Biomedical subjects

C Garbe

Publications and source records attributed to C Garbe.

At least 127 records · Page 7Linked to original sources

PubMed1995

Primary cutaneous melanoma. Optimized cutoff points of tumor thickness and importance of Clark's level for prognostic classification.

BACKGROUND: Maximum tumor thickness and level of invasion are known to be the most important prognostic factors for patients with primary cutaneous melanoma. However, the classification of tumor thickness and the question of whether the combination of tumor thickness and level of invasion provides a better prognostic classification than tumor thickness alone are still matters of debate. The present study examined the relationship between tumor thickness and survival probability to define cutoff points of tumor thickness. Secondly, it investigated the prognostic value of the combination of tumor thickness and level of invasion as proposed in the current TNM classification system. METHODS: A series of 5093 patients with invasive primary cutaneous melanoma followed from 1970 to 1988 at four University centers in Germany (Departments of Dermatology in Tübingen, Würzburg, Berlin-Steglitz, and at the Fachklinik) were analyzed by multivariate Cox models. RESULTS: The relationship between tumor thickness and relative risk of death caused by melanoma was found to be almost linear to a tumor thickness of 6 mm. For tumors greater than 6 mm, no further marked increase in relative risk was observed. The stratification of tumor thickness with endpoints at 1, 2, and 4 mm resulted in the best fit to the authors' data among all classifications with three endpoints, but differences were only slight. By multivariate analysis, the combination of tumor thickness and level of invasion as proposed by the current TNM classification were found to be prognostically less significant than tumor thickness alone. The prognostic influence of level of invasion was proved statistically only for tumor thickness less than or equal to 1 mm. CONCLUSIONS: The proposed stratification of tumor thickness with cutoff points at 1, 2, and 4 mm was supported by multivariate statistical analysis. The analysis of the current TNM staging system indicates the precedence of tumor thickness for the staging of patients with primary cutaneous melanoma in the case of discordance between tumor thickness and level of invasion.

Age Factors↗

PubMed1995

Production of cytokines by human melanoma cells and melanocytes.

Experimental animal models have shown that various cytokines, depending of their specific properties, may support growth and metastasis of tumor cells or even lead to tumor rejection. The analysis of expression of cytokine genes by melanoma cell lines indicated that melanoma cells constitutively produce both autostimulatory and inhibitory cytokines. Using reverse transcriptase polymerase chain reaction analysis, simultaneous expression of several cytokines, including interleukin-1 beta (IL-1 beta), IL-6, IL-8, tumor necrosis factor-alpha, and granulocyte-macrophage colony-stimulating factor, by melanoma cells was found. The same cytokine transcripts were detected in melanocytes, suggesting that cells of the melanocytic lineage express a specific pattern of cytokines in vitro. All these cytokines are known to be able to stimulate effector cells of the host. Additionally, production of mRNA for IL-10, a cytokine with potential immunosuppressive properties, was detected in melanoma cells and melanocytes. These and other cytokines are likely to be involved in the immune response to cancer and at this time it is unknown what the net effects of multiple cytokines are on the outcome of the host response to tumor.

Cells, Cultured↗

PubMed1995

Growth control of melanoma cells and melanocytes by cytokines.

Aberrant proliferation of tumor cells characterizes cancer growth. Investigations of cellular growth control mechanisms have contributed to our understanding of carcinogenesis and to the identification of compounds with specific antitumor activity. Many cytokines have been found to act on melanoma tumors, either produced by the tumor cells themselves or by infiltrating host cells. Purified cytokines allowed direct comparison of the growth response between normal human melanocytes and malignant melanoma cells. The present paper summarizes results of a series of our own experiments not yet published and data from a review of the recent literature. Proliferation of normal human melanocytes is enhanced by several cytokines, including basic fibroblast growth factor (bFGF), melanoma growth stimulatory activity (MGSA), hepatocyte growth factor (HGF), and mast cell growth factor (MGF). Melanoma cells are additionally stimulated by epidermal growth factor (EGF)/transforming growth factor alpha (TGF-alpha) and nerve growth factor (NGF). Tumor necrosis factor alpha (TNF-alpha), transforming growth factor beta 1 (TGF-beta 1), and interleukin (IL)-6 are all potent inhibitors of melanocyte growth, but they are less effective on melanoma cells or even stimulate their growth. Interferon (IFN)-alpha and IFN-gamma inhibited proliferation of melanoma cells but not of melanocytes, whereas IFN-beta showed antiproliferative effects in both cell types. These findings suggest an alteration in growth control mechanisms during melanocyte transformation and possibly play a role in melanoma pathogenesis.

