Antioxidant pattern in uveal melanocytes and melanoma cell cultures

PURPOSE

To investigate the antioxidant status of cultured uveal melanocytes from patients with uveal melanoma and uveal melanoma cells to characterize some of the biochemical properties of these cells in respect to the normal cutaneous melanocytes.

METHODS

The fatty acid pattern of membrane phospholipids, intracellular vitamin E level, and superoxide dismutase (SOD) and catalase activities were studied in uveal melanocytes (n = 10) and uveal melanoma cell (n = 10) cultures, by gas chromatography mass spectrometry or by spectrophotometer.

RESULTS

Among the uveal melanocyte cultures, two groups were differentiated, according to catalase activity: group A with catalase values comparable to those of cutaneous ones and higher SOD activity and group B with catalase values 2 SD lower (P<0.001) and lower SOD activity. Vitamin E concentration was not significantly different between melanoma cells and melanocytes, whereas a significantly higher percentage of polyunsaturated fatty acids was found in melanoma cells and the B group of melanocytes (P = 0.022). In uveal melanoma cells SOD activity was significantly lower than that detected in uveal melanocytes (P< 0.005).

CONCLUSIONS

These results show a different pattern of antioxidants in uveal melanocytes with respect to cutaneous ones, possibly related to the anatomic distribution. However, as in cutaneous melanocytes, two subgroups were identified on the basis of the antioxidant pattern that could be the expression of a constitutional increased susceptibility to oxidative stress in some subjects. Moreover, an imbalance of the antioxidants was observed in melanoma cells, possibly related to the disease status and progression.

3p13 region: a possible location of a tumor suppressor gene involved in uveal melanoma

To contribute to a better understanding of the role of chromosomal rearrangements in the tumorigenesis of uveal melanoma, we present a case in which a structural aberration of chromosome 3 could indicate the specific region in which an uveal melanoma tumor suppressor gene could be located. We obtained a primary cell culture, characterized by cytogenetic study, through GTG- and CBG-banding techniques by using a mechanical dissection of a tumor sample obtained from an uveal melanoma. Cytogenetic analysis performed in the primary cell culture highlighted the presence of a structural rearrangement involving chromosomes 3 and 22. A t(3;22)(p13;p11) was observed as the only present clonal aberration. The 3p13 breakpoint involved in the aberration observed in our case could be essential in restricting the candidate region for the locus of an uveal melanoma tumor suppressor gene located on chromosome 3.

Cytogenetic follow-up in a case with a primary cutaneous melanoma and five metastatic lesions

Cytogenetic analyses conducted on several cases of melanoma have contributed to the identification of the chromosomal regions where the sequences responsible for malignant transformation and the evolution of this tumor are probably located. With regard to these problems, it is very important to have the possibility to analyze, through the use of cytogenetics, both the primary melanoma and the metastatic lesions from the same patient. We present a case in which the primary melanoma and five different metastases were studied by using cytogenetics. The primary tumor showed an inversion of chromosome 1 where the p36 region, often proposed in literature as the location of a melanoma susceptibility gene, was involved. Three cutaneous and one lymphonodal metastases presented the same nine clonal chromosomal aberrations. In particular, one is a further rearrangement of the marker present in the primary tumor; another is a deletion of the 9p21pter region in which the p16 gene is located. Our results can provide a contribution to the hypothesis of the location of a candidate gene for melanoma in the 1p36 region and can also underscore the role of the 9p21 region in the progression of melanoma.

Increased sensitivity to peroxidizing agents is correlated with an imbalance of antioxidants in normal melanocytes from melanoma patients

