We have shown that the small GTPase Rap1b, a protein known to antagonize the mitogenic and transforming activity of Ras, is endowed with both mitogenic and tumorigenic properties. Rap1b can be activated by cAMP, an intracellular message known to either stimulate or inhibit cell proliferation. The oncogenic property of Rap1b was revealed in a model system in which cAMP stimulates cell proliferat...

We present a method for logical analysis of signal-transduction networks, focusing on metabolic and mitogenic signalling by the insulin receptor, with specific emphasis on dependence of the signalling properties on the timing of binding events. We discuss a basic model which demonstrates this dependence (hormone binding leads to activation of the receptor which can lead to a commitment to mitog...

The effects on the mitogenic response of human T lymphocytes were studied for 20 different antibiotics. No apparent inhibitory effect could be detected for penicillins, cephalosporins, aminoglycosides, chloramphenicol, sulfamethoxazole, trimethoprim, nalidixic acid, and 5-fluorocytosine. There were effects at high concentrations with erythromycin, clindamycin, and rifampin, and these antibiotic...

Studies of hormonal growth regulation in cultured human endometrial cancer cells are limited by the requirement of exogenous growth factors, usually supplied by addition of serum. The present report provides evidence that estradiol can stimulate proliferation of endometrial cancer cells of the Ishikawa line in the absence of serum or added growth factors. Mitogenic effects of estrogen were demo...

FGF2 elicits a strong mitogenic response in the mouse Y-1 adrenocortical tumor cell line, that includes a rapid and transient activation of the ERK-MAPK cascade and induction of the c-Fos protein. ACTH, itself a very weak mitogen, blocks the mitogenic response effect of FGF2 in the early and middle G1 phase, keeping both ERK-MAPK activation and c-Fos induction at maximal levels. Probing the mit...

Staphylococcal enterotoxin B is a potent mitogen for mouse and human lymphocytes. Mitogenic activity was retained after detoxification of the enterotoxin by formaldehyde at pH 5.0, 7.5, OR 9.5. The most active toxoid (pH 7.5) was separated into a monomeric, a dimeric, and a polymeric fraction (1 x 10(5) to 3 x 10(5) molecular weight) by gel filtration, and although each fraction demonstrated mi...

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 i...

PURPOSE In the epidermis, proliferative basal cells can be divided into two subpopulations according to their response to phorbol ester tumor promoters. The tumor promoter-sensitive subpopulation ceases mitosis and initiates terminal differentiation and, thus, represents more differentiated transient amplifying cells. In contrast, the tumor promoter-resistant subpopulation that continues to pro...

Retinoids have been shown to exert an anticarcinogenic effect through suppression of the cell cycle, induction of apoptosis and/or differentiation. In rat liver, in particular, retinoic acid has been shown to inhibit regeneration after partial hepatectomy, most probably through repression of the expression of c-fos and c-jun. Surprisingly enough, in spite of the proposed therapeutic effects of ...

Antibodies reactive with cell surface carbohydrates were isolated from normal chicken serum and were found to be mitogenic for mouse splenic lymphocytes as assayed by both blast transformation and [3H]thymidine incorporation. The Fab' fragments of these carbohydrate-binding immunoglobulins were just as mitogenic as the divalent native antibody. Moreover, succinylated Fab' fragments, which proba...