cytochalasin-b and Urinary-Bladder-Neoplasms

Intravesical bacillus Calmette-Guerin (BCG) is a successful therapy for superficial bladder cancer. However, the working mechanism of BCG after intravesical instillation is not completely understood. A functional role of urothelial (tumor) cells in the initiation of the BCG-induced immune reaction should be considered. Here, the possibility of a causal relationship between BCG-induced interleukin-6 (IL-6) synthesis and BCG internalization by urothelial tumor cells was examined in a series of human transitional bladder cancer (TCC) cell lines with different degrees of differentiation. The results showed that the well differentiated TCC cell lines, RT4, SBC-2, and SBC-7, did not possess the capacity to internalize BCG, which was associated with an inability to upregulate IL-6 synthesis when stimulated with BCG. Moreover, these cell lines expressed a low level of constitutive IL-6 synthesis. In contrast, the poorly differentiated TCC cells, T-24, TCC-SUP and J-82, were able to internalize BCG. In T24 and J82, but not in TCC-SUP cells, BCG internalization appeared to result in an upregulation of IL-6 synthesis. Constitutive IL-6 synthesis of the high grade cell lines was found to be cell line-dependent: both TCC-SUP and J82 cells exhibited a high level of constitutive IL-6 synthesis, whereas T24 cells exhibited a low level. The possible relationship between BCG internalization and IL-6 upregulation was studied in detail with the T24 cell line, which exhibited a low constitutive and high BCG-inducible IL-6 synthesis, using anti-BCG antibodies (alphaBCG) and Cytochalasin B as internalization inhibitors. Upregulation of IL-6 synthesis was significantly inhibited by alphaBCG or Cytochalasin B, indicating that internalization is a prerequisite for BCG-induced upregulation of IL-6 synthesis. In conclusion, upregulation of IL-6 production due to BCG internalization by poorly differentiated bladder carcinoma cells may be part of the mode of action of intravesical BCG therapy.

Topics: Administration, Intravesical; Cell Differentiation; Cytochalasin B; Humans; Interleukin-6; Mycobacterium bovis; Phagocytosis; Tumor Cells, Cultured; Up-Regulation; Urinary Bladder Neoplasms

The micronucleus (MN) test has been carefully characterized in four human tumour cell lines of widely differing radiosensitivity. Two radioresistant bladder carcinoma cell lines (MGH-U1 and RT112), one sensitive medulloblastoma cell line (D283MED) and a sensitive neuroblastoma cell line (HX142) were used. The number of MN per Gy of ionising radiation was 0.13 for HX142, 0.17 for D283MED, 0.21 for RT112 and 0.26 for MGH-U1. This does not rank the cell lines in the same order of radiosensitivity as clonogenic cell survival where the surviving fraction at 2 Gy (SF2) was 0.11 for HX142, 0.2 for D283MED, 0.62 for RT112 and 0.53 for MGH-U1. This discrepancy between MN formation and cell death leaves doubt as to the potential usefulness of the MN test as a rapid assay of radiosensitivity but it has potential implications for the mechanistic basis of radiosensitivity in these cells.

Topics: Cell Death; Cell Division; Cell Survival; Cytochalasin B; Humans; Medulloblastoma; Micronuclei, Chromosome-Defective; Neoplasms; Neuroblastoma; Radiation Tolerance; Tumor Cells, Cultured; Urinary Bladder Neoplasms

Mechanisms by which intravesical bacille Calmette-Guerin (BCG) treatment mediates antitumor activity are currently poorly understood. We have determined that both human bladder tumor (T-24) and mouse bladder tumor (MBT-2) cells are capable of internalizing the BCG and have characterized this process in vitro. The internalization of BCG by T-24 and MBT-2 cells was verified by histochemistry and electron microscopy. Time dependent internalization of BCG was observed with a maximum occurring at three hrs. Internalization was significantly inhibited by both incubation at 4C and cytochalasin B; conditions known to inhibit phagocytosis. Ultrastructural studies suggested that BCG were transported to membrane bound intracellular compartments and were degraded. The compartments containing the degraded mycobacteria labeled with the fluid phase marker HRP which is known to be transported to lysosomes in a variety of cell types. To determine if the internalization process occurred in vivo, we examined bladder washings of patients treated with intravesical BCG. The majority of the cells in the bladder washings were inflammatory cells which contained ingested BCG. In addition, internalized and degraded BCG were identified in urothelial cells. These data demonstrate that BCG are internalized by transitional epithelial cells both in vitro and in vivo. The internalization process is inhibitable by temperature and microfilament disruption. The potential therapeutic implications of this process and its relationship to antitumor activity of BCG therapy are currently being investigated.

Topics: Actin Cytoskeleton; Animals; BCG Vaccine; Cytochalasin B; Humans; Leukocyte Count; Lysosomes; Mice; Ribosomes; Tumor Cells, Cultured; Urinary Bladder Neoplasms

Human tumor cell lines derived from melanoma, glioblastoma, and carcinoma of the prostate, bladder, and kidney multinucleated in response to growth in cytochalasin B-supplemented medium, whereas cell lines derived from normal prostate, kidney, skin, lung, and other nonmalignant diseases remained predominantly binucleate under comparable conditions. The multinucleate cytochalasin B phenotype was dissociable from the anchorage-independent phenotype of tumor cells, suggesting that these markers of cellular transformation are under separate control. These results suggest that uncontrolled nuclear division by tumor cells may be a general marker of abnormal growth or regulation.

Topics: Cell Line; Cell Nucleus; Cytochalasin B; Glioma; Humans; Male; Melanoma; Neoplasms; Prostate; Prostatic Hyperplasia; Prostatic Neoplasms; Urinary Bladder Neoplasms