Abstract-Melanocytes and melanoma cells contain melanin, a complex polymer that modulates redox changes in these cells. Relative intracellular hydrogen peroxide levels measured by dichlorodihydrofluorescein are similar in the two cell types, but the levels of superoxide anion measured by dihydroethidium were markedly increased in melanoma cells. Chelator-induced oxidative stress is efficiently suppressed by melanocytes without substantial recruitment of the transcription factors NF-B and AP-1 as measured by electrophoretic mobility shift assay and quantitated by densitometry or by a change in frequency of apoptosis as determined by annexin V binding. In contrast, NF-B in melanoma cells is strongly recruited by changes in redox status and exhibits a correlative relationship to intracellular hydrogen peroxide (but not superoxide anion). However, the response of the NF-B pathway to intracellular hydrogen peroxide is anomalous, including downregulation of p65 and IB␣ RNA expression (Northern blot). Additionally, recruitment of AP-1 binding in melanoma cells was directly correlated with intracellular levels of superoxide anion (but not hydrogen peroxide). Neither the degree of NF-B nor AP-1 binding in melanoma cells was related to the frequency of apoptosis. The responsiveness of NF-B and AP-1 recruitment to intracellular levels of hydrogen peroxide and superoxide anion without concomitant control of apoptosis provides a general mechanism by which these cells can escape noxious injury (e.g., chemotherapy). The marked enhancement of apoptosis in melanoma cells by chelators indicates, however, that this alteration can be circumvented and offers a unique therapeutic window to explore.
Melanoma cells have a poor ability to mediate oxidative stress, which may be attributed to constitutive abnormalities in their melanosomes. We hypothesize that disorganization of the melanosomes will allow chemical targeting of the melanin within. Chemical studies show that under oxidative conditions, synthetic melanins demonstrate increased metal affinity and a susceptibility to redox cycling with oxygen to form reactive oxygen species. The electron paramagnetic resonance (EPR)-active 5,5¢-dimethyl-pyrollidine N-oxide spin adduct was used to show that binding of divalent Zn or Cu to melanin induces a pro-oxidant response under oxygen, generating superoxide and hydroxyl radicals. A similar pro-oxidant behaviour is seen in melanoma cell lines under external peroxide stress. Melanoma cultures grown under 95% O 2 ⁄5% CO 2 atmospheres show markedly reduced viability as compared with normal melanocytes. Cu-and Zn-dithiocarbamate complexes, which induce passive uptake of the metal ions into cells, show significant antimelanoma activity. The antimelanoma effect of metal-and oxygen-induced stress appears additive rather than synergistic; both treatments are shown to be significantly less toxic to melanocytes.
The response of human melanocytes and melanoma cells to hydrogen peroxide stress was measured. Cells were exposed to glucose/glucose oxidase or free H2O2 and reactive oxygen species measured by luminol‐enhanced chemiluminescence. The response was distinctly different between the two types and the addition of superoxide dismutase to melanoma cells paradoxically enhanced the chemiluminescent signal. These findings coupled with other known differences between the way these two types of cells handle oxidative stress at a molecular level suggests that a therapeutic window may be avail‐able for exploitation.
As the fields of counseling and psychotherapy have become more cognizant that individuals, couples, and families bring with them a myriad of diversity factors into therapy, multicultural competency has also become a crucial component in the development of clinicians during clinical supervision and training. We employed a qualitative meta-analysis to provide a detailed and comprehensive description of similar themes identified in primary qualitative studies that have investigated supervisory practices with an emphasis on diversity. Findings revealed six meta-categories, namely: (a) Supervisor's Multicultural Stances; (b) Supervisee's Multicultural Encounters; (c) Competency-Based Content in Supervision; (d) Processes Surrounding Multicultural Supervision; (e) Culturally Attuned Interventions; and (f) Multicultural Supervisory Alliance. Implications for practice are discussed.
This paper describes the development and initial evaluation of a human cell assay to identify potentially efficacious agents for preventing melanoma. Four human cell lines were used: normal melanocytes, a radial growthphase-like melanoma cell line (WM3211), a vertical growthphase-like melanoma cell line (Lu1205), and 83-2c, a cell strain cloned from metastatic melanoma. Four endpoints were evaluated in ultraviolet B-treated cells: annexin V, human leukocyte antigen-DR; E-cadherin, and N-cadherin. Annexin V was induced by nimesulide, 4-hydroxyphenylretinamide, and difluoromethylornithine in ultraviolet-B-treated radial growth-phase-like melanoma cells. None of the agents inhibited human leukocyte antigen-DR expression in ultraviolet-B-treated radial growth-phase-like melanoma cells, the only cells that strongly expressed human leukocyte antigen-DR. E-cadherin was overexpressed only in radial growthphase-like melanoma cells relative to melanocytes, and ultraviolet B exposure dramatically reduced this expression. E-cadherin was only induced by difluoromethylornithine in ultraviolet-B-treated radial growth-phase-like melanoma cells. N-cadherin was overexpressed in all melanoma cell lines relative to melanocytes. In this study, all candidate preventive agents inhibited N-cadherin in ultraviolet B-treated radial growth-phase-like melanoma cells. Four agents inhibited N-cadherin in ultraviolet B-treated vertical growth-phaselike melanoma cells. The mean ratios of N-cadherin to E-cadherin levels and specific endpoint responses for both the radial growth-phase-like melanoma and vertical growth-phase-like melanoma cells were used to rank the agents. Agents were evaluated at clinically relevant concentrations. The rankings were difluoromethylornithine > 4-hydroxyphenylretinamide > nimesulide > 9-cis-retinoic acid > polyphenon E. Diphenylhydramine, D-mannitol, and nordihydroguaiaretic acid were inactive. The results of these initial studies suggest that ultraviolet-B-treated radial growth-phase-like melanoma cells are the most responsive to chemopreventive agents, and may be the cell line of choice for screening melanoma prevention agents.
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