Search

The retinoblastoma protein (pRB) is encoded by the RB1 gene whose promoter contains several putative binding sites for ICBP90 (Inverted CCAAT box Binding Protein of 90 kDa), a transcriptional regulator of the topoisomerase IIalpha gene. ICBP90 has two consensus binding sites for pRB in its primary sequence. Here, we show that pRB and ICBP90 co-immunoprecipitate in cell extracts of proliferating human lung fibroblasts and of proliferating or confluent Jurkat cells. GST pull-down assays and immunocytochemistry, after cell synchronization in late G1 phase, confirmed this interaction. Overexpression of ICBP90 induces downregulation of pRB expression in lung fibroblasts as a result of mRNA decrease. DNA chromatin immunoprecipitation experiment shows that ICBP90 binds to the RB1 gene promoter under its methylated status. Overexpression of ICBP90 increases the S and G2/M phase cell fractions of serum-starved lung fibroblasts as assessed by flow cytometry analysis and increases topoisomerase IIalpha expression. Together, these results show that ICBP90 regulates pRB at the protein and gene transcription levels, thus favoring the entry into the S phase of the cells. We propose that ICBP90 overexpression, found in cancer cells, is involved in the altered checkpoint controls occurring in cancerogenesis.

Toxin B, an exotoxin produced by the anaerobic Gram-positive bacteria Clostridium difficile, is responsible for pseudomembranous colitis in humans. It deeply modifies morphology of cultured cells and enhances their membrane surface area, which suggests a possible alteration of membrane receptor distribution. Since toxin B and bacterial lipopolysaccharide can act synergistically on TNF-alpha production by mononuclear phagocytes, the effect of toxin B on CD14 expression was investigated using flow cytometric analysis. It was shown that monocytes overexpressed CD14 after 5 h of treatment with toxin B. In contrast, after 24 h of treatment, the percentage of CD14 monocytes decreased, although, most frequently, the remaining positive cells expressed high levels of CD14 compared with untreated cells. Macrophages treated for 5 h with toxin B overexpressed CD14, but this effect persisted for at least 24 h. Both the percentage of positive macrophages and the mean level of CD14 per cell were increased. Thus toxin B can modulate expression of CD14 and its modulation depends on the differentiation status and maybe on the activation state, since some individual variations were observed in monocyte response to toxin.

Clonal neurohybridoma NCB-20 cells express a valproate-insensitive succinic semialdehyde reductase activity that transforms succinic semialdehyde into gamma-hydroxybutyrate. This activity (1.14+/-0.16 nmol/min/mg protein) was similar to the lowest activity existing in adult rat brain. [3H]gamma-Hydroxybutyrate labels a homogeneous population of sites on NCB-20 cell membranes (Kd=250+/-44.4nM, Bmax=180+/-16.2fmol/mg protein) that apparently represents specific gamma-hydroxybutyrate binding sites characterized previously on brain cell membranes. Finally, an Na+-dependent uptake of [3H]gamma-hydroxybutyrate was expressed in NCB-20 cells with a Km of 35+21.1 microM and a Vmax of 80+/-14.2 pmol/min/mg protein. A three-day treatment with 1 mM dibutyryl-cyclic-AMP induced a three-fold increase in the cellular succinic semialdehyde reductase activity. In parallel, a K+-evoked release of [3H]gamma-hydroxybutyrate occurred. This release was Ca2+ dependent and was not present in undifferentiated cells. Cyclic-AMP treatment induced a decrease of [3H]gamma-hydroxybutyrate binding sites, which could be due to spontaneous gamma-hydroxybutyrate release. Patch-clamp experiments carried out on differentiated NCB-20 cells revealed the presence of Ca2+ conductances which were partially inhibited by 50 microM gamma-hydroxybutyrate. This gamma-hydroxybutyrate-induced effect was blocked by the gamma-hydroxybutyrate receptor antagonist NCS-382, but not by the GABA(B) antagonist CGP-55845. These results demonstrate the presence of an active gamma-hydroxybutyratergic system in NCB-20 cells which possesses the ability to release gamma-hydroxybutyrate. These cells express specific gamma-hydroxybutyrate receptors which modulate Ca2+ currents independently of GABA(B) receptors.

