Intraoperative Near-Infrared Fluorescence Imaging using indocyanine green in colorectal carcinomatosis surgery: Proof of concept

PURPOSES

This study assesses the value of using Intraoperative Near Infrared Fluorescence Imaging and Indocyanine green to detect colorectal carcinomatosis during oncological surgery. In colorectal carcinomatosis cancer, two of the most important prognostic factors are completeness of staging and completeness of cytoreductive surgery. Presently, intraoperative assessment of tumoral margins relies on palpation and visual inspection. The recent introduction of Near Infrared fluorescence image guidance provides new opportunities for surgical roles, particularly in cancer surgery.

METHODS

The study was a non-randomized, monocentric, pilot "ex vivo" blinded clinical trial validated by the ethical committee of University Hospital of Saint Etienne. Ten patients with colorectal carcinomatosis cancer scheduled for cytoreductive surgery were included. Patients received 0.25 mg/kg of Indocyanine green intravenously 24 h before surgery. A Near Infrared camera was used to detect "ex-vivo" fluorescent lesions.

RESULTS

There was no surgical mortality. Each analysis was done blindly. In a total of 88 lesions analyzed, 58 were classified by a pathologist as cancerous and 30 as non-cancerous. Among the 58 cancerous lesions, 42 were correctly classified by the Intraoperative Near-Infrared camera (sensitivity of 72.4%). Among the 30 non-cancerous lesions, 18 were correctly classified by the Intraoperative Near-Infrared camera (specificity of 60.0%).

CONCLUSIONS

Near Infrared fluorescence imaging is a promising technique for intraoperative tumor identification. It could help the surgeon to determine resection margins and reduce the risk of locoregional recurrence.

Electrochemotherapy guided by intraoperative fluorescence imaging for the treatment of inoperable peritoneal micro-metastases

Surgery is often the first therapeutic indication in cancer. Patient survival essentially depends on the completeness of tumor resection. This is a major challenge, particularly in patients with peritoneal carcinomatosis (PC), where tumors are widely disseminated in the large peritoneal cavity. These small tumors can be difficult to visualize and are often positioned in delicate locations, further increasing the risk of producing serious tissue/organ damage during their ablation. We propose an innovative therapeutic approach based on intraoperative fluorescence (IF) guided electrochemotherapy (ECT) for the treatment of peritoneal micro-metastases. ECT combines the effects of tissue electro-permeabilization (EP) with the administration of an antimitotic agent (bleomycin) that has poor permeability across intact membranes. IF significantly improves the detection of small tumor lesions. ECT is clinically validated for the treatment of cutaneous tumors in animals and humans, but this is the first time that it has been used along with IF imaging for the targeted treatment of peritoneal metastases in a preclinical model. We set up a murine model of PC that develops secondarily to the resection of a distant primary tumor. Tumor growth and metastasis were finely monitored by non-invasive multimodal imaging (bioluminescence and 3D fluorescence/microCT). Once metastases were detected, mice were randomized into three groups: the ECT group (bleomycin injected intravenously followed by EP) and 2 control groups (bleomycin alone and EP alone). Twenty four hours after the intravenous injection of the tumor targeting agent Angiostamp™700, mice in all groups underwent an abdominal surgery for metastases exploration assisted by fluorescence imaging with the Fluobeam®700 portative device. EP was applied to every nodule detected by IF, except in the bleomycin control group. After surgery, the metastatic invasion was tracked by bioluminescence imaging. In mice treated with bleomycin or EP alone, the metastatic load progressed very rapidly and mice showed no significant difference in lifespan compared to non-operated mice (median lifespan: 27days vs. 25days, respectively). In contrast, the mice treated with ECT displayed a decreased metastatic load and an increased survival rate (median lifespan: 34days). These results provide evidence that IF guided ECT is an effective approach for the treatment of inoperable intraperitoneal micro-metastases.

The use of theranostic gadolinium-based nanoprobes to improve radiotherapy efficacy

A new efficient type of gadolinium-based theranostic agent (AGuIX®) has recently been developed for MRI-guided radiotherapy (RT). These new particles consist of a polysiloxane network surrounded by a number of gadolinium chelates, usually 10. Owing to their small size (<5 nm), AGuIX typically exhibit biodistributions that are almost ideal for diagnostic and therapeutic purposes. For example, although a significant proportion of these particles accumulate in tumours, the remainder is rapidly eliminated by the renal route. In addition, in the absence of irradiation, the nanoparticles are well tolerated even at very high dose (10 times more than the dose used for mouse treatment). AGuIX particles have been proven to act as efficient radiosensitizers in a large variety of experimental in vitro scenarios, including different radioresistant cell lines, irradiation energies and radiation sources (sensitizing enhancement ratio ranging from 1.1 to 2.5). Pre-clinical studies have also demonstrated the impact of these particles on different heterotopic and orthotopic tumours, with both intratumoural or intravenous injection routes. A significant therapeutical effect has been observed in all contexts. Furthermore, MRI monitoring was proven to efficiently aid in determining a RT protocol and assessing tumour evolution following treatment. The usual theoretical models, based on energy attenuation and macroscopic dose enhancement, cannot account for all the results that have been obtained. Only theoretical models, which take into account the Auger electron cascades that occur between the different atoms constituting the particle and the related high radical concentrations in the vicinity of the particle, provide an explanation for the complex cell damage and death observed.

