Five continuous cell lines have been established from 29 ocular melanomas and maintained for periods ranging from 3 to 9 years in medium identical to that in which 3 concomitantly studied lines of cutaneous melanoma cells were cultured as controls. The long-term problems to be overcome in establishing uveal cell lines are related to cell-doubling times which ranged from 72 to 432 hr, and plating efficiency, which ranged from 0.5%-6.5%. Tumors and cell lines were found to contain melanosomes. The morphology of uveal cells during the early subcultures exhibited multiple changes. Two different established cell lines were obtained from one ciliary-body tumor. Biochemical studies revealed markers of melanogenesis and neuroendocrine compounds. Cytogenetic studies revealed chromosomal abnormalities that differed between uveal and conjunctival melanomas.
The effects of variations in the concentrations of L-cystine (Cys), L-methionine (Met), and L-glutamine (Glu) on the establishment of melanocyte cell lines obtained from a primary tumor and its metastasis in the same patient were studied. The special role of Glu was also studied in 4 lymph node metastases from other patients. Differentiation in vitro was dependent on the culture conditions, as assessed by morphologic and biochemical studies. Karyologic expression, doubling time, cloning efficiency, and tumorigenicity in nude BALB/c mice varied widely among the cell lines. Cys was an indispensable amino acid and Glu was not. Met and Glu were implicated in melanogenesis. From these observations arose the question of the accuracy of comparative results, concerning differentiation and tumorigenicity, that had been collected for cell lines obtained under different culture conditions.
Dielectrophoretic experiments on pearl-chain formation and collection of human melanocytes were performed as a function of the frequency of the applied nonuniform electric field. Evidence is reported showing that the behavior of malignant melanocytes is markedly dependent upon the type of established cell line (pigmented or achromic), age, and drug treatment (e.g., chlorpromazine).
Variants of the B16 melanoma exhibiting markedly different tumorigenic and metastatic potential in Ay/a and a/a C57BL/6J syngeneic mice were investigated and compared, with respect to their relative growth and metastatic potential after culture under different conditions. Over 2 to 6 months of growth, in vitro cells demonstrated a rapid and significant decrease in their ability to form spontaneous lung colonies. Such a decrease depended on the conditions of culture. We suggest that the in vitro environment influences the phenotype of cells with respect to their capacity for spontaneous metastasis. This possibility must not be ignored, when conclusions obtained from studies of established cell lines are extended to cancers.
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