Characterisation of novel uveal melanoma cell lines under serum-free conditions.

BACKGROUND: The establishment of long-term uveal melanoma (UM) cell lines is difficult. However, studying living cells and their behaviour in the presence of other cells and the extracellular matrix is important in terms of understanding tumour biology and malignant behaviour. We have established three UM cell lines and report a first characterisation of these cell lines.

METHODS: Three established UM cell lines (UMT2, UMT26 and UMT33) were analysed according to their morphologic characteristics, melanocytic differentiation, adhesion on different extracellular matrices and proliferative activity. Copy number changes of chromosomes 1, 3, 6 and 8 were studied by multiplex ligation-dependent probe amplification (MLPA). Oncogenic mutations in UM involving exons 4 and 5 of GNAQ and GNA11, respectively, were analysed by sequencing.

RESULTS: All cell lines grew in suspension. UMT2 cells were homogeneous, UMT26 and UMT33 cells heterogeneous with regard to cell size and pigmentation. All UM cell lines revealed a melanocytic differentiation. UMT2 and 33 adhered on various extracellular matrices, while UMT26 only adhered to basal membrane extract (BME). This difference corresponded to the different expression of various integrins. Ki67 was expressed by 89% of UMT2 and 95% of UMT33 cells, which thus were in a proliferative stage, while only 2% of UMT26 cells revealed immunostaining for this proliferation marker. The doubling time of UMT2 was 3 days, 12 days for UMT33, and circa 3-4 months for UMT26. MLPA revealed disomy 3 in UMT2 and monosomy 3 in UMT33. The same point mutation was found in UMT2, 26 and 33, in exon 5 of GNA11 at codon 209 (p.Q209L).

CONCLUSIONS: The establishment of UM cell lines under serum-free conditions is possible. Characterisation of UMT2, 26, and 33 revealed obvious differences in cytomorphology, melanocytic differentiation, adhesion on extracellular matrices, and proliferative activity. UMT2, 26 and 33 showed the same oncogenic mutation in exon 5 of GNA11.