Contrast-enhanced MR imaging of experimental acute tubular necrosis

Purpose: To demonstrate the involvement of the various renal structures in acute tubular necrosis (ATN).

Material and Methods: In 15 rats, using a T1-/T2-weighted sequence, either gadodiamide alone, or gadodiamide in combination with sprodiamide (a susceptibility agent) were used to enhance the various anatomical substrates of the kidney. The results were compared to those of pathological verification.

Results: Experimentally induced ATN of the rat kidney causes profound changes in the medulla, leaving the cortex largely intact. The difference between the normal cortex and the partially necrotic outer medulla, on the one hand, and the papillary region, was significantly enhanced with the combination, whereas a larger region composed of the inner and outer medulla was enhanced after the gadolinium chelate alone.

Conclusion: The results varied considerably between the two procedures; the double contrast demonstrated a clear difference between the inner and outer medulla, and the gadolinium chelate alone demonstrated a clear difference between the medulla and the cortex. These results demonstrated a clear difference in the compartmentalization between the inner and outer medullary regions, providing complementary information about the pathological condition of the kidney.

[Translational research and Cancer Plan]

The French Cancer Plan 2003-2007 has made translational research central to its research programme, to ensure the care-research continuum and the quickest application possible for the most recent discoveries, for the patients' benefit. This is a new field of research, still little-known or ill-understood. A working group, composed of physicians and researchers from academic research and industrial research, sought to define translational research in cancerology and define the issues at stake in it. Translational research needs to develop in close connection with the patients in order to enable a bi-directional flow of knowledge from cognitive research toward medical applications and from observations made on patients toward cognitive research. Placed under the aegis of the French National Cancer Institute and Leem Research, the group has put forth a strategy for implementing translational research in cancerology in France to make it attractive, competitive and efficient and to foster the development of public-private partnerships.

Increase in PGE2 biosynthesis induces a Bax dependent apoptosis correlated to patients’ survival in glioblastoma multiforme

Prostaglandin E(2) plays multiple roles both in the physiology and the physiopathology of human brain, which are not completely understood. We have identified in a subset of human glioblastoma multiforme (GBM) tumors, the most common form of adult brain cancer, an increased expression of mPGES-1, the enzyme which catalyses the isomerization of PGH(2) into PGE(2) downstream of cyclooxygenase 2 (COX-2). The sensitivity of primary cultures of GBM to apoptosis was augmented by the overexpression of mPGES-1, whereas the knockdown of its expression by shRNA decreased the apoptotic threshold in vitro and stimulated tumor growth in vivo. Adding extracellular PGE(2) in the culture medium failed to reproduce mPGES-1 effect on the cell viability in vitro. However, the intracellular injection of PGE(2) induced a dose-dependent apoptosis in GBM cultures, which was dependent on the presence of Bax, a pro-apoptotic protein. We show that PGE(2) physically associates with Bax, triggering its apoptotic-like change in conformation and its subsequent association with mitochondria. Our results raise questions about the role of PGE(2) in the control of apoptosis and in its potential impact in central nervous system pathologies.

Mitochondrial membrane permeabilization produced by PTP, Bax and apoptosis: a 1H-NMR relaxation study

To analyze the involvement of structured water (bound to macromolecules) in apoptosis-induced mitochondrial outer-membrane permeability, we compared the dynamics of water protons from nuclear magnetic resonance (NMR) data in apoptotic liver mitochondria with that of control mitochondria incubated in vitro with free Ca(2+) (opening of the permeability transition pore, PTP) or with Bax alpha. Our results demonstrate that water molecules in apoptotic mitochondria exhibit an accelerated translational motion of structured water common with that induced by the opening of the PTP, but limited in amplitude. On the other hand, no significant quantitative change in structured water was observed in apoptotic mitochondria, a phenomenon also observed with Bax alpha-induced permeability. We conclude that the changes observed in the different water phases differ both quantitatively and qualitatively during the opening of the PTP and the Bax alpha-induced permeability, and that the apoptotic mitochondria exhibit mixed properties between these model situations.

Constitutive presence of cytochrome c in the cytosol of a chemoresistant leukemic cell line

The release of holocytochrome c (cyt c) from mitochondria into the cytosol is reportedly a landmark of the execution phase of apoptosis. As shown here, the P-glycoprotein- (P-gp) expressing K562/ADR cell line (but not the parental K562 cell line) exhibits both cytosolic and mitochondrial cyt c in the absence of any signs of apoptosis. K562/ADR cells were found to be relatively resistant to a variety of different inducers of apoptosis, and blocking the P-gp did not reverse this resistance. The release of cyt c in non-apoptotic K562/ADR cells was not accompanied by that of any other mitochondrial apoptogenic protein, such as AIF or Smac/DIABLO, and was inhibited by Bcl-2 over expression. In addition, using a cell-free system, we show that mitochondria isolated from K562/ADR cells spontaneously released cyt c. These data suggest that cyt c release may be compatible with the preservation of mitochondrial integrity and function, as well as cell proliferation.

Difference in antigenic determinant profiles between human and rat myeloperoxidase

We tested whether rat and human MPO have similar antigenic determinants using 36 human MPO-ANCA positive sera, one mouse anti-rat MPO and four mouse anti-human MPO monoclonal reagents. Purified rat and human MPO were used in ELISA, with or without crossinhibition by preincubation with human MPO or irrelevant antigen in the liquid phase. Only one human MPO ANCA positive serum exhibited significant binding in rat MPO ELISA. This binding was poorly inhibited by preincubation with human MPO in the liquid phase, but was conserved after adsorption of non specific anti-rat activity in a chromatography column. Three mouse anti-human MPO IgG monoclonal antibodies did not recognize rat MPO. Only one mouse anti-human MPO IgA monoclonal antibody bound to rat MPO. This binding was poorly inhibited by preincubation with human MPO (35% at 2 micro g/ml). Conversely, the mouse anti-rat MPO monoclonal did not bind human MPO. We have concluded that: (1) Most human MPO-ANCA recognize antigenic determinants on human MPO which are absent on rat MPO. Therefore, human auto-antibodies bind to epitopes which recently appeared after species evolution; (2) Inversely, the mouse anti-rat MPO monoclonal do not bind human MPO. Therefore, rat MPO epitopes have been altered during species evolution; (3) Mice injected with human MPO preferentially develop antibodies against xeno-epitopes which are not present in rodents. Therefore, human MPO may not be the best antigen to raise ANCA in animal models and (4) A comparison of the amino acid sequences of rat and human MPO may help elucidate the major antigenic epitopes.

Resistance to apoptosis is increased during metastatic dissemination of colon cancer

Apoptosis dysfunction in metastases has been suggested to participate in their poor response to conventional anticancer treatments. To address this question, we have analyzed the sensitivity to cell death induced by non-steroid anti-inflammatory drug, Sulindac, the most common drug used in colon cancer chemotherapy, 5-fluorouracil (5-FU) and the short chain fatty acid, butyrate (Bu) in cell lines derived from a primary colorectal tumor (ALT-I) as well as the liver (ALT-F) and the lymph-node (ALT-G) metastases. We have previously shown both in vitro by analyzing anchorage-independent cell proliferation and in vivo by subcutaneous injection into athymic nude mice that the ALT-F and ALT-G cells were more tumorigenic than the primary ALT-I cells. All these cell lines, derived from an untreated patient, were highly resistant to apoptosis induced by 5-FU and Sulindac but were sensitive to Bu-induced apoptosis. The resistance to apoptosis was, as quantified by the induction of caspase activity and the relative percentage of apoptotic cells, higher in the metastatic cell lines, than in the ALT cell line. When compared to the primary tumor, more anti-apoptotic bcl-2 and less pro-apoptotic bax were expressed in the liver and lymph node metastatic cell lines. Quite remarkably, the expression of bax was up-regulated during Bu-treatment, a feature that could explain its powerful pro-apoptotic activity.

