Correction: A chemical inhibitor of PPM1D that selectively kills cells overexpressing PPM1D.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

A chemical inhibitor of PPM1D that selectively kills cells overexpressing PPM1D.

The PPM1D gene is aberrantly amplified in a range of common cancers and encodes a protein phosphatase that is a potential therapeutic target. However, the issue of whether inhibition of PPM1D in human tumour cells that overexpress this protein compromises their viability has not yet been fully addressed. We show here, using an RNA interference (RNAi) approach, that inhibition of PPM1D can indeed reduce the viability of human tumour cells and that this effect is selective; tumour cell lines that overexpress PPM1D are sensitive to PPM1D inhibition whereas cell lines with normal levels are not. Loss of viability associated with PPM1D RNAi in human tumour cells occurs via the activation of the kinase P38. To identify chemical inhibitors of PPM1D, a high-throughput screening of a library of small molecules was performed. This strategy successfully identified a compound that selectively reduces viability of human tumour cell lines that overexpress PPM1D. As expected of a specific inhibitor, the toxicity to PPM1D overexpressing cell lines after inhibitor treatment is P38 dependent. These results further validate PPM1D as a therapeutic target and identify a proof-of-principle small molecule inhibitor.

A prospective, blinded analysis of thymidylate synthase and p53 expression as prognostic markers in the adjuvant treatment of colorectal cancer.

BACKGROUND: Despite previous studies, uncertainty has persisted about the role of thymidylate synthase (TS) and p53 status as markers of prognosis in colorectal cancer (CRC). PATIENTS AND METHODS: A total of 967 patients accrued to a large adjuvant trial in CRC were included in a prospectively planned molecular substudy, and of them, 59% had rectal cancer and about 90% received adjuvant chemotherapy (either systemically or randomly allocated to intraportal 5-fluorouracil infusion or both). TS and p53 status were determined, blinded to any clinical data, by immunohistochemistry using a validated polyclonal antibody or the DO-7 clone, respectively, and their relationships with overall survival were examined. RESULTS: High TS expression was observed in 58% and overexpression of p53 in 60% of tumours. TS expression correlated with tumour stage, and p53 overexpression, with rectal cancers. There was no evidence that either marker was significantly associated with survival by either univariate (TS hazard ratio (HR) = 0.94, 95% CI 0.76-1.18 and P = 0.6 and p53 HR = 0.98, 95% CI 0.78-1.23 and P = 0.9) or multivariate analyses (TS HR = 0.99, 95% CI 0.79-1.25 and P = 0.9 and p53 HR = 0.98, 95% CI 0.78-1.23 and P = 0.8). CONCLUSIONS: Neither TS nor p53 expression has significant prognostic value in the adjuvant setting of CRC.

A phase I pharmacokinetic and pharmacodynamic study of BGC9331 and carboplatin in relapsed gynaecological malignancies.

BGC9331 is a rationally designed, specific nonpolyglutamatable thymidylate synthase (TS) inhibitor that is active in gynaecological malignancies. In the light of the sensitivity of human ovarian tumour cell lines to BGC9331 and non-cross resistance to platinum drugs, we studied the combination BGC9331/carboplatin (BCA) in a phase I (PI) pharmacokinetic (PK) and pharmacodynamic (PD) study in platinum pretreated gynaecological malignancies. Patients were >or=18 years or over, with a histologically confirmed gynaecological malignancy, radiological evidence of relapse, and a platinum treatment free interval of at least 6 months. Up to three prior lines of chemotherapy were permitted. Carboplatin (AUC5) and BGC9331 were administered on day 1, and BGC9331 was also given on day 8 of a 21-day cycle. In total, 14 patients were enrolled, and treated with BGC9331 at four dose levels, 40, 65, 85 and 100 mg m-2. The principal grade 3 and 4 haematological toxicity was neutropaenia. The principal nonhaematological toxicities were lethargy and nausea. Dose-limiting toxicities were seen in two patients at 100 mg m-2 BGC9331 (grade 4 neutropaenia>7 days, and grade 4 fatigue>7 days). Plasma BGC9331 was measured by an ELISA that was adapted for use in humans. Carboplatin was assayed by flameless atomic absorption spectrometry. There was no PK interaction between the two drugs. Plasma deoxyuridine was elevated indicating TS inhibition to at least day 12. Antitumour activity was observed in four out of 14 (28%) of patients. In conclusion, the combination of BGC9331 and carboplatin is well tolerated with no significant PK interaction between the two drugs. There is evidence of TS inhibition with the combination. We have demonstrated antitumour activity in platinum pretreated gynaecological malignancy. Further exploration of this combination in this disease is warranted.