Autoreceptors↗

PubMed1995

Role of elective lymph node dissection in stage I malignant melanoma: evaluation by matched pair analysis.

The role of elective lymph node dissection (ELND) in clinical stage I malignant melanoma continues to be controversial. We present a matched pair analysis of 375 patients treated in the Department of Dermatology in Kassel between 1979 and 1991 by wide local excision (WLE) plus ELND. Multivariate analysis revealed tumor thickness, level of invasion, age, sex, and localization as independent prognostic factors, and 375 patients treated by WLE alone were matched as controls to the patients treated by ELND and WLE. There was no significant benefit from WLE plus ELND compared to WLE alone in the total group as shown by the 5-year survival rates (87.3% versus 86.4%) and 10-year survival rates (80.1% versus 77.82%). Increased survival rates were noted for tumor thicknesses 1.51-4.0 mm for the WLE plus ELND group, as shown by the 10-year survival rates of 73.1% versus 60.3%. However, these data were not significant (p = 0.14). Disease-free survival rates were significantly higher in the group treated by additional ELND for all tumor thicknesses (p < 0.05) and even more in intermediate tumor thicknesses of 1.51-4.0 mm (p < 0.001). A significant benefit of elective lymph node dissection was detected for malignant melanoma of the trunk (all tumor thicknesses), as shown by the 5-year survival rates of 92.0% versus 79.7% and 10-year survival rates of 80.4% versus 45.16% (p < 0.05). Malignant melanoma of the extremities revealed no significant differences in survival rates. We conclude that there is a certain benefit from ELND in clinical stage I malignant melanoma for tumor thicknesses of 1.51-4.00 mm. Especially in malignant melanoma of the trunk, WLE plus ELND was more beneficious than WLE alone.

Actuarial Analysis↗

PubMed1995

Perspectives of cytokine treatment in malignant skin tumors.

Cytokines have been tested in the treatment of different skin cancers during the last decade, and treatment schedules have been established or proposed for several malignant skin tumors. Preferentially, the interferons and interleukin-2 were found to be effective in treating skin cancers. Interferons alpha and beta have been approved for the treatment of human immunodeficiency virus (HIV)-associated Kaposi's sarcoma, cutaneous T cell lymphoma, and malignant melanoma in several countries. Interferon alpha was found to be most effective in cutaneous T cell lymphoma with 40%-60% overall responses. When combining interferon alpha with psoralens and ultraviolet A (PUVA) or with retinoids, even higher response rates up to 60%-90% were reported, and long-term remissions have been described. A considerable activity of interferon alpha was found in HIV-associated Kaposi's sarcoma with response rates of 30%-50%. The effectiveness of Kaposi's sarcoma's treatment was further improved by combining interferon alpha and zidovudine. Responses to interferon alpha in metastatic malignant melanoma are rather seldom (10%-15%), but a stabilization of the disease with prolonged survival was reported after interferon alpha treatment. Additionally, interleukin-2 was found to be active in metastatic melanoma, with overall response rates of about 20%, and both biological agents were found to have an additive efficacy in combination. Several combined regimens of interferon alpha, interleukin-2, and polychemotherapy have been described in metastatic melanoma, and overall response rates higher than 50% were found with these combined treatment modalities. Interferon alpha and beta were also intralesionally injected into basal cell carcinomas and other epithelial skin cancers, and complete responses were found in more than 80% of tumors treated. Local applications of interferons and interleukin-2 were likewise found to be effective in the treatment of cutaneous melanoma metastases and cutaneous manifestations of Kaposi's sarcoma. Cytokines and their combination with other treatment modalities has greatly enriched the treatment facilities in malignant skin tumors during recent years, and additional new cytokines will be introduced in skin cancer treatment in near future.

Acquired Immunodeficiency Syndrome↗

PubMed1995

Photodynamic action of ultraviolet A: induction of cellular hydroperoxides.