We have previously shown an imbalance of the antioxidant system in some cultures of normal melanocytes from patients with melanoma. In order to evaluate if the alteration of the antioxidants could be the basis of an increased sensitivity to exposure to peroxidative agents, in cultured melanocytes from normal individuals (n = 11) and from patients with melanoma (n = 11), superoxide dismutase and catalase activities were evaluated by spectrophotometer, and the levels of vitamin E and of the polyunsaturated fatty acid of cell membranes were determined by gas chromatography mass spectrometry. In 5 out of the 11 cultures of melanocytes from melanoma patients, with respect to those from normal individuals, a significant decrease of catalase activity (Cat) associated with an increase of vitamin E (Vit E) concentration was found, whereas no significant modification of superoxide dismutase activity (SOD) was observed. A wide range of variability was detected in the percentage of the polyunsaturated fatty acids of the cell membranes and a correlation was found between the ratio SOD/Cat and the percentage of linoleic acid, indicating that the imbalance of the enzymatic antioxidants leads to a lipoperoxidative process. The electron microscopic examination of these cultures revealed many microvilli in the plasma membranes and nuclear infoldings and in the cytoplasm light vacuoles. Moreover some cells contained several dense bodies with a round shape and numerous spherical lamellae possibly representing immature melanosomes. Treatment with cumene hydroperoxide between 0.66 and 20 microM did not produce a significant modification of cell viability in melanocytes from normal individuals. On the contrary in melanocytes from melanoma patients correlated with the ratio Vit E/Cat, considered as a parameter of the antioxidant imbalance, a stimulatory effect was observed at 0.66 microM CUH and a cytotoxic effect at 20 microM. In conclusion our results suggest that a constitutional alteration of the scavenger system could be present in normal melanocytes from melanoma patients and that this could be the basis for an increased sensitivity to pro-oxidant agents.

HLA-DR and -DQ alleles in Italian patients with melanoma

Controversial data have been reported about HLA alleles and susceptibility to melanoma. Our investigation was undertaken to analyze the relationship between HLA alleles distribution in patients with melanoma and susceptibility to the tumor, in order to study the possible correlation between HLA class II DQA1, DQB1 and DRB1 genes involved in immune recognition, and melanoma, usually considered a highly immunogenic tumor. We therefore typed by means of PCR-SSP (sequence-specific primers) 53 Italian patients and 53 healthy random controls coming from the same geographic area. We observed a decrease of all haplotypes bearing DQB1*0301, DQB1*0302 and DQB1*0303 alleles but not of haplotype DRB1*11;DQA1*0501;DQB1*0301. Our results seem to support the hypothesis of a protective role of some DQ3-bearing haplotypic combinations in melanoma.

Detection of a 46,XX,der(3)t(3;4)(p25;p16.1) by using chromosome microdissection

We performed chromosome microdissection in order to define the "de novo" rearrangement observed in a female patient affected by: frontal microgyria, mild psychomotor retardation, thoracic scoliosis, XIIth rib asymmetry and facial dysmorphisms. Through the use of the micro-FISH we evidenced a deletion of the 3p25pter region and a 4p16.1 duplication. We performed a karyotype-phenotype correlation in our patient and in the ones previously reported in literature which had a 3p25pter deletion or the 4p16 duplication.

Increased sensitivity to peroxidative agents as a possible pathogenic factor of melanocyte damage in vitiligo

To examine the sensitivity of vitiligo melanocytes to external oxidative stress, we studied enzymatic and non-enzymatic anti-oxidants in cultured melanocytes of normal subjects (n = 20) and melanocytes from apparently normal skin of vitiligo patients (n = 10). The activity of superoxide dismutase and catalase and the intracellular concentrations of vitamin E and ubiquinone were evaluated in cultures at the fourth or fifth passage. In addition, cells were exposed to various concentrations of a peroxidizing agent, cumene hydroperoxide (CUH, 0.66-20 microM), for 1 and 24 h. Compared to normal melanocytes, vitiligo melanocytes showed normal superoxide dismutase and significantly lower catalase activities and higher vitamin E and lower ubiquinone levels. At the concentration used, CUH did not significantly affect cell number or viability of melanocytes after either period of culture. On the contrary, vitiligo melanocytes were susceptible to the toxic effect of CUH after 24 h of continuous treatment at concentrations greater than 6.6 microM. The degree of CUH toxicity correlated strictly with the anti-oxidant pattern, defined as the ratio between vitamin E concentration and catalase activity, suggesting that the alteration in the antioxidants was the basis for sensitivity to the external oxidative stress. Our results demonstrate the presence of an imbalance in the anti-oxidant system in vitiligo melanocytes and provide further support for a free radical-mediated damage as an initial pathogenic event in melanocyte degeneration in vitiligo.

