Involvement of chromosome losses in the progression and metastasis formation of a human malignant melanoma

EGFR gene copy number alterations in primary cutaneous malignant melanomas are associated with poor prognosis

Copy number alterations of the epidermal growth factor receptor (EGFR) gene have been extensively analyzed in different cancers, but no data are available for primary malignant melanoma. The aim of the present study was to simultaneously investigate the EGFR gene and chromosome 7 copy number alterations in 81 cutaneous malignant melanomas by interphase FISH and correlate the data with clinicopathological parameters of patients. EGFR mRNA levels were detected by Affymetrix GeneChip Human Genome U133 Plus 2.0 expression arrays for 16 lesions. Both increased gene dosage and chromosome 7 alterations were found in 70% of tumors. Extra EGFR copies were detected in an additional 10% of samples. Polysomy 7 was associated with EGFR gene amplification. Significant correlation was found between EGFR alterations and histological subtypes, tumor thickness, ulceration and metastases formation. Amplification was significantly higher in lesions that developed metastases within 2 years after surgical excision of the primary tumor. Gene copy alterations were associated with elevated mRNA expression in 77% of lesions when compared to tumors with disomic EGFR status, the correlation was not directly proportional to gene copy number. Associations between protein expression and mRNA levels were even less prominent. In conclusion, our study indicates that amplification of the EGFR gene and polysomy 7 are frequent alterations in primary melanomas and are associated with bad prognosis. Further studies are required to clarify whether melanoma patients with EGFR alterations can benefit from anti-EGFR therapy.

Simultaneous appearance of acute myeloid leukemia in a patient with bilateral primary uveal melanoma

We report a rare case of a patient with bilateral uveal melanoma (the first eye surgically treated 6 years before the occurrence of melanoma in the contralateral eye), who developed an acute myeloid leukaemia.

Analysis of ameloblastomas by comparative genomic hybridization and fluorescence in situ hybridization

In order to characterize the chromosomal alterations in ameloblastomas, a combination of comparative genomic hybridization (CGH) and fluorescence in situ hybridization (FISH) techniques was performed on 9 tumors. Chromosomal alterations including a gain at 1q and losses at 1pter, 10q, and 22q could be detected by CGH only in 1 tumor. Interphase FISH analysis, using centromeric probes for chromosomes 1, 10, and 22 as well as region-specific probes for 1p36 and 10q26, revealed the most frequent alterations to exist in the tumor with the abnormal CGH profile. These alterations included marked to slight increases of monosomic cells for chromosome 10 (91.5%), 10q26 (35.8%), 1p36 (24.4%), and chromosome 22 (18.8%), as well as significant elevations of trisomic cells for chromosome 1 (41.2%). Moreover, FISH analysis revealed a frequent loss of chromosome 22 in all tumors examined, except for one lesion, indicating that loss of the entire or a part of this chromosome is a common event in ameloblastomas, possibly being a predisposing factor to ameloblastoma tumorigenesis.

Extra copies of c-mycare more pronounced in nodular melanomas than in superficial spreading melanomas as revealed by fluorescence in situ hybridisation

BACKGROUND

Amplification of c-myc is a common genetic alteration and associated with a poor prognosis in a variety of cancers. Extra copies of the gene have been found in large numbers of melanoma metastases, but only few primary tumours have been studied. We investigated the c-myc copy number alterations in two different subtypes of primary melanomas with different biological behaviours.

METHODS

Fluorescence in situ hybridisation was performed using c-myc and centromeric 8 (C8) probes on 68 lesions (28 nodular melanomas [NMs], 26 superficial spreading melanomas [SSMs], and 14 metastases). To assess the ploidy pattern, copy number distribution of seven different chromosomes was also investigated.

RESULTS

All tumours showed aneuploid populations for at least three chromosomes. Whereas 61% of the NMs exhibited extra c-myc copies, only 27% of SSMs showed increased gene dosage. The c-myc/C8 ratio exceeding 1.5 was significantly higher in NMs (P = 0.01). High level amplification was seen only in NMs. An elevated c-myc/C8 ratio was higher than 1.5 in only four metastases.

CONCLUSION

Our data show that c-myc copy number alterations differ in the two melanoma subtypes and are associated with the advanced stage of the disease. The less frequent amplification of the c-myc gene in metastatic lesions indicates that it may play an important role in the development of an invasive potential rather than in the metastatic process.

