摘要:

Protein tyrosyl phosphorylation is an essential component in intracellular signalling, with diverse and crucial functions including mediation of cell proliferation, survival, death, differentiation, migration and attachment. It is regulated by the balance between the activities of protein tyrosine kinases (PTKs) and protein tyrosine phosphatases. A number of PTKs are encoded by proto-oncogenes or viral oncogenes, and are thus strongly implicated in cancer. While a role for PTKs in human melanoma is less firmly established, human melanomas or melanoma cells have been reported to contain more tyrosine phosphate than normal melanocytes, and some receptor PTKs (EPH-A2/ECK and EPH-B3) are overexpressed in over 90% of melanoma cell lines. Other specific PTKs are also frequently overexpressed, including KDR and fibroblast growth factor receptor-4 (FGF-R4), while, interestingly, yet others, such as KIT and FES, are consistently downregulated in melanoma cell lines. All of these differentially expressed PTKs are candidates for gene products important in melanoma development. In addition, PTKs expressed in significant amounts in both benign and malignant melanocytes, such as insulin-like growth factor-1 receptor (IGF1-R), FGF-R1, HER2/NEU and FAK, are likely to play a role in melanoma genesis and progression.

ISSN:0960-8931    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Phorbol esters, which activate protein kinase C, stimulate the growth of normal human melanocytes yet inhibit the growth of most melanoma cells. We investigated whether apoptosis mediates the effects of 12-O-tetradecanoylphorbol-13-acetate (TPA) on melanocyte and melanoma cell growth. Few apoptotic cells were present when melanocytes were cultured with TPA. Upon removal of TPA, the number of apoptotic cells increased over 10 days. Addition of TPA did not induce apoptosis in a metastatic melanoma cell line, Demel, although it strongly inhibited its growth. Protection of normal melanocytes from apoptosis was associated with high levels of Bcl-2. Following withdrawal of TPA from melanocytes, the expression of Bcl-2 decreased steadily. Bax and Bcl-XLlevels did not differ between melanoma cells or melanocytes and were unaffected by the addition of TPA. These results suggest that TPA plays an important role in stimulating the growth of melanocytes by promoting anti-apoptotic mechanisms associated with high levels of Bcl-2.

ISSN:0960-8931    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Erythropoietin is well known for its role in the control of erythropoiesis, where it acts by binding to its cognate receptor (EpoR) on the surface of erythroid progenitor cells. Here we present the novel finding that the EpoR is also expressed in cells of the melanocytic lineage. It is expressed in transformed cell lines established from normal melanocytes and also in established human melanoma cell lines derived from melanoma metastases, but not in normal primary human melanocytes. The analysis of individual subclones isolated from spontaneously transformed melanocytes revealed that approximately 50% of all the clones examined expressed the EpoR. Further analysis of the individual growth characteristics of EpoR-positive and EpoR-negative clones indicated that, under standard cell culture conditions, expression of the receptor did not affect cell growth. Expression of this receptor is consequently most likely driven by an event that is associated with, but not absolutely required for, the transformed phenotype. While the definite function of this receptor in melanoma cells is still unknown and additional studies are required, our findings support the hypothesis that the EpoR may serve as a progression marker for human melanoma. This observation might be useful in the early diagnosis of melanoma.

ISSN:0960-8931    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

The events occurring during the penetration of melanoma cells through the dermal-epidermal junction, which is the first crucial step in the process of metastasis, are poorly understood, partly because no suitable tissue models exist. In thein vitromodel reported here, two melanoma clones (T1C3, which generates lung metastases in experimental animals, and IC8, which does not) derived from a single parental cell line were co-seeded with normal allogenic keratinocytes onto acellular human de-epidermized dermis with preserved intact basement membrane and cultured for up to 1 month at an air-liquid interface. Histological, immunohistochemical and ultrastructural studies showed that melanoma cells from the metastatic clone (T1C3), but not from the non-metastatic clone (IC8), penetrated the dermal-epidermal junction to invade the dermis after 3 weeks of culture. Local invasion was associated with the dissolution of the native epidermal basement membrane collagens type IV and VII. Confocal laser scanning microscopy analysis demonstrated that numerous T1C3 cells were able to colonize the interstitial dermis and to rapidly penetrate empty dermal cavities. Our model represents a significant technical advance over others currently available since: (i) the organized three-dimensional architecture of the native dermal-epidermal junction is preserved; (ii) the active invasion process coincides with the dissolution of native components of the epidermal basement membrane, i.e. collagen types IV and VII; and (iii) the ability of melanoma cells to cross the dermal-epidermal junction correlates with their metastatic potential. This model provides a valuable tool for the study of the time-course of the cellular and molecular events that occur during the earliest steps of invasion in cutaneous melanoma. It also offers new opportunities to study the possible role of the keratinocyte environment in melanoma invasion.