Imbalance in the antioxidant pool in melanoma cells and normal melanocytes from patients with melanoma

In order to evaluate the free radical defense systems of melanocytes and their possible correlation with melanoma, we have studied in cultured normal human melanocytes (20), normal melanocytes from melanoma patients (15), and melanoma cells (40) the fatty acid pattern of membrane phospholipids as a target of peroxidative damage and the superoxide dismutase and catalase activities, vitamin E, and ubiquinone levels as intracellular antioxidants. Cells were cultured in the same medium and analyzed at III or IV passage. Compared to the values obtained in normal human melanocytes, melanoma cells showed on average: a) higher levels of polyunsaturated fatty acids, b) increased superoxide dismutase and decreased catalase activities, higher vitamin E, and lower ubiquinone levels. Among the normal melanocytes from melanoma patients studied, two groups were differentiated: a) cultures (7) with enzymatic and non-enzymatic antioxidants level similar to those of normal human melanocytes; b) cultures (8) with antioxidant patterns similar to those observed in melanoma cells. Polyunsaturated fatty acids were also increased in the latter group. The results indicate that in melanoma cells and in a percentage of normal melanocytes from melanoma patients, an imbalance in the antioxidant system can be detected that can lead to endogenous generation of reactive oxygen species and to cellular incapability of coping with exogenous peroxidative attacks. These alterations could be correlated with the malignant transformation of cells and with the progression of the disease.

Involvement of the 4q21 region in human malignant melanomas: cytogenetic and immunocytochemical characterization of three primary cell cultures

The GRO1 oncogene (melanoma growth-stimulating activity alpha) has been localized in region 4q21. The involvement of this chromosomal region in clonal aberrations found in primary melanoma cell cultures could have an important role in the etiology and pathogenesis of this tumor. We characterized three primary cell cultures obtained from different patients, each of which showed clonal chromosomal aberrations involving the 4q21 region.

Inv dup(15): contribution to the clinical definition of phenotype

One of the primary goals in medical genetics is a precise clinical definition of chromosomal diseases. This is now possible because of the increased number of case reports and new techniques. A male patient, without a clear-cut syndrome, was cytogenetically investigated. Chromosomal analysis showed a small unidentified bisatellited supernumerary marker. In situ hybridization with a biotin-labeled DNA probe for the chromosome 15 centromere (D15Z1) demonstrated that the marker was derived from chromosome 15. Hybridization with the Prader-Willi Syndrome Cosmid biotinylated probe (localized to band 15q11-q13) showed a signal on both ends suggesting a marker with a symmetrical inv dup(15) and a breakpoint localized in q13. It was then possible to define the karyotype as: 47,XY,+ inv dup(15) (pter-q13::q13-pter). All cases of inv dup(15) reported in the literature were reviewed, paying particular attention to the different breakpoints involved, in order to provide a better clinical definition of this syndrome.

Cytogenetic findings in 20 melanomas

We report cytogenetic studies performed on 20 patients with cutaneous malignant melanoma, characterized by clinical and histological parameters. Cytogenetic analyses were performed on peripheral blood lymphocytes, in order to exclude the presence of constitutional chromosomal aberrations, and on primary cell cultures obtained from neoplastic skin lesions. A metastasis was also cultured in order to characterize chromosome markers. Specific markers found in more than one patient were t(1;14)(q21;q32) and aberrations of the 4q21,8q24 and 10q24q26 regions. The research aims to identify possible subtypes of melanomas related to specific chromosomal markers. It is hoped that this will contribute to understanding of the aetiology and evolution of the disease in order to obtain a more exact classification. We compare our results with the data reported in the literature and discuss the possible role of the cytogenetic analyses in human malignant melanoma.

[Ring chromosome 4 in twins]

A case of ring chromosome 4 in an eleven months old male child with severe mental retardation, microcephaly and craniofacial anomalies is described. The karyotype was: 46,XY, r(4) p16----q35). The patient shows only few elements of the Wolf syndrome, whose phenotype is observed in most of the other cases with analogue karyotype.