Involvement of the N-terminus of Bax in its intracellular localization and function

We have identified, using site-directed mutagenesis, a proline located at position 13 of Baxalpha (Bax) as crucial for the maintenance of its cytosolic conformation. The substitution of this proline by a valine results in a strong binding of Bax to mitochondria and to conformational changes monitored by a decreased sensitivity of Bax to mild proteolysis and the enhancement of its oligomerization state. Deletion of the C-terminus of Bax does not modify its intracellular localization. On the other hand, the pro-apoptotic activity of Bax is enhanced by a deletion of the C-terminus in the absence of the N-terminus but is decreased in its presence. These results suggest that both extremities functionally interact to control the activity but not the subcellular localization of Bax.

Standardized generation of fully mature p70 IL-12 secreting monocyte-derived dendritic cells for clinical use

Dendritic cells (DC) have been shown to be efficient antigen-presenting cells (APC) and, as such, could be considered ideal candidates for cancer immunotherapy. Immature DC (iDC) efficiently capture surrounding antigens; however, only mature DC (mDC) prime naive T lymphocytes. Clinical trials using DC-based tumor vaccines have achieved encouraging, but limited, success, possibly due to the use of immature or incompletely mature DC. Thus, it was apparent that a method capable of generating large numbers of fully functional iDC, their pulsing with desired form of tumor antigens and the subsequent complete and reproducible maturation of iDC is needed. Therefore, we compared two different methods of producing large numbers of iDC. Both protocols yielded comparable numbers of cells with an iDC phenotype with phagocytic function. We next determined which of the clinically applicable activators could induce the complete and reproducible maturation of DC, in order to define the most suitable combination for future clinical trials. Only a combination of TNFalpha + Poly (I:C), or a previously described cytokine cocktail of TNFalpha + IL-1beta + IL-6 + prostaglandin E2, induced the complete activation of the whole DC population, as assessed by the cell surface expression of CD83 and costimulatory molecules. The matured DC were functionally superior to iDC in their ability to stimulate the proliferation of allogeneic lymphocytes and autologous keyhole limpet hemocyanin (KLH)-specific T lymphocytes. Furthermore, only the combination of TNFalpha + Poly (L:C) activated DC to produce large amounts of biologically active p70 IL-12. Thus DC maturation by TNFalpha + Poly (I:C) could efficiently bias T cell response towards Th1 response. Implementation of our results into clinical protocols used for DC generation could be beneficial for future immunotherapy trials.

Hepatocyte-mediated transport to the bile of AMI-HS, a particulate contrast agent

RATIONALE AND OBJECTIVES

The elimination of hepatocyte-directed particulate contrast agents has not been studied in the same detail as particles eliminated mainly by the mononuclear phagocyte system. The aim of the present study was to elucidate the fate of these particles by a multidisciplinary approach.

METHODS

After intravenous injection of AMI-HS particles directed to the hepatocytes, rats were killed and cytological studies, by both electron microscopy and histochemistry, and spectroscopic studies of the bile were performed. The data were compared with a dynamic magnetic resonance study of the heart and liver.

RESULTS

The particles were rapidly cleared from the blood by Kupffer cells and hepatocytes and then found first in the vascular and later in the biliary pole of the hepatocytes. After 24 hours, a relaxometric characterization of the bile showed the presence of unchanged particles in the bile.

CONCLUSIONS

These results show the capacity of the liver to excrete unchanged AMI-HS particles directly into the bile.

Induction of chemoresistance in HL-60 cells concomitantly causes a resistance to apoptosis and the synthesis of P-glycoprotein

The appearance of multidrug-resistant (MDR) proteins or the acquisition of a defective apoptotic programme are major drawbacks in the treatment of cancers since both induce a resistance to classical chemotherapy. However, a link between the two mechanisms has not, as yet, been clearly established. In this study, HL-60 cells cultured in the continual presence of a sub-lethal dose of doxorubicin (dox; HL-60/Dox) were used as a model to study acquired chemoresistance. During the induction of chemoresistance, the appearance of a functional P-glycoprotein (P-gp), in addition to the expression of anti-apoptotic Bcl-2, Bcl-XL and pro-apoptotic Bax proteins was assessed. Parental cells which are sensitive to dox, have no P-gp activity and express Bcl-2 and Bax. After 4 weeks of treatment, a functional P-gp was detected in HL-60/Dox cells. In addition, the synthesis of Bcl-2 appeared to be replaced by Bcl-XL while that of Bax remained unchanged. These cells were also resistant to apoptosis induced by both P-gp and non-P-gp substrates. This inability to induce apoptosis could have resulted from the induction of the expression of the inhibitor of apoptosis protein (XIAP). Our data show that acquired chemoresistance could involve a parallel induction of P-gp and an impairment of the apoptotic pathway.

Cytokine mRNA expression in mouse colon: IL-15 mRNA is overexpressed and is highly sensitive to a fibre-like dietary component (short-chain fructo-oligosaccharides) in an Apc gene manner

On the basis of studies using the Min mouse model of colon carcinogenesis, we have recently proposed that a fibre-like food (short-chain fructo-oligosaccharides, sc-FOS) fermented in the colon may stimulate a mechanism of cancer immunosurveillance. In the present paper, we have investigated the expression of cytokines as potential effector molecules. Interleukin (IL-)4, IL-5, IL-13, IL-15 and interferon (INF)-gamma mRNAs were detected by a multi-probe ribonuclease protection assay in C57BL/6J and Min mouse colons. IL-15 mRNA expression was significantly amplified (P=0.01) by the sc-FOS-enriched diet in the colon of Min mice.

Expression of bcl-2, bax and bcl-xl in human gliomas: a re-appraisal

We have analyzed the expression of the anti-apoptotic proteins bcl-2, bcl-xl and that of bax, a pro-apoptotic protein, in human WHO grade II astrocytomas (LGA) and WHO grade IV glioblastoma multiforme (GBM). Tumors were obtained immediately after surgical resection and were analyzed by immunohistochemistry (IHC), laser confocal microscopy (LCM) and immunoblots. Both IHC and immunoblot analysis indicated that the expression of bcl-xl was not significantly different between LGA and GBM. IHC indicated that the expression of bcl-2 was inversely correlated to the grade of the tumors (i.e more cells were bcl-2 positive in LGA than in GBM) while the expression of bax was unaffected by the grade of the tumor. In contrast, immunoblots revealed a parallel increase in the expression of bcl-2 and bax from the low to high grade tumor, suggesting a co-regulation of the expression of these two proteins during tumoral progression. Confocal analyses provide us with another possible level of complexicity in the regulation of apoptosis in these tumors, as these markers exhibited different subcellular localizations: bcl-2 was strictly associated with mitochondria and bcl-xl was present in both cytosolic and mitochondrial compartments while bax was found essentially in the cytosol of the tumoral cells. Taken together, our data suggest that the role of bcl-2 related proteins could be regulated at different levels in human astrocytomas (expression, subcellular localization, antigen exposure ...) which should be studied by different techniques.

