Watkins D
Department of Medicine, McGill University, Montreal, Que.
Clin Invest Med. 1998 Jun;21(3):151-8.
To identify the defect in cobalamin metabolism in the human melanoma cell line MeWoLC1, and to determine how frequent this defect is in other methionine-dependent tumour cell lines.
Biochemical and somatic cell genetics study.
Aspects of cobalamin metabolism were measured in a panel of 14 human tumour cell lines that were unable to proliferate normally in medium in which methionine had been replaced by its metabolic precursor homocysteine (methionine-dependent cell lines).
The human melanoma cell line MeWoLC1 was unique among these cell lines, in that it was characterized by decreased uptake of cobalamin, decreased synthesis of coenzyme derivatives, and decreased functional activity of the cobalamin-dependent enzymes methionine synthase and methylmalonylCoA mutase. This phenotype was identical to that observed in fibroblasts from patients with the cblC and cblD inborn errors of cobalamin metabolism. The defect in cobalamin metabolism in MeWoLC1 was complemented in somatic cell complementation analysis by cblA, cblB, cblD, cblE and cblG fibroblasts, but not by cblC fibroblasts, strongly suggesting that the defect in this cell line affects the cblC locus. Similar changes in cellular cobalamin metabolism were not seen in any other methionine-dependent cell line in the panel, suggesting that there may be multiple causes of methionine dependence, and that inactivation of the cblC locus may not be a common cause of this phenotype in transformed cells.
The defect underlying methionine dependence in MeWoLC1 appears to involve the locus that is affected in patients with the cblC inborn error of metabolism. This defect does not seem to be common among other methionine-dependent cell lines.
确定人黑色素瘤细胞系MeWoLC1中钴胺素代谢缺陷，并确定该缺陷在其他依赖甲硫氨酸的肿瘤细胞系中的出现频率。
生化与体细胞遗传学研究。
在一组14种人肿瘤细胞系中检测钴胺素代谢的各个方面，这些细胞系在甲硫氨酸被其代谢前体同型半胱氨酸替代的培养基中无法正常增殖（依赖甲硫氨酸的细胞系）。
人黑色素瘤细胞系MeWoLC1在这些细胞系中独一无二，其特征是钴胺素摄取减少、辅酶衍生物合成减少以及钴胺素依赖性酶甲硫氨酸合酶和甲基丙二酰辅酶A变位酶的功能活性降低。该表型与钴胺素代谢先天性缺陷cblC和cblD患者的成纤维细胞中观察到的表型相同。在体细胞互补分析中，MeWoLC1中钴胺素代谢缺陷可被cblA、cblB、cblD、cblE和cblG成纤维细胞互补，但不能被cblC成纤维细胞互补，强烈提示该细胞系中的缺陷影响cblC位点。在该组中任何其他依赖甲硫氨酸的细胞系中均未观察到细胞钴胺素代谢的类似变化，这表明甲硫氨酸依赖性可能有多种原因，并且cblC位点失活可能不是转化细胞中该表型的常见原因。
MeWoLC1中甲硫氨酸依赖性的潜在缺陷似乎涉及cblC先天性代谢错误患者中受影响的位点。这种缺陷在其他依赖甲硫氨酸的细胞系中似乎并不常见。
