[Patient's resistance: to what? to whom?]. / La résistance du patient: à quoi ?, contre qui?

An approach for "resisting patients" to treatments and weight loss programme is proposed. Patient's resistance is a sign of vitality, a source of information for the health care provider and an invitation to question the nature of therapeutic relationship. Resistance can constitute a "block road" which the health care provider may not be able to avoid unless initiating a process of changes based on reciprocal responsibilities and implications. Towards a patient resisting to change, it is appropriate to understand how he resists, to what and, perhaps to whom. Practical proposals to "do and to be with a resisting patient" can be applied by health care providers taking care of patients suffering from binge eating disorders and obesity.

Identification of tumor-infiltrating macrophages as the killers of tumor cells after immunization in a rat model system.

Immunization can prevent tumor growth, but the effector cells directly responsible for tumor cell killing in immunized hosts remain undetermined. The present study compares tumor grafts that progress in naive syngeneic rats with the same grafts that completely regress in hosts preimmunized with an immunogenic cell variant. The progressive tumors contain only a few macrophages that remain at the periphery of the tumor without direct contact with the cancer cells. These macrophages do not kill tumor cells in vitro. In contrast, tumors grafted in immunized hosts and examined at the beginning of tumor regression show a dramatic infiltration with mature macrophages, many of them in direct contact with the cancer cells. These macrophages are strongly cytotoxic for the tumor cells in vitro. In contrast to macrophages, tumor-associated lymphocytes are not directly cytotoxic to the tumor cells, even when obtained from tumor-immune rats. However, CD4(+) and CD8(+) T cells prepared from the regressing tumors induce tumoricidal activity in splenic macrophages from normal or tumor-bearing rats and in macrophages that infiltrate progressive tumors. These results strongly suggest that the main tumoricidal effector cells in preimmunized rats are macrophages that have been activated by adjacent tumor-immune lymphocytes.

Early increase in DcR2 expression and late activation of caspases in the platelet storage lesion.

Platelet transfusion is widely used to prevent bleeding in patients with severe thrombocytopenia. The maximal storage duration of platelet concentrates is usually 5 days, due to the platelet storage lesion that impairs their functions when stored for longer times. Some of the morphological and biochemical changes that characterize this storage lesion are reminiscent of cell death by apoptosis. The present study analyzed whether proteins involved in nucleated cell apoptosis could play a role in the platelet storage lesion. Storage of leukocyte-depleted platelets obtained by apheresis is associated with a late and limited activation of caspases, mainly caspase-3. This event correlates with an increased expression of the pro-apoptotic BH3-only protein Bim in the particulate fraction and a slight and late release of the pro-apoptotic mitochondrial protein Diablo/Smac in the cytosol. Platelets do not express the death receptors Fas, DR4 and DR5 on their plasma membrane, while the expression of the decoy receptor DcR2 increases progressively during platelet storage. Addition of low concentrations of the cryoprotector dimethylsulfoxide accelerates platelet caspase activation during storage, an effect that is partially prevented by the caspase inhibitor z-VAD-fmk. Altogether, DcR2 expression on the plasma membrane is an early event while caspase activation is a late event during platelet storage. These observations suggest that caspases are unlikely to account for the platelet storage lesion. As a consequence, addition of caspase inhibitors may not improve the quality of platelet concentrates stored in standard conditions.

Flt3 ligand lessens the growth of tumors obtained after colon cancer cell injection in rats but does not restore tumor-suppressed dendritic cell function.

A defective function of the antigen-presenting cells may represent one of the ways used by cancer cells to escape the immune response. We have previously shown that human and rat colon carcinomas were infiltrated by dendritic cells that did not express the B7 co-stimulatory molecules required for inducing an efficient T-cell response. Flt3 ligand is a cloned hematopoietic growth factor that markedly augments the number of functional dendritic and NK cells in lymphoid and non-lymphoid tissues and exerts anti-tumor activity in various experimental models. We show here that repeated Flt3 ligand administration delays the s.c. growth of rat colon cancer cells in syngeneic animals without inducing tumor regression. In tumor-bearing animals, Flt3 ligand has a limited stimulatory effect on the antigen-presenting capacity of intra-tumoral and splenic dendritic cells, without restoring the high functional level of dendritic cells from tumor-free animals. Moreover, Flt3 ligand-mediated activation of NK cell cytotoxicity decreases when the tumor mass increases. Our results indicate that Flt3 ligand treatment of tumor-bearing animals does not sufficiently overcome tumor-induced immunosuppression to restore the inhibited functions of dendritic and NK cells and allow complete tumor regression.

Role of tumor cell apoptosis in tumor antigen migration to the draining lymph nodes.