Only fibres promoting a stable butyrate producing colonic ecosystem decrease the rate of aberrant crypt foci in rats

BACKGROUND

Dietary fibres have been proposed as protective agents against colon cancer but results of both epidemiological and experimental studies are inconclusive.

AIMS

Hypothesising that protection against colon cancer may be restricted to butyrate producing fibres, we investigated the factors needed for long term stable butyrate production and its relation to susceptibility to colon cancer.

METHODS

A two part randomised blinded study in rats, mimicking a prospective study in humans, was performed using a low fibre control diet (CD) and three high fibre diets: starch free wheat bran (WB), type III resistant starch (RS), and short chain fructo-oligosaccharides (FOS). Using a randomised block design, 96 inbred rats were fed for two, 16, 30, or 44 days to determine the period of adaptation to the diets, fermentation profiles, and effects on the colon, including mucosal proliferation on day 44. Subsequently, 36 rats fed the same diets for 44 days were injected with azoxymethane and checked for aberrant crypt foci 30 days later.

RESULTS

After fermentation had stabilised (44 days), only RS and FOS produced large amounts of butyrate, with a trophic effect in the large intestine. No difference in mucosal proliferation between the diets was noted at this time. In the subsequent experiment one month later, fewer aberrant crypt foci were present in rats fed high butyrate producing diets (RS, p=0.022; FOS, p=0.043).

CONCLUSION

A stable butyrate producing colonic ecosystem related to selected fibres appears to be less conducive to colon carcinogenesis.

The substitution of the C-terminus of bax by that of bcl-xL does not affect its subcellular localization but abrogates its pro-apoptotic properties

The interaction of the anti-apoptotic members of the Bcl-2 family with mitochondria, through their hydrophobic C-terminus, has been proposed to play a crucial role in the execution phase of apoptosis. We report here that a substitution of the C-terminal end of pro-apoptotic bax by that of anti-apoptotic bcl-xL (baxCxL) does not modify its association with mitochondria in human and rat cells or in Saccharomyces cerevisiae. In addition, while bax sensitizes these cells to apoptotic stimuli, the construct baxCxL does not affect the apoptotic response in transfected cells. These results suggest that the C-terminus of bax plays an important role in apoptosis independently of its membrane addressing/targeting mechanism.

Identification of an apoptotic cleavage product of BARD1 as an autoantigen: a potential factor in the antitumoral response mediated by apoptotic bodies

We have shown previously that rats can be cured from induced peritoneal colon carcinomatosis by injections of apoptotic bodies derived from tumor cells and interleukin 2. This curative treatment generated a tumor-specific cytotoxic T-cell response associated with a humoral response. Autoantibodies from sera of cured rats strongly recognized a Mr 67,000 protein from apoptotic bodies and weakly reacted with a protein of Mr approximately 97,000 in PROb parental cells. We now show that these autoantibodies are directed against BARD1, originally identified as a protein interacting with the product of the breast cancer gene 1, BRCA1. We demonstrate that the Mr 67,000 antigen is a cleaved form of BARD1 present in apoptotic bodies derived from rat and human colon and mammary carcinoma cell lines. Moreover, we show that the cleavage site of BARD1 is located NH2 terminally but downstream of the RING domain essential for BARD1 and BRCA1 protein interaction. In vitro studies using [35S]methionine-labeled human BARD1 and apoptotic cellular extracts derived from SW48 carcinoma cells indicate that BARD1 proteolysis occurs at an early stage of apoptosis and in a cell cycle-dependent manner. This hydrolysis is inhibited by EGTA, and the calpain inhibitor I, N-acetyl-leu-leu-norleucinal, but not by several caspases inhibitors, suggesting that BARD1 is hydrolyzed by the calcium-dependent cysteine proteases, calpains. Thus, the highly immunogenic form of cleaved BARD1 could contribute to the antitumoral response mediated by apoptotic bodies.

Influence of bcl-2-related proteins on matrix metalloproteinase expression in a rat glioma cell line

The expression of bcl-2-related proteins has been shown to be a key element in tumoral malignancy. The degradation of the extracellular matrix (ECM) by specialized matrix metalloproteinases (MMPs) is another major step in tumor invasion and metastasis. We have examined, in a rat glioma cell line A15A5, the effect of the stable transfection of human bcl-2, bax and bcl-xl on MMPs expression. Using a zymographic assay, we found that all transfected cell lines expressed a gelatinase activity which is predominantly associated with MMP-9. In bcl-2 and bcl-xl transfected cells, the transcription of MMP-9 was decreased compared to that of control or bax transfected cells. In addition, in bax transfected A15A5, we observed a down regulation of TIMP-1, the inhibitor of MMP-9. These results suggest that the ratio between MMP-9 and its inhibitor TIMP-1 is tightly controlled in cells overexpressing bcl-2 related proteins (i.e., high ratio in bax transfected A15A5 and low ratio in bcl-2 transfected A15A5). However, MMPs secreted by bcl-2 transfected cells were still capable of hydrolyzing FasL present on human lymphocytes. Our results suggest that the expression of bcl-2 related proteins could participate in the regulation of MMP-9/TIMP-1 in gliomas.

Role of antigen-presenting cells in long-term antitumor response based on tumor-derived apoptotic body vaccination

Cellular therapy prospects for cancer are based on the development of T cell response, resulting in efficient tumor rejection and long-term protection. We have previously shown that treatment combining injection of interleukin-2 and tumor-derived apoptotic bodies, but not tumor cell extracts, permits to reject parental tumor in 40% of rats. We observed the implication of antigen-presenting cells (APCs) and tumor-derived apoptotic bodies in the rejection of established peritoneal carcinomatosis. We demonstrated that apoptotic bodies could be efficiently phagocytosed by monocytes, triggering them to an APC phenotype. When using these phagocytosing APCs, derived from peritoneal or blood monocytes, the remission rate reached 80% of rats. However, due to the lack of specific markers of rat monocyte-derived cells, the precise role of APCs, dendritic cells and/or macrophages responsible for this therapeutic improvement remained to be clarified. In order to elucidate this question, we developed an in vivo preventive cellular therapy based on tumor-derived apoptotic bodies, where macrophages were either depleted or activated. We report here that in a preventive antitumoral apoptotic body vaccination that allows survival for 40% of treated rats, the antitumor response was characterized by a specific long-term memory (cured rats rejected a second parental tumor cell challenge). Depletion of resident macrophages with silica or clodronate liposomes appeared to promote apoptotic body vaccination efficiency, increasing the treatment to 66% of success. In this case, FACS analysis showed that peritoneal cells present are essentially immature APCs and freshly recruited NK cells. In contrast, the onset of peritoneal inflammation by thioglycollate, inducing massive recruitment and activation of macrophages, reduced the overall survival, whatever the treatment was. Also, even though the surviving rate was better in silica-treated rats than control, no long-term protection was elicited. Our data suggest that massive inflammation, recruiting numerous activated macrophages, could inhibit tumor antigen presentation by 'professional' APCs having phagocytosed apoptotic bodies, and defavor a specific antitumoral T cell response. Although effective responses were developed against parental tumor cells with silica/apoptotic body treatment, they seemed only partial, limited to primary cytotoxic efficiency. In conclusion, even if macrophages did not appear necessary for a primary response to tumor cells, these cells seemed to be implicated in the establishment of memory and long-term antitumor response.

