Bízik J, Lizonová A, Grófová M, Matoŝka J, Doré J F, Bertrand S, Blaŝko M, Vaheri A
Cancer Research Institute of the Slovak Academy of Sciences, Bratislava, Czechoslovakia.
Cancer Res. 1989 Feb 15;49(4):983-90.
alpha 2-Macroglobulin (alpha 2-M) is known as a wide-spectrum proteinase inhibitor and to bind covalently certain growth factors. We have previously characterized tumor-associated alpha 2-M synthesized and secreted by human tumor cell lines. Of the cell lines studied, the melanoma cell line HMB-2 produced the largest amount of this glycoprotein. Immunofluorescence staining of cultured HMB-2 cells suggested that the cell population is heterogeneous with respect to alpha 2-M production. We have now isolated clones from the parental HMB-2 cells and characterized eight representative ones in detail. They varied considerably in the quantity of alpha 2-M secreted, from 4.2 to 46.5% of total protein. No relationship between the production of alpha 2-M by these clones and their pigmentation or tumorigenicity in nude mice was found. However, statistically there was a strong correlation between the modal chromosome number and population doubling time (r2 = 0.88, P less than 0.001) and also between the modal chromosome number and alpha 2-M production (r2 = 0.73, P less than 0.01). The growth rate of the clones correlated with the level of alpha 2-M in culture medium (r2 = 0.69, P less than 0.01). Clones with lower alpha 2-M production had a proportionally shorter population doubling time than the clones with intermediate or high production. Northern hybridization indicated quantitative variation in the alpha 2-M mRNA expressed by the parental cells and the clones, that was comparable but not identical with the quantity of alpha 2-M in the respective culture media; both parental cells and clones expressed platelet-derived growth factor A-chain mRNAs with little difference in levels. Serum-free medium from low alpha 2-M producer clones stimulated normal stationary fibroblasts significantly more than clones producing intermediate or high amounts of alpha 2-M. alpha 2-M decreased and anti-alpha 2-M IgG increased the stimulation. These results suggest that production of tumor-associated alpha 2-M is related to both autocrine and paracrine growth-stimulating activity of the tumor cells.
α2-巨球蛋白（α2-M）是一种广谱蛋白酶抑制剂，能与某些生长因子共价结合。我们之前已对人肿瘤细胞系合成并分泌的肿瘤相关α2-M进行了表征。在所研究的细胞系中，黑色素瘤细胞系HMB-2产生的这种糖蛋白量最大。对培养的HMB-2细胞进行免疫荧光染色表明，就α2-M的产生而言，细胞群体是异质的。我们现在已从亲本HMB-2细胞中分离出克隆，并详细表征了八个有代表性的克隆。它们分泌的α2-M量差异很大，占总蛋白的4.2%至46.5%。未发现这些克隆产生α2-M与其在裸鼠中的色素沉着或致瘤性之间存在关联。然而，从统计学上看，众数染色体数与群体倍增时间之间存在很强的相关性（r2 = 0.88，P < 0.001），众数染色体数与α2-M产生之间也存在相关性（r2 = 0.73，P < 0.01）。克隆的生长速率与培养基中α2-M的水平相关（r2 = 0.69，P < 0.01）。α2-M产生量较低的克隆与α2-M产生量中等或较高的克隆相比，群体倍增时间相应较短。Northern杂交表明亲本细胞和克隆表达的α2-M mRNA存在定量差异，这与各自培养基中α2-M的量相当但不相同；亲本细胞和克隆均表达血小板衍生生长因子A链mRNA，水平差异不大。来自低α2-M产生克隆的无血清培养基对正常静止成纤维细胞的刺激明显大于产生中等或大量α2-M的克隆。α2-M减少而抗α2-M IgG增加了这种刺激。这些结果表明，肿瘤相关α2-M的产生与肿瘤细胞的自分泌和旁分泌生长刺激活性均有关。