Establishment of an immune response against cancer may depend on the capacity of dendritic cells to transfer tumor Ags into T cell-rich areas. To check this possibility, we used a colon cancer cell variant that yields tumors undergoing complete T cell-dependent rejection when injected into syngeneic rats. We previously demonstrated that immunogenicity of these tumors depended on the early apoptosis of a part of these tumor cells. In this paper we show that fluorescent tumor cell proteins are released from FITC-labeled tumor cells and undergo engulfment by tumor-infiltrating monocytes without a phenotype of mature dendritic cells or macrophages. Fluorescence-labeled mononuclear cells with a phenotype of MHC class II+ dendritic cells are also found in the T cell areas of the draining lymph nodes. Interestingly, no fluorescent cell can be found in lymph nodes after a s.c. injection of Bcl2-transfected apoptosis-resistant tumor cells that yielded progressive tumors. Proliferation of tumor-immune T lymphocytes was induced by dendritic cells isolated from the draining lymph nodes recovered after a s.c. injection of apoptosis-sensitive, but not apoptosis-resistant, tumor cells. These results show that tumor cell apoptosis releases proteins that are engulfed by inflammatory cells in the tumor, then transported to lymph node T cell areas where they can induce a specific immune response leading to tumor rejection.

Heat shock protein 27 enhances the tumorigenicity of immunogenic rat colon carcinoma cell clones.

The REG and PRO cell clones were obtained from a colon adenocarcinoma induced in a BDIX rat by 1,2-dimethylhydrazine. When injected s.c. into syngeneic hosts, REG cells induce tumors that regress in less than 3 weeks, whereas PRO cells, like parental cells, induce progressive tumors. Here, we show that compared to PRO cells, REG cells are more sensitive to cell death induced by anticancer drugs. The small heat shock protein (HSP) 27 is not expressed or inducible in REG clones, whereas it is abundantly expressed and inducible by heat shock in PRO clones. The expression of HSP27 in REG cells increases their resistance to apoptosis in vitro and dramatically enhances their tumorigenicity when injected s.c. into syngeneic rats. HSP27 expression in REG cells both increases tumor size and delays tumor regression. This increased tumorigenicity is associated with a substantial decrease of in vivo tumor cell apoptosis. We conclude that HSP27 expression in malignant cells increases their tumorigenicity in syngeneic animals. In combination with the role of HSP27 in tumor cell resistance to cytotoxic agents, its contribution to tumorigenicity makes this protein a potential target for antitumoral therapy.

Bcl-2-mediated inhibition of apoptosis prevents immunogenicity and restores tumorigenicity of spontaneously regressive tumors.

Tumor cell clones from a rat colon carcinoma differ in their tumorigenicity and immunogenicity. The PRO clones give rise to progressive tumors, whereas the REG clones yield tumors that regress in a few weeks through a specific immune response. REG cells were more sensitive than PRO cells to apoptosis triggered by serum withdrawal in vitro. Furthermore, a fraction of REG cells, but no PRO cells, underwent apoptosis in the hours following injection into syngeneic rats. To further analyze the role of apoptosis, we overexpressed the antiapoptotic protein Bcl-2 in REG cells. Unlike parental or fake-transfected REG cells, Bcl-2-overexpressing REG cells resisted serum withdrawal-induced apoptosis, did not undergo apoptosis at 48 h postinjection into naive syngeneic rats, and gave rise to progressive, metastatic, and lethal tumors. Interestingly, REG-bcl2 cells were rejected by syngeneic hosts that had been preimmunized by an injection of parental REG cells, indicating that Bcl-2 overexpression did not alter tumor cell sensitivity to the effector cells of the immune response. Taken together, these observations indicate that tumor cell apoptosis may contribute to immunogenicity.

Glutathione peroxidase mimics prevent TNFalpha- and neutrophil-induced endothelial alterations.

Based on the assumption that glutathione peroxidase (GPx) activity might be limiting in preventing peroxide-induced impairment of endothelial regulatory functions, we studied the effect of a series of new selenium-containing GPx mimics on endothelial cells exposed to an inflammatory stress. The two compounds that have the highest GPx activity, BXT-51072 and BXT-51077, were shown to be the most efficient inhibitors of leukocyte recruitment by human umbilical vein endothelial cells (HUVEC), upon incubation with neutrophils (10-fold excess over HUVEC) and with 1 ng/ml TNF-alpha for 1 or 3.5 h. When HUVEC were pre- and cotreated with 10 microM of either compound, neutrophil adhesion and endothelial alteration were markedly inhibited, as assessed by immunoassays of myeloperoxidase and von Willebrand factor, respectively. These two GPx mimics were also found to be the most efficient inhibitors of the TNFalpha-induced endothelial expression of P- and E-selectin and of the TNFalpha- or interleukin1-induced endothelial release of interleukin-8. Our results demonstrate that GPx mimics such as BXT-51072 behave as potent antagonists of TNF-alpha and interleukin-1 through the downregulation of endothelial proinflammatory responses.

