Prognostic impact of breast cancer subtypes in elderly patients.

We aimed to analyse the impact of breast cancer (BC) subtypes on the clinical course of disease with special emphasis on the occurrence of brain metastases (BM) and outcome in an elderly BC population. A total number of 706 patients ≥65 years receiving treatment for BC from 2007 to 2011 were identified from a BC database. 62 patients diagnosed with DCIS and 73 patients with incomplete datasets were excluded, leaving 571 patients for this analysis. Patient characteristics, biological tumour subtypes, and clinical outcome including overall survival (OS) were obtained by retrospective chart review. 380/571 (66, 5 %) patients aged 65-74 years were grouped among the young-old, 182/571 (31.9 %) patients aged 75-84 years among the old-old, and 29/571 (5.1 %) patients aged ≥85 years among the oldest-old. 392/571 (68.8 %) patients presented with luminal BC, 119/571 (20.8 %) with HER2-positive, and 59/571 (10.3 %) with triple-negative BC (TNBC). At 38 months median follow-up, 115/571 (20.1 %) patients presented with distant recurrence. A higher recurrence rate was observed in the HER2-positive subtype (43/119 (36.1 %)), as compared to TNBC (15/59 (25.4 %)) and luminal BC (57/392 (14.5 %); p < 0.001). BM were detected at a significantly higher rate in HER2-positive BC patients (9/119 (7.6 %)), as compared to TNBC (2/59 (3.4 %)) and luminal BC patients (6/392 (1.5 %); p = 0.003). Diagnosis of metastatic disease (HR 7.7; 95 % CI 5.2-11.4; p < 0.001) as well as development of BM (HR 3.5; 95 % CI 1.9-6.4; p < 0.001) had a significantly negative impact on OS in a time-dependent covariate cox regression model. In contrast to younger BC patients, outcome in this large cohort of elderly patients suggests that HER2-positive disease-not TNBC-featured the most aggressive clinical course with the highest rates of metastatic spread and BM. In-depth analysis regarding a potentially distinct biology of TNBC in elderly is therefore warranted.

Fulvestrant induces resistance by modulating GPER and CDK6 expression: implication of methyltransferases, deacetylases and the hSWI/SNF chromatin remodelling complex.

BACKGROUND: Breast cancer is the leading cause of cancer death in women living in the western hemisphere. Despite major advances in first-line endocrine therapy of advanced oestrogen receptor (ER)-positive breast cancer, the frequent recurrence of resistant cancer cells represents a serious obstacle to successful treatment. Understanding the mechanisms leading to acquired resistance, therefore, could pave the way to the development of second-line therapeutics. To this end, we generated an ER-positive breast cancer cell line (MCF-7) with resistance to the therapeutic anti-oestrogen fulvestrant (FUL) and studied the molecular changes involved in resistance. METHODS: Naive MCF-7 cells were treated with increasing FUL concentrations and the gene expression profile of the resulting FUL-resistant strain (FR.MCF-7) was compared with that of naive cells using GeneChip arrays. After validation by real-time PCR and/or western blotting, selected resistance-associated genes were functionally studied by siRNA-mediated silencing or pharmacological inhibition. Furthermore, general mechanisms causing aberrant gene expression were investigated. RESULTS: Fulvestrant resistance was associated with repression of GPER and the overexpression of CDK6, whereas ERBB2, ABCG2, ER and ER-related genes (GREB1, RERG) or genes expressed in resistant breast cancer (BCAR1, BCAR3) did not contribute to resistance. Aberrant GPER and CDK6 expression was most likely caused by modification of DNA methylation and histone acetylation, respectively. Therefore, part of the resistance mechanism was loss of RB1 control. The hSWI/SNF (human SWItch/Sucrose NonFermentable) chromatin remodelling complex, which is tightly linked to nucleosome acetylation and repositioning, was also affected, because as a stress response to FUL treatment-naive cells altered the expression of five subunits within a few hours (BRG1, BAF250A, BAF170, BAF155, BAF47). The aberrant constitutive expression of BAF250A, BAF170 and BAF155 and a deviant stress response of BRG1, BAF170 and BAF47 in FR.MCF-7 cells to FUL treatment accompanied acquired FUL resistance. The regular and aberrant expression profiles of BAF155 correlated directly with that of CDK6 in naive and in FR.MCF-7 cells corroborating the finding that CDK6 overexpression was due to nucleosome alterations. CONCLUSION: The study revealed that FUL resistance is associated with the dysregulation of GPER and CDK6. A mechanism leading to aberrant gene expression was most likely unscheduled chromatin remodelling by hSWI/SNF. Hence, three targets should be conceptually addressed in a second-line adjuvant therapy: the catalytic centre of SWI/SNF (BRG1) to delay the development of FUL resistance, GPER to increase sensitivity to FUL and the reconstitution of the RB1 pathway to overcome resistance.

