Michael J. Lind

The analysis of doxorubicin resistance in human breast cancer cells using antibody microarrays

Doxorubicin is considered to be the most effective agent in the treatment of breast cancer patients. Unfortunately, resistance to this agent is common, representing a major obstacle to successful treatment. The identification of novel biomarkers that are able to predict treatment response may allow therapy to be tailored to individual patients. Antibody microarrays provide a powerful new technique, enabling the global comparative analysis of many proteins simultaneously. This technology may identify a panel of proteins to discriminate between drug-resistant and drug-sensitive samples. The Panorama Cell Signaling Antibody Microarray was exploited to analyze the MDA-MB-231 breast cancer cell line and a novel derivative, which displays significant resistance to doxorubicin at clinically relevant concentrations. The microarray comprised 224 antibodies selected from a variety of pathways, including apoptotic and cell signaling pathways. A standard ≥2.0-fold cutoff value was used to determine differentially expressed proteins. A decrease in the expression of mitogen-activated protein kinase–activated monophosphotyrosine (phosphorylated extracellular signal-regulated kinase; 2.8-fold decrease), cyclin D2 (2.5-fold decrease), cytokeratin 18 (2.5-fold decrease), cyclin B1 (2.4-fold decrease), and heterogeneous nuclear ribonucleoprotein m3-m4 (2.0-fold decrease) was associated with doxorubicin resistance. Western blotting was exploited to confirm results from the antibody microarray experiment. These results suggest that antibody microarrays can be used to identify novel biomarkers and further validation may reveal mechanisms of chemotherapy resistance and identify potential therapeutic targets. [Mol Cancer Ther 2006;5(8):2115–20]

Plasma and salivary pharmacokinetics of caffeine in man

SummaryPlasma and salivary caffeine concentrations were measured by gas-liquid chromatography in 6 healthy caffeine-free volunteers following oral administration of 50, 300, 500 and 750 mg caffeine. Caffeine was also given to a single subject intravenously in doses of 300, 500 and 750 mg. Caffeine was rapidly absorbed and was completely available at all doses. The apparent first-order elimination rate constant decreased linearly with dose and was 0.163±0.081 h−1 for 50 mg and 0.098±0.027 h−1 for 750 mg. The total body clearance was unaffected by dose and was 0.98±0.38 ml/min/kg. There was a trend towards increasing apparent volume of distribution with increasing dose. A linear relationship existed between the area under the plasma concentration, time curve and dose and dose-normalised plasma concentration, time plots were superimposable. These findings suggest that caffeine obeys linear pharmacokinetics over the dose range investigated. Despite significant inter-individual differences in pharmacokinetic parameters there was good reproducibility within 5 subjects given 300 mg caffeine orally on 3 occasions. Salivary caffeine levels probably reflect the unbound plasma caffeine concentration and can be used to estimate the pharmacokinetic parameters of the drug. Overall the saliva/plasma concentration ratio was 0.74±0.08 but within subjects some time-dependence of the ratio was found with higher ratios initially (even after intravenous administration) and lower ratios at longer time intervals after the dose. Urinary elimination of caffeine was low and independent of dose: 1.83% of the dose was eliminated unchanged.

Do β-tubulin mutations have a role in resistance to chemotherapy?

Summary β-tubulin is the target of various antitubulin agents used in the treatment of cancer. After β tubulin was shown to confer resistance to antitubulin agents in established cell lines, several studies have investigated the DNA sequence of this compound in clinical samples. However, these findings are highly controversial, since sequencing experiments showed that the original clinical observation of mutations in the gene resulted from inclusion of non-functional β-tubulin pseudogenes. At least nine such pseudogenes are known, and all share substantial sequence homology with the functional gene. Subsequent studies have concluded that β-tubulin mutations in clinical samples are rare, and unlikely to contribute to drug resistance. Here, we overview the β-tubulin gene family and summarise the results of studies done comparing β-tubulin mutations with antitubulin drug resistance.