Phase I trial of interleukin-2 and high-dose arginine butyrate in metastatic colorectal cancer

INTRODUCTION

Interleukin-2 (IL-2) and sodium butyrate allow rats to be cured of peritoneal carcinomatosis from colon cancer. We performed a phase I trial of IL-2 and high-dose arginine butyrate (ArgB) in patients with advanced metastatic colorectal cancer.

PATIENTS AND METHODS

From April to July 1997, six patients were included in the trail; they had a median age of 52 years, four had a performance status of 0, two had a performance status of 1 with normal biological functions. All patients had received at least two prior lines of chemotherapy. A fixed dose of 18 MIU/m2 IL-2,was administered by subcutaneous injection and ArgB was delivered via continuous intravenous infusion on days 1-6 with escalating doses starting at 2 g kg(-1) day(-1).

RESULTS

The planned dose escalation was not possible because of toxicities. A daily ArgB dose of 2 g/kg was delivered for nine cycles. Level 2 (4 g/kg) could not be delivered in three of the six patients because of liver toxicity. The dose-limiting toxicities were fatigue and liver function disturbances. The maximum tolerated dose for ArgB was 3 g kg(-1) day(-1), in combination with IL-2 at 12 MIU m2 day(-1). No clinical response was seen. Pharmacokinetic analysis showed large intra- and interindividual variations.

CONCLUSION

This schedule with a high dose of ArgB proved to be highly toxic with liver insufficiency. We will be running another trial with lower doses of ArgB calculated from the schedule used in the experimental model, starting at a dose of 20 mg kg(-1) day(-1) for ArgB and 200000 UI kg(-1) day(-1) IL-2, every 8 h.

Role for alpha1,2-fucosyltransferase and histo-blood group antigen H type 2 in resistance of rat colon carcinoma cells to 5-fluorouracil

5-Fluorouracil (5-FU) is a drug of standard use in chemotherapy of colon carcinoma. However, its efficacy is limited by inherent and acquired cell resistance. Major changes in histo-blood group antigenic expression, at times associated with poor prognosis, occur on colon cancer cells. To assess whether these antigens might play a role in the resistance to 5-FU, a rat model of colon carcinoma was used. We observed that in vivo treatment of tumors with the drug increased expression of antigen H type 2. The increase was also observed after in vitro short-term exposure to 5-FU, as well as on a cell-resistant variant selected by continuous exposure to the drug, and was accompanied by an increase in alpha1,2-fucosyltransferase activity, the key enzyme involved in synthesis of H antigens. Transfection of cells devoid of this enzymatic activity by an alpha1, 2-fucosyltransferase cDNA allowed expression of H type 2 antigen and increased resistance to 5-FU. Inversely, transfection of cells which possess enzymatic activity by a cDNA in anti-sense orientation reduced both H type 2 cell-surface antigen and resistance to the drug. These results demonstrate that, in this experimental model, alpha1,2-fucosyltransferase and H type 2 antigen are involved in cellular resistance to 5-FU.

T cell status influences colon tumor occurrence in min mice fed short chain fructo-oligosaccharides as a diet supplement

We have previously shown that addition of short chain fructo-oligosaccharides (indigestible carbohydrates) to food prevented colon tumors in C57BL/6-Apc(Min/+) mice, a model for human colon cancer. As gut-associated lymphoid tissue was concomitantly developed, we suggested that the immune response generated by this food may interfere with carcinogenesis due to involvement of mucosal cells in the regulation of tissue homeostasis. In the present experiment, we tested whether T cell status may influence colon tumor formation in Min mice fed a food supplement of short chain fructo-oligosaccharides. Min mice depleted of CD4(+) and CD8(+) lymphocytes developed twice as many tumors as immunocompetent mice (0.8 as compared with 0.4, the mean number in 7-week-old Min mice when food supplementation began; P = 0.02). It is concluded that food supplementation with a substrate (a known prebiotic) fermented in the colon may stimulate a mechanism of immunosurveillance that would otherwise remain inefficient.

Production and characterisation of a monoclonal antibody specific for apoptotic bodies derived from several tumour cell lines

We have recently shown that apoptotic bodies (apobodies) derived from rat colon carcinoma cell lines (PROb) after sodium butyrate (NaB) treatment were able to cure rats with induced peritoneal carcinomatosis ( [BOISTEAU] ). A specific immune response was assumed to be involved since the serum of cured rats contained antibodies specific for apobodies. In the present study, a mAb (clone 6E8) produced by immunisation of rats with apobodies strongly recognized apobodies but had little reactivity with parental tumour cell lines, as demonstrated by enzyme-linked immunosorbent assay (ELISA), immunostaining and flow cytometry. Immunoelectron microscopy showed that 6E8 mAb mainly stained the hyaloplasm or cytosol of apobodies. A protein was detected at 67 kDa by immunoprecipitation of apobodies with mAb, followed by immunoblotting, using serum of rats immunised with apobodies. The 6E8 mAb recognized apobodies derived from several rat or human colon cancer cell lines and a rat glioma cell line, regardless of the apoptosis stimulus used (NaB, staurosporine or UV). Our results clearly show that 6E8 mAb defines an epitope specifically generated during apoptosis, which suggests that the protein recognized may be involved in the molecular cascade of apoptotic cell death.

Antigen-presenting cells that phagocytose apoptotic tumor-derived cells are potent tumor vaccines

We have reported recently that treatments combining injections of apoptotic bodies from tumor cells and interleukin 2 led to tumor regression and induced specific protection. In the present study, we show that tumor-bearing rats were cured with an 80% success rate by injection of antigen-presenting cells (APCs) that had phagocytosed apoptotic bodies derived from poorly immunogenic tumor cells, whereas phagocytic cells exposed to nonapoptotic tumor cell extracts were essentially without effect. In addition, curative vaccination using APCs that had phagocytosed apoptotic bodies generated a tumor-specific cytotoxic T-cell response and long-term protection from parental tumor challenge. Thus, systems using the processing and presentation of antigenic molecules by professional APCs after phagocytosis of apoptotic bodies appear to offer new possibilities for anticancer treatment.

The C-terminus of bax is not a membrane addressing/anchoring signal

It has been suggested that BCL-2 family members associate with certain organelles through their hydrophobic C-terminus which in the case of bcl-2, appears to play a key role in the regulation of apoptosis. We have investigated the association of bax with microsomal, nuclear and mitochondrial membranes using a cell-free system and found, contrary to bcl-2, that bax binds poorly to these organelles. Deletion of the C-terminal of bax (baxDeltaC) or exchanging the C-terminal ends of bax and bcl-XL suggests that the bax C-terminus is not an addressing/anchoring signal. In agreement with this observation, HL-60 cells transfected with either bax or baxDeltaC show no difference in sensitivity to an apoptotic signal. In the cell-free system, at low pH, bax becomes associated with mitochondria after a change of conformation, a result consistant with its structural homology with certain bacterial toxins. In HL-60 cells, as observed in the cell-free system, bax acquired a protease resistant conformation upon its translocation from the cytosol to the mitochondria after the induction of apoptosis.