Impact of anti-HER2 therapy on overall survival in HER2-overexpressing breast cancer patients with brain metastases.

BACKGROUND: Trastuzumab-based therapy after diagnosis of brain metastases (BM) may improve survival due to prolonged systemic disease control. We investigated whether lapatinib may yield additional survival benefit. METHODS: Eighty patients with BM from HER2-positive breast cancer were identified. Karnofsky Performance Score (KPS) of at least 70 was required. We included a control group of 37 patients treated before 2003, when continuation of trastuzumab after diagnosis of BM was not yet recommended. Remainders received either trastuzumab or lapatinib and trastuzumab (either concomitantly or sequentially) with or without chemotherapy. RESULTS: Median overall survival (OS) in patients receiving trastuzumab after diagnosis of BM was 13 months; corresponding numbers were 9 months in patients treated with chemotherapy, and 3 months with radiotherapy alone. Median OS was not reached in the lapatinib group. Addition of lapatinib prolonged OS over trastuzumab alone (P=0.002). After correction for potential confounders, lapatinib therapy remained an independent positive predictor for survival (HR 0.279; P=0.012). INTERPRETATION: This retrospective single-centre study suggests that the introduction of lapatinib improved survival in patients with BM from HER2-positive breast cancer. Patients with KPS ≥70 may benefit when treated with lapatinib in addition to trastuzumab after completion of local therapy.

Brain metastases free survival differs between breast cancer subtypes.

BACKGROUND: Brain metastases (BM) are frequently diagnosed in patients with HER-2-positive metastatic breast cancer; in addition, an increasing incidence was reported for triple-negative tumours. We aimed to compare brain metastases free survival (BMFS) of breast cancer subtypes in patients treated between 1996 until 2010. METHODS: Brain metastases free survival was measured as the interval from diagnosis of extracranial breast cancer metastases until diagnosis of BM. HER-2 status was analysed by immunohistochemistry and reanalysed by fluorescent in situ hybridisation if a score of 2+ was gained. Oestrogen-receptor (ER) and progesterone-receptor (PgR) status was analysed by immunohistochemistry. Brain metastases free survival curves were estimated with the Kaplan-Meier method and compared with the log-rank test. RESULTS: Data of 213 patients (46 luminal/124 HER-2/43 triple-negative subtype) with BM from breast cancer were available for the analysis. Brain metastases free survival differed significantly between breast cancer subtypes. Median BMFS in triple-negative tumours was 14 months (95% CI: 11.34-16.66) compared with 18 months (95% CI: 14.46-21.54) in HER-2-positive tumours (P=0.001) and 34 months (95% CI: 23.71-44.29) in luminal tumours (P=0.001), respectively. In HER-2-positive patients, co-positivity for ER and HER-2 prolonged BMFS (26 vs 15 m; P=0.033); in luminal tumours, co-expression of ER and PgR was not significantly associated with BMFS. Brain metastases free survival in patients with lung metastases was significantly shorter (17 vs 21 months; P=0.014). CONCLUSION: Brain metastases free survival in triple-negative breast cancer, as well as in HER-2-positive/ER-negative, is significantly shorter compared with HER-2/ER co-positive or luminal tumours, mirroring the aggressiveness of these breast cancer subtypes.

