Generation and characterization of novel metastatic variants of the human melanoma cell line Mel-Juso

Introduction: Melanoma is a highly metastatic tumor with early metastasis in distant organs like lymph nodes, lungs, liver and brain. In order to understand the complex process of metastasis and to identify molecules involved, suitable in vivo and in vitro models are essential. The aim of this study was to establish variants of the human melanoma cell line Mel-Juso with same genetic background but different metastatic potential.
Material and Methods: Mel-Juso cells were inoculated into the tail vein of athymic nude mice. Lung metastases were harvested, pooled, cultured in vitro and injected in another set of mice. Different melanoma variants were generated by repeated cycles of in vivo passage. The obtained metastatic variants (L3 and L5) were characterized genetically and concerning the expression of a melanoma marker, certain Eph receptor tyrosine kinases, growth properties, and in vivo metastasis.
Results and Discussion: STR DNA genotyping showed no differences between the parental cell line and two selected metastatic variants. Moreover, no differences in the expression of the melanoma-associated chondroitin sulfate proteoglycan and in Eph receptors could be detected. Interestingly, we detected a reduced proliferation in metastatic variants accompanied by reduced or even lost capability of colony formation, indicating some substantial changes in metastatic properties despite of genetic similarity. Nevertheless, these in vitro differences between Mel-Juso and the metastatic variants could not be confirmed in an in vivo metastasis assay. Therefore, we started an additional cycle of in vivo passage with preparation of metastatic variants (L6) from individual lung metastases. By now 15 individual cell clones could be established derived from lungs of 4 individual mice and are currently analyzed concerning their cellular properties.
Conclusion: The generation of melanoma cell line variants with same genetic background and different metastatic potential showed no success when using pooled lung metastases. Further steps will focus on the generation of variants from individual metastases to better reflect the varying tumorigenic potential of individual melanoma cells. Using such variants would facilitate the identification of molecules involved in metastasis, which show promise to be potential targets for the diagnosis and therapy of metastatic melanoma.