Clonal variation in the production of tumor-associated alpha 2-macroglobulin in a malignant human melanoma and association with growth stimulation.
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.
Bízik
J
J
Cancer Research Institute of the Slovak Academy of Sciences, Bratislava, Czechoslovakia.
Lizonová
A
A
Grófová
M
M
Matoŝka
J
J
Doré
J F
JF
Bertrand
S
S
Blaŝko
M
M
Vaheri
A
A
D014408:Biomarkers, Tumor / Q000032:analysis / Q000096:biosynthesis; D002455:Cell Division; D002460:Cell Line; D002999:Clone Cells; D004261:DNA Replication; D014644:Genetic Variation; D006801:Humans; D007124:Immunoenzyme Techniques; D008545:Melanoma / Q000235:genetics* / Q000473:pathology; D012333:RNA, Messenger / Q000235:genetics; D000511:alpha-Macroglobulins / Q000032:analysis / Q000096:biosynthesis / Q000235:genetics*
D014408:Biomarkers, Tumor; D012333:RNA, Messenger; D000511:alpha-Macroglobulins