The gamma-hydroxybutyrate biosynthetic enzyme succinic semialdehyde reductase (SSR) was purified to homogeneity from rat brain. Peptides were generated by tryptic cleavage and sequenced. PCR primers were designed from the amino acid sequences of two of the peptides showing a similarity (75-85%) to a mitochondrial aldehyde dehydrogenase. A PCR-amplified DNA fragment was generated from recombinant plasmids prepared by a mass excision procedure from a rat hippocampal cDNA library and used as a probe to screen this cDNA library. One cDNA of 1341 bp had an open reading frame encoding a protein of 447 residues with a deduced molecular mass of 47967 Da. The enzyme was expressed in Escherichia coli. Immunoblotting analysis revealed the existence of a protein with the same electrophoretic mobility as the SSR purified from rat brain and with an estimated molecular mass of 45 kDa. Northern blot experiments showed that this enzyme was not expressed in the kidney or in the liver. In the brain tissue, a single but rather broad band was labelled under high stringency conditions, suggesting the presence of more than one messenger species coding for SSR. Hybridization in situ performed on brain tissue slices showed specific labelling of the hippocampus, the upper cortex layer, the thalamus, the substantia nigra, the cerebellum, the pons medulla and the olfactory tract. The recombinant enzyme showed catalytic properties similar to those of the SSR purified from rat brain, particularly in regard to its substrate affinities and Ki for inhibition by phthalaldehydic acid. Valproic acid did not inhibit the cloned SSR. This enzyme had 20-35% identity in highly conserved regions involved in NADPH binding with four other proteins belonging to the aldo-oxo reductase family.

The increasing interest in mononuclear phagocytes for adoptive cellular immunotherapy (ACI) trials in cancer patients led us to define a procedural approach to harvest reproducibly highly purified single-cell suspensions of large numbers of functional human circulating blood monocytes (Mo). A semiclosed counterflow centrifugal elutriation (CCE) system has been developed, using a new large capacity Beckman JE 5.0 rotor with one interchangeable 40 ml or 5 ml separation chamber, to purify Mo from mononuclear cell (MNC) concentrates of healthy donors and cancer patients obtained by continuous flow centrifugation leukapheresis (CFCL). This method does not require a Ficoll density gradient centrifugation step. A total of 115 leukapheresis procedures were carried out in 35 patients and in 30 healthy donors by either Cobe 2997 or Cobe Spectra, with a similar efficiency in MNC apheresis. The average yield per leukapheresis procedure was 5.6 x 10(9) MNC of purity 90-100% (25-45% Mo, 40-65% lymphocytes). The average yields per elutriation procedure (R/O fraction) were 1.1 x 10(9) cells (purity 93% Mo) using the 5 ml separation chamber, and 1.5 x 10(9) cells (purity 91%) using the 40 ml separation chamber, with a respective recovery of 82 +/- 7% and 78 +/- 8% Mo. In vitro analysis of the viability and function of the purified Mo shows that neither morphological integrity nor physiological activity was compromised by this two-step isolation procedure, which additionally provides highly purified human Mo suspensions, in a quantity suitable for ACl of cancer patients.

