Note: On the measurement of plasma potential fluctuations using emissive probes

In this Note, it is pointed out that emissive probes cannot be used to directly and reliably measure plasma potential fluctuations. An experimentally validated model demonstrates indeed that the floating potential fluctuations of an emissive probe which floats at the mean plasma potential depend not only on the plasma potential fluctuations but also on electron density and temperature fluctuations.

Design and validation of the ball-pen probe for measurements in a low-temperature magnetized plasma

Ball-pen probes have been used in fusion devices for direct measurements of the plasma potential. Their application in low-temperature magnetized plasma devices is still subject to studies. In this context, a ball-pen probe has been recently implemented on the linear plasma device Mirabelle. Produced by a thermionic discharge, the plasma is characterized by a low electron temperature and a low density. Plasma confinement is provided by an axial magnetic field that goes up to 100 mT. The principle of the ball-pen probe is to adjust the saturation current ratio to 1 by reducing the electron current contribution. In that case, the floating potential of the probe is close to the plasma potential. A thorough study of the ball-pen probe operation is performed for different designs of the probe over a large set of plasma conditions. Comparisons between ball-pen, Langmuir, and emissive probes are conducted in the same plasma conditions. The ball-pen probe is successfully measuring the plasma potential in these specific plasma conditions only if an adapted electronics and an adapted probe size to the plasma characteristic lengths (λ(D), ρ(ce)) are used.

Effects of antisense oligonucleotides targeting k-ras expression in pancreatic-cancer cell-lines

The K-ras oncogene is activated in more than 75% of pancreatic cancers and represents a compelling target for therapeutic intervention. We have examined the potential of K-ras antisense oligonucleotides in human pancreatic cancer cell lines. Dose-dependent antiproliferative effects are seen, but these do not correlate with reduced K-ras levels in the treated cells. Although patterns of uptake can be altered by treatment with cationic lipids, this does not enhance antiproliferative effects nor reduce K-ras expression. The antisense approach requires considerable development before useful anti-cancer agents can emerge and alternative approaches are needed for K-ras to be a target for genetic intervention therapy for human cancer.

Pathobiological characteristics of the 1st primary and risk of metachronous contralateral invasive breast-carcinoma - clinical implications

The study was undertaken to determine the clinico-pathobiological characteristics in a series of 49 patients who developed metachronous breast carcinoma. Possible differences between the two tumours of conventional clinico-pathological features and of some biological markers such as DNA ploidy, c-erbB-2 oncoprotein overexpression and tumour angiogenesis were evaluated. The McNemar's test for independence showed that all the characteristics analyzed between the two tumours, in the same case, were not significantly different. After a median follow-up time of 69 months the overall survival of the series was 87.5% and the only significant prognostic factor for clinical outcome was peritumoural lymphatic vessel invasion (PLVI). The median second tumour-free interval was of 32 months ( 13 to 160 months) and none of the variables analyzed on the first primary was predictive of the timing of appearance of the second tumour. To assess the association between the characteristics of the first tumour and the odds of developing a metachronous carcinoma a case-control analysis was conducted. For each woman of the present series who developed bilateral cancer (case) a woman who had unilateral breast cancer (control) was matched for the length of the follow-up. A log-logistic regression model for matched sets was also performed to assess the risk of developing the second tumour. Applying multivariate analysis we found that progesterone receptor (PgR) status was the most important prognostic factor for the odds of bilateral tumour (odds ratio 0.22, p=0.013) followed by histological grade (odds ratio 0.20, p=0.063) and presence of PLVI (odds ratio 3.13, p=0.067). These findings suggest that the knowledge on the initial primary of PgR, grading and PLVI could be important to assess the individual risk of developing metachronous breast cancer. The determination of these factors could improve our ability to identify subsets of patients operated for breast cancer with different risks for bilateral tumour, allowing for a better selection of those patients who need intensive surveillance of their contralateral breast, and eligible for chemoprevention.