Long-term persistence of acquired resistance to 5-fluorouracil in the colon cancer cell line SW620.

Treatment resistance to antineoplastic drugs represents a major clinical problem. Here, we investigated the long-term stability of acquired resistance to 5-fluorouracil (FU) in an in vitro colon cancer model, using four sub-clones characterised by increasing FU-resistance derived from the cell line SW620. The resistance phenotype was preserved after FU withdrawal for 15weeks (~100 cell divisions) independent of the established level of drug resistance and of epigenetic silencing. Remarkably, resistant clones tolerated serum deprivation, adopted a CD133(+) CD44(-) phenotype, and further exhibited loss of membrane-bound E-cadherin together with predominant nuclear ß-catenin localisation. Thus, we provide evidence for a long-term memory of acquired drug resistance, driven by multiple cellular strategies (epithelial-mesenchymal transition and selective propagation of CD133(+) cells). These resistance phenomena, in turn, accentuate the malignant phenotype.

Serum levels of tumour necrosis factor-alpha and interleukin-6 and their correlation with body mass index, weight loss, appetite and survival rate--preliminary data of Viennese outpatients with metastatic cancer during palliative chemotherapy.

The serum cytokine levels (in particular interleukine-6 (IL-6) and tumour necrosis factor-alpha (TNF-alpha)) of 61 advanced stage cancer patients receiving palliative chemotherapy as outpatients were determined with quantikine immunoassays. The values were correlated with body mass index (BMI), weight loss and appetite. Furthermore cytokine levels of patients who have died within one year were compared with those of patients who have survived more than a year. Serum levels of IL-6 (median: 1.93 pg/ml, range: 0.32-42.87) and of TNF-alpha (median: 2.55 pg/ml, range: 1.03-34.06) did not correlate with BMI, weight loss and appetite. Serum IL-6 levels of patients with survival time less than one year were significantly higher than the levels of patients who survived more than one year, no significant differences in TNF-alpha serum levels were evident. The data of this observation are consistent with current literature. Due to changes in serum levels of proinflammatory cytokines in response to chemotherapy and additional therapy, it is unlikely that IL-6 and TNF-alpha can be used as independent indicators for weight loss and appetite. Nevertheless, high serum levels of IL-6 correlate with short-time mortality.

Fate of 5-fluorouracil, doxorubicin, epirubicin, and daunorubicin in hospital wastewater and their elimination by activated sludge and treatment in a membrane-bio-reactor system.

Antineoplastic agents are applied in cancer therapy and end up in hospital wastewater by human excretions. In this study, the raw wastewater of the sewer of the oncologic in-patient treatment ward of the Vienna University Hospital was monitored for 98 d over 2 years for the cytostatics 5-fluorouracil (5-FU), doxorubicin (DOX), epirubicin, and daunorubicin. In a next step, the elimination of the drugs by a membrane-bio-reactor system was investigated. In addition, their fate in wastewater and elimination by activated sludge was investigated with radio-labelled substances. During the monitoring periods, concentration levels ranging from <8.6 to 124 microgl(-1) for 5-FU and from <0.26 to 1.35 microgl(-1) for DOX were determined. The concentrations analysed fitted the lower ranges calculated by an input-output model. Treatment of oncologic wastewater in the membrane bio-reactor as well as the analysis of the effluents of the Vienna University Hospital resulted in concentrations below the limit of detection. Investigations with radio-labelled compounds showed that 5-FU is eliminated from the liquid phase below the limit of detection. But, up to 25% of radio-labelled equivalents of the drug's amount were found in the gaseous phase and only a marginal part in the solid phase, this indicates that at least one part of the drug is biodegraded. For the anthracyclines more than 90% was eliminated from the liquid phase. In this case, adsorption to suspended solids seems to be the major elimination pathway, as up to 30% of the radio-labelled equivalents of the drug's amount was detected in the solid phase. Our results indicate that the investigated anticancer drugs are eliminated by sewage treatment plants, either by biodegradation or adsorption.