Long-wavelength ultraviolet radiation (UVA) can cause cancer. A carcinogenic mechanism involved may be the induction of harmful reactive oxygen species resulting from photodynamic effects. UVA is generally assumed to induce photodynamic effects, but evidence from experiments with viable biological materials has been indirect until present. Here we measured the induction of (lipid) hydroperoxides as direct indicators of photodynamic reactions. Cultured human fibroblasts were irradiated with 10J UVA/cm2. The induced hydroperoxides were measured by an enzymatic method using glutathione peroxidase and glutathione reductase (GR). Additionally, reduced glutathione (GSH) was determined as parameter for the constitutive antioxidant defense. UVA was found to increase lipid hydroperoxides in fibroblasts by 116% (p < 0.001), when compared to nonirradiated controls. Conversely GSH was decreased in the irradiated cells by 51% (p < 0.001). Because of the induced hydroperoxides, it is concluded that the UVA effects were mediated by a photodynamic mechanism. The photodynamic mechanism resulted in the formation of reactive oxygen species and the consumption of constitutive antioxidants. This suggests a role for antioxidants during the photodynamic mechanism. Photodynamic mechanisms may play a crucial role in carcinogenic events, especially after UVA.

Antioxidants↗

PubMed1995

Protein patterns of benign and malignant human melanocytes show consistent changes in gene expression.

For human malignant melanoma, no pattern of oncogene activation has yet been identified which consistently occurs in the malignant cells. In order to better understand the transformation process, we studied the overall gene expression at the protein level in human melanoma cells in vitro by two-dimensional gel electrophoresis. For that, four established cell lines, MEWO, M5, SKMEL13, and IGR39, were used and compared with newly established cultures of normal human melanocytes. Considerable variations in the protein patterns of the different melanoma cell lines were found, whereas the patterns of normal human melanocytes correlated fairly well with each other. With respect to the expression of single proteins, we identified four major proteins which were consistently found in cultured melanocytes and stringently repressed in the four melanoma cell lines examined. On the other hand, induction of new proteins in the different melanoma cell lines was found to be less stringent and also less uniform. We propose that malignant transformation of melanocytes may be more associated with the suppression of melanocytic proteins rather than with new expression of melanoma specific proteins.

Cells, Cultured↗

PubMed1995

Identification of genes specifically regulated in human melanoma cells.

In order to improve the characterization of human malignant melanoma cells and their variant gene expression in vitro, a search for specifically regulated genes was performed. Four melanoma cell lines (M5, MEWO, IGR39, SKMEL13) and newly cultured normal human melanocytes were included in a comparative hybridization (differential screening) of a human melanoma cDNA-library. Six cDNAs were isolated showing a stronger expression (four genes) or a weaker expression (two genes) in melanoma cells than in normal human melanocytes. Quantification of the expression patterns of the two repressed genes in Northern blots revealed general expression in all melanocyte cultures examined, no expression in three cell lines (M5, IGR39, SKMEL13) and weak expression in MEWO. The four induced genes were found to be only weakly expressed in normal human melanocytes, but showed an elevated expression in all of the four melanoma cell lines tested. Thus, using the technique of differential screening, consistent gene regulation at the messenger RNA level was identified, which distinguishes the four melanoma cell lines tested from normal melanocytes. We conclude from the expression patterns that specific gene regulation in melanoma cells in vitro is characterized both by strong repression of some melanocyte genes, as well as by the induction of other genes, but there was no indication of new expression of genes specific for melanoma cells. Because of the uniform induction or repression in different melanoma cell lines, it is conceivable that the cloned genes may be involved in the malignant transformation of melanocytic cells.

Base Sequence↗

PubMed1995

Tumour necrosis factors and several interleukins inhibit the growth and modulate the antigen expression of normal human melanocytes in vitro.

In the present study the action of various cytokines as regulators of human melanocyte growth and differentiation was examined in vitro. Primary melanocyte cultures were obtained in complete medium free of 12-O-tetradecanoylphorbol-13-acetate or serum. First passage melanocytes were treated with various concentrations of recombinant tumour necrosis factor alpha and beta (rTNF-alpha, rTNF-beta), as well as with various recombinant interleukins (rIL-1a, rIL-1b, rIL-2, rIL-3, rIL-4 and rIL-6) for 6 days in complete medium and for 6 and 12 days in a mitogen-reduced medium variant. The 4-methylumbelliferyl heptanoate fluorometric microassay and Ki-67 staining were used for assessing cell proliferation, and the immunophenotype was evaluated using various monoclonal antibodies. Melanocyte proliferation in complete medium was inhibited by rTNF-alpha (-24%), rTNF-beta (-17%), rIL-1a (-21%), rIL-1b (-18%) and rIL-6 (-29%); in contrast, rIL-2, rIL-3 and rIL-4 had no antiproliferative effect. Measurements of Ki-67-positive nuclei confirmed these results. In the reduced medium variant, none of the above cytokines inhibited melanocyte proliferation. Recombinant TNF-alpha and rTNF-beta markedly reduced the expression of the pigment cell-associated antigens HMB-45 and K.1.2, and they enhanced the expression of VLA-2, ICAM-1 and HLA class I antigens and strongly induced HLA-DR. Similar changes were induced by rIL-1a, rIL-b and rIL-6, and rIL-2 decreased the expression of HLA class I antigens and of ICAM-1. In conclusion, several cytokines inhibited the growth and modulated the phenotype of melanocytes in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)

