Perioperative intravenous contrast administration and the incidence of acute kidney injury after major gastrointestinal surgery: prospective, multicentre cohort study

BACKGROUND

This study aimed to determine the impact of preoperative exposure to intravenous contrast for CT and the risk of developing postoperative acute kidney injury (AKI) in patients undergoing major gastrointestinal surgery.

METHODS

This prospective, multicentre cohort study included adults undergoing gastrointestinal resection, stoma reversal or liver resection. Both elective and emergency procedures were included. Preoperative exposure to intravenous contrast was defined as exposure to contrast administered for the purposes of CT up to 7 days before surgery. The primary endpoint was the rate of AKI within 7 days. Propensity score-matched models were adjusted for patient, disease and operative variables. In a sensitivity analysis, a propensity score-matched model explored the association between preoperative exposure to contrast and AKI in the first 48 h after surgery.

RESULTS

A total of 5378 patients were included across 173 centres. Overall, 1249 patients (23·2 per cent) received intravenous contrast. The overall rate of AKI within 7 days of surgery was 13·4 per cent (718 of 5378). In the propensity score-matched model, preoperative exposure to contrast was not associated with AKI within 7 days (odds ratio (OR) 0·95, 95 per cent c.i. 0·73 to 1·21; P = 0·669). The sensitivity analysis showed no association between preoperative contrast administration and AKI within 48 h after operation (OR 1·09, 0·84 to 1·41; P = 0·498).

CONCLUSION

There was no association between preoperative intravenous contrast administered for CT up to 7 days before surgery and postoperative AKI. Risk of contrast-induced nephropathy should not be used as a reason to avoid contrast-enhanced CT.

Schistosoma mansoni Infection as a Predictor of Low Aerobic Capacity in Ugandan Children

Using the 20-meter shuttle run test (20mSRT) as a morbidity metric, we assessed whether Schistosoma mansoni infection was associated with decreased aerobic capacity in Ugandan children across a range of altitudes, either at low (∼600 m) or high (∼1,000 m) altitudes. A total of 305 children were recruited from six schools within the Buliisa District, Lake Albert, Uganda. A subset (n = 96) of these had been previously assessed and treated for schistosomiasis ± malaria 2 weeks prior. Fitness scores on the 20mSRT were translated into VO2max using a standardized equation. Unadjusted and multivariable-adjusted analyses were performed using VO2max as the primary outcome. Analysis of fitness scores from 304 children, inclusive of the subset follow-up cohort, revealed a median VO2max of 45.4 mL kg-1 min-1 (interquartile range: 42.9-48.0 mL kg-1 min-1). Children residing at high altitudes demonstrated increased aerobic capacities (46.3 versus 44.8 mL kg-1 min-1, P = 0.031). The prevalence of stunting, wasting, S. mansoni egg patent infection, malaria, giardiasis, anemia, and fecal occult blood were 36.7%, 16.1%, 44.3%, 65.2%, 21.4%, 50.6%, and 41.2%, respectively. Median VO2max was elevated in those previously treated, compared with those newly recruited (46.3 versus 44 mL kg-1 min-1, P < 0.001). Multivariable-adjusted analysis revealed a strong negative association between S. mansoni egg patent infection and VO2max at low altitude (beta coefficient: -3.96, 95% CI: -6.56 to -137, P = 0.004). This is the first study to document a negative association between S. mansoni infection and aerobic capacity at low altitudes using the 20mSRT.

Meta-analysis of the diagnostic accuracy of laparoscopic ultrasonography and intraoperative cholangiography in detection of common bile duct stones

Introduction During laparoscopic cholecystectomy, intraoperative cholangiography (IOC) is currently regarded as the gold standard in the detection of choledocholithiasis. Laparoscopic ultrasonography (LUS) is an attractive alternative with several potential advantages. Methods A systematic review was undertaken of the published literature comparing LUS with IOC in the assessment of common bile duct (CBD) stones. Results Twenty-one comparative studies were analysed. There were 4,566 patients in the IOC group and 5,044 in the LUS group. The combined sensitivity and specificity of IOC in the detection of CBD stones were 0.87 (95% confidence interval [CI]: 0.83-0.89) and 0.98 (95% CI: 0.98-0.98) respectively with a pooled area under the curve (AUC) of 0.985 and a diagnostic odds ratio (OR) of 260.65 (95% CI: 160.44-423.45). This compares with a sensitivity and specificity for LUS of 0.90 (95% CI: 0.87-0.92) and 0.99 (95% CI: 0.99-0.99) respectively with a pooled AUC of 0.982 and a diagnostic OR of 765.15 (95% CI: 450.78-1,298.76). LUS appeared to be more successful in terms of coming to a clinical decision regarding CBD stones than IOC (random effects, risk ratio: 0.95, 95% CI: 0.93-0.98, df=20, z=-3.7, p<0.005). Furthermore, LUS took less time (random effects, standardised mean difference: 0.95, 95% CI: 0.93-0.98, df=20, z=-3.7, p<0.005). Conclusions LUS is comparable with IOC in the detection of CBD stones. The main advantages of LUS are that it does not involve ionising radiation, is quicker to perform, has a lower failure rate and can be repeated during the procedure as required.

