# Altered methionine auxotrophy of a human melanoma cell line associated with exposure to serum.

 Title: Altered methionine auxotrophy of a human melanoma cell line associated with exposure to serum. Author: Jurewicz, Teresa J. Abstract: The highly metastatic MeWo-LC1 cell line, derived from MeWo, the poorly metastatic human melanoma cell, exhibits a markedly reduced ability to synthesize DNA under conditions where methionine is replaced by 5$\sp\prime$-deoxy-5$\sp\prime$-methylthioadenosine in the medium. The difference in methionine auxotrophy between MeWo and MeWo-LC1 cells is not due to a lack of the enzyme necessary to degrade 5$\sp\prime$-deoxy-5$\sp\prime$-methylthioadenosine. However, when MeWo-LC1 cells are cultured in serum-free medium containing transferrin and supplemented with the nucleoside in place of methionine, DNA synthesis occurs normally. The presence of serum in the culture medium appears to alter the response of MeWo-LC1 cells to 5$\sp\prime$-deoxy-5$\sp\prime$-methylthioadenosine. The uptake of the nucleoside by MeWo-LC1 cells is not decreased in the presence of serum and therefore the substrate is likely to be available to the cell. Further, the incorporation of 5$\sp\prime$-deoxy-5$\sp\prime$-methylthioadenosine into cellular macromolecules appears to be unaffected by the presence of serum. However, under conditions where methionine is not limiting, the nucleoside has a greater inhibitory effect on DNA synthesis in MeWo-LC1 cells in the presence of serum than in serum-free medium supplemented with transferrin. The component(s) responsible for the inhibitory effect of serum on the 5$\sp\prime$-deoxy-5$\sp\prime$-methylthioadenosine-dependent synthesis of DNA remains elusive. (Abstract shortened by UMI.) Date: 1990 URI: http://hdl.handle.net/10393/5782

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