A Phase I study of the angiogenesis inhibitor SU5416 (semaxanib) in solid tumours, incorporating dynamic contrast MR pharmacodynamic end points.

SU5416 (Z-3-[(2,4-dimethylpyrrol-5-yl)methylidenyl]-2-indolinone; semaxanib) is a small molecule inhibitor of the vascular endothelial growth factor receptor (VEGFR2). A Phase I dose escalation study was performed. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) was used as a pharmacodynamic assessment tool. In all, 27 patients were recruited. SU5416 was administered twice weekly by fixed rate intravenous infusion. Patients were treated in sequential cohorts of three patients at 48, 65, 85 110 and 145 mg m-2. A further dose level of 190 mg m-2 after a 2-week lead in period at a lower dose was completed; thereafter, the cohort at 145 mg m-2 was expanded. SU5416 showed linear pharmacokinetics to 145 mg m-2 with a large volume of distribution and rapid clearance. A significant degree of interpatient variability was seen. SU5416 was well tolerated, by definition a maximum-tolerated dose was not defined. No reproducible changes were seen in DCE-MRI end points. Serial assessments of VEGF in a cohort of patients treated at 145 mg m-2 did not show a statistically significant treatment-related change. Parallel assessments of the impact of SU5416 on coagulation profiles in six patients showed a transient effect within the fibrinolytic pathway. Clinical experience showed that patients who had breaks of therapy longer than a week could not have treatment reinitiated at a dose of 190 mg m-2 without unacceptable toxicity. The 145 mg m-2 dose level is thus the recommended dose for future study.

A human capecitabine excretion balance and pharmacokinetic study after administration of a single oral dose of 14C-labelled drug.

An excretion balance and pharmacokinetic study was conducted in cancer patients with solid tumors who received a single oral dose of capecitabine of 2000 mg including 50 microCi of 14C-radiolabelled capecitabine. Blood, urine and fecal samples were collected until radioactive counts had fallen to below 50 dpm/mL in urine, and levels of intact drug and its metabolites were measured in plasma and urine by LC/MS-MS (mass spectrometry) and 19F-NMR (nuclear magnetic resonance) respectively. Based on the results of the 6 eligible patients enrolled, the dose was almost completely recovered in the urine (mean 95.5%, range 86-104% based on radioactivity measurements) over a period of 7 days after drug administration. Of this, 84% (range 71-95) was recovered in the first 12 hours. Over this time period, 2.64% (0.69-7.0) was collected in the feces. Over a collection period of 24-48 h, a total of 84.2% (range 80-95) was recovered in the urine as the sum of the parent drug and measured metabolites (5'-DFCR, 5'-DFUR, 5-FU, FUH2, FUPA, FBAL). Based on the radioactivity measurements of drug-related material, absorption is rapid (tmax 0.25-1.5 hours) followed by a rapid biphasic decline. The parent drug is rapidly converted to 5-FU, which is present in low levels due to the rapid metabolism to FBAL, which has the longest half-life. There is a good correlation between the levels of radioactivity in the plasma and the levels of intact drug and the metabolites, suggesting that these represent the most abundant metabolites of capecitabine. The absorption of capecitabine is rapid and almost complete. The excretion of the intact drug and its metabolites is rapid and almost exclusively in the urine.

Vinblastine pharmacokinetics in patients with non-small cell lung cancer given cisplatin.

The pharmacokinetics of vinblastine were studied in 16 patients with non-small cell lung cancer after a bolus intravenous dose of 3 mg/m2 given before or after cisplatin (100 mg/m2). Venous blood was collected at 0, 10, and 36 hr for analysis by radioimmunoassay. The mean plasma vinblastine concentration at 10 hr was similar when vinblastine was given before (4.8 ng/ml; 95% CI, 3.2-6.3) or after cisplatin (4.9 ng/ml; 95% CI, 2.7-7.1). Plasma vinblastine concentrations in patients given cisplatin were higher than previously reported in patients given vinblastine alone. Patients with plasma vinblastine concentrations less than 2.75 ng/ml at 10 hr experienced less severe neutropenia (37% fall in neutrophil count; 95% CI, 18-55) than those with levels greater than 2.75 ng/ml (69% fall in neutrophil count; 95% CI, 62-77). In conclusion, the pharmacokinetics of vinblastine predict the severity of neutropenia and may be altered when given in conjunction with cisplatin.

Metabolism, excretion and pharmacokinetics of a single dose of [14C]-raltitrexed in cancer patients.