Toxin B from Clostridium difficile is cytopathic in vitro for various types of cells, including polymorphonuclear cells, lymphocytes, and monocytes. Since intestine lamina propria is rich in macrophages, we studied the effect of toxin B on human monocytes and on human macrophages generated in vitro by long-term culture of purified circulating blood monocytes. Upon addition of toxin B, human monocytes exhibited few modifications whereas macrophages adopted a stellate morphology, with rounding up of the perikaryon. Toxin B made microfilaments of actin disappear and induced an important reorganization of vimentin and a redistribution of tubulin. Membrane area increased by approximately 16%. Toxin B did not affect the viability of human mononuclear phagocytes and did not exert any significant lytic effect. It profoundly altered the phagocytic function of macrophages. When activated by gamma interferon in the presence of toxin B, monocytes were more cytotoxic for U-937 target cells than control monocytes activated in absence of toxin. Finally, the combined treatment of monocytes with gamma interferon and toxin B increased significantly the secretion of tumor necrosis factor alpha, whereas toxin B alone was unable to induce tumor necrosis factor production. These results suggest that morphological and functional alterations induced in human mononuclear phagocytes by toxin B from C. difficile are due to the disorganization of the cytoskeleton and the resulting impairment of the membrane traffic equilibrium.

Antitumoral macrophages (MAK) were obtained by the culture of human mononuclear cells in hydrophobic bags. From one cytapheresis, up to 10(9) mature macrophages could be purified by elutriation after one week of culture in IMDM medium in the presence of 2% human AB serum. These MAK cells were used for adoptive treatment in metastatic cancer patient with no dose-limiting toxicity. The present study aimed to improve the average MAK yield by addition of GM-CSF and of dihydroxy-cholecalciferol. The differentiated macrophages obtained presented higher antitumoral functionality in response to rh-IFN gamma than in their absence. These MAK presented all the differentiation antigens of cytotoxic macrophages compared to MAK cells differentiated in standard medium. They killed human tumor targets effectively in vitro at a low (1/1) effector/tumor ratio; furthermore, the antitumoral activity reached by MAK cells after IFN gamma activation appeared to be stabilized for several days.

Human low-density lipoprotein (LDL) was glycated in vitro (5 days, glucose 50 mmol/l), labelled with 125I, and its binding and uptake by human monocyte-derived macrophages studied. Glycation produced lower binding and lower uptake. Competition experiments using unlabelled LDL (control, glycated, and acetyl-LDL) showed that most glycated LDL was taken up by the apolipoprotein-B100: E receptor pathway. Results suggest that less of the glycated LDL may enter the cells via scavenger receptors, and very minute amount via non-saturable receptor-independent pathways.

We have conducted a phase I study with autologous monocytes activated ex vivo and administered intraperitoneally in nine patients with peritoneal carcinomatosis. Blood monocytes were collected by leukapheresis and then purified by counterflow elutriation (up to 10(9) cells, with a purity of greater than 90%). Ex vivo activation was obtained by incubating these cells with 1 micrograms liposomal MTP-PE/10(6) monocytes for 18 hours in hydrophobic culture bags at 37 degrees C in 5% carbon dioxide humidified air. The activated monocytes were then infused in the peritoneal cavity once a week for 5 consecutive weeks through an implanted peritoneal infusion system, Port-A-Cath (Pharmacia Deltec, St Paul, MN), on an intrapatient dose-escalating schedule (10(7) to 10(9) monocytes). No severe adverse reactions occurred. Toxicity was mild, the chief acute reactions being fever (27%), chills (13%), and abdominal pain (25%). None of the side effects led to dose reduction. No consistent change in hemostatic function, liver function, or renal function was observed. Significant increases in granulocyte counts, neopterine, and acute phase reactants (fibrinogen, C-reactive protein) occurred in the peripheral blood. In vitro monocyte activation was demonstrated by the relapse of procoagulant activity and monokines (interleukin-1 [IL-1], IL-6, and tumor necrosis factor-alpha [TNF alpha]) in the supernatants of cultured monocytes. Evidence for in vivo monocyte activation was provided by the increase of these monokines in the peritoneal fluids. Kinetic studies with indium-111 (111In)-labeled activated autologous monocytes in five patients suggest that these infused monocytes may remain in the peritoneal cavity for up to 7 days. This locoregional immunotherapeutic approach seems to be encouraging in view of adjuvant therapeutic modality in ovarian cancer patients with minimal residual intraabdominal disease following second-look laparotomy.