Antitumour prodrug development using cytochrome P450 (CYP) mediated activation

An ideal cancer chemotherapeutic prodrug is completely inactive until metabolized by a tumour-specific enzyme, or by an enzyme that is only metabolically competent towards the prodrug under physiological conditions unique to the tumour. Human cancers, including colon, breast, lung, liver, kidney and prostate, are known to express cytochrome P450 (CYP) isoforms including 3A and 1A subfamily members. This raises the possibility that tumour CYP isoforms could be a focus for tumour-specific prodrug activation. Several approaches are reviewed, including identification of prodrugs activated by tumour-specific polymorphic CYPs, use of CYP-gene directed enzyme prodrug therapy and CYPs acting as reductases in hypoxic tumour regions. The last approach is best exemplified by AQ4N, a chemotherapeutic prodrug that is bioreductively activated by CYP3A. This study shows that freshly isolated murine T50/80 mammary carcinoma and RIF-1 fibrosarcoma 4-electron reduces AQ4N to its cytotoxic metabolite, AQ4 (T50/80 Km = 26.7 microM, Vmax = 0.43 microM/mg protein/min; RIF-1 Km = 33.5 microM, Vmax = 0.42 microM/mg protein/min) via AQM, a mono-N-oxide intermediate (T50/80 Km = 37.5 microM; Vmax = 1.4 microM/mg protein/min; RIF-1 Km = 37.5 microM; Vmax = 1.2 microM/mg protein/ min). The prodrug conversion was dependent on NADPH and inhibited by air or carbon monoxide. Cyp3A mRNA and protein were both present in T50/80 carcinoma grown in vivo (RIF-1 not measured). Exposure of isolated tumour cells to anoxia (2 h) immediately after tumour excision increased cyp3A protein 2-3-fold over a 12 h period, after which time the cyp protein levels returned to the level found under aerobic conditions. Conversely, cyp3A mRNA expression showed an initial 3-fold decrease under both oxic and anoxic conditions; this returned to near basal levels after 8-24 h. These results suggest that cyp3A protein is stabilized in the absence of air, despite a decrease in cyp3A mRNA. Such a 'stabilization factor' may decrease cyp3A protein turnover without affecting the translation efficiency of cyp3A mRNA. Confirmation of the CYP activation of AQ4N bioreduction was shown with human lymphoblastoid cell microsomes transfected with CYP3A4, but not those transfected with CYP2B6 or cytochrome P450 reductase. AQ4N is also reduced to AQ4 in NADPH-fortified human renal cell carcinoma (Km = 4 microM, Vmax = 3.5 pmol/mg protein/min) and normal kidney (Km = 4 microM, Vmax = 4.0 pmol/mg protein/min), both previously shown to express CYP3A. Germane to the clinical potential of AQ4N is that although both normal and tumour cells are capable of reducing AQ4N to its cytotoxic species, the process requires low oxygen conditions. Hence, AQ4N metabolism should be restricted to hypoxic tumour cells. The isoform selectivity of AQ4N reduction, in addition to its air sensitivity, indicates that AQ4N haem coordination and subsequent oxygen atom transfer from the active-site-bound AQ4N is the likely mechanism of N-oxide reduction. The apparent increase in CYP3A expression under hypoxia makes this a particularly interesting application of CYPs for tumour-specific prodrug activation.     

Diabetes care: who are the experts?

OBJECTIVES--To identify issues that patients and professionals consider important in diabetes care and differences in their priorities for care and to determine patients' and professionals' judgements of the relative importance of their chosen priorities. DESIGN--Structured group interviews using the nominal group technique. SETTING--Five district health authorities on Tyneside. SUBJECTS--Five nominal groups: expert (seven), non-expert (seven) health care professionals; insulin dependent (four), non-insulin dependent patients (eight); and carers of diabetic patients (eight). MAIN MEASURES--Items important in diabetes care to each nominal group (themes of care), ranked into a series of "top 10" items for each group, and allocated a score according to relative importance to individual members; scores were standardised by individual weighting and group weighting for comparison within and between groups. RESULTS--Patients and professionals agreed that information given to patients, interaction between professionals and patients, patient autonomy, and access were important for good diabetes care, but the importance assigned to each differed. Thus the professionals emphasised empathy and aspects of good communication and patients the desire to know enough to live a "normal" life. Differences were also found within the patient groups; these related to changes in patients' needs at specific points in the development of their illness and in their orientations to care. CONCLUSION--Patients differ from professionals in their orientation to diabetes care, and they can, and should, be involved in setting priorities for care. Since these priorities are dynamic further work is needed to explore the nature of patient satisfaction with diabetes care.     

Reliability of Testing the Knee Extensors and Flexors in Healthy Adult Women Using a Cybex II Isokinetic Dynamometer

This work was supported by NIH grant P50-AR39221. The purpose of this study was to determine intraobserver and interobserver reliability using a Cybex II isokinetic dynamometer for the measurement of isometric and isokinetic strength (0, 60, 180, 300 degrees /sec) and endurance (240 degrees /sec) in 20 healthy untrained females. Subjects were randomly assigned to one of two testers. Intraobserver reliability coefficients for tester one and tester two ranged from 0.89 to 0.98 and 0.72 to 0.97, respectively. Interobserver reliability coefficients ranged from 0.69 to 0.95 across speeds and movements. Although the testers differed significantly in reliability (p < 0.01), no systematic differences in measured levels of performance were noted between testers one and two for the majority of the measurements. The results indicate that comparable muscular strength and endurance values can be obtained from knee extension/flexion tests at various speeds using a Cybex II isokinetic dynamometer. Comparable values were obtained whether subjects were tested by a single tester on two separate occasions or whether subjects were tested by a different tester on two separate occasions. J Orthop Sports Phys Ther 1991;14(1):37-41.     

Reading the mind in cartoons and stories: an fMRI study of 'theory of mind' in verbal and nonverbal tasks

Previous functional imaging studies have explored the brain regions activated by tasks requiring 'theory of mind'--the attribution of mental states. Tasks used have been primarily verbal, and it has been unclear to what extent different results have reflected different tasks, scanning techniques, or genuinely distinct regions of activation. Here we report results from a functional magnetic resonance imaging study (fMRI) involving two rather different tasks both designed to tap theory of mind. Brain activation during the theory of mind condition of a story task and a cartoon task showed considerable overlap, specifically in the medial prefrontal cortex (paracingulate cortex). These results are discussed in relation to the cognitive mechanisms underpinning our everyday ability to 'mind-read'.     

Patient compliance and blood pressure control on a nuclear-powered aircraft carrier: impact of a pharmacy officer

The impact of a pharmacy officer on patient compliance and blood pressure control on a deployed nuclear-powered aircraft carrier for a 2-week at-sea period was evaluated. Before any counseling by a pharmacy officer, 43 crewmembers on chronic medications anonymously completed a compliance questionnaire. The pharmacy officer then counseled these crewmembers. A follow-up compliance questionnaire was completed 2 weeks later. After counseling, compliance had increased 58% (p < 0.0001) from compliance measured before counseling. The pharmacy officer also initiated therapeutic interventions. Among 26 crewmembers diagnosed as hypertensive, preintervention blood pressure (BP) measurements were obtained. Ten to 14 days after the initial BP measurement, BP was remeasured. After intervention, 31% (p < 0.02) more crewmembers were at BP goal compared with before intervention. A pharmacy officer, working closely with a medical officer, improved patient compliance and blood pressure control. One problem identified was that these warships require computer software that can prospectively identify drug-drug interactions.