Electron microscopy study of intrahepatic ultrasmall superparamagnetic iron oxide kinetics in the rat. Relation with magnetic resonance imaging

Ultrasmall superparamagnetic iron oxide (USPIO) contrast agents for use in magnetic resonance imaging (MRI) are currently undergoing clinical evaluation. However, the images observed and the kinetic profiles obtained differ from one agent to another. In this study, BD IX rats received an intravenous penis injection of the USPIO contrast agents AMI-HS and AMI-227. A cytologic study of the liver was performed, and the data obtained were compared with those of MRI. Images acquired in light microscopy, transmission electron microscopy, microanalysis and electron diffraction provided data on the cell categories involved in the processing of these contrast agents, the importance and modalities of each category relative to this processing, and the modalities of agent elimination. AMI-HS was rapidly removed from the bloodstream by Kupffer's cells and hepatocytes and then eliminated through bile ducts. AMI-227 remained much longer in the blood compartment since it was processed very slowly by endothelial and Kuppfer's cells in the near absence of hepatocytic participation and thus of elimination by the bile ducts. These results allowed us to base our interpretation of MRI sequences on cytologic observations.

Immunomodulatory effects of tumor-associated fibroblasts in colorectal-tumor development

In order to elucidate the role of myofibroblasts in tumor development, we compared fibroblastic reactions and their implications in the immune response in progressive and regressive rat colorectal-tumor models. Immunohistochemical analyses revealed that T lymphocytes and monocytes/macrophages were found outside progressive tumors that were surrounded by a large sheath of myofibroblasts. In vitro experiments using fibroblast- vs. myofibroblast-containing collagen gels showed that the mechanical properties of these tumor-activated myofibroblasts prevent penetration of T lymphocytes and macrophages within tumor nodules. These results indicate that tumor-activated myofibroblasts may prevent physical contact between cancer-cells and immune cells, an essential phenomenon for effective destruction of cancer cells. Successful immunotherapy against cancer should therefore include complementary treatments against these tumor-associated fibroblasts.

Increased tumorigenicity of rat colon carcinoma cells after alpha1,2-fucosyltransferase FTA anti-sense cDNA transfection

Accumulation of histo-blood group antigens such as Lewis b, Lewis Y and H increases tumor cell motility and tumorigenesis. Alpha1,2-fucosylation is a key step in the synthesis of these antigens. Two alpha1,2-fucosyltransferases, expressed in colorectal carcinomas, have been characterized (FUT1 and FUT2 in humans, FTA and FTB in rats). To define the relative contribution of each of these enzymes in tumor cell behavior, we have used an anti-sense transfection approach in rat colon carcinoma PROb cells, which synthesize mRNA encoding for both enzymes. We have previously reported that anti-sense transfection of a cDNA fragment of the FTB enzyme decreased H antigenic cell-surface levels and concomitantly decreased tumorigenicity. H antigens, detected by antibodies specific for H type 1, 3 or 4, were detected only on a splice variant of CD44 containing the product of exon v6. We now report the anti-sense transfection of an FTA cDNA fragment into PROb cells, which resulted in decreased enzymatic activity on a type 2 precursor and decreased cell-surface H type 2 antigen exclusively. Compared to controls, FTA anti-sense-transfected cells were significantly more tumorigenic in syngeneic animals but not in immunodeficient SCID mice. The UEA-I lectin, specific for H type 2, revealed that these structures were present on the CD44v6 variant and on an uncharacterized 80-kDa glycoprotein. Our results indicate that FTA and FTB fucosylate distinct glycan chains in the same cell, leading to opposite effects, under control of the immune system.

Potentiation of apoptosis by mitochondria in a cell-free system

Using a cell-free system, we show that rat liver mitochondria, but not mitochondrial extracts, potentiated apoptosis triggered by cytosols derived from apoptotic cells. Apoptosis potentiated by mitochondria appeared to be inhibited by caspase 3 but not by caspase 1 inhibitors. A cytosolic caspase-3-like activity was increased by the addition of mitochondria to apoptotic cytosols; the latter activation was inhibited by the addition of bcl-2. Chelation of calcium by EGTA significantly and specifically inhibited the apoptosis potentiated by mitochondria as well as the increase of caspase-3-like activity. The incubation of mitochondria with apoptotic cytosols led to the release of cytochrome c, this latter phenomenon being inhibited by EGTA. Calcium or cytochrome c and dATP, however, did not reproduce the mitochondrial potentiation in the absence of the organelle. Thus, mitochondria can initiate and potentiate apoptosis through similar but not identical mechanisms.

Interleukin-2/sodium butyrate treatment cures rats bearing liver tumors after acquired 5-fluorouracil resistance

We studied the effect of immunotherapy using recombinant interleukin-2 (rIL-2) in combination with a differentiating agent, sodium butyrate (NaBut), on experimental 5-fluorouracil (5-FU)-resistant liver metastasis from colorectal cancer in rats. For this purpose, we used direct liver injection of 5-FU resistant cells, PRObRI, in syngeneic BDIX rats to establish liver tumors. The growth of liver metastasis was followed before and after NaBut/rIL-2 treatment by magnetic resonance imaging (MRI). The presence of liver tumors was checked by MRI 7 days after tumor cell injection. Evaluable rats were then assigned randomly to a control and an experimental group. The different treatments were started on day 10 and administered intraperitoneally (i.p.). Combined NaBut/rIL-2 treatment followed by MRI on days 56 and 91 was shown both to significantly reduce the growth of liver tumors and to prevent extrahepatic spread. In addition, NaBut/rIL-2 treatment induced a complete regression in 50% of the rats which remained free of disease.

Effect of resistant starch and/or fat-soluble vitamins A and E on the initiation stage of aberrant crypts in rat colon

This study reports the modulating effects of resistant starch (RS) and the fat-soluble vitamins A or E, alone or in combination, on initiation of preneoplastic lesions in rat colon aberrant crypt foci (ACF) induced by 1,2-dimethylhy-drazine. One group of male Sprague-Dawley rats was fed a basic diet and five groups were fed experimental diets supplemented with 25% RS, 200 IU vitamin A, 5 IU vitamin E, 25% RS + 200 IU vitamin A, or 25% RS + 5 IU vitamin E for four weeks. After induction by 1,2-dimethylhydrazine, all the animals were fed basic diets for four more weeks before sacrifice. Compared with the basic diet, only the vitamin A-supplemented diet significantly reduced the incidence of ACF. The vitamins incorporated in the animals' diets increased the vitamin concentrations in hepatic and colonic cells compared with the animals fed the basic diet. The preventive effect of vitamin A seems to be due to a direct effect on colonic epithelial cells. The three diets supplemented with RS significantly decreased cecal pH and bacterial beta-glucuronidase activity and increased cecal weight and fecal output. The retrograde high-amylose maize, type 3, used in this study does not significantly decrease ACF. This RS has an effect on the colon similar to that of nonstarch polysaccharides. Neither biochemistry nor four weeks of dietary supplementation is likely sufficient for adaptation of the rat colonic flora.