ISSN:0960-8931    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Theophylline-treated B16-F10 melanoma cells show a lower experimental metastatic potentialin vivo. To identify the possible mechanism(s) involved and on the basis of previous reports, we tested the induction of apoptosis in B16-F10 cells. Fluorescence activated cell sorter (FACS) analysis and p53 overexpression in theophylline-treated B16-F10 melanoma cells appeared to suggest enhanced cell death by apoptosis. Thein vivoeffects of orally administered theophylline in mice were investigated using different treatment schedules in mice that had undergone hepatic or pulmonary colonization with tumour cells. Mice received theophylline in their drinking water according to different protocols: (i) from 3 days before tumour cell inoculation until animal sacrifice (`early treatment'); (ii) from 3 days before until 3 days after tumour cell inoculation (`short treatment'); or (iii) from 3 days after tumour cell inoculation until animal sacrifice (`late treatment'). In the ‘early treatment’ group, the number of melanoma foci was reduced by 92.3% in the liver and 81.4% in the lung compared with control animals (P< 0.001). In the ‘short treatment’ group, there was an 80.2% and 72.2% reduction in liver and lung metastases, respectively (P< 0.001). In the ‘late treatment’ group, the inhibition of metastasis was 59.7% for liver and 45.3% for lung (P< 0.005). Survival studies showed that 50% of the ‘early’ theophylline-treated animals died 33.2 ± 2.0 days after intrasplenic injection (control group: 23.1 ± 1.8 days;P< 0.001) and 33.9 ± 2.5 days after tail vein injection (control group: 24.1 ± 1.4 days;P< 0.001). Taken together, these observations provide useful information for the potential clinical application of theophylline as a chemotherapeutic agent against malignant melanoma.

ISSN:0960-8931    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

This study was designed in order to evaluate the feasibility of establishing an animal model of human uveal melanoma. IPC227, a cell line established from the biopsy of a patient with a spindle cell ciliary body melanoma, was transplanted into the anterior chamber of the eye in immunosuppressed New Zealand rabbits. In a second step, a tumour fragment from the anterior chamber was implanted transclerally into the posterior choroid. Complete ophthalmological examinations were then performed on the animals. Characteristic growth patterns were noted depending on the location of implantation. In the anterior chamber, diffuse, flat, heavily pigmented tumours appeared 8 days after the injection of the cell suspension that covered the iris and the angle by day 25, with a success rate of 100%. Nodular, lightly pigmented tumours were obtained 6–7 weeks after subchoroidal implantation, with a 25% success rate. Clinical examination, including fundus photography, ultrasound and magnetic resonance imaging, demonstrated the same characteristics as those of human uveal melanoma, confirming the value of this model for the evaluation of new therapeutic and diagnostic methods in the management of uveal melanoma.

ISSN:0960-8931    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

A number of recent reports suggest serum protein S100 as a prognostic parameter in patients with metastatic melanoma. In the present study, serum protein S100 was investigated as a tumour marker for screening for melanoma metastasis in patients attending regular follow-up examinations. During the period from September 1997 to December 1998, serum protein S100 levels were measured by an immunoluminometric assay in 411 consecutive high risk melanoma patients (666 samples) and in 120 control subjects. Melanoma patients with resected primary tumours with a tumour thickness of 1.5 mm or more with resected metastasis were included in the study. Overall, 41 of the 411 patients developed metastasis during the period of observation. According to the distribution of protein S100 levels, the following different cut-off values were examined: 0.08 μg/l (95 percentile of the control group) and 0.13 μg/l (95 percentile of the group of melanoma patients without metastasis). The test efficiency for protein S100 as a diagnostic test for the detection of metastasis was highest for the cut-off value of 0.13 μg/l. In eight of the 41 patients (19.5%), elevation of protein S100 was the first sign of recurrence. Of the 41 patients with metastatic disease, 13 had elevated protein S100, giving a sensitivity of 0.32. The specificity for the detection of metastasis was 0.96. In eight of the 14 patients (57%) who developed distant metastasis, elevated S100 values were the first sign of tumour progression. In conclusion, determination of serum protein S100 levels enables earlier detection of distant metastasis in patients at high risk for metastasis. The impact on survival time needs to be investigated in follow-up studies.

