Potential applications of therapeutic drug monitoring in treatment of neoplastic disease by antineoplastic agents

Therapeutic drug monitoring of antineoplastic agents must be considered in terms of cytotoxicity to stem cells and toxicity of normal tissues. The dose-limiting toxicity which is myelosuppression is believed to be a necessary effect for maximal antitumour effect. The areas in which therapeutic drug monitoring can play a role include: predicting patients at risk of toxicity, e.g. high dose methotrexate therapy; low bioavailability, e.g. oral 6-mercaptopurine; identifying patients at risk of treatment failure, e.g. methotrexate clearance in acute lymphoblastic leukemia. Although therapeutic drug monitoring is not clinically useful at present, the potential role it can play is illustrated for cytosine arabinoside, adriamycin and cyclophosphamide. Two problems encountered with drug monitoring of antineoplastic disease are tumour heterogeneity manifested by clonal, nutritional and physical characteristics and the common practice of combination chemotherapy. These problems must be addressed in order to make therapeutic drug monitoring a practical tool in cancer chemotherapy. Future applications of therapeutic drug monitoring will require more studies to define therapeutic ranges for single agents, patient-to-patient variation, course-to-course variation and the effects of drug combinations on pharmacokinetic profiles of the drugs used.     

Plasma pharmacokinetics of 5-FU given by continuous infusion with allopurinol

We determined the steady-state plasma levels of 5-FU when the drug was administered by continuous infusion for 5 days during 21 courses in patients with metastatic colorectal carcinoma receiving concomitant oral allopurinol given at a dose of 300 mg orally three times/day. The steady-state plasma level increased from 3.37 to 7.49 microM with dose increases from 1.25 to 2.25 g/m2/day. Clearance ranged from 1.79 to 2.41 L/min/m2. Although we observed a large day-to-day variation and a large patient-to-patient variation in plasma 5-FU levels at any given dose level, these were not significant. The plasma level of 5-FU increased linearly with dose. The difference between 5-FU plasma levels with dose was significant (P = 0.002). When the levels were adjusted for patient-to-patient and day-to-day variation the difference remained significant (P = 0.02). The results indicate that: (a) plasma levels of 5-FU may show large but insignificant variation from patient to patient and from day to day; and (b) steady-state plasma levels and 5-FU increased linearly with dose.     

Heterogeneous role of caspase-8 in fenretinide-induced apoptosis in epithelial ovarian carcinoma cell lines

The mechanism of action of fenretinide, a synthetic retinoid currently undergoing testing as a chemopreventive and chemotherapeutic agent, is incompletely understood. In the present study, fenretinide caused apoptotic changes, including DNA fragmentation and cleavage of caspase substrates, in six low-passage ovarian cancer cell lines. However, the caspase activation pathway used by this agent varied. Transient transfection of cDNA-encoding cytokine response modifier A (CrmA), a caspase-8 inhibitor, diminished fenretinide-induced death in OV177 cells. Likewise, IETD(OMe)-fluoromethylketone (fmk) inhibited fenretinide-induced apoptosis by >80% in OV177 or OV266 cells and by approximately 50% in OV17, OV167, or OV207 cells. Further analysis demonstrated that inhibition of Fas ligand, tumor necrosis factor-alpha, or TRAIL signaling with blocking reagents did not affect fenretinide-induced apoptosis, raising the possibility that fenretinide activates caspase-8 in a death receptor-independent manner. In contrast, CrmA transfection or IETD(OMe)-fmk treatment did not inhibit fenretinide-induced apoptosis in OV202 cells. These divergent behaviors did not correlate with increased levels of procaspase-10, which is relatively resistant to CrmA and IETD(OMe)-fmk, nor with the expression of procaspase-8 and -9, apoptotic protease activating factor-1, or cellular FLICE-like inhibitory protein. Similarly, fenretinide treatment increased ceramide levels equally in cells that do (OV177) and do not (OV202) rely on caspase-8 to initiate apoptosis. These results indicate that synthetic retinoids can use caspase-8 as an initiating caspase, but they also indicate unexpected heterogeneity in caspase activation pathways among closely related cell lines.     

Sulfhydryl reagent-induced insulin release and 45Ca++ fluxes in Syrian hamster insulinoma cells.

Dispersed single cell suspensions of Syrian hamster insulinoma cells were used to study the effects of a variety of sulfhydryl-binding reagents on insulin release and 45Ca++ flux. Incubation of cells with several organic mercurials resulted in a rapid increase in 45Ca++ uptake as well as increased efflux in cells which had been prelabeled with 45Ca++. Concomitant with increased calcium uptake was a 4- to 5-fold increase in insulin released into the medium. Incubation with alkylating reagents such as iodoacetamide and N-ethyl maleimide or dithiol reagents such as 5,5'-dithiobis (2-nitrobenzoic acid) failed to stimulate either 45Ca++ flux or insulin release. Elimination of medium calscium or preincubation of cells with N-ethyl maleimide resulted in approximately 50% inhibition of mercurial-induced insulin release from these cells. 8-(N,N2-diethylamino)Octyl-3,4,5-trimethoxybenzoate or alpha-isopropyl-alpha [(N-methyl-N-homoveratryl)-gamma-aminopropyl]3,4,5'-trimethoxyphenylacetonitrite hydrochloride, agents which block potassium (40 mM)-stimulated calcium flux and insulin release, failed to inhibit mercurial-induced calcium flux or insulin secretion. These results indicate that sulfhydryl-binding reagents, through their interaction with critical thiol groups, promote insulin release in these insulinoma cells by inducing changes in calcium fluxes. It is possible that these thiol groups regulate calcium metabolism and, thus, insulin release under physiological conditions.     