Induction of antigen presentation by macrophages after phagocytosis of tumour apoptotic cells

Due to their resistance to classical chemotherapies, most human colorectal cancers have a high incidence and a poor prognosis. Immunotherapy using interleukin 2 (IL2) has provided disappointing results in the treatment of these cancers. Recently, however, we have demonstrated that a treatment combining a cell-differentiating agent, sodium butyrate (NaBut) with IL2 resulted in a remission of established peritoneal colorectal carcinomatosis in rats. Separately, neither NaBut nor IL2 treatment cured these tumour-bearing rats. NaBut is known to induce cell differentiation and subsequent apoptosis in epithelial cells, while IL2 stimulates the immune cells capable of participating in tumour rejection. We postulated that the significant therapeutic effect of NaBut/IL2 treatment could be attributed to a NaBut-induced increase in the immunogenicity of the cancer cells. We report here that NaBut induced an apoptotic process in rat colon tumour cells in vivo and in vitro. We observed, in an efficient cure, colocalization of apoptotic bodies and monocytes/macrophages at the periphery of the tumour. We propose that these apoptotic bodies are phagocytosed in vivo by the macrophages. We also showed in vitro that a subpopulation of macrophages involved in the phagocytic clearance of apoptotic cells expresses cell surface molecules associated with antigen presentation and stimulates the proliferation of naive splenocytes. Our data suggest that therapies that recruit massive induction of the apoptotic process in tumour cells could favour tumour antigen presentation via their specific phagocytosis by antigen-presenting cells (APCs). We propose that the development of specific therapies that stimulate both tumour cell apoptosis and the immune system could offer new opportunities in anti-cancer treatments of poorly immunogenic cancer cells.

Induction of a caspase-3-like activity by calcium in normal cytosolic extracts triggers nuclear apoptosis in a cell-free system

Calcium is involved in several steps of the apoptotic process. In nuclei, endonucleases are presumed to be the main targets of calcium; however, little is known about its role during the cytosolic phase of apoptosis. We used a cell-free system to address this question. Our results show that CaCl2 triggered nuclear apoptosis (i.e. typical morphological change and DNA fragmentation) at concentrations of 5 mM. This concentration was lowered 10-fold by the co-incubation with cytosolic extracts from nonapoptotic cells. Apoptotic changes induced by the incubation of nuclei with CaCl2 in the presence of these cytosols were strongly reduced in the presence of an inhibitor of caspase-3 and to a lesser extent by an inhibitor of caspase-1. We also show that calcium-induced apoptosis is affected by protease inhibitors such as N-tosyl-L-phenylalanine chloromethyl ketone, but not by calpain or several lysosomal protease inhibitors. The addition of CaCl2 to the cell-free system increased a caspase-3 activity in nonapoptotic cytosols as shown by specific antibodies and an enzymatic assay. No activation of a caspase-3-like activity by the addition of cytochrome c was observed in these extracts under similar conditions. The enhanced caspase-3 activity induced by calcium was inhibited by protease inhibitors affecting morphological nuclear apoptosis except for those responsible for the degradation of lamin A. These results suggest that CaCl2 could trigger, in normal cells, an apoptotic cascade through the activation of cytosolic caspase-3 activity.

Synergistic effects of relaxation and susceptibility in differentiation between compartmentalized and noncompartmentalized tissues

RATIONALE AND OBJECTIVES

This study illustrates the synergistic effects of relaxation- and susceptibility-based contrast enhancement. Using a combination of gadolinium (Gd) and dysprosium (Dy) complexes and a sequence capable of taking advantage of the particular relaxation behavior of this combination, the difference between compartmentalized and noncompartmentalized regions was significantly enhanced.

METHODS

Magnetic resonance imaging of the rat kidney was performed before and immediately after the administration of a combination of Gd and Dy chelates (Gd-DTPA-BMA and Dy-DTPA-BMA).

RESULTS

The signal intensity (SI) of the renal parenchyma was reduced by 85%, whereas the collecting tubes had a 100% increase of their SI as demonstrated by a short repetition time (600 msec), long echo time (50 msec), and spin-echo sequence.

CONCLUSIONS

The high R2* effect, specific to the compartmentalized tissues, associated with the moderately high R1 and R2 developed in the remaining areas, results in an important improvement in tissue differentiation, which potentially is useful for the evaluation of pathological changes as in tubular necrosis.

5-Fluorouracil-resistant colonic tumors are highly responsive to sodium butyrate/interleukin-2 bitherapy in rats

Advanced colorectal cancer is generally refractory to 5-fluorouracil (5-FU) chemotherapy. This is linked to the emergence of resistant cell populations, probably due to a selection process. The identification of molecular markers and the improvement of alternative therapies thus remain important. We have used as an experimental model a rat colon cancer cell line (PROb), which exhibits features similar to those of the human situation. 5-FU treatment of rats bearing PROb tumors enhanced their survival but did not lead to cure. A PROb 5-FU-resistant subline (PRObR1) was obtained by continuous in vitro exposure to 5-FU. Resistance to 5-FU was accompanied by a 2-fold increase in thymidylate synthase activity and a substantially higher incorporation of thymidine in the presence of 5-FU, compared with parental PROb cells. Unexpectedly, in syngeneic rats, PRObR1 tumors exhibited delayed growth when compared with parental PROb tumors. This was ascribed to an increased sensitivity of PRObR1 cells to host immune response since no growth delay was observed in immunocompromised nude mice and since there was no detectable difference in proliferation rates between PROb and PRObR1 cells. 5-FU treatment was inefficient in prolonging the survival of rats bearing PRObR1 tumors. In contrast, an immunotherapeutic protocol combining sodium butyrate and recombinant interleukin-2 (NaBut/rIL-2) cured 80% of the rats bearing established PRObR1 tumors. Our results suggest that NaBut/rIL-2 treatment is efficient against 5-FU-chemoresistant rat colon cancer.

Delineation of liver necrosis using double contrast-enhanced MRI

The purpose of this study was to demonstrate the potential usefulness of the combination of gadolinium and dysprosium to enhance the different between normal and necrotic liver tissue. Small regions of acute necrosis were induced by injecting 200-300 microliters of 95% alcohol into the liver of 26 rats. MRI was performed 24 hours after necrosis induction, before and immediately after injection of one or both contrast agents. Using a mixed T1/T2-weighted sequence, the signal intensity of (SI) of the normal liver was reduced by 70%, whereas the necrotic regions had more than a 50% increase in SI after double contrast. The region that was enhanced corresponded largely with the region of necrosis as observed postmortem. The lesion size, when identified, was largely underestimated using either of the agents along, albeit using the common pulse sequences. The double contrast effect of simultaneous administration of gadolinium and dysprosium allows accurate delineation of liver necrosis.

Increase of rat colon carcinoma cells tumorigenicity by alpha(1-2) fucosyltransferase gene transfection

Fucosylated histo-blood group antigens such as Lewis b, Lewis Y, and H accumulate in colon carcinoma and this is accompanied by a clear increase in alpha(1-2)fucosyltransferase activity, a key enzyme for the biosynthesis of these antigens. Yet the biological significance of alpha(1-2) fucosylated structures is not well defined. We have transfected a poorly tumorigenic rat colon carcinoma cell line with the human H blood group alpha(1-2)fucosyltransferase cDNA. This resulted in cell surface expression of H antigens with a concomitant decrease of sialic acid substituted and free beta-galactosides. Immunoprecipitation experiments showed that H antigens were essentially borne by variants of CD44 carrying amino acid sequences encoded by exon v6. The transfected cells showed increased motility in a wound healing assay, without changing their proliferation rates. Parental and control cells transfected with an empty vector formed small tumors that always regressed after 30 days when injected subcutaneously to syngeneic rats. In contrast, alpha(1-2)fucosyltransferase transfectants were able to form progressive tumors. Increased tumorigenicity was also visible in nude mice. These results demonstrate that alpha(1-2)fucosylated antigens contribute directly to aggressiveness of colon carcinoma cells. This could occur by altering a function of CD44 variants.