ICAM-1 and VCAM-1 expression induced by TNF-alpha are inhibited by a glutathione peroxidase mimic.

Intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) are respectively involved in the endothelial recruitment of neutrophils, and in that of lymphocytes or tumor cells, in response to specific signals. We have used the glutathione peroxidase (GPx) mimic BXT-51072 to assess the possibility that endogenous hydroperoxides play a role in the tumor necrosis factor-alpha (TNFalpha)-induced expression of ICAM-1 and VCAM-1 by monolayers of human endothelial cells. The GPx mimic BXT-51072 strongly inhibits the TNFalpha-induced and cycloheximide-sensitive expression of ICAM-1 and VCAM-1. It also inhibits the TNFalpha-induced reorganization of the actin network and the associated formation of stress fibers. Actin reorganization induced by cytochalasin D treatment did not inhibit ICAM-1 expression. Our results are compatible with specific and synergistic effects of endogenous hydroperoxides on the biosynthesis and processing of cell adhesion molecules and cytoskeleton components.

Inflammatory cells infiltrating human colorectal carcinomas express HLA class II but not B7-1 and B7-2 costimulatory molecules of the T-cell activation.

Colon cancer cells express potentially immunogenic proteins but are not rejected by the immune system. To induce an effective immune response, antigenic peptides have to be presented to T lymphocytes by professional antigen-presenting cells in association with HLA class II molecules. Antigen-presenting cells also have to express B7 family molecules, B7-1 and B7-2, which deliver the costimulatory signals that are required to prevent T cell anergy. We studied B7-1 and B7-2 expression by the antigen-presenting cells that infiltrate colorectal cancer stroma. In 25 samples of colorectal carcinomas, a panel of monoclonal antibodies was used to label macrophages, dendritic cells, and T lymphocytes that infiltrate the tumor stroma and the morphologically normal distant mucosa. The expression of HLA class II and B7 molecules involved in T-cell activation was studied using specific monoclonal antibodies. Biopsy pieces from two patients with active Crohn's disease were used as controls. All of the samples were heavily infiltrated by macrophages and/or dendritic cells that strongly expressed HLA class II molecules. In contrast, antibodies to B7-1 and/or B7-2 stained no cells in 16 of the 25 samples of colorectal tumors and less than 1% of the inflammatory cells that infiltrated tumor stroma of the other nine tumor samples. B7 molecules were also poorly expressed by rare cells in the lamina propria of the morphologically normal colorectal mucosa. In contrast, many inflammatory cells that infiltrated the two Crohn's disease samples strongly expressed B7-1 and B7-2, especially in the granulomas. We conclude that most HLA class II+ inflammatory cells that infiltrate colorectal cancers do not express the B7-1 and B7-2 costimulatory molecules. This defect may contribute to the failure of the immune system to recognize tumor cells as antigenic.

Expression of fibronectin ED-A+ and ED-B+ isoforms by human and experimental colorectal cancer. Contribution of cancer cells and tumor-associated myofibroblasts.

Alternative splicing of primary fibronectin (FN) mRNA results in the synthesis of different isoforms. ED-A+ and ED-B+ FN isoforms are absent from plasma FN and are representative of cellular FN. Their expression was studied in human and rat normal colon, in human colorectal carcinomas, and in transplanted tumors derived from a chemically-induced rat colon cancer. In normal colon, only the ED-A+ FN isoform was expressed as a thin deposit between crypt colonocytes and pericryptal myofibroblasts. Conversely, heavy ED-A+ FN deposits and lighter ED-B+ FN expression were found in the stroma of colorectal tumors in association with myofibroblasts surrounding tumor glands. Some colonic cancer cells also contained intracellular FN isoform granules and expressed FN mRNA. Tumor-associated myofibroblasts and some cancer cell lines were able to synthesize and deposit extracellular ED-A+ and ED-B+ FN in vitro. FN isoform deposition by tumor-associated myofibroblasts was not modulated by colon cancer cell-conditioned medium, but was strongly enhanced when myofibroblasts were cultured on colon cancer cell extracellular matrix or on laminin. These results show that the ED-A+ and ED-B+ FN isoforms were overexpressed in colorectal cancer. Cancer cells can deposit these FN isoforms directly and also stimulate their deposition by tumor-associated myofibroblasts.

[Pharmacological modulation of alterations of endothelial cytoskeleton induced by hydrogen peroxyde and by TNF-alpha]. / Modulation pharmacologique des altérations du cytosquelette endothélial induites par le péroxyde d'hydrogène et par le TNF-alpha.