Analysis of airway epithelial regeneration and repair following endobronchial brush biopsy in sheep

Understanding the fundamental processes involved in repairing the airway wall following injury is fundamental to understanding the way in which these processes are perturbed during disease pathology. Indeed complex diseases such as asthma and chronic obstructive pulmonary disease (COPD) have at their core evidence of airway wall remodeling processes that play a crucial functional role in these diseases. The authors sought to understand the dynamic cellular events that occur during bronchial airway epithelial repair in sheep. The injury was induced by endobronchial brush biopsy (BBr), a process that causes epithelial débridement and induces a consequential repair process. In addition, the current experimental protocol allowed for the time-dependent changes in airway wall morphology to be studied both within and between animals. The initial débridement was followed by evidence of dedifferentiation in the intact epithelium at the wound margins, followed by proliferation of cells both within the epithelium and in the deeper wall structures, notably in association with the submucosal glands and smooth muscle bundles. Seven days after injury, although the airway wall was thickened at the site of damage, the epithelial layer was intact, with evidence of redifferentiation. These studies, in demonstrating broad agreement with previous studies in small animals, indicate the wider relevance of this system as a comparative model and should provide a solid basis upon which to further characterize the critical cellular and molecular interactions that underlie both effective restitution and pathological repair.

Preclinical analysis of the analinoquinazoline AG1478, a specific small molecule inhibitor of EGF receptor tyrosine kinase

The tyrphostin 4-(3-chloroanilino)-6,7-dimethoxyquinazoline (AG1478) is a potent and specific inhibitor of EGFR tyrosine kinase whose favourable preclinical profile supports progression towards clinical trials. Microphysiometric evaluation revealed a short (<24 min) effective inhibition of cellular receptor response to EGF challenge in BaF/ERX cells indicating a need to maintain sustained levels of inhibitor. Initial pharmacokinetic evaluation in mice of novel AG1478 formulations in a beta-cyclodextrin (Captisol) showed monoexponential elimination from plasma (half-life 30 min) following subcutaneous administration. A two-fold dose escalation gave a 2.4-fold increase in the total AUC. Bolus i.v. and 6 h continuous infusion were investigated in rats to mimic a more clinically relevant administration regimen. Drug elimination following bolus i.v. administration was biphasic (terminal elimination half-life 30-48 min). The linear relationship between dose and AUC(0-->infinity) (r2=0.979) enabled the prediction of infusion rates and doses for sustained delivery using continuous 6 h infusions, where steady state was reached in 120 min. Plasma levels of AG1478>10 microM were achieved over the duration of the infusion. At the lowest dose, plasma drug levels after the cessation of infusion declined with a half-life of approximately 43 min. EGFR activity, measured both by autophosphorylation and downstream signalling, was inhibited in a dose-dependent manner by injection of AG1478 in mice bearing xenografts of the human glioblastoma cell line U87MG.delta2-7, which expresses a constitutively active variant of the EGF receptor. Taken together, these experiments provide essential data to assess the anti-tumour efficacy of AG1478 and will assist in the rational design of dose regimens for clinical studies.