Monitoring, removal and risk assessment of cytostatic drugs in hospital wastewater.

Cytostatic agents are applied in cancer therapy and subsequently excreted into hospital wastewater. As these substances are known to be carcinogenic, mutagenic and toxic for reproduction, they should be removed from wastewater at their source of origin. In this study the fate and effects of the cancerostatic platinum compounds (CPC) cisplatin, carboplatin, oxaliplatin, 5-fluorouracil (5-FU) and the anthracyclines doxorubicin, daunorubicin and epirubicin were investigated in hospital wastewater. Wastewater from the in-patient treatment ward of a hospital in Vienna was collected and monitored for the occurrence of the selected drugs. A calculation model was established to spot the correlation between administered dosage and measured concentrations. To investigate the fate of the selected substances during wastewater treatment, the oncologic wastewater was treated in a pilot membrane bioreactor system (MBR) and in downstream advanced wastewater treatment processes (adsorption to activated carbon and UV-treatment). Genotoxic effects of the oncologic wastewater were assessed before and after wastewater treatment followed by a risk assessment. Monitoring concentrations of the selected cytostatics in the oncologic wastewater were in line with calculated concentrations. Due to different mechanisms (adsorption, biodegradation) in the MBR-system 5 - FU and the anthracyclines were removed < LOD, whereas CPC were removed by 60%. In parallel, genotoxic effects could be reduced significantly by the MBR-system. The risk for humans, the aquatic and terrestrial environment by hospital wastewater containing cytostatic drugs was classified as small in a preliminary risk assessment.

5-fluorouracil kinetics in the interstitial tumor space: clinical response in breast cancer patients.

Several anticancer drugs fail to exhibit sufficient activity against solid tumors in vivo despite effective inhibition of tumor cell growth in vitro. This may be due to impaired drug transfer from plasma into solid tumors. The present study, therefore, aimed at measuring interstitial tumor 5-fluorouracil (5-FU) pharmacokinetics and 5-FU transfer rates from plasma into the tumor interstitium in breast cancer patients. Microdialysis probes were inserted into the primary tumor and the periumbilical s.c. adipose layer of 10 breast cancer patients (8 females and 2 males) scheduled to receive neoadjuvant chemotherapy due to locally advanced breast cancer. Thereafter, patients received 5-FU (600 mg/m2, i.v). 5-FU kinetics were followed in plasma and tumor and s.c. interstitial fluid. Mean interstitial 5-FU load, expressed as area under curve (AUC), in breast tumors was 61 +/- 11% (means +/- SE) of the mean plasma 5-FU load. 5-FU displayed similar kinetics in the interstitial space of s.c. adipose tissue and tumor tissue. A high interstitial tumor AUC was associated with increased tumor response. There was no association with tumor response for s.c. or plasma AUC of 5-FU. Measurement of interstitial drug concentrations in breast tumors by in vivo microdialysis may predict response to chemotherapy. This information may explain drug resistance in some patients and help to optimize dosing and administration schedules. In the future, selection of novel cytotoxic compounds with favorable tumor penetration characteristics may become possible.

Interstitial methotrexate kinetics in primary breast cancer lesions.

The transfer of cytotoxic agents across the tumor endothelium into the interstitial tumor space is considered a critical step in clinical resistance of solid tumors to antineoplastic chemotherapy. However, experimental data on drug transfer from the blood into the interstitium of solid tumors are scarce. Therefore, in this study, we used an innovative technique, in vivo microdialysis, for measuring interstitial tumor pharmacokinetics and plasma-to-tumor transfer rates of methotrexate (MTX) in breast cancer patients. Microdialysis probes were inserted into the primary tumor and the periumbilical s.c. adipose layer of nine previously chemotherapy-naive breast cancer patients to monitor interstitial concentrations following i.v. administration of MTX (40 mg/m2) during a three-drug treatment regimen. Mean interstitial MTX load in breast tumors, expressed as area under curve (AUC), was 60 +/- 20% (mean +/- SE; coefficient of variation = 100%) of mean plasma MTX load. There was no correlation between plasma AUC and the AUC in the interstitial space of tumor tissue (P = 0.93). Not one of the parameters plasma, interstitial tumor load, and transfer rate of MTX to the interstitial space was associated with favorable clinical response. In conclusion, plasma levels of MTX are not predictive of intratumor levels. There is a high interindividual variability in transendothelial MTX transfer. Under the present conditions, access of MTX to the interstitial space is not a rate-limiting step for clinical response to chemotherapy.

