Molecular Cytogenetic Characterization of the Murine Melanoma Cell Lines S91 Clone M3 and B16-F1 with Variant B16-4A5.

Melanoma is considered to be one of the most aggressive human tumors. Thus, early molecular diagnosis with risk factor stratification could be an efficacious strategy to increase the survival rates in affected patients. Murine cell lines B16-F1, B16-4A5, and S91 clone M3 are the ones most commonly applied in melanoma research. However, genetic peculiarities of these 3 cell lines have not been studied in detail before. Here, we closed this gap by molecular cytogenetic and array-comparative genomic hybridization studies and the translation of the characterized imbalances into the human genome. This study revealed severely rearranged karyotypes with in parts similar imbalances for all 3 cell lines. Interestingly, they involve genes known to play major roles in human melanoma. These are specifically the oncogenes and tumor suppressor genes, being associated with aggressive forms of melanoma. B16-F1, B16-4A5, and S91 clone M3 revealed aberrations which were similarly observed in human eye and skin but not in human uveal melanoma. Thus, they can be considered as model systems for advanced eye and skin melanoma.

Chromosomes in a genome-wise order: evidence for metaphase architecture.

BACKGROUND: One fundamental finding of the last decade is that, besides the primary DNA sequence information there are several epigenetic "information-layers" like DNA-and histone modifications, chromatin packaging and, last but not least, the position of genes in the nucleus. RESULTS: We postulate that the functional genomic architecture is not restricted to the interphase of the cell cycle but can also be observed in the metaphase stage, when chromosomes are most condensed and microscopically visible. If so, it offers the unique opportunity to directly analyze the functional aspects of genomic architecture in different cells, species and diseases. Another aspect not directly accessible by molecular techniques is the genome merged from two different haploid parental genomes represented by the homologous chromosome sets. Our results show that there is not only a well-known and defined nuclear architecture in interphase but also in metaphase leading to a bilateral organization of the two haploid sets of chromosomes. Moreover, evidence is provided for the parental origin of the haploid grouping. CONCLUSIONS: From our findings we postulate an additional epigenetic information layer within the genome including the organization of homologous chromosomes and their parental origin which may now substantially change the landscape of genetics.

Mitotic stability of small supernumerary marker chromosomes depends on their shape and telomeres - a long term in vitro study.

Mosaicism is present in more than 50% of the cases with small supernumerary marker chromosomes (sSMCs) and karyotype 47,XX,+mar/46,XX or 47,XY,+mar/46,XY. Recently we provided first evidence that the mitotic stability of sSMC is dependent on their structure, i.e. their shape. Thus, here we performed a long term in vitro study on 12 selected cell lines from the Else Kröner-Fresenius-sSMC-cellbank (http://ssmc-tl.com/ekf-cellbank.html) to test mitotic sSMC stability systematically. The obtained results showed that inverted duplicated shaped and also the so-called complex sSMCs (group 1) are by far more stable, than centric-minute- or ring-shaped sSMCs (groups 2). Generally speaking, the percentage of cells with group-1-sSMCs remained stable over 90 days of cell culture, while that of group-2-sSMCs in parts dramatically decreased. In one group-2-cell line the sSMC was even lost completely after 30 days of in vitro culture, in others the sSMC was depleted in up to 40% of the cells. Still the highest rate of sSMC loss was recorded during EBV-transformation. Overall, the major difference between groups 1 and 2 was the number of telomeres per sSMC. In group 1 the sSMCs had "original" telomeres at both of their ends; in group 2 the sSMCs had either no, possibly secondary acquired and/or only one original telomere. This absence of protective telomeric sequences in group 2 seems to make sSMC more susceptible for loss during cell division. Still, also a growth advantage of cells without sSMC cannot be neglected entirely.