Regulation of pulmonary and systemic bacterial lipopolysaccharide responses in transgenic mice expressing human elafin

The control of lung inflammation is of paramount importance in a variety of acute pathologies, such as pneumonia, the acute respiratory distress syndrome, and sepsis. It is becoming increasingly apparent that local innate immune responses in the lung are negatively influenced by systemic inflammation. This is thought to be due to a local deficit in cytokine responses by alveolar macrophages and neutrophils following systemic bacterial infection and the development of a septic response. Recently, using an adenovirus-based strategy which overexpresses the human elastase inhibitor elafin locally in the lung, we showed that elafin is able to prime lung innate immune responses. In this study, we generated a novel transgenic mouse strain expressing human elafin and studied its response to bacterial lipopolysaccharide (LPS) when the LPS was administered locally in the lungs and systemically. When LPS was delivered to the lungs, we found that mice expressing elafin had lower serum-to-bronchoalveolar lavage ratios of proinflammatory cytokines, including tumor necrosis factor alpha (TNF-alpha), macrophage inflammatory protein 2, and monocyte chemoattractant protein 1, than wild-type mice. There was a concomitant increase in inflammatory cell influx, showing that there was potential priming of innate responses in the lungs. When LPS was given systemically, the mice expressing elafin had reduced levels of serum TNF-alpha compared to the levels in wild-type mice. These results indicate that elafin may have a dual function, promoting up-regulation of local lung innate immunity while simultaneously down-regulating potentially unwanted systemic inflammatory responses in the circulation.

Evaluation of nebulised hay dust suspensions (HDS) for the diagnosis and investigation of heaves. 1: Preparation and composition of HDS

Currently, heaves is investigated by exposing susceptible horses to dusty hay. Consequently, the response will be dependent on the organic dust content and composition of the hay. It was hypothesised that the use of a hay dust suspension (HDS) would reduce the variability of the challenge and therefore standardise experimental protocols. Furthermore, analysis of HDS would also permit further investigation of the organic dust components responsible for the response. Three hay dust suspensions (HDS-1, 2 and 3) were prepared for use in the diagnosis and investigation of heaves. HDS were produced from fine dust particles, comprising mostly fungal spores, collected from 3 batches of dusty hay. HDS-1 and 3 were analysed for endotoxin, beta-D-glucan and protein concentrations, general protease activity and enumeration and size distribution of particulates. Protease activity was mainly attributable to a 28 kDa serine protease and to 85 kDa and 160 kDa metalloproteases. The particulate and soluble components of HDS could be aerosolised by jet nebulisation. We therefore conclude that detailed analysis of HDS is possible, that such a challenge system provides a method of standardising experimental protocols and that all components of HDS (both soluble and particulate) can be delivered to the lung using standard nebulisation techniques. For the above reasons, nebulised HDS offers considerable advantages over conventional hay/straw challenge for the diagnosis and investigation of heaves.

Heterogeneity in schizophrenia; mixture modelling of age-at-first-admission, gender and diagnosis

OBJECTIVE

Identifying and explaining sources of heterogeneity in schizophrenia would help elucidate its aetiology and course. In this paper we examine heterogeneity in terms of age-at-first-admission, diagnosis and gender by decomposing a large dataset using mixture modelling.

METHOD

Using the Queensland Mental Health Statistics System, we first extracted age-at-first-admission data for schizophrenia (ICD8/9 295) to represent a 'narrow' definition of schizophrenia (N= 7651); we then added paraphrenia (297) and other non-organic psychoses (298) for a 'broad' definition (N= 10 199). Mixture models were fitted to these narrowly and broadly defined distributions for both males and females.

RESULTS

For narrowly defined schizophrenia a three-component model best fitted both male and female distributions. While the mean ages of these components were very similar for both males and females, the ratios of males to females crossed from an excess of males in the 'youngest' component to an excess of females in the 'oldest' component. When using the broad definition, four components best fitted the underlying distributions. While the first three were similar to those found for narrowly defined schizophrenia, the additional fourth component reverted to a male excess; however, the mean age for males was 10 years younger than for females.

CONCLUSION

Our findings suggest that subtypes based on age-at-first-admission can be identified, although the number identified depends on how inclusively schizophrenia is defined. While there appear to be the same number with similar mean ages for both genders, there are differences in the proportions of males to females. Further work to fully characterize their nature is warranted.

Bacterial DNA is implicated in the inflammatory response to delivery of DNA/DOTAP to mouse lungs

Phase 1 clinical trials of liposome-mediated gene therapy for cystic fibrosis have been completed and in all cases the expression level achieved has been low and transient. Clearly, improvements in the efficiency of gene transfer are required. It is now being recognised that delivery of high doses of DNA/liposomes to the mouse airway epithelium can achieve reproducible evidence of transgene, but is often associated with an unacceptable level of inflammation/ toxicity. It has recently been shown that instillation of bacterial DNA causes inflammation in the lower respiratory tract of rodents. The increased number and unmethylated status of CpG motifs, particularly when present in a particular base context, was identified as an important factor in this response. It was suggested that the immune system recognises this molecular pattern as 'foreign' thus activating appropriate immune responses. We have found that methylation of DNA decreases the level of several inflammatory cytokines in lavage fluid and surprisingly has a differential effect on expression of the plasmids pCMV CFTR-int6ab and pCMV CAT which only differ in the actual transcription cassette. The severe lung pathology observed did not show a corresponding decrease with methylation suggesting that these cytokines are not the only contributors to the toxicity/inflammation observed. Gene Therapy (2000) 7, 384-392.