Conventional versus stealth lipid nanoparticles: formulation and in vivo fate prediction through FRET monitoring

The determination of the nanocarrier fate in preclinical models is required before any translation from laboratory to clinical trials. Modern fluorescent imaging techniques have gained considerable advances becoming a powerful technology for non-invasive visualization in living subjects. Among them, Forster (fluorescence) resonance energy transfer (FRET) is a particular fluorescence imaging which involves energy transfer between 2 fluorophores in a distance-dependent manner. Considering this feature, the encapsulation of an acceptor/donor pair in lipid nanoparticles (LNEs: lipid nanoemulsions, LNCs: lipid nanocapsules) allowed the carrier integrity to be tracked. Accordingly, we used this FRET technique to evaluate the behavior of LNEs, conventional LNCs and newly designed stealth LNCs. After the development through a one-step (OS) PEGylation process of these stealth LNCs (OS LNCs), in vitro guest exchange dynamics and release kinetics were evaluated for both LNC formulations. We thereafter assessed in vivo biodistribution of all types of lipid nanoparticles. Results showed enhanced stability of encapsulation in OS LNCs in comparison to conventional LNCs. Additionally, the presence of the long PEG chains on the lipid nanoparticle surface altered the biodistribution pattern. Despite different release kinetic profiles, OS LNCs and LNEs showed extended blood circulation time associated with a good structure stability over several hours after intravenous injection.

Inhibition of cardiac leptin expression after infarction reduces subsequent dysfunction

Leptin is known to exert cardiodepressive effects and to induce left ventricular (LV) remodelling. Nevertheless, the autocrine and/or paracrine activities of this adipokine in the context of post-infarct dysfunction and remodelling have not yet been elucidated. Therefore, we have investigated the evolution of myocardial leptin expression following myocardial infarction (MI) and evaluated the consequences of specific cardiac leptin inhibition on subsequent LV dysfunction. Anaesthetized rats were subjected to temporary coronary occlusion. An antisense oligodesoxynucleotide (AS ODN) directed against leptin mRNA was injected intramyocardially along the border of the infarct 5 days after surgery. Cardiac morphometry and function were monitored by echocardiography over 11 weeks following MI. Production of myocardial leptin and pro-inflammatory cytokines interleukin (IL)-1β and IL-6 were assessed by ELISA. Our results show that (1) cardiac leptin level peaks 7 days after reperfused MI; (2) intramyocardial injection of leptin-AS ODN reduces early IL-1β and IL-6 overexpression and markedly protects contractile function. In conclusion, our findings demonstrate that cardiac leptin expression after MI could contribute to the evolution towards heart failure through autocrine and/or paracrine actions. The detrimental effect of leptin could be mediated by pro-inflammatory cytokines such as IL-1β and IL-6. Our data could constitute the basis of new therapeutic approaches aimed to improve post-MI outcome.

The transcription factor E2F1 and the SR protein SC35 control the ratio of pro-angiogenic versus antiangiogenic isoforms of vascular endothelial growth factor-A to inhibit neovascularization in vivo

The transcription factor E2F1 has a crucial role in the control of cell growth and has been shown to regulate neoangiogenesis in a p53-dependent manner through inhibition of activity of the VEGF-A (vascular endothelial growth factor) promoter. Besides being regulated by transcription, VEGF-A is also highly regulated by pre-mRNA alternative splicing, resulting in the expression of several VEGF isoforms with either pro-(VEGF(xxx)) or anti-(VEGF(xxx)b) angiogenic properties. Recently, we identified the SR (Ser-Rich/Arg) protein SC35, a splicing factor, as a new transcriptional target of E2F1. Here, we show that E2F1 downregulates the activity of the VEGF-A promoter in tumour cells independently of p53, leading to a strong decrease in VEGF(xxx) mRNA levels. We further show that, strikingly, E2F1 alters the ratio of pro-VEGF(xxx) versus anti-VEGF(xxx)b angiogenic isoforms, favouring the antiangiogenic isoforms, by a mechanism involving the induction of SC35 expression. Finally, using lung tumour xenografts in nude mice, we provide evidence that E2F1 and SC35 proteins increase the VEGF(165)b/VEGF ratio and decrease tumour neovascularization in vivo. Overall, these findings highlight E2F1 and SC35 as two regulators of the VEGF(xxx)/VEGF(xxx)b angiogenic switch in human cancer cells, a role that could be crucial during tumour progression, as well as in tumour response to antiangiogenic therapies.

Optical small animal imaging in the drug discovery process

Molecular imaging of tumors in preclinical models is of the utmost importance for developing innovative cancer treatments. This field is moving extremely rapidly, with recent advances in optical imaging technologies and sophisticated molecular probes for in vivo imaging. The aim of this review is to provide a succinct overview of the imaging modalities available for rodents and with focus on describing optical probes for cancer imaging.