Detection of three novel translocations and specific common chromosomal break sites in malignant melanoma by spectral karyotyping

Chromosomal aberrations in malignant melanoma cells have been reported using standard chromosome banding analysis and comparative genomic hybridization. To identify marker chromosomes and translocations that are difficult to characterize by standard banding analysis, 15 early passage malignant melanoma cell lines were examined using spectral karyotyping. All 15 tumor cell lines had lost all or part of 1p and 10q. Losses of material on chromosome arms 4p (12/15), 6q (12/15), 9p (15/15), 12p (13/15), 12q (13/15), 13q (11/15), and 19q (14/15) were the next most frequent events. Gain of chromosome arms 1q (11/15), 6p (13/15), and 20q11 (14/15) was also observed. Interestingly, we identified translocations der(12)t(12;20)(q15;q11), der(19)t(10;19)(q23;q13), and der(12)t(12;19)(q13;q13) in 4/15 tumors. Three recurring translocations involving four of the most frequent break points were detected. The identification of recurring translocations and unique chromosome break points in melanoma will aid in the identification of the genes that are important in the neoplastic process.

Chromosomal imbalances in primary and metastatic melanomas revealed by comparative genomic hybridization

Characteristic genetic changes underlying the metastatic progression of malignant melanoma is incompletely understood. The goal of our study was to explore specific chromosomal alterations associated with the aggressive behavior of this neoplasm. Comparative genomic hybridization was performed to screen and compare genomic imbalances present in primary and metastatic melanomas. Sixteen primary and 12 metastatic specimens were analyzed. We found that the pattern of chromosomal aberrations is similar in the two subgroups; however, alterations present only in primary and/or metastatic tumors were also discovered. The mean number of genetic changes was 6.3 (range 1-14) in primary and 7.8 (range 1-16) in metastatic lesions. Frequent losses involved 9p and 10q, whereas gains most often occurred at 1q, 6p, 7q, and 8q. Distinct, high-level amplifications were mapped to 1p12-p21 and 1p22-p31 in both tumor types. Amplification of 4q12-q13.1, 7q21.3-qter and 8q23-qter were detected only in primary tumors. The 20q13-qter amplicon was present in a metastatic tumor. The number of genetic alterations were significantly higher in primary tumors which developed metastases within one year after the surgery compared to tumors without metastasis during this time period. Fluorescence in situ hybridization with centromeric and locus-specific probes was applied to validate CGH results on a subset of tumors. Comparison of FISH and CGH data gave good correlation. The aggressive behavior of melanoma is associated with accumulation of multiple genetic alterations. Chromosome regions, which differ in the primary and metastatic lesions, may represent potential targets to identify metastases-related chromosomal alterations.

Liver metastatic ability of human melanoma cell line is associated with losses of chromosomes 4, 9p21-pter and 10p

Genetic changes underlying the aggressive progression of human cutaneous melanoma are not completely understood. In order to characterise genetic alterations associated with the metastatic behaviour of this neoplasm we used comparative genomic hybridisation (CGH) in combination with fluorescence in situ hybridisation (FISH) on an experimental metastatic model of three related human melanoma cell lines. Tumour lines were selected based on their various metastatic capacity to liver in immunosuppressed mice. The parental cell line (A2058) was a human amelanotic melanoma cell line, adaptation of this line to in vivo growth as xenograft the HT168 tumour and its cell line was established. After intrasplenic transplantation of HT168 cells into immunosuppressed mice, a highly metastatic variant (HT168-M1) was selected. Several chromosomal aberrations common to all three lines indicating common clonal origin, as well as additional non-shared chromosomal changes were found. The original cell line (A2058) exhibited the highest number of genetic changes. Chromosomal alterations present only in the highly metastatic line (HT168-M1) involved losses on chromosome 4, 9p21.3-pter and 10p. Chromosome copy number patterns and the nature of chromosome 4 loss were further investigated by FISH using different centromeric probes and a chromosome 4 painting probe. According to our CGH and FISH results we assume that alterations present only in the aggressive metastatic subline are associated with the increased - metastatic potential. Our observations further support the hypothesis, based on some recently published data, that certain (so far unidentified) suppressor genes having an important role in tumour progression are located on these chromosomes.