Insertion of natural intron 6a-6b into a human cDNA-derived gene therapy vector for cystic fibrosis improves plasmid stability and permits facile RNA/DNA discrimination

BACKGROUND

The gene therapy vector pCMV-CFTR containing human CFTR cDNA shows high segregational instability during growth in Escherichia coli.

METHODS

By host strain screening and optimization of fermentation, satisfactory levels of pCMV-CFTR production were achieved. However, the vector was also vulnerable to structural instability manifested by the appearance during fermentation of a more stable mutant form in which the bacterial insertion sequence IS1 had transposed into exon 7 of plasmidborne CFTR. The instability of pCMV-CFTR is attributable to transcription from an upstream cryptic promoter leading to the production of CFTR peptide fragments known to be toxic when expressed in E. coli. To address this, we inserted the 1.1 kb natural human 6a-6b intron into pCMV-CFTR.

RESULTS

The new vector pCMV-CFTR-int6ab is more stable in E. coli than either pCMV-CFTR or the IS1 mutant, grows to high cell density giving higher DNA yields and expresses CFTR appropriately in transfected cells. Thus, the intron has a stabilizing effect comparable to the IS1 insertion yet retains full functionality for gene therapy. We describe a PCR assay using primers directed to sequences flanking the intron that allows differentiation between DNA and mature mRNA. The T936C mutation present only in vector DNA has also been exploited to allow transgene CFTR to be distinguished and its dose-dependent expression to be detected in human cellular backgrounds.

CONCLUSIONS

Instability of a plasmid vector for gene therapy has been minimized by rational modification. The introduction of an intron for this purpose offers the additional advantage of providing a discriminatory RT-PCR assay.

pSURF-2, a modified BAC vector for selective YAC cloning and functional analysis

A modified bacterial artificial chromosome (BAC) vector, pSURF-2, adapted for the selective subcloning of yeast artificial chromosome (YAC) sequences was constructed. DH10B-U, a pyrF derivative of the highly transformable E. coli strain DH10B was also constructed and used for the detection of Ura+ recombinants carrying DNA linked to YAC right arms. The vector's properties were illustrated in two main ways. (i) An intact 25-kb YAC containing a mouse tyrosinase minigene was cloned into pSURF-2. Appropriately spliced tyrosinase RNA was detected by reverse transcription (RT)-PCR in extracts of cells transiently lipofected with the cloned YAC. (ii) Cells expressing human cystic fibrosis transmembrane conductance regulator (CFTR) from an integrated pSURF-2 recombinant containing a cDNA expression cassette were selected using the hygromycin-resistance (HyTK) marker of the vector and characterized by RT-PCR and immunoprecipitation. The unique I-SceI site and HyTK marker of pSURF-2 are designed to facilitate subsequent functional studies of cloned DNA.

Evidence for safety and efficacy of DOTAP cationic liposome mediated CFTR gene transfer to the nasal epithelium of patients with cystic fibrosis

In cystic fibrosis (CF), mutation of the cystic fibrosis transmembrane conductance regulator (CFTR) gene results in defective transepithelial ion transport, leading to life shortening inflammatory lung disease. Before lung studies, we tested the safety and efficacy of gene delivery to the nasal epithelium of CF patients using pCMV-CFTR-DOTAP cationic liposome complex. A single dose of 400 micrograms pCMV-CFTR:2.4 mg DOTAP was administered in a randomised, double-blinded fashion to the nasal epithelium of eight CF patients, with a further eight receiving buffer only. Patients were monitored for signs and symptoms for 2 weeks before treatment and 4 weeks after treatment. Inflammatory cells were quantified in a nasal biopsy taken 3 days after treatment. There was no evidence for excess nasal inflammation, circulating inflammatory markers or other adverse events ascribable to active treatment. Gene transfer and expression were assayed by the polymerase chain reaction. Transgene DNA was detected in seven of the eight treated patients up to 28 days after treatment and vector derived CFTR mRNA in two of the seven patients at +3 and +7 days. Transepithelial ion transport was assayed before and after treatment by nasal potential difference during drug perfusion and by SPQ fluorescence halide ion conductance. Partial, sustained correction of CFTR-related functional changes toward normal values were detected in two treated patients. The level of gene transfer and functional correction were comparable to those reported previously using adenoviral vectors or another DNA-liposome complex, but here were sustained and uncompromised by false positives. These results justify further studies with pCMV-CFTR-DOTAP aimed at treating CF lung disease.