Intraoperative near-infrared image-guided surgery for peritoneal carcinomatosis in a preclinical experimental model

Background

This study compared the quality of surgery performed under conventional light with near-infrared (NIR) image-guided surgery using a tumour-targeting probe and a portable clinical grade imaging device in a mouse model of peritoneal carcinomatosis.

Methods

Peritoneal carcinomatosis was induced by injection of luciferase-positive tumour cells, leading to the formation of small nodules in the peritoneal cavity. One day after intravenous injection of RAFT-c(RGDfK)4-Alexa Fluor® 700, a fluorescent tumour-targeting probe, the surgeon operated using the Fluobeam®, a portable device that illuminated the mouse with NIR light and allowed NIR vision. The quality of the surgery was evaluated using bioluminescence, a highly sensitive method that detected the remaining tumour cells, and operating time was measured.

Results

Under normal light, the surgeon detected and removed a mean(s.d.) of only 50·6(2·3) per cent of the nodules that were visible under NIR light. The duration of surgery was reduced from 19·5(3·3) min under normal light to 14·0(2·6) min when NIR light was used (P = 0·025). The sensitivity of the NIR system allowed the detection of nodules containing as few as 227 tumour cells.

Conclusion

NIR image-guided surgery improved the quality of surgery for peritoneal carcinomatosis by doubling the number of nodules detected and significantly reducing the duration of surgery.

Drug development in oncology assisted by noninvasive optical imaging

Early and accurate detection of tumors, like the development of targeted treatments, is a major field of research in oncology. The generation of specific vectors, capable of transporting a drug or a contrast agent to the primary tumor site as well as to the remote (micro-) metastasis would be an asset for early diagnosis and cancer therapy. Our goal was to develop new treatments based on the use of tumor-targeted delivery of large biomolecules (DNA, siRNA, peptides, or nanoparticles), able to induce apoptosis while dodging the specific mechanisms developed by tumor cells to resist this programmed cell death. Nonetheless, the insufficient effectiveness of the vectorization systems is still a crucial issue. In this context, we generated new targeting vectors for drug and biomolecules delivery and developed several optical imaging systems for the follow-up and evaluation of these vectorization systems in live mice. Based on our recent work, we present a brief overview of how noninvasive optical imaging in small animals can accelerate the development of targeted therapeutics in oncology.

Non-invasive in vivo optical imaging of the lacZ and luc gene expression in mice

The bacterial lacZ gene encoding for beta-galactosidase (beta-gal) is a common reporter gene used in transgenic mice. Nonetheless, the absence of fluorigenic substrates usable in live animals greatly hampered the non-invasive follow-up of this reporter gene expression. We used far-red fluorescence for imaging beta-Gal expression in live cells in vitro or in vivo. The 9H-(1,3-dichloro-9,9-dimethylacridin- 2-one-7-yl) beta-D-galactopyranoside substrate was used to monitor beta-Gal expression as a reporter of tumor growth, or of the physiological levels of an endogenous gene or of gene transfer in lung. A quantitative evaluation of this method as well as a comparison of its sensitivity with Firefly Luciferase-based bioluminescence was also performed. In vivo measurements showed that 10(3) beta-Gal tumor cells located under the skin were detectable. In deeper organs like lung, as little as 5 ng of beta-Gal or Luciferase enzymes per mg of proteins were measured, confirming that both techniques reached similar sensibilities. Nonetheless, quantitative comparison of beta-Gal levels measured with far-red imaging or with a standardized enzymatic evaluation after killing revealed that the 2D-fluorescent reflectance imaging method is submitted to a color-dependent disparity of the organs and cannot supply quantitative measurements but that a simple correction can be applied.

Characterization of immunophilins in the silkmoth Bombyx mori

The FK506-binding proteins (FKBPs) perform an extensive variety of functions in numerous organisms from archaea to humans. The FKBPs are distinguished by their peptidyl-prolyl cis-trans isomerase (PPIase) activity and ability to bind the immunosuppressive drugs FK506 and rapamycin. Here, we report the isolation and characterization of FKBP45, a novel member of the FKBP family obtained from U1 small nuclear RNA (snRNA) binding assays using Bombyx mori nuclear extracts. The protein, an apparent orthologue of FKBP46 from the armyworm, Spodoptera frugiperda, was found to associate with U1 stem-loop I RNA in vitro. The FKBP45 cDNA was isolated and the genomic sequence was characterized, including the positions of exon/intron junctions and consensus splice sites. Using bioinformatics, transcription factor consensus binding sites were identified and subsequent Western blotting from developing eggs indicate that FKBP45 is differentially expressed during embryogenesis. A database was assembled using more than 1,800 available FKBP amino acid sequences and pairwise sequence alignments revealed several putative FKBP45 orthologues in various species. Analysis of these sequences revealed the position of an RNA binding domain within this new protein. In addition, FKBP45 possesses similar characteristics to several potential orthologues, including the presence of bipartite nuclear localization signals (NLSs) and phosphorylation sites.

