Extra copies of c-myc are 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.


CONCLUSIONS
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.
Treszl
Andrea
A
Department of Preventive Medicine, School of Public Health, Medical and Health Science Centre, University of Debrecen, Debrecen, Hungary.
Adány
Róza
R
Rákosy
Zsuzsa
Z
Kardos
László
L
Bégány
Agnes
A
Gilde
Katalin
K
Balázs
Margit
M
D000328:Adult; D000367:Age Factors; D002503:Centromere / Q000235:genetics; D005260:Female; D018628:Gene Dosage; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D008297:Male; D008545:Melanoma / Q000235:genetics* / Q000473:pathology / Q000556:secondary; D008875:Middle Aged; D011003:Ploidies; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics*; D012878:Skin Neoplasms / Q000235:genetics* / Q000473:pathology
D016271:Proto-Oncogene Proteins c-myc