Localization of expression of fibroblast growth-factors and their receptors in pancreatic adenocarcinoma by in-situ hybridization

Growth factors may play a role in autocrine or paracrine growth control of tumour cells. We have now examined the expression pattern in vivo by in situ hybridization (ISH) on a series of 13 ductal adenocarcinomas of the pancreas using the non-radioactive digoxigenin system to generate specific antisense orientated riboprobes for FGF-1 and FGF-2, and the four FGFRs (FGFR-1, -2, -3 and -4). We confirmed the expression of both FGF/FGFR by tumour cells, with the potential of a potential autocrine loops in 46% of the cases studied. FGF-2 and FGFR-3 were the most commonly expressed ligand and receptor (46% and 76% respectively). Endothelial cells lining vessels within an around invasive tumours were frequently positive for expression of FGFR-1 and/or FGFR-3. In the normal pancreas remote from the tumour, the acinar cells were found to have a heterogeneous expression pattern for FGFRs while duct cells, islet cells and stromal components including nerves and vascular endothelium were negative. The data suggest a role for FGFs and their high affinity receptors in the control of growth of human pancreatic adenocarcinoma and its supporting stroma.

Spectroscopic interpretation and velocimetry analysis of fluctuations in a cylindrical plasma recorded by a fast camera

Fast visible imaging is used on a cylindrical magnetized argon plasma produced by thermionic discharge in the Mirabelle device. To link the information collected with the camera to a physical quantity, fast camera movies of plasma structures are compared to Langmuir probe measurements. High correlation is found between light fluctuations and plasma density fluctuations. Contributions from neutral argon and ionized argon to the overall light intensity are separated by using interference filters and a light intensifier. Light emitting transitions are shown to involve a metastable neutral argon state that can be excited by thermal plasma electrons, thus explaining the good correlation between light and density fluctuations. The propagation velocity of plasma structures is calculated by adapting velocimetry methods to the fast camera movies. The resulting estimates of instantaneous propagation velocity are in agreement with former experiments. The computation of mean velocities is discussed.

Loss of expression of antigen-presenting molecules in human pancreatic cancer and pancreatic cancer cell lines

Tumours evade immune recognition and destruction through loss or down-regulation of expression of antigen processing and antigen-presenting molecules such as the human leucocyte antigen (HLA class I) and transporter for antigen presentation (TAP). This study examined the expression of HLA class I, class II and TAP in human pancreatic carcinoma tissue and 19 immortalized pancreatic cancer lines using a panel of antibodies directed against allele-specific as well as monomorphic determinants of these molecules. In tissue samples, reduction or loss of HLA class I and TAP was observed in 76% of cases, loss or down-regulation of TAP expression in 53%. In pancreatic cell lines down-regulation or loss of class I and TAP expression was also observed frequently. However, reductions in class I and TAP expression were reversible upon exposure to interferon-gamma in vitro, suggesting a regulatory rather than structural defect in these genes. De novo class II expression was observed in 26% of tumours and 42% of cell lines and may reflect the differentiation status of the cells. The high rate of class I and TAP loss has implications for immunotherapy strategies for pancreatic cancer, as such changes could facilitate a selective growth advantage for malignant cells. However, the reinduction of expression of these molecules with cytokines such as interferon-gamma may ultimately allow their cytotoxic T cell-mediated destruction.

Induction of viral and tumour specific CTL responses using antibody targeted HLA class I peptide complexes

The production of cytotoxic T cells with specificity for cancer cells is a rapidly evolving branch of cancer therapeutics. A variety of approaches aim to amplify anti-tumour cytotoxic T cell responses using purified peptides, tumour cell lysates or recombinant HLA/peptide complexes in differing antigen presenting systems. Using a two-step biotin-streptavidin antibody targeting system, recombinant HLA-class I/peptide complexes were attached to the surface of B cells via the anti-CD20 B9E9-scFvSA antibody-streptavidin fusion protein. Flow cytometry with a conformation dependant monoclonal antibody to HLA class I indicated that targeted HLA-class I/peptide complexes remain on the surface of B cells in culture for periods in excess of 72 h. PBMCs were stimulated in vitro for 8-14 days using the autologous B cells as antigen presenting cells. Following a single cycle of stimulation specific cytotoxic T cell responses to targeted HLA-A2 complexes containing the M1, BMLF1 and Melan A peptides could be demonstrated by tetramer staining and Cr release assays. With the HLA-A2/BMLF1 complex up to 2.99% of CD8+ve cells were tetramer positive producing 20% lysis (E : T 10 : 1) of CIR-A2 target cells in an in vitro cytotoxicity assay compared to baseline levels of 0.09% tetramer +ve and 2% lysis in the unstimulated population. PBMCs from a healthy donor treated with two cycles of stimulations with targeted HLA-A2/Melan A complexes, demonstrated expansion of the melanA tetramer +ve population from 0.03% to 1.4% producing 15% lysis of Melan A pulsed target cells. With further consideration to the key variables of HLA/peptide complex density, the ratio of stimulator to effector cells and optimum cytokine support, this system should offer an easy and effective method for the in vitro amplification of specific cytotoxic T cell responses and warrants development for the in vivo induction of cytotoxic T cell responses in cancer therapy.