Port-a-Cath extravasation of vesicant cytotoxics: surgical options for a rare complication of cancer chemotherapy.

BACKGROUND: Although implantation of a central venous device such as a Port-a-Cath was initially considered safe, extravasation rates up to 4.7% have been reported. Therefore, the objective of this study was to propose a structured procedure for the management of extravasation of a cytotoxic treatment. METHODS: A total of eight patients were evaluated after port extravasation of epirubicin (n = 3), platinum compounds (n = 3), paclitaxel (n = 1), or trabectedin (n = 1) into the subcutaneous space. Immediate explantation of the port was performed in combination with a "Subcutaneous Wash-Out Procedure" (SWOP). When removal of the port was delayed, débridement and flap coverage were performed as necessary. Epirubicin concentrations present in the samples obtained during surgical intervention were subsequently analysed using high-performance liquid chromatography (HPLC). Patients were followed for at least six months and were examined for sequelae such as pain, induration, redness, and limited movement. RESULTS: All three patients whose extravasation event was detected during chemotherapy administration benefited from SWOP with acceptable side effects (e.g., erythema). The analysis of epirubicin concentrations demonstrated the active removal of relevant amounts of the compound by wound rinsing. In contrast, late detection of extravasation led to major débridement and flap coverage in four out of five patients. A high body mass index (BMI) value was associated with all of the patients that experienced port extravasation. CONCLUSION: Depending on when Port-a-Cath extravasations into subcutaneous tissue are detected, different treatments are appropriate. When extravasation is detected early, the SWOP was found to be beneficial.

Transcription and activity of 5-fluorouracil converting enzymes in fluoropyrimidine resistance in colon cancer in vitro.

Cellular resistance to 5-fluorouracil (5-FU) is not completely understood. Since 5-FU shares the pyrimidine pathway with the physiological pyrimidines, we investigated the relationship between fluoropyrimidine metabolism, nucleic acid uptake and cytotoxicity of 5-FU in eight colon tumour cell lines including 5-FU-resistant subclones. The cytotoxicity of 5-FU was increased up to 423-fold when the anabolites 5-fluorouridine (FUrd), 5-fluorodeoxyuridine (FdUrd), and 5-fluorodeoxyuridine monophosphate (FdUMP) were compared with the parent drug in vitro. The enzymes uridine phosphorylase and thymidine phosphorylase were predictive for the cytotoxicity of 5-FU in 5/7 cell lines. Inhibition of uridine phosphorylase and thymidine phosphorylase by antisense strategies effectively antagonised 5-FU, abolishing 84% and 79% of its toxicity. The importance of thymidine phosphorylase was supported by a highly restricted enzyme activity in 5-FU-resistant cells. In 5-FU naive cells, a stimulating effect of 5-FU on thymidylate synthase mRNA and ribonucleotide reductase mRNA expression was observed. In these cells, antisense oligonucleotides to ribonucleotide reductase significantly reduced cell growth. Downregulation of ribonucleotide reductase mRNA in 5-FU-resistant subclones suggests different mechanisms in primary and secondary resistance to 5-FU. Most of the intracellular 5-FU was selectively incorporated into RNA (range: 45-91%) and generally spared DNA (range: 0.2-11%). In synthesising our data, we conclude that drug resistance could be overwhelmed through bypassing limiting steps in the activation of 5-FU. In the majority of colonic tumours, the activity of uridine phosphorylase and thymidine phosphorylase may have prognostic relevance for the cytotoxicity of 5-FU in vitro.

The in vitro effects of interleukin-12 upon tumor-infiltrating lymphocytes derived from renal cell carcinoma.