Intercellular trafficking and enhanced in vivo antitumour activity of a non-virally delivered P27-VP22 fusion protein

VP22, a structural protein from herpes simplex virus type I, exhibits the unique property of intercellular trafficking. This protein is exported from primary expressing cells and subsequently imported into neighbouring cells. This property is conserved when VP22 is genetically fused to a protein, making it a promising tool to enhance the delivery of a gene product. We chose to study the intercellular transport and biological effect of a fusion protein between the putative tumour suppressor gene p27(Kip1) and VP22. We show that in vitro, P27VP22 is able to spread as efficiently as VP22. Functionality of the P27VP22 protein was demonstrated by its ability to inhibit cyclin/CDK2 complexes activity. In proliferation and clonogenicity assays, transfection with the P27VP22 plasmid resulted in a stronger cell growth inhibition when compared to transfection with the p27(Kip1) vector. In vivo, sub cutaneous tumours established in nude mice were injected with naked DNA encoding P27 or P27VP22. Our results show that P27VP22 can spread in vivo and that injections of the P27VP22 plasmid resulted in a significantly greater antitumour activity than injections of the P27 plasmid. This study confirms the usefulness of VP22-mediated delivery and suggests that P27VP22 may have applications in cancer gene therapy.

Cell cycle arrest is sufficient for p53-mediated tumor regression

p53 gene therapy can induce tumor regression, but the low efficacy of in vivo gene transfer has greatly hampered the mechanistic analysis of this antitumoral activity. We therefore used a p53-null human NSCLC cell line in which we reintroduced the wild-type p53 gene under control of a tetracycline-dependent promoter. P53 induction provokes cell cycle arrest in G0/G1 and G2/M phase, an up-regulation of p21, a down-regulation of cyclin B1 and appearance of senescence features without down-regulation of human telomerase reverse transcriptase. No detectable morphological changes of apoptosis nor procaspase-3 activation are observed. In subcutaneous tumors grafted in nude mice, the induction of p53 expression leads to a complete and longlasting tumor regression in 28 days which is associated with cell cycle arrest, but not detectable apoptosis nor inhibition of angiogenesis. These results show that irreversible cell cycle arrest is sufficient to elicit tumor regression after p53 gene transfer in p53-deficient tumor cells.

Caffeine sensitizes human H358 cell line to p53-mediated apoptosis by inducing mitochondrial translocation and conformational change of BAX protein

The mechanisms involved in p53-mediated cell death remain controversial. In the present study, we investigated this cell death pathway by stably transfecting the p53-null H358 cell line with a tetracycline-dependent wild type p53-expressing vector. Restoration of p53 triggered a G(2)/M cell cycle arrest and enhanced BAX protein expression, without inducing apoptosis or potentiating the cytotoxic effect of etoposide, vincristine, and cis-platinum. Accordingly, overexpression of BAX in H358 cells, through stable transfection of a tetracycline-regulated expression vector, did not induce cell death. Interestingly, the methylxanthine caffeine (4 mm) promoted the translocation of BAX from the cytosol to the mitochondria. In the setting of an overexpression of BAX, caffeine induced a conformational change of the protein and apoptosis. The consequences of caffeine were independent of its cell cycle-related activities. All together, caffeine synergizes with p53 for inducing cell death through a cell cycle-independent mechanism, involving mitochondrial translocation and conformational change of BAX protein.

In vivo delivery to tumors of DNA complexed with linear polyethylenimine

Synthetic gene delivery vectors have shown promise in several organs, including brain and lung. Tumor cell targeting, however, is still hindered by their low efficacy. A linear polyethylenimine (L-PEI, Exgen 500) was found to be effective in vivo. Our first attempts to use L-PEI for intratumoral gene delivery were not successful, presumably because of poor diffusion of the complexes within the tumor mass after injection with a syringe. Here we show that L-PEI-mediated transfection can be strongly enhanced when the complexes are delivered slowly into a solid tumor mass, using a micropump. Furthermore, L-PE/DNA complexes actively transfect pseudocystic tumor cells when injected into the cyst cavity. In both cases L-PEI induced a significant and long-lasting (> or =15 days) expression of the reporter gene. Finally, even though systemic delivery of L-PEI/DNA complexes leads to high levels of expression in the lung, this method is not adapted for transfection of subcutaneous tumors implanted in the thigh nor for transfection of lung metastases. Altogether, these results show that L-PEI has promising features for transfection of tumor cells, provided that the mode of delivery is adapted.

Transfection and physical properties of various saccharide, poly(ethylene glycol), and antibody-derivatized polyethylenimines (PEI)

BACKGROUND

The ideal non-viral vector should be cell-type directed and form complexes with DNA that are physically stable, small and electrically neutral.

METHODS

We have synthesized several PEI derivatives that coat the PEI/DNA complexes with water-soluble residues able to stabilize the particles, to mask their surface charge and eventually to direct them to a particular tissue. The morphologies and sizes of the complexes were observed by TEM and DLS techniques, and their apparent surface charge was quantitated by zeta potential measurements; in vitro transfection efficacies were determined in serum-containing cell culture medium.