Raltitrexed (Tomudex) is a specific inhibitor of thymidylate synthase and has recently been licensed in Europe for use in the treatment of advanced colorectal carcinoma. This study evaluated the metabolism, excretion and pharmacokinetics after a single dose of 3.0 mg/m2 [14C]-raltitrexed in patients with advanced solid malignancies not amenable to curative therapy. From April 1994 to July 1995, nine patients (six men and three women) were recruited into the study. Pharmacokinetics analysis was performed during the first cycle of treatment in all patients and, in two patients, limited sampling was done prior to and during the second cycle of treatment. The mean observed peak plasma concentration (Cmax) was 700.6 ng/ml and the median time (tmax) to reach maximal raltitrexed concentrations was 15 min after the initiation of the infusion. After reaching Cmax the drug declined in a triexponential manner with a terminal half-life of 257 h. The AUC0-infinity as predicted by the pharmacokinetic model was 2341.7 ng h ml(-1). Clearance was 41.3 ml/min, of which renal clearance accounted for 50-60%. Urinary collection for the measurement of radiolabeled drug revealed that renal excretion extrapolated to infinity accounted for 40% of the total radioactive dose. Faecal excretion accounted for only 3% of the dose when samples were collected to day 5 in the first six patients. Collection was extended to 10 days in the last three patients and faecal elimination accounted for 14% in these patients. Raltitrexed measurements prior to subsequent doses suggest that there was no accumulation of the drug with repeated administration. Low levels of radioactivity measured in the red cell pellets on days 15, 22 and 29 are likely to represent drug retained by newly forming red cells at the time of dosing. Examination of the urine revealed that the drug was excreted unchanged. The toxicities seen were in line with those encountered in previous studies. Grade 3 and 4 thrombocytopenia occurred in three patients and grade 3 neutropenia occurred in two patients.

Development of an enzyme-linked immunosorbent assay for isoproturon in water.

A competitive enzyme-linked immunosorbent assay (ELISA) suitable for the determination of the urea herbicide isoproturon [3-(4-isopropylphenyl)-1,1-dimethyl urea] in water has been developed. A derivative of isoproturon [3-(4-isopropylphenyl)-1-carboxypropyl-1-methyl urea] has been synthesized and linked to thyroglobulin using the N-hydrosuccinimide reaction. The immunogen was used to immunize two sheep, which both responded by producing specific antibodies to isoproturon with little cross-reactivity to various structurally related and unrelated pesticides. The enzyme label was prepared by coupling the hapten to horseradish peroxidase using the above reaction. The coated-antibody competitive ELISA, which has a sensitivity of 0.03 microgram l-1, permits the direct determination of isoproturon in various water matrices and can facilitate the monitoring of water quality in drinking-water supplies.

The measurement of deoxynucleotide (dNTP) pools by radioimmunoassay (RIA).

Radioimmunoassay provides an alternative, sensitive and reproducible high throughput method for the measurement of dNTP pools. The extent and duration of inhibition of TS can be investigated by determination of the TTP and "dUMP" pools and the effects of D1694 and ZD9331 have confirmed their biochemical profiles. The RIAs will be useful in providing information for the design of treatment protocols for TS inhibitors and with the specific assay of dUTP, on mechanisms of cell death in different cell lines.

Histologic, pharmacologic, and immunocytochemical effects of injection of bleomycin into viral warts.

BACKGROUND: The plasma concentration of bleomycin after injection of bleomycin into warts is unknown, as is the long-term stability of bleomycin solution. OBJECTIVE: Our purpose was to measure plasma bleomycin concentration after injection of bleomycin into warts, to relate histologic and immunocytochemical changes in warts to possible mechanisms of action of bleomycin, and to asses the long-term stability of stored frozen bleomycin solution. METHODS: One milligram of bleomycin was injected into warts on the hands of seven men. Blood samples were taken 15 to 120 minutes after injection, and plasma bleomycin was measured by radioimmunoassay. Warts were removed 2 hours and 48 hours after treatment and studied histologically by light microscopy and for the presence of bleomycin by immunocytochemistry. The bleomycin concentration in 8 aliquots of solution stored at -20 degrees C for varying periods was measured by radioimmunoassay. RESULTS: Peak levels of bleomycin of 7 to 113 ng/ml were reached by 45 minutes after injection. Plasma bleomycin exposure ranged from 515 to 5137 ng/ml/min between 15 and 120 minutes after injection. The most pronounced histologic changes at 48 hours were individual keratinocyte apoptosis throughout the epidermis merging into areas of complete epidermal necrosis, diffuse neutrophil accumulation, and microabscess formation at the granular layer. Immunocytochemistry demonstrated tissue-fixed bleomycin in all levels of the epidermis except the basal layer and most prominently in the granular layer. Bleomycin in solution stored for up to 27 months at -20 degrees C in glass showed no significant loss of immunoreactivity. CONCLUSION: The use of bleomycin for the treatment of warts results in significant systemic drug exposure; thus it would be prudent to exclude pregnancy before treating women of child-bearing age. Bleomycin probably has a direct toxic effect on keratinocytes. Dilute bleomycin solution stored at -20 degrees C in glass is stable.