ISSN:0960-8931    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

The transmembrane receptor Fas/APO-1, together with its protein-binding partner (Fas ligand), is a key regulator of programmed cell death and induces apoptosis when it binds Fas ligand (FasL) or soluble Fas ligand (sFasL). However, soluble Fas (sFas) blocks apoptosis by inhibiting binding between Fas and FasL or sFasL. At present, the status of sFas and sFasL in metastatic malignant melanoma remains unknown. This study sought to evaluate the relationship between plasma levels of sFas and/or sFasL and clinical response in 45 metastatic malignant melanoma patients treated by biochemotherapy. sFas and sFasL were measured by specific enzyme-linked immunosorbent assay (ELISA) tests in the sera from patients and 34 healthy donors. Overall, sFas and sFasL levels in patients were significantly higher (P< 0.0001) than in healthy donors. Before the biochemotherapy treatment the sFas level was about the same in biochemorefractory (n= 26) as in responder patients (n= 19). In contrast, the sFasL level was very high only in biochemorefractory patients. At the end of the treatment, in biochemorefractory patients the sFas level was extremely significantly increased (P< 0.0001) and a significant decrease in the plasma levels of sFasL was observed (P= 0.0002). In responder patients, no change in sFas and sFasL was detected. In conclusion, elevated levels of sFas and sFasL might be associated with poor prognosis in advanced melanoma; their possible role in the regulation of apoptosis in influencing the response to biochemotherapy should be further explored.

ISSN:0960-8931    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Electrochemotherapy is a new anticancer therapy in which transient permeabilization of cells by an electric field induces a significant increase in the bleomycin concentration and toxicity in tumour cells. We report a clinical study of electrochemotherapy in malignant melanoma. The main issues addressed were the effect of the size of the nodules, the optimization of the electrical parameters, and post-treatment clinical observations. Four patients were enrolled in the study. They received a 10 mg/m2dose of bleomycin administered intravenously, followed by short, intense electric pulses applied directly to the skin at the tumour sites. Antitumour effects were obtained, especially in the smallest nodules. Objective responses were obtained in more than 90% of the 55 nodules treated, with a complete response rate of 9%. All patients tolerated the treatment well. No residual effects from the electric pulses were observed, even when a high number of pulses were required or when two consecutive treatments were applied. These results are encouraging and the study should be continued.

ISSN:0960-8931    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

The aim of this study was the evaluation of both the antitumour activity and toxicity of an immunochemotherapeutic regimen consisting of interferon-α2b and interleu-kin-2 in combination with fotemustine for patients with metastatic melanoma. To improve the penetration of fotemustine into the brain, it was given immediately after immunotherapy, when the blood-brain barrier is still disturbed. Of the 19 patients treated, three complete remissions (CRs) and one partial remission (PR) were induced, giving an objective response rate of 21% (95% confidence interval 6–46%). The durations of the CRs were 9, 19 and 44 months; the PR lasted for 59+ months. The overall survival times for the patients with CR were 21, 25 and 70+ months, and 59+ months for the PR. For nine patients (47%, 95% confidence interval 24–71%) disease was stabilized for a median period of 8 months (range 2–18 months), resulting in a median survival of 18 months (range 10–41+ months). No haematological toxicity of World Health Organization grade 3 or more was observed and in general toxicity was low. In summary, this immunochemotherapy regimen led to long-term survival in occasional patients, and about half of the patients achieved stable disease, with prolonged treatment- and progression-free survival compared with non-responding patients. The occurrence of brain metastases, however, was not prevented, and in fact was the site of recurrence in those patients achieving a CR. Due to its low toxicity, this protocol can be applied at a community hospital level.

ISSN:0960-8931    

出版商:OVID    

年代:2000

数据来源: OVID