Antigens↗

PubMed1995

Synergistic interactions between interferon beta and carboplatin on SK-MEL 28 human melanoma cell growth inhibition in vitro.

Carboplatin and interferon beta (IFN beta) were tested alone and in combination for their antiproliferative activity on the human melanoma cell line SK-MEL 28 in vitro. Cells were incubated for 4 days in the presence of carboplatin (0.1 mM and 0.1 microM) and interferon beta (5 pM and 5 nM) and cell growth inhibition was determined by the sulphorhodamin B assay. The antiproliferative effects of the drug combinations were analysed using Berenbaum's hyperplane theorem to determine additive, synergistic and antagonistic effects. IFN beta was found to be 10,000 times more active in inhibiting cell growth of SK-MEL 28 cells than carboplatin on the basis of IC50 values (IFN beta: IC50 = 1.24 nM, carboplatin: IC50 = 18.2 microM). The addition of IFN beta at 0.5 nM reduced the IC50 value of carboplatin 18.0-fold; with IFN beta at 0.05 nM a dose reduction of 1.84 was measured. At the carboplatin: IFN beta molar concentration ratios of 2000:1 and 6000:1, interaction indices (I) of 0.66 and 0.83 were determined respectively, indicating synergistic interactions between the two drugs. At higher carboplatin: IFN beta molar ratios (20,000:1 and 60,000:1) an additive interaction was observed (I = 1.07 and 1.20). However, further in vitro studies with several melanoma cell lines are necessary to evaluate the potential effectiveness of the drug combination of carboplatin and IFN beta for eventual clinical utilisation.

Carboplatin↗

PubMed1995

[Risk factors for the development of malignant melanoma and identification of risk groups in German-speaking regions].

Risk factors for development of malignant melanoma have been investigated in several case control studies during the last decade, with some variation in results, partly with geographical region. Four studies have been conducted under the auspices of the Central Malignant Melanoma Registry of the German Dermatological Society; these have yielded consistent results allowing the identification of risk factors for melanoma development. The numbers of common melanocytic naevi, of atypical melanocytic naevi and the frequency of actinic lentigines were found by multivariate regression analysis to be the most important independent risk factors for melanoma development. Additional factors were hair colour, skin type and a history of naevus growth. A classification of relative risks was established by considering the first three risk factors mentioned, without any clear improvement of classification when further additional significant factors were taken into account. For example, in individuals with more than 50 common melanocytic naevi, 5 or more atypical melanocytic naevi and simultaneous presence of actinic lentigines the risk of developing melanoma was found to be 100-fold that in persons with 10 common melanocytic naevi or fewer and without atypical melanocytic naevi or actinic lentigines. Early recognition of melanomas may be substantially improved if these risk factors are considered. Furthermore, intermittent intensive sun exposure (sunburns as indicator) before the age of 20 induces the development of actinic lentigines; both factors are associated with an increased risk of melanoma development.

Europe↗

PubMed1995

[The Malignant Melanoma Central Register of the German Society of Dermatology 1983-1993. Epidemiologic developments and current therapeutic management of malignant melanoma of the skin].