Short-chain fructo-oligosaccharides reduce the occurrence of colon tumors and develop gut-associated lymphoid tissue in Min mice

C57BL/6J-Min/+ mice, which are heterozygous for a non-sense mutation in the Apc gene, provide a model for both familial adenomatous polyposis and sporadic colon cancers. In our study, gut tumors and small intestine lymphoid nodules were counted in Min mice fed fiber-enriched diets for 6 weeks. Neither starch-free wheat bran nor resistant starch modified the number of tumors. However, short-chain fructo-oligosaccharides dramatically reduced the incidence of colon tumors and concomitantly developed gut-associated lymphoid tissue. Our experiment shows that short-chain fructo-oligosaccharides counteract advanced stages of colon carcinogenesis, possibly via stimulation of antitumoral immunity by modulation of the colonic ecosystem.

Apoptosis induced by sodium butyrate treatment increases immunogenicity of a rat colon tumor cell line

We have recently demonstrated that a treatment combining the cell differentiating agent sodium butyrate (NaBut) and interleukin-2 (IL2) resulted in a remission of established peritoneal colorectal carcinomatosis in rats. NaBut or IL2 treatment alone, never cured these tumour-bearing rats. In the present investigation, we report that NaBut-treatments induce apoptosis in the colonic cancer cells both in vitro and in vivo. We postulated that the significant therapeutic effect of NaBut/IL2 treatment can be mainly attributed to a NaBut-induced apoptosis of the tumoural cells increasing their immunogenicity. Indeed, treatment which combined apoptotic bodies (apobodies) as cell vaccine, plus IL2 immunotherapy significantly increased tumour remission and survival rate of the vaccinated rats, whereas IL2 treatment alone did not. We observed that the cured rats presented long-term protection against subsequent challenge with the parental tumour cells. This latter result suggests that these treatments generate an immune protection. This was confirmed by the presence, in the sera of the cured rats, of anti-tumoural antibodies directed against both the apobodies and the tumour cells, but not against normal colonocytes. In addition, we show that injections of apobodies before administration of the parental tumour cells results in a partial protection. We provide the first evidence that apobodies, derived from cancer cells after NaBut-treatment, induce a specific immune response against parental tumours cells. These data suggest that the distinctive immunologic properties of apobodies could provide a valuable tool in colorectal cancer immunotherapy.

Vitamin A and apoptosis in colonic tumor cells

The mechanism by which vitamin A prevents or delays chemical carcinogenesis remains unclear. In addition to these antimutagenic and antiproliferative activities, vitamin A seems able to induce programmed cell death. In this study, we assess the suggested role of vitamin A on the in vitro apoptosis induction in a rat colonic tumor cell line. Several concentrations of retinyl palmitate were added in the culture media. We observed cell proliferation by measuring the (3H)thymidine incorporation, cell differentiation by measuring the intestinal alkaline phosphatase expression, and apoptosis induction by DNA fragmentation and morphological evolution of adherent and floating cells. The results show that vitamin A decreases (3H)thymidine incorporation after 1 day of treatment, induces alkaline phosphatase expression, and increases the number of cells falling in apoptosis. This report confirms the role of vitamin A on the induction of cell differentiation, on the inhibition of cell proliferation and shows the vitamin A capacity to induce apoptosis. These results could be attractive to prevent development of colon cancer by vitamin A supplemented diets.

Effects of resistant starch- and vitamin A-supplemented diets on the promotion of precursor lesions of colon cancer in rats

We have evaluated the potential protective effect of resistant starch (RS)- and vitamin A-supplemented diets on the promotion of preneoplasic lesions of rat colon, aberrant crypt foci (ACF), induced by 1,2-dimethylhydrazine dihydrochloride (DMH). We have tried to show whether the association of these two dietary constituents in the same diet could have synergistic effects. RS, vitamin A, and RS+ vitamin A were incorporated into the rat diets. Experimental diets were given one week after DMH injection and maintained for 12 weeks until the animals were sacrificed. The total number of ACF decreased with the three experimental diets. For RS- and RS + vitamin A-supplemented diets, this decrease is primarily due to a decrease in small ACF. For the vitamin A-supplemented diet, small and large ACF have a tendency to decrease. The effects of the diets on parameters influencing colon carcinogenesis were also studied. Only RS- and RS + vitamin A-supplemented diets have modified cecal pH, fecal and cecal butyrate contents, fecal excretion, cecal weight, and colon length. Vitamin A has been observed in colonic epithelial cells of rats receiving vitamin A- and RS+ vitamin A-supplemented diets. The association between RS and vitamin A shows neither a cumulative nor a synergistic protective effect.

Over-expression of a novel member of the immunoglobulin superfamily in Min mouse intestinal adenomas

Germline mutations of the APC (adenomatous polyposis coli) gene lead to multiple intestinal tumors in familial adenomatous polyposis patients and in Min (multiple intestinal neoplasia) mice. Consequently, these mice provide an excellent model for familial colon cancer. We have identified an Mr approx. 66 kDa glycoprotein which is preferentially expressed at the cell surface of cell lines established from chemically induced rat colon carcinomas. Cloning of the corresponding Tage4 cDNA has revealed that this protein contains the conserved amino acids characteristic of members of the immunoglobulin gene superfamily. Here, we analyze expression of the mouse Tage4 gene in Min mouse intestinal adenomas. RT-PCR analysis allowed us to detect expression of this gene in all the mouse adenomas tested. In contrast, lower levels of Tage4 mRNA were found in the intestinal tract and barely detectable levels in other tissues of normal mice. Furthermore, Tage4 mRNA was detected in a series of mouse intestinal adenomas by in situ hybridization. A strong signal was seen in the samples analyzed.

Induction of fibroblast gelatinase B expression by direct contact with cell lines derived from primary tumor but not from metastases

During cancer progression, tumor cells interact with stromal cells. As a consequence, matrix metalloproteinases are produced that contribute to the degradation of the extracellular matrix. This study used coculture systems to investigate fibroblast interaction with three colon cancer cell lines isolated from a single patient. Cells from primary colorectal carcinoma, but not from corresponding liver or lymph node metastases, induced gelatinase B expression by fibroblasts of different tissue origin. Remarkably, direct cell-cell contact was required for this induction, which occurred at the pretranslational level (as revealed by Northern blot analysis) and was completely blocked by anti-beta1 integrin monoclonal antibody, but only partially blocked by anti-alpha5 or anti-alpha(v). Induction was also inhibited by cytochalasin D, staurosporine, or dexamethasone, suggesting the need, respectively, for an organized actin cytoskeleton, protein kinase C, and AP-1-driven gene transcription. Our data suggest that direct tumor-stromal cell contact is one inductive event involved in matrix metalloproteinase expression by stromal cells.