New selenium containing compounds which act as mimics of glutathione peroxidase (GPx) protect vascular endothelial cells (HUVEC) from the toxicity of 140 microM hydrogen peroxide. In the absence of GPx mimic, hydrogen peroxide destroys the tightness of the cellular monolayer and transforms the actin network into compact stress fibers. The pre-treatment of the cells by 4 microM of the lead-compound BXT-51072 for 1 hours inhibits the morphological modifications induced by hydrogen peroxide. This GPx mimic can also prevent the alterations of the endothelial cytoskeleton which are induced by Tumor Necrosis Factor-alpha (TNF-alpha) and which consist in a reorganization of actin filaments with the formation of stress fibers. Fluorescent labeling of polymerized actin has been performed by means of phalloidine coupled with rhodamine. The protective effect of this antioxidant catalyst against the toxicity of hydrogen peroxide and TNF-alpha includes the maintenance of a structural configuration of the cytoskeleton which is required for the function of endothelial barrier.

[Antioxidant and anti-inflammatory protection of vascular endothelial cells by new synthetic mimics of glutathione peroxidase]. / Protection antioxydante et anti-inflammatoire des cellules endothéliales vasculaires par de nouveaux mimes synthétiques de la glutathion peroxydase.

New selenium-containing compounds behave as GPx mimics and protect endothelial cells (HUVEC) from damage upon exposure to 55 microM linoleic acid hydroperoxide or to 200 microM hydrogen peroxide. The simultaneous presence of the GPx mimic and the hydroperoxyde is not necessary, since a pre-treatment of endothelial monolayers with 1 to 10 microM of such compounds, preserves their morphology, their cell density and their longer-term viability. The compounds which are most efficient in this model of oxidative stress also protect endothelial monolayers which have been incubated with an excess (10:1) of polymorphonuclear neutrophils (PMN) and with 1 ng/ml of TNF-alpha, if such monolayers are pre- and co-treated (10 microM). They inhibit the adhesion of activated neutrophils which show-up as polymorphous and very dense particles, in the vicinity of which endothelial alterations can be seen. The inhibition of leucocyte adhesion and that of endothelial activation/alteration have been quantified by means of immunoassays of myeloperoxidase and von Willebrand factor (vWf). The lead-compound BXT-51072 is not a direct inhibitor of the NADPH oxidase of PMN. TNF-alpha alone induces the endothelial release of Interleukin-8 (Il-8) as well as the expression of P- and E-selectin. The extent and the kinetics of inhibition of such processes by compound BXT-51072 would explain several of the effects observed in the presence of PMN. The GPx mimics also inhibit the endothelial production of Il-8 which is induced by Interleukin-1 alpha. Finally, compound BXT-51072 inhibits the endothelial expression of the adhesion factor VCAM-1 which is more slowly induced by TNF-alpha. Such antioxidant catalysts therefore protect endothelial cells from the toxic effects of TNF-alpha through mechanisms which include a down-regulation of cytokines and cell-adhesion factors.

Spectrophotometric assay of superoxide dismutase activity based on the activated autoxidation of a tetracyclic catechol.

A new spectrophotometric assay of superoxide dismutase (SOD) activity is described. The assay is based on the SOD-mediated increase in the rate of autoxidation of 5,6,6a,11b-tetrahydro-3,9,10-trihydroxybenzo[c]fluorene (BXT-01050) in aqueous alkaline solution. This autoxidation yields a chromophore with a maximal absorbance wavelength of 525 nm. The optimized assay of SOD activity is performed at pH 8.8, 37 degrees C, in 50 mM air-saturated 2-amino-2-methyl-1,3- propanediol buffer containing 3 mM boric acid and 0.1 mM diethylenetriaminepentaacetic acid. The kinetic measurement of 525-nm absorbance is performed for 1 min upon addition of BXT-01050. BXT-01050 is stabilized in stock solution acidified at pH 1.5. The SOD activity is determined from the Vs/Vc ratio of the autoxidation rates measured in the presence (Vs) and in the absence (Vc) of sample. One SOD activity unit (U-525) has been defined as the activity that doubles the autoxidation background (Vs/Vc = 2). The equation that fits the standard curve is the same with all studied SODs. Another reagent, 1,4,6-trimethyl-2-vinylpyridinium trifluoromethanesulfonate, directly eliminates interference due to sample mercaptans such as glutathione by means of a very fast alkylation reaction. A fast and reproducible measurement of SOD activity requires only a single determination per sample. At pH 8.8, an optimal assay sensitivity is achieved without strongly affecting the activity of known SODs such as Cu/Zn-, Mn-, or Fe-SOD.