The Central Malignant Melanoma Registry of the German Dermatological Society was founded in 1983 and has meanwhile developed into a major continuously updated multicentre project. Up to June 1994, 19,250 reports of cutaneous melanoma had been received, from 41 departments of dermatology in the former Federal Republic of Germany, from 14 departments in the former German Democratic Republic, from 2 departments in Austria, and from 1 department in Switzerland. Analysis of the data revealed some epidemiological trends over time during the years 1983 to 1993. (1) During the last 10 years the percentage of male patients has steadily increased, from an average of 38% in the year 1983 to 46% in 1993. (2) Early diagnosis of malignant melanoma improved during the period of time investigated. The percentage of diagnoses of primary tumour alone increased between 1983 and 1993. The mean tumour thickness (Breslow) decreased in the West Germany from 1.8 mm to 1.3 mm and in East Germany from 2.5 mm to 1.7 mm. The proportion of nodular melanoma decreased correspondingly from 29% to 14% in the former Federal Republic of Germany and from 40.6% to 22.6% in the former Germany Democratic Republic. During the years 1990 and 1993, 64% of melanoma patients with the primary tumour alone were operated on in two consecutive sessions in the former Federal Republic of Germany and 34.2% of those in the former Germany Democratic Republic. During this period 73.7% of all melanoma patients were operated on under local anaesthesia. In recent years surgical operations were more often performed in two consecutive sessions, mostly under local anaesthesia and with decreasing safety margins, in keeping with the decrease in tumour thickness. The present analysis shows that the Central Malignant Melanoma Registry is an important instrument for investigating trends in clinical epidemiology and treatment of malignant melanoma in the German-speaking countries.

Adult↗

PubMed1995

[Management of primary malignant melanoma of the skin in German-speaking countries 1983-1993. A study of the Malignant Melanoma Central Register of the German Society of Dermatology].

During the past decade more than 90% of all melanoma patients in the German-speaking countries have been diagnosed with a primary tumour alone. Therefore, surgical intervention has been the most important element in the management of these patients. The present investigation was performed to analyse the different surgical procedures used in the treatment of primary melanoma during the years 1983-1993. The primary treatment of 15,054 patients with malignant melanoma and without recognizable metastasis has been examined. During the time period under investigation the percentage of cases treated with two-step surgical management increased from 30% to 60%. Primary excision was performed in local anaesthesia in 40% of all patients in 1983, whereas in 1993 surgical intervention under local anaesthesia had increased up to 80%. Over the same time, the average safety margin decreased from 33 mm to 21 mm for the final excision of primary melanomas, and this decrease was paralleled by marked decrease in the average thickness of the tumours excised from 2.1 to 1.5 mm. Elective node dissection was performed in 5% of all patients in 1983, whereas 9% of patients underwent elective node dissection in 1993. The different centres participating were found to differ noticeably in the therapeutic procedures applied for similar indications. In conclusion, the management of primary malignant melanoma has changed considerably during the years 1983-1993 in the German speaking area in favour of a two-step surgical procedure, local anaesthesia for the excision of the primary tumour and smaller safety margins. It seems that earlier diagnosis of the tumour and also ideas about treatment design may be responsible for these changes.

Adult↗

PubMed1995

Prothymosin alpha 1 modulates lymphokine-activated killer cell activity and IL-2 production by peripheral blood lymphocytes from melanoma patients in vitro.

The effects of prothymosin alpha 1 (Pro alpha 1) on the natural killer (NK), lymphokine (IL-2)-activated killer (LAK) cell activity and the phytohaemagglutinin (PHA)-induced IL-2 secretion of peripheral blood T-lymphocytes (PBL) from 34 malignant melanoma patients of all clinical stages were studied in vitro. On average, melanoma patients showed lower NK and LAK cell activities than healthy donors. In particular, patients with metastases revealed an impaired NK cell activity. However, individuals showed a broad range of LAK cell sensitivity to Pro alpha 1 depending, among other factors, on the disease stage. LAK cell activities were not correlated to tumour stage. Patients' impaired LAK cell activity could be restored by Pro alpha 1. Only patients at stage II (regional metastases) responded to Pro alpha 1. The IL-2 secretion from PBL melanoma and healthy donors did not differ, Pro alpha 1 administration was without any significant effect. However, stage III (distant metastases) PBL expressed significantly lower IL-2 levels, compared to stage I (primary tumours). The highest IL-2 levels was found to be associated with tumour stage II. Pro alpha 1 enhanced the IL-2 secretion from stage I PBL. Therefore Pro alpha 1 administration abrogated the defective LAK cell activity and IL-2 secretion of PBL, mainly from patients at early melanoma stages.

Adult↗

PubMed1995

Role of high-resolution magnetic resonance imaging for differentiating melanin-containing skin tumors.