Laboratory and clinical studies in support of cystic fibrosis gene therapy using pCMV-CFTR-DOTAP

The first phase I study of cystic fibrosis gene therapy using cationic liposomes to deliver the cystic fibrosis conductance regulator gene to the nose reported partial and transient correction of the nasal transepithelial ion transport defect, While encouraging, further improvements will be required if this form of treatment is to be of therapeutic value. We tested a new formulation, pCMV-CFTR-DOTAP. The complex is stable for 10 days and effective at correcting the electrophysiological deficit in the trachea of CF mutant mice at 8 or 9 days after intratracheal instillation. Reliable protocols for consistent detection of as few as 10 molecules of CFTR mRNA and DNA in nasal brushing samples are described, Both vector and DNA have been produced to Good Manufacturing Practice standard, Nasal potential difference measurements developed at the National Heart and Lung Institute to assess the CFTR ion channel activity in CF patients replicated well at the Scottish Adult Cystic Fibrosis Service. The SPO fluorescence assay for halide ion conductance in nasal brushings has also been tested. These establish baseline conditions in the Scottish CF cohort from which evidence for correction can be judged under clinical trial conditions. These studies formed the basis for regulatory approval of a randomised, placebo controlled double-blind phase I research study.

Plasmid DNA molecules complexed with cationic liposomes are protected from degradation by nucleases and shearing by aerosolisation

The cationic liposome DOTAP was complexed with plasmid DNA encoding beta-galactosidase in various ratios. As the concentration of DOTAP increased, the DNA became increasingly refractory to staining with ethidium bromide, presumably because the DNA was becoming condensed and being encapsulated by the liposomes. Transfection by DNA-DOTAP complexes at all ratios tested was unaffected by treatment of the complexes with DNase I. This finding has relevance to clinical trials for gene therapy of cystic fibrosis, in which patients are normally removed from treatment with DNase before receiving administration of DNA. We additionally tested the effect of aerosolisation of the liposome-DNA complex and of the DNA alone on the efficiency of in vitro transfection. Aerosolised DNA complexed with fresh DOTAP led to much lower reporter gene expression in Cos 7 cells than non-aerosolised complex, since aerosolisation appeared to destroy almost all of the plasmid. However, complexing the plasmid before passage through the nebuliser did protect most of the DNA from degradation, as reflected in the levels of transfection obtained. These findings contribute towards an overall understanding of both how DNA-cationic liposome complexes are formed and their fate following administration in vivo.

Evaluation in vitro and in vivo of cationic liposome-expression construct complexes for cystic fibrosis gene therapy

We have tested the cationic liposome N-(1-(2,3-dioleoyloxy)propyl)-N,N,N-trimethyl-ammoniummethylsul phate, (DOTAP), for gene delivery in vitro and in vivo with a view to clinical use in gene therapy for cystic fibrosis. Delivery of lacZ cDNA-DOTAP complexes via aerosol showed promoter-dependent differences in the pattern and longevity of expression. Repeated administration was well tolerated. The potential for the transfer of foreign genes into reproductive tissue was investigated by intravenous injection of DNA-DOTAP into female mice. Foreign DNA was undetectable in the ovaries by Southern blot analysis at 1 and 7 days after injection. Our results suggest that DOTAP merits testing in cystic fibrosis patients for delivery of the cystic fibrosis transmembrane conductance regulator (CFTR) gene to the respiratory tract and that substitution of the cytomegalovirus (CMV) promoter for the simian virus (SV) promoter may improve on the transitory response reported previously.

Lung disease in the cystic fibrosis mouse exposed to bacterial pathogens

Lung disease is the major cause of death in cystic fibrosis (CF), but there is no evidence for overt lung involvement at birth. We show here that the same is true for the gene targeted cftrm1HGU mutant mouse. Furthermore, this CF mouse model demonstrates an impaired capacity to clear Staphylococcus aureus and Burkholderia (Pseudomonas) cepacia, two opportunistic lung pathogens closely associated with lung disease in CF subjects. The cftrm1HGU homozygotes display mucus retention and frank lung disease in response to repeated microbial exposure. Thus, lung disease in the cftrm1HGU mouse develops in response to bacterial infection, establishing a model to dissect the pathogenesis of CF pulmonary disease and providing a clinically relevant end point to assess the efficacy of pharmacologic or genetic interventions.