Clinical trials utilising interleukin (IL)-2 with tumor-infiltrating lymphocytes (TIL) have demonstrated efficacy in the treatment of metastatic renal cell carcinoma (RCC). Several cytokines, as well as growth factors have demonstrated modulatory effects upon the biological properties of TIL from RCC, suggesting a potentially important role for cytokines other than IL-2 in the development of active and tumor-specific TIL. IL-12 was recently characterized as a natural-killer-cell-stimulatory factor or cytotoxic-T-cell-maturation factor. These properties of IL-12 prompted us to investigate the impact of this cytokine upon the activation of TIL from human RCC. In an attempt to enhance the in vitro growth and activity of renal TIL, we have grown eight renal TIL cultures in varying concentrations of IL-2 (8, 40, 80, 400 U/ml) and IL-12 (200 U/ml). In addition, IL-12 (200 U/ml) was added to TIL cultures pre-activated with IL-2 (400 U/ml). Growth, cell expansion, and the ability of TIL to release certain cytokines upon tumor stimulation were determined. Proliferation assays, phenotypic analysis, and cytotoxicity assays were performed at an early and a late culture stage. IL-12, alone and when added to suboptimal concentrations of IL-2, failed to induce TIL growth. While the addition of IL-12 to optimal doses of IL-2 suppressed TIL culture expansion, sequential culture exposure first to IL-2 and then to IL-2+IL-12 increased the number of cells expressing CD3+/CD56+ and these cultures demonstrated enhanced in vitro lysis of autologous tumor. IL-12 clearly demonstrated a sequence-dependent impact of the biological behaviour of TIL from RCC. The optimal use of IL-12 in the in vitro expansion of renal TIL may result in cells with an enhanced specific anti-tumor effect.

Double modulation of 5-fluorouracil by high-dose leucovorin and interferon alpha 2b in advanced colorectal cancer: a phase I and a phase II study of weekly administration.

In an attempt to evaluate the feasibility of 5-fluorouracil (FU) treatment modulated by (R,S)-leucovorin (LV) and interferon alpha (IFN alpha) in patients with advanced colorectal cancer, we conducted a phase I trial with increasing doses of subcutaneous IFN alpha (3 x 1 x 10(6) U, 3 x 3 x 10(6) U, 3 x 3 x 10(6) U, 3 x 5 x 10(6) U and 3 x 10 x 10(6) U/week) and 500 mg/m2 LV i.v. as a 2-h infusion with 600 mg/m2 FU i.v. as a midpoint injection. Unacceptable side-effects occurred in all 3 patients at the highest dose level of IFN alpha, while toxicity was tolerable at 3 x 5 x 5 x 10(6) U IFN alpha/week. Thus, this dose was defined as the maximal tolerable dose for IFN alpha in combination with FU and LV. In a subsequent phase II study a total of 83 treatment courses (median: 2.8, range: 2-10) were administered to 30 evaluable patients. Side-effects were acceptable with no WHO grade IV toxicities. Grade III toxicities consisted in thrombopenia (2/30), stomatitis (2/30), diarrhoea (3/30) and nausea/vomiting (4/30). After a median observation time of 17 months (range: 8-22 months), no complete remission was observed and 9 patients experienced a partial response lasting for a median of 6.6 months (range: 3-13+ months), for an overall response rate of 30% (95% confidence interval: 15%-49%). These results show that the described regiment of FU doubly modulated by LV and IFN alpha is active in colorectal cancer and can be safely administered in an out patient setting with acceptable toxicity. Thus, this regimen is suitable to be used for further evaluation in clinical trials.

Instability of the anticancer agent etoposide under in vitro culture conditions.

Degradation of etoposide is rapid under in vitro culture conditions. At pH 7.4 and 37 degrees C, the isomerisation of trans-etoposide to the inactive compound cis-etoposide has a half-life of 2 days in Dulbecco's modified Eagle's medium and results in the loss of 90% of the active drug within 1 week. As a consequence, prolonged incubations with etoposide in in vitro assays may lead to erroneous interpretations ignoring the real in vitro situation. The degradation is not influenced by organic compounds such as bovine serum albumin or amino acids but depends strongly on the pH value and, to a lesser degree, on the ionic strength of the medium. Therefore, we propose a mathematical correction based on the pH value so as to obtain the real exposure of cells to trans-etoposide during in vitro assays.