RATIONALE AND OBJECTIVES: The aim of the study was to evaluate the use of high resolution magnetic resonance imaging (MRI) for differentiation of melanin-containing skin tumors. METHODS: Twenty-seven melanocytic nevi and 18 malignant melanomas were examined by high resolution MRI. Signal intensities and signal-to-noise (SNR) and contrast-to-noise ratios (CNR) of the tumors were determined in enhanced (T1, T2, water-suppression, and fat-suppression sequences) and contrast-enhanced images (T1 and fat-suppression sequences). The differences were tested for significance by a Wilcoxon test. RESULTS: Malignant melanomas differed from melanocytic nevi in that they displayed a higher SNR in T2-weight and unenhanced and contrast-enhanced fat-suppression scan. Malignant melanomas exhibited a higher CNR than did benign lesions in unenhanced and contrast-enhanced fat-suppression sequences with dermis as reference tissue (P < 0.05) and in enhanced fat-suppression sequences with subcutis as reference tissue (P < 0.05). CONCLUSIONS: The usefulness of SNR and CNR analysis on MRI for the differentiation of malignant skin tumors from benign skin tumors of the melanin-containing system is limited. Clinical and histologic examinations are, further, the important step in evaluation of melanin-containing skin tumors.

Adipose Tissue↗

PubMed1995

Elective lymph node dissection in primary malignant melanoma: a matched-pair analysis.

The role of elective lymph node dissection (ELND) in primary malignant melanoma is still controversial. Our purpose in this study was to evaluate the benefit from ELND on survival and disease-free survival in malignant melanoma of the trunk and extremities. We performed a matched-pair analysis on 750 patients. There was no significant benefit from wide local excision (WLE) plus ELND compared with WLE in the total group. Increased survival rates were noted for tumour thicknesses of 1.51-4.0 mm for the WLE+ELND group, as shown by 10-year survival rates of 73.1% vs 60.3% (p = 0.14). A significant benefit of ELND was detected for malignant melanoma of the trunk (p < 0.05). Disease-free survival rates were significantly higher in the collective treated by additional ELND for all tumour thicknesses (p < 0.05) and even more in intermediate tumour thicknesses of 1.51-4.0 mm (p < 0.001). Our data give further support that ELND may be valuable in improving the prognosis in case of malignant melanoma of intermediate Breslow thickness.

Adult↗

PubMed1995

Cutaneous metastatic angiosarcoma with a lethal outcome, following radiotherapy for a cervical carcinoma.

A cutaneous metastatic angiosarcoma was diagnosed in a 79-year-old woman 19 years after radiotherapy for a carcinoma of the uterine cervix. The diagnosis was confirmed by immunohistochemical staining (factor VIII-related antigen and BMA 120) and electron microscopic examination. Surgical treatment of the large tumour, which was situated in the gluteal region, was not feasible, but electron beam therapy resulted in complete remission. However, a further metastasis occurred in the inguinal region, and management by total excision, radiotherapy, and interferon-alpha treatment was unsuccessful. The patient died 28 months after the initial diagnosis of the neoplasm.

Buttocks↗

PubMed1995

Incomplete expression of the tyrosinase gene family (tyrosinase, TRP-1, and TRP-2) in human malignant melanoma cells in vitro.

Sequence analysis of two clones found repressed in melanoma cell lines in earlier studies showed 9F2 to be identical with the TRP-1 gene and 6F5 with TRP-2 containing a long untranslated 3' end. For further investigation of the expression of the tyrosinase gene family in normal and malignant melanocytic cells, a series of melanoma cell lines and of cultured melanocytes were analyzed by Northern blotting and by reverse transcriptase-polymerase chain reaction (RT-PCR). The Northern blots were probed with cDNA fragments specific for TRP-1, TRP-2, and tyrosinase, for nested tyrosinase-PCR the outer primers specified a 284 bp and the nested primers a 207 bp fragment. Investigations on 14 established melanoma cell lines grown in different media compared with seven normal human melanocyte (NHM) cultures revealed that all three pigment genes were expressed in NHM, whereas pigment gene expression was found repressed in nearly all melanoma cell lines and was completely absent in 4 of 14 specimen. In particular, tyrosinase and TRP-2 genes were found always to be expressed together, and TRP-1 mRNA alone was absent in four melanoma cell lines. Negativity of cultured melanoma cells for tyrosinase mRNA was confirmed by nested RT-PCR, and gene deletion was ruled out by genomic Southern blots. The gene expression seemed independent from the type of medium used for cultivation. These findings indicate repressed or lacking expression of pigment genes in melanoma cell lines, most likely due to regulatory mechanisms, and that differences may exist between tyrosinase and TRP-2 on one hand and TRP-1 on the other. Overall, it seemed that RT-PCR for tyrosinase has limited value for identifying melanoma cells in the peripheral blood of melanoma patients; TRP-1, TRP-2, and other, additional markers may be required.

Base Sequence↗