RESULTS

When compared to DNA complexes formed with the unmodified PEI, extensive grafting with maltose (15-25% of the amine functions) led to beneficial electrostatic shielding of the particle surface, but was unable to prevent aggregation in physiological salt concentration. More extended hydrophilic residues were therefore explored as a mean of physical repulsion between the particles. Low grafting (2.7%) with a linear dextran non-asaccharide led to small and stable toroids having no apparent surface charge, yet still reaching effective transfection levels. Electron microscopy of complexes with a higher extent of grafting showed worm-like structures unsuited for cell entry. Conjugation of PEI with as little as 0.5% of a terminally galactose-derivatized polyethyleneglycol (PEG)-3400 also gave neutral complexes of another worm-like structure that failed to transfect receptor-expressing hepatocytes.

CONCLUSION

These results show that conjugation of large and flexible hydrophilic residues to PEI, while protecting the complexes from parasitic interactions also interfere with DNA condensation. PEG conjugation after PEI/DNA complex formation may avoid this problem, provided intracomplex reorganization is slow. Finally an anti-GD2 antibody (mAb) grafted with PEI was synthesized. The corresponding protein-coated DNA complexes were compact and small (50-60 nm), yet did not enhance transfection of GD2 ganglioside-expressing cells.

Antitumor activity of bax and p53 naked gene transfer in lung cancer: in vitro and in vivo analysis

In vitro and in vivo data have demonstrated that virus-mediated p53 gene transfer can induce active cell death and lung tumor regression. In contrast, the therapeutic potential of bax, another apoptosis-inducing gene, has not been described. We compared p53 and bax cytotoxic effects by transient transfection of an average of 25 +/- 5% of the H-322 and H-358 bronchioloalveolar carcinoma cell lines in vitro. Under these conditions, bax expression killed 70 to 90% of the transfected cells whereas p53 killed only 40% of them. The killing activity of both genes involved apoptosis, as shown by TUNEL staining. Surprisingly, BrdU incorporation indicated that the cells that did resist Bax toxicity were blocked in the pre-S phase of the cell cycle, a result expected for p53 only. In vivo, repeated injections of naked DNA encoding Bax or p53 inhibited the growth of 4-mm preestablished H-322 tumors in nude mice. Growth retardation only, and not inhibition, was observed in H-358, a poorly transfectable and rapidly growing tumor. These results indicate that Bax and p53 share a similar, strong antitumor activity in vivo, even if the former is a more potent inducer of apoptosis in vitro.

p53 mutant immunophenotype and deregulation of p53 transcription pathway (Bcl2, Bax, and Waf1) in precursor bronchial lesions of lung cancer

Lung cancer is the end result of a multistep process in which genetic and molecular changes accompany, in an unknown temporal sequence, histological precursor (preinvasive) bronchial lesions. Biomarkers allowing prediction of the rate of progression of precursor lesions at different locations in the anatomical field may be clinically useful. Toward this aim, we analyzed, using immunohistochemistry, the expression of the p53 gene and of its transcriptional target genes bax, bcl2, and waf1 in preinvasive bronchial lesions from 69 patients with lung cancer and in similar lesions from 20 patients with no cancer progression. p53 accumulation occurred with increasing frequency, from 19% in mild dysplasia to 36% in moderate dysplasia and 59% in carcinoma in situ, and was exclusively observed in patients with p53-positive carcinoma. The higher frequency of the p53-positive immunophenotype in lesions adjacent to the p53-positive carcinoma, as compared to lesions distant from it, suggests that p53 mutant preneoplastic lesions had a higher rate of progression to invasion than did p53-negative lesions. Similar lesions in patients with no progression to lung cancer were all p53 negative. Bcl2 overexpression and Bax down-regulation, as shown by immunostaining, occurred in preinvasive lesions and were mainly maintained during invasion. The expressions of bax, bcl2, and waf1 did not correlate with p53 status. We conclude that p53 stabilization in preinvasive lesions has high predictive value for progression to invasion and that Bax/Bcl2 imbalance contributes to the clonal expansion during premalignant states.

Rescue of the mutant phenotype by reexpression of full-length vinculin in null F9 cells; effects on cell locomotion by domain deleted vinculin

Vinculin plays a role in signaling between integrins and the actin cytoskeleton. We reported earlier that F9-derived cells lacking vinculin are less spread, less adhesive, and move two times faster than wild-type F9 cells. Expression of intact vinculin in null cells restored all wild-type characteristics. In contrast, expression of the head (90 kDa) fragment exaggerated mutant characteristics, especially locomotion, which was double that of vinculin null cells. Expression of the tail domain also had a marked effect on locomotion in the opposite direction, reducing it to very low levels. The expression of the head plus tail domains together (no covalent attachment) effected a partial rescue towards wild-type phenotype, thus indicating that reexpressed polypeptides may be in their correct location and are interacting normally. Therefore, we conclude that: (1) the head domain is part of the locomotory force of the cell, modulated by the tail, and driven by the integrin/matrix connection; (2) intact vinculin is required for normal regulation of cell behavior, suggesting that vinculin head-tail interactions control cell adhesion, spreading, lamellipodia formation and locomotion.