Herpes simplex virus thymidine kinase/ganciclovir-induced cell death is enhanced by co-expression of caspase-3 in ovarian carcinoma cells

There is a need to enhance the efficacy of genetic prodrug activation therapy using herpes simplex virus thymidine kinase (tk) and ganciclovir (GCV) following disappointing results in early clinical trials. tk/GCV has been shown to lead to the activation of caspase-3, a potent executor of apoptosis. We demonstrate that co-expression of pro-caspase-3 with tk/GCV leads to enhanced cell death in ovarian carcinoma cells in vitro. Following transfection with recombinant adenoviral vectors encoding tk, GCV treatment leads to greater cell death in pro-caspase-3-expressing clones of SKOV3 and IGROV1 than control cells, as well as more rapid activation of caspase-3 and more rapid cleavage of PARP. Flow cytometry suggests that there is a greater degree of S-phase block in the pro-caspase-3-expressing clones than in control cells following treatment with tk/GCV. None of these effects is seen following transfection with a control adenovirus that does not encode tk. The increased cell death, early caspase-3 activation and PARP cleavage, and flow cytometric changes seen in pro-caspase-3-expressing cells can be partially inhibited by treatment with benzyloxycarbonyl-val-ala-asp fluoromethylketone, a synthetic caspase inhibitor. Our data suggest that co-expression of pro-caspase-3 may lead to a significant enhancement of the efficacy of tk/GCV therapy.

K-ras oncogene subtype mutations are associated with survival but not expression of p53, p16(INK4A), p21(WAF-1), cyclin D1, erbB-2 and erbB-3 in resected pancreatic ductal adenocarcinoma

Previous studies of molecular prognostic markers following resection for exocrine pancreatic cancer have produced conflicting results. Our aim was to undertake a comprehensive analysis of potentially useful molecular markers in a large, multicentre patient population and to compare these markers with standard pathological prognostic variables. Formalin-fixed, paraffin-embedded specimens of pancreatic ductal adenocarcinoma were analysed from 157 patients [100 men and 57 women with a median (range) age of 60 (33-77) years] who had undergone pancreatectomy. Immunohistochemistry was used to detect expression of p16(INK4), p53, p21(WAF1), cyclin D1, erbB-2 and erbB-3. Mutations in codons 12 and 13 of the K-ras oncogene were detected by SSCP and sequencing following DNA extraction and amplification by PCR. The median (range) survival post-resection was 12.5 (3-83) months. Abnormalities of p16(INK4), p53, p21(WAF1), cyclin D1, erbB-2 and erbB-3 expression were found in 87%, 41%, 75%, 72%, 33% and 57% of cases, respectively. There was no significant correlation between expression of any of these markers and patient survival. K-ras mutations were found in 73 (75%) of 97 cases with amplifiable DNA. The presence of K-ras mutation alone did not correlate with survival, but there were significant differences in survival according to the type of K-ras mutation (p = 0.0007). Reduced survival was found in patients with GaT, cGT and GcT K-ras mutations compared to GtT, aGT and GaC mutations. In conclusion, survival was associated with type of K-ras mutation but not expression of p16(INK4), p53, p21(WAF1), cyclin D1, erbB-2 and erbB-3.