Chronopharmacology.

The time of day that drugs are given can have a profound effect upon both their pharmacodynamics, i.e. their effectiveness and toxicity, and their pharmacokinetics, i.e. the way they themselves behave in the body. The chronopharmacokinetics of relatively few drugs have been investigated and are mostly those used for the treatment of cancer. We have shown that the toxicity and chronopharmacokinetics of drugs can be altered by pretreatment with steroids or melatonin.

A reappraisal of the stathmokinetic technique. II. Metaphase degeneration and its correction.

The rate at which proliferating cells enter mitosis is an important cytokinetic measure. It is estimated by the metaphase arrest (or stathmokinetic) technique. This technique depends on the persistence of arrested metaphases in the tissue in question. But arrested metaphases do not, in fact, persist for long; some estimates of the rate at which cells are entering mitosis, based on a count of metaphases, are therefore underestimates. This paper presents a mathematical analysis of this phenomenon and a method of calculating the initial metaphase index from the depleted index at any given time.

Methotrexate absorption in children with acute lymphoblastic leukemia.

The absorption of oral methotrexate (MTX) has been studied in 124 children with acute lymphoblastic leukemia (ALL). Blood levels of MTX were very variable and unpredictable. There was a 20-fold difference between the highest and lowest peak level achieved. Division into two groups has shown that those children who absorb MTX slowly have a worse disease-free survival. It is possible that MTX damages the intestinal mucosa and causes a malabsorption of itself in some children. It is suggested that future protocols for the treatment of ALL should include pharmacokinetic studies, which may help to explain the unexpected relapses of good prognosis patients and lead to the development of more effective treatment.

Cytokinetic changes in the thymus of tumour-bearing and of dexamethasone-treated mice.

Changes in the cell population kinetics of the Balb/c mouse thymus were studied (a) during the growth of a syngeneic transplantable sarcoma and (b) following intraperitoneal injection of dexamethasone. The weight of the thymus fell briefly after tumour transplantation, then recovered with overshoot and eventually declined profoundly. After dexamethasone injection the weight of the thymus fell to roughly one-third of its normal value in 36 hr. Similar cytokinetic changes were observed in both sets of experiments; thymic wasting was accompanied by a small increase in thymocyte cell cycle time, a prolongation of the S-phase of the cycle, a marked decrease in the thymocyte cell production rate and a marked reduction in the growth fraction of the thymocyte population in the superficial cortex. It is suggested that thymic atrophy in tumour bearing animals may be a stress phenomenon.

Fibrinolytic therapy in subacute bacterial endocarditis: an experimental study.

The effect of adding fibrinolytic to penicillin therapy in experimentally induced streptococcal bacterial endocarditis has been studied in the rabbit. In 9 day old infected lesions, the vegetations could be substantially reduced in size after a 3 day course of intravenous streptokinase. Quantitative microbiological techniques demonstrated that the addition of streptokinase to standard intravenous penicillin treatment led to more rapid sterilisation of the vegetations. Embolism to lungs and kidneys was assessed in treated and untreated rabbits. Penicillin reduced the rate of embolism but the addition of streptokinase reversed this effect and gave values similar to those recorded in untreated animals.

A radioimmunoassay for methotrexate adapted to the Centria System 2.

An automated radioimmunoassay for methotrexate using an iodinated tracer has been applied to the centrifugal analyser, Centria System 2. Results obtained for serum samples correlated closely with those using a manual radioimmunoassay method. A major advantage of the assay is its potential for processing large numbers of samples rapidly, making it highly suitable for routine clinical use.

The effects of dexamethasone on the cell kinetics of a murine malignant lymphoma.

The effects of dexamethasone on the cell kinetics of a rapidly growing syngeneic B cell malignant lymphoma in Balb/c mice have been studied. Growth curves, stathmokinetic studies and frequency of labelled mitoses (FLM) experiments were performed in groups of dexamethasone treated and control animals. These studies showed that tumour growth was arrested after 8 days treatment at which time the tumour weights were approximately half those of control animals. Dexamethasone increased the duration of the cell cycle with a particular increase in the duration of DNA synthesis. The results indicated that the effect on tumour growth could be attributed to a reduction in the growth fraction.