Cell death and cancer: replacement of apoptotic genes and inactivation of death suppressor genes in therapy

This review provides a critical evaluation of the increasing use of gene therapy in the treatment of malignancies to induce active cell death (ACD, apoptosis). This approach is consistent with the notion that cancer is an anomalous accumulation of cells largely resulting from diminished cell death. The review details the main genes potentially useful for therapy. Among these, p53 has received the majority of the investigators' attention and provided encouraging results. Even greater hope is offered by newly tried direct inducers of apoptosis, such as bax, bclXs and caspases. Another fruitful direction is the association of apoptosis-inducing gene transfer with radio- and chemotherapy, which are also inducers of ACD. There is a delicate balance between cell gain through mitosis and cell loss in neoplasia because spontaneous apoptosis is widely present in tumors. In fact, the tumor environment favors bystander cell killing which appears to be a fundamental mechanism insofar as the rate of observed cell mortality cannot be accounted for by the known methods of gene transduction with efficiencies far below 100%. We conclude that apoptosis offers a mainstream approach for cancer gene therapy since ACD is highly inducible and only limited gains in malignant cell apoptosis may displace tumors from growth to regression.

Long-term survival of immunocompetent rats with intraperitoneal colon carcinoma tumors using herpes simplex thymidine kinase/ganciclovir and IL-2 treatments

We evaluated the gain in long-term survival of BDIX rats bearing DHDProB colon cancer developed in the peritoneal cavity after in vivo therapy with the tk gene and GCV. The sensitivity and the bystander effect of DHDProB cells stably transduced with the tk gene evaluated in vitro were low, as one tk+ cell killed two tk- cells. This correlated with the low ability of a fluorescent dye to diffuse through gap junctions. In vivo, more than 75% of tk-transduced cells were required and at least 100 mg/kg/day of GCV had to be injected no later than day 5 after tumor implantation to obtain a curative effect. A partial protection of the cured animals against rechallenge with the parental cells was also observed. Based on these results, a protocol of in vivo gene therapy was designed in which the tk/GCV treatment was combined with IL-2 gene expression. When the tk- and IL-2 encoding plasmids were injected twice i.p. with DOTAP and the animals treated with GCV, three of five rats were cured. This antitumoral activity resulted from the combined toxic effects of DNA/DOTAP and tk/GCV plus a potential immune response mediated by IL-2.

In vitro targeting and specific transfection of human neuroblastoma cells by chCE7 antibody-mediated gene transfer

We developed a new vector for gene targeting of neuroblastoma (NB) cells, based on the utilization o a monoclonal antibody (chCE7) covalently linked to polylysine (PL). In the presence of chloroquine, chCE7-PL-DNA complexes transfected NB cells as efficiently as DOTAP, transfectam, TF-X50, or lipofectamine. This was demonstrated by transfection of the luciferase or beta-galactosidase reporter genes in three different NB cell lines. This transfection was specific, since it was inhibited in the presence of competing unconjugated chCE7 antibody (Ab), and was not observed in cell lines negative for the CE7 antigen. We tested the potential biological activity of a plasmid coding for gamma-interferon (gamma IFN) transfected with chCE7-PL. HLA ABC expression on NB cells was induced after transfection with pCMV-gamma IFN at a higher level than after incubation with 1000 IU/ml of purified gamma IFN. Moreover, these HLA ABC-positive NB cells were able to activate autologous cytotoxic T lymphocytes in vitro. Thus chCE7-PL is able to target a plasmid to NB cells and to allow the expression of the transfected gene in a biologically active form.

Clinical relevance of TRKA expression on neuroblastoma: comparison with N-MYC amplification and CD44 expression

TRKA expression was evaluated on 122 untreated neuroblastomas by immunohistochemistry using an antibody with predetermined specificity. This procedure is simple and reliable for protein detection at cellular level in a routine clinical setting. Fourteen tumours were classified as benign ganglioneuroma with a restricted expression of TRKA on ganglion cells; these patients were excluded from the following analysis. A total of 108 tumours were classified as neuroblastoma or ganglioneuroblastoma; 74 expressed TRKA protein, which strongly correlated with low stage, absence of N-MYC amplification, age (<1 year), CD44 expression and favourable clinical outcome. In a univariate analysis including tumour stage, age, histology, N-MYC amplification, CD44 and TRKA expression, all parameters had significant prognostic value. The absence of TRKA expression on CD44-positive or N-MYC non-amplified tumours permits the characterization of a subgroup of patients with intermediate prognosis. However, in a multivariate analysis taking into consideration the prognostic factors mentioned above, CD44 and tumour stage were the only independent prognostic factors for the prediction of patients' event-free survival.