Altered glycosylation of alpha(s)beta 1 integrins from rat colon carcinoma cells decreases their interaction with fibronectin

Malignant cell transformation is generally accompanied by changes in their interactions with environing matrix proteins in a way to facilitate their migration and generate invasion. Our results show the binding of rat colon adenocarcinoma PROb cells to fibronectin strongly reduced when compared to normal rat intestine epithelial cells. This decrease was not due to the level of alpha(s)beta 1 integrins expressed at the surface of the cell line. However, beta 1- and alpha(s)-associated subunits appeared to be structurally altered as shown by immunoprecipitation followed by electrophoresis. Pulse chase experiments using 35S methionine evidenced differences in the biosynthesis of beta 1- and alpha(s)associated integrins: normal epithelial IEC18 cells required 16 h for maximal biosynthesis of the completely mature beta 1 subunit, while PROb cells did it within 4-6 h. Studies using endoglycosidases O, H, D, and N glycanase confirmed that the molecular weight alterations were due to abnormal glycosylation and suggested that alpha(s)beta 1 integrins of PROb cells could bear both mature complex and immature high mannose types while IEC18 cells borne only mature complex type oligosaccharidic chains. Treatment of both cell types with castanospermine, an inhibitor of N-glycosylation, reduced the differences observed in their adhesion to the fibronectin without significantly affecting beta 1 receptors expression at the cell surface. These results strongly suggest a role of the glycosylation of beta 1 receptors in the adhesion of rat colon adenocarcinoma PROb cells to fibronectin substrata.

[Vaccination with genetically modified IL-2 secreting cells in a rat model of colonic carcinoma]

Genetically engineered tumor cells secreting immunostimulatory molecules could facilitate the obtention of a vaccination against tumor antigens. To test this approach, we transfected genes encoding for rat and mouse IL-2 into PROb cells. These cells originate from a dimethylhydrazine induced colon carcinoma of BD IX rats. We observed an inhibition of the in vivo tumor growth directly proportional to the IL-2 secretion. An immunohistochemical analysis revealed that the tumors were infiltrated by leucocytes expressing the IL-2 receptor, suggesting their activation within the tumor. A strong delay of tumor growth was observed in rats challenged with PROb cells after a previous rejection of IL-2 secreting cells. Yet two rats out of six were completely protected. This protection is specific since rejection of PROb-IL-2 does not confer protection towards the syngeneic glioma A15A5. In addition, we could show by depletion experiments that NK/LAK, CD8, and CD4 lymphocytes were involved in the rejection of cells secreting large amounts of IL-2. Macrophages appear to be involved in the rejection process too, but also in the induction of an immune memory. Vaccination experiments using irradiated PROb IL-2 cells were performed. Only a partial protection towards a challenge with parental PROb cells could be obtained, also depending on the amount of secreted IL-2: the best protection being obtained after vaccination with cells synthesizing a small amount of IL-2. However, this protection was not superior to that obtained by coinjection of irradiated PROb cells and BCG.

[Induction of apoptosis, in vitro and in vivo, on colonic tumor cells of the rat after sodium butyrate treatment]

Sodium butyrate (NaB) is known to induce the process of cell differentiation, particularly for epithelial colonic cells. We previously observed that treatment with NaB in association with interleukin 2 (IL2), cures 60% of peritoneal carcinomatosis induced by injection of DHDK12/TRb cells in syngenic rats [15]. In the present work, we evidenced in vitro metabolic alterations of the DHDK12/TRb cell line treated with NaB, followed by an apoptotic process. Flow cytometric analysis evidenced that the tumour cells were arrested in the G1 and G2 phases of the cell cycle for the adherent cells to the plastic. Biological analysis of cells and debris released in the culture medium were essentially apoptotic cells. Complementary, the NaB-induced apoptotic process was confirmed by the staining of the nucleus from releasing cells by Hoechst 33258 and the DNA fragmentation revealed by DNA electrophoresis. Mitochondrial activity and glucose consumption were significantly stimulated after NaB treatment, which reveal an alteration of the metabolic activity of the treated tumour cells. As a consequence, we measured a significant increase of the active TGF beta 1 production, a cytokine previously described to participate to the epithelial cell differentiation. These in vitro data were confirmed in vivo showing a significant expression of apoptotic tumour cells in NaB- or NaB/IL2-treated tumours. Thus, the present results in the rat peritoneal carcinomatosis treatment show that combination of apoptotic process induced by NaB with immunostimulation by IL2 has powerful therapeutic properties.

Immunization against a rat colon carcinoma by sodium butyrate-treated cells but not by interleukin 2-secreting cells

BACKGROUND & AIMS

Vaccination of patients with colon cancer with irradiated autologous tumor cells and bacille Calmette-Guérin (BCG) was reported to augment mean survival. It was recently observed that a local treatment combining recombinant interleukin 2 and the differentiation agent sodium butyrate cured rats with colon cancer peritoneal carcinomatosis. To optimize vaccination protocols, the comparison of the efficacy of irradiated tumor cells mixed with BCG with that of interleukin 2-gene-transfected cells and of tumor cells pretreated with sodium butyrate was performed.

METHODS

The poorly immunogenic rat colon carcinoma cells PROb were used in a vaccination assay. Interleukin 2-transfected PROb cells, either proliferating or irradiated, were used. The efficiency of irradiated PROb cells mixed with BCG, of interleukin 2-transfected cells, or of cells pretreated with sodium butyrate was tested.

RESULTS

Vaccination with irradiated parental cells and BCG did not provide protection. Irradiated interleukin 2-transfected cells were poorly efficient in the vaccination assay. Conversely, vaccination with irradiated parental cells pretreated with sodium butyrate before injection provided good protection.

CONCLUSIONS

Interleukin 2-secreting cells efficiently vaccinated animals when injected while replicating but not after irradiation. Conversely, sodium butyrate pretreatment provided a simple and efficient vaccination scheme that generated a long-term immune memory and allowed the use of irradiated cells.

Leukaemia Inhibitory Factor derived from rat colon carcinoma cells increases host susceptibility to tumour growth

We have tested Leukaemia Inhibitory Factor (LIF) production by 12 rat colon tumour clones isolated from a single cell line that display various degrees of tumorigenicity. A highly significantly relationship was found between levels of soluble LIF produced by the clones and their in vivo tumorigenicity. Such results suggested a role for LIF as a tumour facilitating agent. To test this hypothesis, the highly tumorigenic and LIF producing PROb clone was transfected with the LIF cDNA in antisense orientation in order to decrease LIF production. Conversely, REGb, a low LIF producer that is rejected by syngeneic animals, as well as nude mice, was transfected with the LIF cDNA to increase its production. PROb cells transfected with antisense cDNA were shown to have decreased LIF production along with decreased tumorigenicity. LIF-transfected REGb cells expressing high LIF levels still regressed in syngeneic rats, but could form progressive tumours in nude mice. We did not detect LIF receptors on PROb or REGb cells and their in vitro proliferation was not modified by the addition of exogenous LIF. Therefore, LIF was not an autocrine growth regulator for PROb and REGb cells. Instead, LIF appears to facilitate in vivo tumour growth, without being an immunosuppressive factor sufficient on its own to allow growth of immunogenic cells in fully immunocompetent hosts.