High Procedure Volume Is Strongly Associated With Improved Survival After Lung Cancer Surgery

PURPOSE Studies have reported an association between hospital volume and survival for non-small-cell lung cancer (NSCLC). We explored this association in England, accounting for case mix and propensity to resect. METHODS We analyzed data on 134,293 patients with NSCLC diagnosed in England between 2004 and 2008, of whom 12,862 (9.6%) underwent surgical resection. Hospital volume was defined according to number of patients with resected lung cancer in each hospital in each year of diagnosis. We calculated hazard ratios (HRs) for death in three predefined periods according to hospital volume, sex, age, socioeconomic deprivation, comorbidity, and propensity to resect. RESULTS There was increased survival in hospitals performing > 150 surgical resections compared with those carrying out < 70 (HR, 0.78; 95% CI, 0.67 to 0.90; Ptrend < .01). The association between hospital volume and survival was present in all three periods of follow-up, but the magnitude of association was greatest in the early postoperative period. CONCLUSION High-volume hospitals have higher resection rates and perform surgery among patients who are older, have lower socioeconomic status, and have more comorbidities; despite this, they achieve better survival, most notably in the early postoperative period.

The level of haemoglobin in anaemic cancer patients correlates positively with quality of life

The aim of this study was to assess the relationship between haemoglobin level and quality-of-life in anaemic cancer patients. Patients, diagnosed with one of four cancers, were recruited if their haemoglobin level was <12 g dl−1 (female) or <13 g dl−1 (male). The condition-specific Functional Assessment of Cancer Therapy – Anaemia and the generic SF-36 were used to assess quality-of-life. Thirty-six per cent of the 179 recruited patients had breast cancer, 28% ovarian cancer, 25% lung cancer, and 11% multiple myeloma. Their mean (s.d.) haemoglobin level was 10.66 (1.04) g dl−1. Partial correlations controlling for the potentially confounding effects of age, gender, and time since diagnosis found significant positive relationships between haemoglobin and all domains of the Functional Assessment of Cancer Therapy – Anaemia, and with all but two of the SF-36 domains. On linear regression controlling for the same factors, each unit haemoglobin rise equalled an average 8.19 Functional Assessment of Cancer Therapy – Anaemia, and an average 6.88 Functional Assessment of Cancer Therapy–Fatigue, increase. Haemoglobin accounted for a similar amount of variability (8%) in SF-36 scores. In conclusion, quality-of-life has been found to be significantly positively related to haemoglobin level in anaemic cancer patients. This suggests that normalisation of haemoglobin in cancer patients is likely to increase their quality-of-life. The greater sensitivity of the condition-specific Functional Assessment of Cancer Therapy – Anaemia compared with the generic SF-36 suggests that the Functional Assessment of Cancer Therapy – Anaemia can be used alone to assess quality-of life in this patient group.

O6-methylguanine-DNA methyltransferase in pretreatment tumour biopsies as a predictor of response to temozolomide in melanoma.

Resistance of tumour cells to methylating and monochloroethylating agents in vitro and in vivo has been linked to levels of the DNA repair protein O6-methylguanine-DNA methyltransferase (MGMT). In a clinical trial of temozolomide in advanced malignant melanoma, the relationship between pretreatment MGMT levels in biopsies of cutaneous tumours and involved lymph nodes and clinical response to the drug has been studied. Among 50 evaluable patients, there were three complete responses (CR), four partial responses (PR), six with stable disease (SD) and 37 with progressive disease (PD), with an overall response rate of 14%. In 33 patients in whom MGMT level and clinical response could be evaluated, the tumour MGMT levels (fmol mg(-1) protein) were: CR, 158 +/- 119; PR, 607 +/- 481; NC, 171 +/- 101; PD, 185 +/- 42.3. Thus, measurements of pretreatment levels of MGMT in melanoma did not predict for response to temozolomide.

The effect of ifosfamide and its metabolites on intracellular glutathione levels in vitro and in vivo.

The effect of ifosfamide and its metabolites on intracellular levels of glutathione in P388 cells in vitro has been studied. It is demonstrated that glutathione depletion occurs only in the presence of 4-hydroperoxyifosfamide and chloroacetaldehyde. In contrast isophosphoramide mustard had no effect on glutathione levels in intact cells. The concentration of 4-hydroperoxyifosfamide required to reduce glutathione levels by 50% was approximately 1 mM and this represents a concentration far in excess of that achievable in patients receiving the drug. However the concentration of chloroacetaldehyde (approximately 100 microM) required to reduce intracellular levels of glutathione to a similar extent is attained in patients receiving ifosfamide. The glutathione levels in lymphocytes isolated from a patient undergoing an eight hour infusion of ifosfamide showed a marked decrease to about 30% of their original value. We conclude that ifosfamide causes glutathione depletion in vivo and the majority of this can be accounted for by the production of chloroacetaldehyde.