Pharmacokinetics of 4'-O-tetrahydropyranyladriamycin given on a weekly schedule in patients with advanced breast cancer.

Improved quality of life has gained importance over shortly lasting remissions in yet incurable metastatic breast cancer. Fractionation of drug administration is one of the possible approaches to reduce the concentration-dependent toxicity of anthracyclines. We evaluated the pharmacokinetics of 4'-O-tetrahydropyranyladriamycin (THP-ADM) under weekly administration in patients with advanced breast cancer (dose escalation, from 20 to 27 mg/m2 THP-ADM). The concentration-time curves of THP-ADM in plasma were best described by an open three-compartment model [half-life of the first disposition phase (t1/2 alpha), 3.15 min; terminal elimination half-life (t1/2 gamma), 13.9 h] with a mean area under the curve (AUC) of 12.2 ng h ml-1mg-1 m-2, resulting in a mean plasma clearance of 86.9 1h-1 m-2. Metabolism included the formation of Adriamycin (ADM), Adriamycinol (ADM-OH), 13-dihydro-4'-O-tetrahydropyranyladriamycin (THP-OH), 7-deoxyadriamycinone (7H-ADn), and 7-deoxy-13-dihydroadriamycinone (7H-ADn-OH), with maximal plasma concentrations ranging from 2.8 to 5.5 ng/ml. The mean total amount of cytotoxic anthracyclines excreted into urine, mainly as the parent drug, was 5% of the delivered dose. ADM and ADM-OH, but not the parent drug, were observed in urine at up to 4 weeks after the last therapeutic cycle. There was a significant correlation between the leukocyte nadir under therapy and the AUC of ADM-OH (r = 0.800, P < 0.05). Since no shift in the plasma kinetics was observed from the first to the sixth cycle, the favorable ratio of the AUCs of THP-ADM and ADM after fractionation of THP-ADM suggests lower toxic side effects attributable to ADM. This hypothesis was confirmed in a clinical study, where no severe cardiotoxicity and only mild alopecia were observed in 19 patients. Thus, pharmacokinetics studies might be helpful in both individualization of therapy with THP-ADM and optimization of the administration schedule.

Modulation of 5-fluorouracil resistance in human colon tumor cell lines by azidothymidine.

5-fluorouracil (5-FU), an inhibitor of thymidylate synthase (EC 2.1.1.45), is clinically used in the treatment of several solid tumors, including colorectal, head and neck, gastric, and pancreatic cancer. The drug effectively inhibits deoxynucleoside triphosphate de novo synthesis. However, this inhibition can be circumvented by increased thymidine kinase (EC 2.7.1.21) activity. In the present study we examined the effects of 5-FU combined with azidothymidine (AZT), a competitive inhibitor of thymidine kinase in human colon tumor cells in vitro, including three 5-FU resistant cell lines. The cells were simultaneously incubated with various concentrations of 5-FU (0.015 to 150 microM) and AZT (20 to 300 microM) for 6 days. 5-FU alone yielded an IC50 of 18 microM in the parental CCL 227 cell line and IC50s of 470 and 1100 microM in the 5-FU resistant cell lines as determined by a MTT chemosensitivity assay. Addition of 100 microM AZT alone, a drug concentration that can be achieved in patients, had no effect on the growth of the cell lines examined. However, when added simultaneously with 5-FU, the IC50s of 5-FU synergistically decreased to 10 microM in the sensitive and to 360 or 760 microM in the resistant cell lines, respectively. Our results demonstrate that the combination of 5-FU with AZT synergistically inhibited the growth of 5-FU resistant cells, suggesting the use of 5-FU in combination with AZT for the treatment of 5-FU sensitive as well as resistant human colon tumors.