K-ras oncogene subtype mutations are associated with survival but not expression of p53, p16(INK4A), p21(WAF-1), cyclin D1, erbB-2 and erbB-3 in resected pancreatic ductal adenocarcinoma

Previous studies of molecular prognostic markers following resection for exocrine pancreatic cancer have produced conflicting results. Our aim was to undertake a comprehensive analysis of potentially useful molecular markers in a large, multicentre patient population and to compare these markers with standard pathological prognostic variables. Formalin-fixed, paraffin-embedded specimens of pancreatic ductal adenocarcinoma were analysed from 157 patients [100 men and 57 women with a median (range) age of 60 (33-77) years] who had undergone pancreatectomy. Immunohistochemistry was used to detect expression of p16(INK4), p53, p21(WAF1), cyclin D1, erbB-2 and erbB-3. Mutations in codons 12 and 13 of the K-ras oncogene were detected by SSCP and sequencing following DNA extraction and amplification by PCR. The median (range) survival post-resection was 12.5 (3-83) months. Abnormalities of p16(INK4), p53, p21(WAF1), cyclin D1, erbB-2 and erbB-3 expression were found in 87%, 41%, 75%, 72%, 33% and 57% of cases, respectively. There was no significant correlation between expression of any of these markers and patient survival. K-ras mutations were found in 73 (75%) of 97 cases with amplifiable DNA. The presence of K-ras mutation alone did not correlate with survival, but there were significant differences in survival according to the type of K-ras mutation (p = 0.0007). Reduced survival was found in patients with GaT, cGT and GcT K-ras mutations compared to GtT, aGT and GaC mutations. In conclusion, survival was associated with type of K-ras mutation but not expression of p16(INK4), p53, p21(WAF1), cyclin D1, erbB-2 and erbB-3.

A phase I/II study of hepatic artery infusion with wtp53-CMV-Ad in metastatic malignant liver tumours

Colorectal cancer (CRC) is the second commonest cause of cancer death in the UK, with greater than 40% of these patients destined to die of the disease despite current medical management. Death is commonly due to liver metastases with sequelae including progressive liver dysfunction. Most patients with liver metastases present with tumours that are unresectable and incurable with existing therapies. The median survival for CRC patients after diagnosis with liver metastases is approximately 6 months or less. The human p53 gene is a tumour suppressor gene involved in the control of cell proliferation. Loss of wild-type p53 function is associated with the uncontrolled growth of many types of human cancers. The reintroduction and expression of wild-type p53 into p53 altered tumour cells has been shown to suppress tumour growth or induce apoptosis in both in vitro and in vivo models. In our experience greater than 50% of CRC tumours have p53 alterations. This study seeks to evaluate the safety, biological efficacy and the effectiveness of wtp53-CMV-Ad treatment which is a recombinant adenoviral vector containing the wild-type human p53 gene. It will be administered by infusion via the hepatic artery, for the regional gene therapy of malignant liver tumours. Study patients will have incurable metastatic (CRC) malignant tumours of the liver with evidence of p53 alteration in their liver tumours. In vitro studies have demonstrated p53-specific antiproliferative effects of wtp53-CMV-Ad on human liver tumour cells and in vivo studies have demonstrated p53-specific antiproliferative effects on human liver tumour cells. The vector Ad-p53 is a recombinant, replication-defective adenovirus based on adenovirus serotype 5. It contains a sequence encoding wild-type p53 whose expression is under the control of the human cytomegalovirus immediate early promoter-enhancer. This construct will be growth in 293 cells which contain the adenoviral E1A and E1B coding sequences which have been removed from the vector to render it replication defective. The study design is an open-label, non-randomised, single-dose, dose escalation Phase I/II clinical trial anticipated to involve a maximum of 19 patients. wtp53-CMV-Ad will be administered by infusion in a reservoir connected to the hepatic artery, for regional gene therapy (surgically implanted pump) in 3 escalating doses to successive cohorts of 3 patients each until the maximum tolerated dose is determined. Subsequently, 10 patients will be treated with this dose. Regional wtp53-CMV-Ad therapy will be administered as a single bolus infusion via hepatic artery catheter. The route of administration of wtp53-CMV-Ad via hepatic artery infusion is designed to maximise gene therapy exposure to the malignant tumours while minimising exposure to normal tissues outside the liver. The clinical protocol is designed to monitor treatment toxicity. Another objective is to evaluate the biological efficacy, including efficiency and stability of gene transfer by analysis of tumour tissues following therapy. As an important part of this objective the pharmacokinetics of wtp53-CMV-Ad will be studied. Clinical evidence of anti-tumour efficacy will also be collected. In addition, the safety and efficacy of different doses levels of wtp53-CMV-Ad will be studied.

