A STUDY ON THE MECHANISM OF INTERCELLULAR ADHESION : Effects of Neuraminidase, Calcium, and Trypsin on the Aggregation of Suspended HeLa Cells

Aggregation of suspended HeLa cells is increased on removal of cell surface sialic acid. Calcium ions promote aggregation whereas magnesium ions have no effect. The calcium effect is abolished by previous treatment of the cells with neuraminidase. Trypsinization of the HeLa cells followed by thorough washing diminishes the rate of mutual cell aggregation. Subsequent incubation with neuraminidase restores the aggregation rate to the original value before trypsin treatment. Cells which had acquired a greater tendency for aggregation after removal of peripheral sialic acid lose this property when subsequently treated with trypsin. Calcium ions have no aggregative effect on trypsinized cells. In contrast to HeLa cells, aggregation of human erythrocytes was not increased after treatment with neuraminidase or on addition of calcium. The results with HeLa cells are interpreted as follows: (a) Trypsin-releasable material confers adhesiveness upon the cells. (b) The adhesive property of this material is counteracted by the presence of cell surface sialic acids. (c) Calcium ions exert their effect by attenuating the adverse effect of sialic acid

The Heregulin/Human Epidermal Growth Factor Receptor as a New Growth Factor System in Melanoma with Multiple Ways of Deregulation

In a screening for new growth factors released by melanoma cells, we found that the p185-phosphorylating capacity of a medium conditioned by a melanoma cell line was due to the secretion of heregulin, a ligand for the human epidermal growth factor receptor (HER) family of receptor tyrosine kinases. Expression of heregulin, including a new isoform, and secretion of functionally active protein was found in several cell lines. Receptor activation by heregulin, either autocrine or paracrine, resulted in a potent growth stimulation of both melanocytes and melanoma cells. Heregulin receptor HER3 and coreceptor HER2 were the main receptors expressed by these cells. Nevertheless, none of the cell lines in our panel overexpressed HER2 or HER3. In contrast, loss of HER3 was found in two cell lines, whereas one cell line showed loss of functional HER2, both types of deregulations resulting in unresponsiveness to heregulin. This implies the heregulin/HER system as a possible important physiologic growth regulatory system in melanocytes in which multiple deregulations may occur during progression toward melanoma, all resulting in, or indicating, growth factor independence

Author Correction: Ionizing radiation modulates human macrophages towards a pro-inflammatory phenotype preserving their pro-invasive and pro-angiogenic capacities.

This Article contains an error in the description of the data presented in Figure 2. Each blot demonstrating a protein of interest, or of its phosphorylated form, is matched with the expression of β-actin, used as loading control. The majority of the proteins were separated in different gels, apart from proteins p105, p50 and Bcl-xL which were run in the same gel and have the same loading control. As a result, the Figure 2 legend, “Ionizing radiation induces macrophage NF-κB activation and increases Bcl-xL expression. (A) Evaluation of RelA phosphorylation (Ser536) and RelB, cRel, p100/p52 and p105/p50 subunit expression, 1 and 6 h after irradiation (2, 6 and 10 Gy). (B) RelB nuclear translocation 6 h after macrophage irradiation (10 Gy). Histone deacetylase 1 (HDAC1) and β-actin were used as loading controls for nuclear and cytoplasmic fractions, respectively. (C) Evaluation of Bcl2 and Bcl-xL expression after macrophage irradiation. Western blot images are representative of protein expression/phosphorylation status in distinct donors (at least n = 4), evaluated in two independent experiments.” should read: “Ionizing radiation induces macrophage NF-κB activation and increases Bcl-xL expression. (A) Evaluation of RelA phosphorylation (Ser536) and RelB, cRel, p100/p52 and p105/p50 subunit expression, 1 and 6 h after irradiation (2, 6 and 10 Gy). (B) RelB nuclear translocation 6 h after macrophage irradiation (10 Gy). Histone deacetylase 1 (HDAC1) and β-actin were used as loading controls for nuclear and cytoplasmic fractions, respectively. (C) Evaluation of Bcl2 and Bcl-xL expression after macrophage irradiation. Western blot images are representative of protein expression/phosphorylation status in distinct donors (at least n = 4), evaluated in two independent experiments. The β-actin loading control of the panels comprised by p105, p50 (2A) and Bcl-xL (2C) is the same, since proteins were separated in the same gel electrophoresis.