A phase II study of pemetrexed disodium (LY231514) in patients with locally recurrent or metastatic breast cancer.

A phase II study was conducted to evaluate the activity of pemetrexed in patients with locally recurrent or metastatic breast cancer. 38 patients, median age 52 years (range 36-71 years), were given pemetrexed 600 mg/m(2) as a 10-min intravenous (i.v.) infusion every 3 weeks. Median time from diagnosis to study entry was 48 months (range 14.7-310 months). 33 of 38 patients had prior chemotherapy; 16 adjuvant, 12 metastatic and 5 in both settings. Sites of disease included skin and soft tissue (19/38) nodes (18/38), lung (17/38), liver (13/38) and bone (3/38). An overall response rate of 28% (95% confidence interval (CI): 14.2-45.2%) in 10/36 evaluable patients (1 complete response (CR), 9 partial responses (PR)), included reductions in hepatic and pulmonary metastases. 5 of 10 responders had received taxoid or anthracycline therapy for metastatic disease; 3 of these 5 had also received adjuvant chemotherapy. Median duration of response was 8 months (range 1.6-14+ months), and median survival was 13 months (95% CI 9.56-17.38 months). 167 courses were given (median five per patient; range 1-9), with 37 reductions and 33 delays. Reasons for reduction included neutropenia (11%) and mucositis (5%), with delays due to raised LFTs (21%), neutropenia (12%) and other non-treatment related events. The major haematological toxicities (Common Toxicity Criteria) (CTC) were grade 3/4 neutropenia (47%) and thrombocytopenia (15.7%) of patients. There was one report of a grade 3 infection. Non-haematological toxicities (all grades 2/3) included elevated transaminases (92%), vomiting (34%), nausea (34%) and mucositis (32%). One episode of grade 4 diarrhoea was reported. Other toxicities included a skin rash, grade 2 (42%), 3 (5%) and 4 (13%), which was ameliorated by the use of prophylactic dexamethasone. These results suggest that pemetrexed has significant antitumour activity in advanced breast cancer with responses in patients who had previously received anthracyclines and taxoids.

Prolongation of ifosfamide elimination half-life in obese patients due to altered drug distribution

SummaryThe pharmacokinetics of intravenous ifosfamide were determined in 16 patients with carcinoma of the bronchus. In all 25% (4) of these patients were obese (i.e. >20% over their ideal body weight). The terminal elimination half-life (t1/2 β) was found to be higher in the obese group than in the control group (6.36 h, range 5.77–7.45 h) vs 4.95 h, range 1.82–6.48 h( (P< 0.05). This prolongation of the elimination half-life was due to an increased volume of distribution (Vdβ) in the obese group (42.81 l, range 35.49–51.90 l) vs 33.70 l range (17.76–50.62 l) (P<0.05). There was therefore no significant difference in total plasma clearance between the obese and normal groups. No correlation of ifosfamide plasma half-life was observed with total body weight (TBW) or ideal body weight (IBW). However, a significant positive correlation was observed between the percentage of IBW and plasma half-life. A strong positive correlation was observed between IBW and the plasma clearance of ifosfamide. The Vdβ correlated with both TBW and the percentage of IBW, but not with IBW itself. When Vdβ was normalised for IBW, there was a strong positive correlation with the percentage of IBW, suggesting that ifosfamide distribution into the TBW is higher than that into the IBW.

The effect of route of administration and fractionation of dose on the metabolism of ifosfamide.

SummaryThe measurement of urinary ifosfamide, isophosphoramide mustard, dechloroethyl ifosfamide and carboxyifosfamide using high-performance thin-layer chromatography with photographic densitometry (TLC-PD) is described. This technique was also used to demonstrate the large inter-individual variation in the ifosfamide metabolic profile of patients receiving the drug as single-agent therapy for non-small-cell lung cancer. In addition, oral administration was shown to result in higher levels of these metabolites in the urine. Fractionation of the ifosfamide dose over several days resulted in increasing levels of metabolites in the urine, consistent with auto-induction of ifosfamide metabolism.