Apoptosis-related factors p53, Bcl2, and Bax in neuroendocrine lung tumors

Neuroendocrine (NE) lung tumors comprise four classes of progressive aggressiveness for which proliferation and apoptosis rates could both contribute to their distinctive behavior. As p53 mutations may favor escape from apoptosis through changes in Bcl2-Bax expression balance, which are survival and apoptotic genes, respectively, we studied 121 NE lung tumors (16 typical carcinoids (TC), 5 atypical carcinoids (AC), 29 large-cell NE carcinomas (LCNECs), and 71 small-cell lung carcinomas (SCLCs) using immunohistochemistry. We quantified apoptosis by terminal-deoxynucleotidyl-transferase-mediated deoxyuridine triphosphate nick end labeling (TUNEL) in 31 of these cases. There was a significant increase of p53 mutant immunophenotype (defined as immunoreactivity with at least two antibodies for at least 20% of tumor cells) between atypical/typical carcinoids group and the LCNEC/SCLC group (P = 0.0003). There was an inverse correlation (P < 0.0001) between the scores of Bax and Bcl2 expression in individual tumors and a significant inversion of the Bcl2. Bax ratio between low-grade (typical and atypical carcinoids) and high-grade (LCNECs and SCLCs) tumors with a predominant Bax expression in the first group and predominant Bcl2 expression in the second. Whereas carcinoids had variable apoptotic indexes, LCNECs had high indexes (1.3 to 6.8%), Bcl2 overexpression, Bax down-regulation, and Bcl2.Bax ratio > 1 correlated with lower apoptotic index in both LCNEC and the pool of LCNECs and SCLCs (P < 0.05) and a lower survival rate in the group of atypical and typical carcinoids and LCNECs (P < 0.002). The highest levels of Bcl2 expression and Bcl2.Bax ratios were associated with p53 mutant immunophenotype (P = 0.02). Our results suggest that aggressiveness in NE lung tumors could be linked, in addition to proliferation, to apoptosis-related factors.

Targeted disruption of vinculin genes in F9 and embryonic stem cells changes cell morphology, adhesion, and locomotion

Vinculin, a major constituent of focal adhesions and zonula adherens junctions, is thought to be involved in linking the microfilaments to areas of cell-substrate and cell-cell contacts. To test the role of vinculin in cell adhesion and motility, we used homologous recombination to generate F9 embryonal carcinoma and embryonic stem cell clones homozygous for a disrupted vinculin gene. When compared to wild-type cells, vinculin-mutant cells displayed a rounder morphology and a reduced ability to adhere and spread on plastic or fibronectin. Decreased adhesion of the mutant cells was associated with a reduction in lamellipodial extensions, as observed by time-lapse video microscopy. The locomotive activities of control F9 and the vinculin-null cells were compared in two assays. Loss of vinculin resulted in a 2.4-fold increase in cell motility. These results demonstrate an important role for vinculin in determining cell shape, adhesion, surface protrusive activity, and cell locomotion.

Focal adhesion formation by F9 embryonal carcinoma cells after vinculin gene disruption

The assembly of focal adhesions was investigated in F9 embryonal carcinoma cells in which the expression of vinculin was eliminated by a targeted disruption of the vinculin gene. Vinculin-deficient F9 cells were capable of adhering to fibronectin-coated surfaces, though they displayed a reduced spreading compared to the parental cells. Transmission electron microscopy as well as interference reflection microscopy of live cells showed that vinculin-null F9 cells formed focal adhesions that were indistinguishable from those of the control cells. Fluorescent labeling for actin, talin, alpha-actinin, paxillin and phosphotyrosinated components indicated that the organization of all these focal contact-associated components was essentially identical in the vinculin-containing and vinculin-null cells. However, quantitative, digitized microscopy indicated that the intensity of fluorescence labeling in focal adhesions for alpha-actinin, talin and paxillin was significantly higher in cells lacking vinculin. The results suggest that there are multiple molecular mechanisms for the formation of focal adhesions in the absence of vinculin.

Expression of the nmpC gene of Escherichia coli K-12 is modulated by external pH. Identification of cis-acting regulatory sequences involved in this regulation

Using a set of gene fusions generated with TnphoA, we previously identified the phmA locus, whose expression is modulated as a function of external pH (pHo). The phmA::phoA fusion was cloned and sequenced and the phmA locus was identified with the nmpC gene. This gene lies within the defective lambdoid prophage qsr' and NmpC is an outer membrane protein which functions as a porin. We demonstrated that nmpC is sensitive to catabolite repression and dependent on the CRP-cAMP complex. However, cAMP is not a signal for the pHo-dependent expression of nmpC. By generating step deletions in the sequence 5' to the nmpC coding region, we identified a DNA region in position -345 to -127 which is involved in nmpC repression, mainly during growth at acid pHo. Four regions with strong homologies and a very well-conserved organization of the functional sequence were found in the nmpC and ompF promoters. We propose that the negative regulation of nmpC during growth at low pHo might involve DNA looping of the nmpC promoter.

