair enzyme hMSH-2 in normal skin and basal cell carcinomas. hMSH-2 protein was investigated immunohistochemically (normal human skin: n=10; basal cell carcinomas: n=16) on frozen sections using a highly sensitive streptavidin–peroxidase technique and a specific mouse monoclonal antibody (clone FE11). In normal human skin, we found nuclear immunoreactivity for hMSH-2 in epidermal keratinocytes of the basal and first 1–3 suprabasal cell layers. All basal cell carcinomas analysed revealed strong nuclear imunoreactivity that was pronounced in peripheral tumour cells and cells of the palisade. Expression of hMSH-2 protein was consistently and strongly upregulated in tumour cells of the carcinomas as compared to adjacent unaffected epidermis or epidermis of normal human skin. Twelve of the sixteen carcinomas analysed revealed no visual correlation in comparing the labelling patterns for hMSH-2 with the labelling pattern for the proliferation marker Ki-67. Our findings indicate that (a) hMSH-2 is expressed in human epidermal keratinocytes, predominantly in lower cell layers of the viable epidermis; (b) expression of hMSH-2 protein is strongly upregulated in basal cell carcinomas as compared to unaffected epidermis; (c) the level of hMSH-2 proteins in the carcinomas is not exclusively regulated by the proliferative activity of these tumour cells; (d) inactivating mutations of the hMSH-2 gene may in the carcinomas not be involved in the carcinogenesis or microsatellite instability secondary to replication errors; (e) expression of hMSH-2 may be of importance for the genetic stability of basal cell carcinomas in vivo.

Treatment of Melanoma and Nonmelanoma Skin Cancer

The incidence of skin cancer is increasing in Caucasian populations worldwide. Treatment approaches for Nonmelanoma skin cancer (NMSC) are predominantly curative and surgery can be regarded as standard of care. Nevertheless, novel and less invasive topical therapy modalities like photodynamic therapy or local immune modifiers are in progress. In contrast to NMSC, the mortality of melanoma has not changed considerably over the last years and decades. Melanoma survival mainly depends on primary tumor thickness underlining the importance of primary and secondary prevention by avoidance or early detection of the disease. The chance to cure melanoma patients is steadily decreasing with tumor stage. As the prognosis in distant metastatic disease is still poor, except for single situations therapy approaches are palliative and accompanied by an optimal supportive care of the patients concerned. Albeit removal of localized metastases is currently the most effective approach in metastatic melanoma, chemo- and chemoimmunotherapy has to be regarded as standard treatment in most of the cases. Novel and promising therapeutic options accrue from growing insights in tumor biology and immunology. Not only in melanoma, development and application of targeted therapies currently attract the most attention in the treatment of advanced tumors. First clinical experiences with those antiproliferative, antiangiogenic and proapoptotic agents reveal only moderate antitumoral activity in melanoma, so that future efforts aim at defining more effective combination strategies using chemo-, targeted and vaccination therapy approaches.