Characterization of the E-cadherin-catenin complexes in pancreatic carcinoma cell lines

E-cadherin and its associated cytoplasmic proteins alpha-, beta-, and gamma-catenins play important roles in cell adhesion and signal transduction, as well as in maintenance of the structural and functional organization of polarized epithelial cells. In this study, the expression, distribution, and complex assembly of catenins with E-cadherin was analysed at the steady state in a panel of human pancreatic adenocarcinoma cell lines (BxPc3, HPAF, T3M4, and PaTuII cell lines). The expression and subcellular distribution were determined by western blotting and immunocytochemistry. Co-immunoprecipitation and cross-linking studies were performed to examine the complex assembly in both Triton X-100 (TX-100)-soluble and -insoluble fractions. In BxPc3 and T3M4 cells, E-cadherin exists in two complexes, one with alpha- and gamma-catenin, and the other with beta-catenin alone. In HPAF cells there are two complexes, one consisting of E-cadherin with alpha- and beta-catenin, and another of E-cadherin with gamma-catenin. In PaTuII cells, there is only a single complex of E-cadherin with alpha-catenin and gamma-catenin. Modification of E-cadherin-catenin complexes in HPAF and PaTuII cells was associated with loss of membranous E-cadherin immunolocalization. The common denominator is impaired beta-catenin association with either E-cadherin (PaTuII) or alpha-catenin (BxPc3 and T3M4). This may suggest the presence of distinct mechanisms that modulate the assembly of each complex, which could disturb the tumour suppressor function of E-cadherin and the catenins.

Fibroblast growth factor 1 and fibroblast growth factor 2 immunoreactivity in gastrointestinal tumours

Acidic and basic fibroblast growth factors (FGF-1 and FGF-2) are mitogenic polypeptides that may play a role in autocrine and paracrine growth control of malignant tumours. We have examined the expression of FGF-1 and FGF-2 in a series of 41 colorectal tumours (24 adenomas, 17 adenocarcinomas) and 50 gastric adenocarcinomas (23 intestinal, 27 diffuse), using immunohistochemistry. Whereas the FGF-1 distribution was cytoplasmic, FGF-2 was restricted to the nuclei of the epithelial cells. FGF-1 immunoreactivity was detected in all samples (100 per cent), whereas FGF-2 immunoreactivity was seen in 17 adenomas (71 per cent), 13 colorectal carcinomas (76 per cent), and 29 gastric carcinomas (58 per cent). Compared with the normal mucosa, FGF-1 was overexpressed in 42 per cent of colorectal adenomas, 76 per cent of colorectal cancers, and 54 per cent of gastric cancers. Conversely, FGF-2 expression was reduced in 16 (66 per cent), 8 (47 per cent), and 40 (80 per cent) adenomas and colorectal and gastric samples, respectively. We found a significant correlation only between reduced FGF-2 and gastric tumour grade. These data indicate that FGF-1 overexpression occurs in a large proportion of human colorectal and gastric cancers. This may play a role in the progression of these tumours. The topographic variation in FGF-2 expression between normal (nuclear) and tumour (cytoplasmic) cells implies a corresponding functional change that may in turn facilitate tumour growth.

In vitro transformation of epithelial cells by ras oncogenes

Genes of the ras family of dominant transforming genes are frequently activated by specific point mutations in common human epithelial malignancies and also in many experimental tumour models. Testing of the hypothesis that ras activation is a critical event in tumorigenesis involves reconstruction of genetic events in vitro using appropriate epithelial models. This article reviews experimental transformation of human and rodent epithelial cells by ras oncogenes in vitro, alone and in combination with cooperating oncogenic events.

Effect of serum growth factors and phorbol ester on growth and survival of human thyroid epithelial cells expressing mutant ras

We previously demonstrated a high incidence of ras mutation in thyroid follicular (epithelial) cell neoplasms and showed that expression of mutant ras is a potent mitogenic stimulus for normal human follicular cells in culture. Here we show that induction of cell proliferation in primary follicular cells by a mutant human Ha-ras (val 12) expressed from a retroviral vector was absolutely dependent on the presence of serum growth factors. Induction of DNA synthesis showed partial dependence. Mutant ras-induced growth was also inhibited by exposure to phorbol ester at concentrations sufficient to downregulate protein kinase C. More importantly, we observed an unexpected toxic effect of phorbol ester in this system that was specific to cells expressing mutant ras. This has potential significance both for elucidating the basic mechanism of ras action in epithelial cells and also as a pointer to a novel therapeutic strategy.