Relationship of platelet aggregation to bleeding after cardiopulmonary bypass

Excessive bleeding after cardiopulmonary bypass operations is a persistent problem. This study assessed the influence of platelet function on blood loss for 134 patients undergoing cardiopulmonary bypass. Platelet function was measured by platelet aggregation in platelet-rich plasma and whole blood using collagen as the agonist. Adenosine triphosphate release was assessed concurrently. Measurements were made 1 day before operation and 1 hour after the cessation of cardiopulmonary bypass. Three important findings were made. First, statistically significant correlations were shown between preoperative and postoperative platelet aggregation and blood drainage for the first 3 hours postoperatively. Second, correlations were greatest when preoperative measurement was performed on whole blood and postoperative measurement was performed on platelet-rich plasma. Third, patients with reduced postoperative platelet aggregation in platelet-rich plasma had significantly greater transfusion requirements in the first 24 hours postoperatively. In defining the 16 patients who bled excessively among the 134 patients studied, the preoperative aggregation in whole blood had a sensitivity of 62%, specificity of 75%, positive predictive value of 26%, and negative predictive value of 94%. The postoperative aggregation in platelet-rich plasma had a sensitivity of 86%, specificity of 69%, positive predictive value of 28%, and negative predictive value of 97%. These results indicate that preoperative and postoperative measurement of platelet aggregation may provide a rationale for the prophylaxis or treatment of patients to reduce blood loss after cardiopulmonary bypass.

Effects of cyclosporin A on growth and polyamine metabolism of MOLT-4 T-lymphoblastic leukaemia cells

We have examined the effects of Cyclosporin A (CsA) on growth and polyamine metabolism of MOLT-4, human T lymphoblastic leukaemia cells to ascertain the role of the polyamine biosynthetic pathway in the antitumour action of CsA. We observed that CsA had a dose-dependent inhibitory effect on growth of the cells in vitro, decreasing protein content, cell number and the rate of incorporation of 3H-thymidine into the cells. However, CsA treatment had no significant effect on intracellular polyamine levels in the cells. Contrary to previous reports, simultaneous addition of the diamine, putrescine, with CsA did not block or lessen the growth inhibitory effects of CsA. On the other hand, ornithine decarboxylase activity, the rate limiting enzyme of polyamine biosynthesis which converts ornithine to putrescine, was decreased by CsA treatment. This decrease appeared to be reversible and contrasts with the inhibition by alpha-difluoromethyl-ornithine, which is irreversible and can be overcome by addition of putrescine. This suppression of ornithine decarboxylase by CsA is more likely to occur by indirect effects on translation and/or transcription rather than a direct effect on the enzyme. It may be a contributory factor in the overall antiproliferative effects of CsA but is more likely to be a response to these growth inhibitory effects rather than a direct effect of the drug.

The potential of cyclosporin A as an anti-tumour agent

Cyclosporin A (CsA) has become established as the agent of choice for the prevention of organ allograft rejection and has shown considerable promise in the clinical management of certain autoimmune disorders. The impact of CsA as an immunotherapeutic agent of major importance is attributable to its powerful, selective inhibitory action on T-lymphocyte activation and proliferation. Moreover, CsA lacks the myelotoxic and other major side effects associated with cytotoxic immunosuppressive agents, such as cyclophosphamide or azathioprine. It is now clear that CsA has a potential therapeutic role in the treatment of malignancies, especially T-cell cancers. Recent studies suggest that there may be several areas of application for CsA, either as a direct antiproliferative agent or in combination with other drugs, including inhibitors of polyamine biosynthesis or cytotoxic anti-tumour agents, including vincristine and adriamycin. In addition, CsA and non-immunosuppressive analogues have been shown to restore multi-drug sensitivity in cancer cells with acquired drug resistance. A further application of CsA may be to prevent the induction of human immune responses to therapeutic mouse monoclonal antibodies directed against tumour antigens, thereby enhancing the efficiency and safety of this form of cancer immunotherapy. Due to our incomplete understanding of the antiproliferative properties of CsA, further exploration of its potential as an anti-tumour agent must be accompanied by detailed studies aimed at elucidating its action on subcellular molecular events in both normal and malignant cells.