Evidence for autocrine mitogenic stimulation by somatomedin-C/insulin-like growth factor I on an established human lung cancer cell line.
The production of immunoreactive somatomedin-C/insulin-like growth factor I (Sm-C/IGF-I) by the established cell line derived from a human lung carcinoma CALU-6 has been evidenced in the serum-free medium in increasing concentrations as a function of the incubation time. Gel filtration in acid conditions of cell-conditioned medium collected after 72 h showed peaks of immunoreactive Sm-C/IGF-I in the elution volume corresponding to the molecular weight of the synthetic Sm-C/IGF-I, and in the high molecular weight region, where specific binding sites for Sm-C/IGF-I could be also demonstrated. These results indicate that this established cell line produces high amounts of immunoreactive Sm-C/IGF-I and of Sm-C/IGF-I carrier protein. The pooled fractions corresponding to the molecular weight of synthetic Sm-C/IGF-I showed a competitive binding curve parallel to the standard in the Sm-C/IGF-I RIA system, and a mitogenic activity on cells from the same line similar to the one observed using two different pure Sm-C/IGF-I preparations, obtained by chemical synthesis or by DNA recombinant technology. When a monoclonal antibody (sm-1.2) raised against Sm-C/IGF-I was added into the medium, the mitogenic effect observed by both synthetic and cell-derived Sm-C/IGF-I peptide was completely abolished; the monoclonal antibody also partially inhibited the effect of 10% fetal calf serum and the thymidine incorporation observed in serum-free medium without growth factors. In serum-free medium the monoclonal antibody produced a 45% reduction of cells in S phase by thymidine labeling index without modification of the growth fraction as determined by primer-dependent alpha-DNA polymerase labeling index. In conclusion it seems that Sm-C/IGF-I has a critical role in the autocrine stimulation of the replication of this cell line.
Minuto
F
F
Cattedre di Fisiopatologia Endocrina, Universita' di Genova, Italy.
Del Monte
P
P
Barreca
A
A
Alama
A
A
Cariola
G
G
Giordano
G
G
D000911:Antibodies, Monoclonal / Q000276:immunology; D000937:Antigen-Antibody Reactions; D002455:Cell Division / Q000187:drug effects*; D004273:DNA, Neoplasm / Q000096:biosynthesis; D006801:Humans; D066298:In Vitro Techniques; D007334:Insulin-Like Growth Factor I / Q000276:immunology / Q000494:pharmacology*; D008175:Lung Neoplasms / Q000473:pathology*; D011994:Recombinant Proteins; D013002:Somatomedins / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
D000911:Antibodies, Monoclonal; D004273:DNA, Neoplasm; D011994:Recombinant Proteins; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I