Expression of integrin and CD44 adhesion molecules on neuroblastoma: the relation to tumor aggressiveness and embryonic neural-crest differentiation

The immunohistological expression of integrins and CD44 cell adhesion molecule was analyzed on neuroblastoma (NB) specimens to study the potential role of these molecules in normal differentiation and in the transformation of neural crest derivatives. None of the specimens expressed the alpha 5 beta 1 integrin heterodimer; the expression of alpha 3 beta 1 heterodimer was maintained during all stages of differentiation; alpha 1 beta 1 heterodimer was expressed on undifferentiated neuroblasts and on Schwann cells, but was lost on ganglion cells. In contrast alpha 2 beta 1, alpha 6 beta 1, alpha 6 beta 4 and alpha V beta 1 expression was usually restricted to cells differentiated in the Schwann cell lineage. Alpha V beta 3 was expressed on tumors developed in the mediastinum. CD44 was strongly detected on differentiated ganglioneuroblastomas, stage 1 and 2 ganglioneuromas, as well as low-grade stage 4S NB and normal neuroblasts migrating in the fetal adrenal gland. CD44 expression was observed on Schwann cells and ganglion cells; in contrast, it was expressed on only 50% stage 3 and 4 undifferentiated NB. None of these specimens expressed exons V5, V7 or V6. In a few specimens, an intracellular expression of exons V8-V10 was observed in ganglion cells. The expression of CD44 on NB may reflect its pattern of expression on sympatho-adrenal precursors and arrest differentiation at these stages. Conversely, CD44 expression may be silenced during malignant transformation.(ABSTRACT TRUNCATED AT 250 WORDS)

Expression of chicken vinculin complements the adhesion-defective phenotype of a mutant mouse F9 embryonal carcinoma cell

A mutant cell line, derived from the mouse embryonal carcinoma cell line F9, is defective in cell-cell adhesion (compaction) and in cell-substrate adhesion. We have previously shown that neither uvomorulin (E-cadherin) nor integrins are responsible for the mutant phenotype (Calogero, A., M. Samuels, T. Darland, S. A. Edwards, R. Kemler, and E. D. Adamson. 1991. Dev. Biol. 146:499-508). Several cytoskeleton proteins were assayed and only vinculin was found to be absent in mutant (5.51) cells. A chicken vinculin expression vector was transfected into the 5.51 cells together with a neomycin-resistance vector. Clones that were adherent to the substrate were selected in medium containing G418. Two clones, 5.51Vin3 and Vin4, were analyzed by Nomarski differential interference contrast and laser confocal microscopy as well as by biochemical and molecular biological techniques. Both clones adhered well to substrates and both exhibited F-actin stress fibers with vinculin localized at stress fiber tips in focal contacts. This was in marked contrast to 5.51 parental cells, which had no stress fibers and no vinculin. The mutant and complemented F9 cell lines will be useful models for examining the complex interactions between cytoskeletal and cell adhesion proteins.

Identification of Escherichia coli genes whose expression increases as a function of external pH

Using transposon TnphoA and a plate screening method, we have isolated a set of Escherichia coli strains carrying phoA fusions with genes whose expression is modulated as a function of external pH. Besides fusions with the ompF gene and the malB locus, thirteen independent fusions were analysed whose expression is maximal during growth at pHs ranging from 7.0 to 8.5 and minimal during growth at pH 5.0. Six different genetic loci, called phmA, phmB, phmC, phmD, phmE and phmF (for pH modulated) were characterized and localized on the E. coli chromosome at approx. 12, 18, 41, 45, 75 and 84 min, respectively. Expression of phmA::phoA fusions is also influenced when internal pH or environmental conditions such as osmolarity or anaerobiosis are modified. EnvZ protein is not involved in the regulation of phm::phoA fusions.

Extracellular matrix production by embryonic epithelium cultured on type IV collagen. Deposition of a primary corneal stroma-like structure containing large irregular type I fibrils without type II collagen

The corneal stroma of the chick embryo is deposited in two steps. The primary stroma is laid down by the corneal epithelium and it contains type I, type II and type IX collagens. Its formation is subsequent to the presumptive epithelial cells' migration onto the lens capsule (which is rich in type IV collagen). The secondary, ultimate stroma is synthesized by fibroblasts which, on day 5 of development, invade the swollen primary stroma. It is composed of a matrix of thin (25 nm), regular fibrils containing type I and type V collagens. We found that a chick corneal epithelium isolated from either a 6-day or a 14-day embryo was able to produce, in vitro, stroma-containing type I collagen fibrils. However, the amount of collagen deposited and its organization were highly dependent on the substratum used. Plastic or purified bovine type I collagen substrata led to the release of very few fibrils. Purified human type IV collagen induced the production of an abundant matrix made of large irregular collagen fibrils. When compared to native corneal stroma, there were two aspects in which this matrix differed: (1) it contained only type I collagen, as shown by indirect immunofluorescence, and (2) there were numerous large, irregular fibrils of about 100 to 130 nm in diameter. In conclusion, it is suggested that purified type IV collagen substitutes, in part, for the basement membrane and allows the production of a corneal stroma-like matrix by an embryonic corneal epithelium in culture. This production is possible even with a 14-day epithelium which, in vivo, is no more involved in the synthesis of the stroma collagens. Moreover, the regulatory effect of type II collagen, previously suggested by in vivo observations, may be confirmed in this in vitro system by the appearance of large fibrils in the newly deposited stroma that are made only by type I collagen.