Growth factors and oncogenes in human solid tumors: clinical aspects

Monosomy 6 in human cultured fibroblast-like cells permanently stimulated by fibroblast growth factor 1: evidence for selection

The appearance of cells with monosomy 6 (mono6 cells) in cultures of human fibroblast-like cells during long-term stimulation with acidic fibroblast growth factor (FGF1) was confirmed in five of the six lines newly investigated. Aneugenic pretreatment at the start of the cultures accelerated the emergence of mono6 cells, as would be expected if selection, rather than induction, is the main mechanism involved. This could be confirmed by using an incidental rearrangement, der(8)t(6p;8p), that emerged in one of the lines by monitoring the proliferation of the mono6 cells (here monosomic for 6p22.1-->qter) in mixtures with normal cells. During growth in the presence of FGF1, the proportion of mono6 cells increased six fold, whereas in the absence of FGF1, it declined to background levels. Selection rather than induction of the mono6 cells is further supported by their clonal origin, as ascertained on the basis of X-inactivation patterns in three informative cases. In addition, colonies grown in the presence of FGF1 from single cells did not reveal higher proportions of mono6 cells by fluorescence in situ hybridization analysis than those grown without the growth factor. During permanent stimulation with FGF1, the growth of mono6 cells did not become dependent on FGF1, nor did these cells lose their responsiveness to FGF1. Although evidence in favor of selection of preexistent mono6 cells by FGF1 is provided in this study, the contribution of a primary inducing mechanism cannot be entirely excluded.

Epidermal growth factor and glucocorticoid effects on blood prostaglandin E2 level in DENA-induced carcinogenesis

This paper describes results on carcinogenesis in rats induced with diethylnitrosamine (DENA; 280 mg/kg single dose, i.p.). After inducing chemical carcinogenesis, the animals were treated with different compounds that affect cell proliferation and the effects on the blood prostaglandin E2 (PGE2) levels were observed. These compounds were epidermal growth factor (EGF, 10 micrograms/kg/24 h i.p., 7 days) and dexamethasone (4 mg/kg/24 h i.p., 7 days). The blood PGE2 levels of rats were measured by RIA (Radioimmunoassay). The blood PGE2 levels increased significantly following DENA and EGF administrations alone or together. Dexamethasone administration decreased the blood PGE2 levels. In conclusion the data show that the increase in the plasma PGE2 level by DENA treatment was enhanced by EGF but opposed by dexamethasone. This suggests that EGF may be effective as a promoter in chemical carcinogenesis.

Mitogenic effects of insulin and insulin-like growth factors on PA-III rat prostate adenocarcinoma cells: characterization of the receptors involved

Four transplantable cell lines (PA-I, II, III, and IV) derived from four Lobund-Wistar (L-W) rats that manifested spontaneous prostate cancer have demonstrated metastatic capacity in visceral organs. Interestingly, PA-III cells, when deposited over the scapula or calvarium of the Lobund-Wistar rat, could produce lytic and blastic reactions on rat skeleton. Since growth factors and growth factor receptors have been implicated in bone remodeling, cancer biology, and metastatic growth of cancer cells, we have examined 1) the effects of insulin and insulin-like growth factors (IGF-I and IGF-II) on the proliferation of PA-III cells; and 2) the presence of specific receptors for these peptides. IGF-I (0.5 to 100 ng/ml), IGF-II (0.5 to 100 ng/ml), and insulin (0.5 to 10 micrograms/ml) stimulated tritiated thymidine uptake and increased the number of PA-III cells in culture. Receptor studies demonstrated the presence of specific bindings sites for IGF-I and II but not for insulin. The number and affinity of the receptor sites were: IGF-I (nb = 675 fmol/100 g protein, Kd = 0.56 nmol) and IGF-II (nb = 225 fmol/100 g protein, Kd = 0.71 nmol). Molecular characterization of IGF binding sites by polyacrylamide gel electrophoresis under denaturing conditions indicated only the presence for the type I IGF receptor. The presence of the IGF-I receptor and the absence of IGF-II and insulin receptors are discussed in relation to the capacity of PA-III cells to produce bone lesions on the L-W rat.