Aspergillus infection in a patient receiving immunosuppressive drugs.

A rare case of an indolent Aspergillus infection in a deep neck space in an immunologically compromised patient is reported. Aggressive measures were taken to identify the cause of the infection. Despite concerted antifungal therapy, the patient died.     

Levamisole and 5-fluorouracil therapy for resected colon cancer: a new indication.

OBJECTIVE: To evaluate the benefits and risks of postoperative treatment with levamisole plus 5-fluorouracil (5-FU) in patients with colon cancer. DESIGN: Computerized searches of MEDLINE and CANCERLIT were performed, and the reference list of each retrieved article was checked. Only randomized trials of therapy with levamisole alone or combined with 5-FU for colon cancer without distant metastases were included. The studies were then evaluated with the use of four criteria. RESULTS: We reviewed six randomized trials, of which three satisfied our criteria. Two studies demonstrated a significant improvement in the survival rate with levamisole plus 5-FU among patients with colon cancer and pathologically confirmed metastases to adjacent lymph nodes (Dukes' stage C). A subgroup analysis in another study demonstrated a similar benefit. The toxic effects of the drugs were generally mild. The three other studies showed no difference in survival rates between the treatment groups; however, the samples were too small to detect a clinically or statistically important difference. CONCLUSIONS: Because many patients with colon cancer will suffer a relapse we recommend that they be offered the opportunity to participate in clinical trials of adjuvant therapy. For those with stage C disease not entering a clinical trial levamisole plus 5-FU is appropriate adjuvant therapy.     

Adjuvant therapy of colon cancer: a review

Colon cancer is a common cause of cancer-related mortality. Complete surgical resection of the primary tumor and/or select metastatic lesions can be curative in many patients. The risk of recurrence after resection can be predicted by pathologic staging. Large prospective randomized trials over the past 2 decades have clearly shown an increased overall survival for patients with resected stage III colon cancer who are treated with adjuvant 5-fluorouracil-based chemotherapy. The benefit of adjuvant chemotherapy for patients with stage II disease remains controversial. There is indirect evidence to support adjuvant chemotherapy after resection of metastatic disease. Locoregional approaches such as radiation, hepatic arterial infusion, or portal vein chemotherapy remain investigational. Adjuvant immunotherapy with monoclonal antibodies is emerging as a therapeutic option that might complement chemotherapy. Future challenges include improving adjuvant chemotherapy with the addition and/or substitution of new agents, resolving which subset of patients with stage II and resected stage IV colon cancer might benefit from therapy, validating the benefit of immunotherapy, and investigating locoregional therapies compared with systemic therapy.     

A phase I and pharmacologic study of pyrazoloacridine (NSC 366140) and carboplatin in patients with advanced cancer

Background: Pyrazoloacridine (PZA) is thefirst of a new class of rationallysynthesized acridine derivatives to undergoclinical testing as an anticancer agent. We previously demonstrated cytotoxicsynergy between combinations of PZA andplatinum compounds. Subsequent studiesrevealed that PZA inhibits removal ofplatinum-DNA adducts in cultured A549cells. Based on these results, weundertook a phase I study of thecombination of PZA and carboplatin (CBDCA). Patients and methods: Twenty-eightpatients received 76 28-day courses (median2.5, range 1–6) of CBDCA (30-minuteinfusion) followed by PZA (3-hourinfusion), through six dose levels [PZA/CBDCA] (200/AUC 3,400/AUC 3, 400/AUC 4,400/AUC 5, 500/AUC 5, 600/AUC5 mg/m²/AUC). Pharmacokineticanalyses were performed to evaluate thedisposition of PZA. Retention ofplatinum-DNA adducts in peripheral bloodmononuclear cells of patients was alsoevaluated. Results: The most common anddose-limiting toxicity wasmyelosuppression, consisting of neutropeniaand leukopenia. Non-hematologic toxicitiesof anorexia, nausea and stomatitis weremild to moderate. In six patientsevaluated at the MTD, CBDCA did not appearto affect the pharmacokinetics of PZA. Onepatient with malignant melanoma had apartial response. Disease stabilizationfor greater than 4 courses of treatmentoccurred in 4 patients. Conclusion: The combination of PZAand CBDCA was well tolerated and may haveutility in some tumor types.     

Limited sampling models for CPT-11, SN-38, and SN-38 glucuronide

PURPOSE: To determine the ability of WMC26, a prototypic bisimidazoacridone (BIA), to induce apoptosis in sensitive colon adenocarcinoma cells and to advance the hypothesis that cancer cells that are growth-arrested by WMC26 are predisposed to undergo apoptotic death by abrogators of cell cycle checkpoints. METHODS: The antiproliferative activity of WMC26 was examined in detail by a 4-day MTT assay, cell counting, BrdU incorporation and a two-color LIVE/DEAD assay. To detect apoptosis a number of established techniques were used, including gel electrophoresis, flow cytometry, and confocal laser microscopy of treated cells. The activity of senescence-associated beta-galactosidase in treated cells was also analyzed. RESULTS: WMC26, at physiological concentrations, induced complete and longlasting growth arrest of HCT116 cells in culture but did not trigger cell death. The growth-arrested cells (blocked at G1 and G2/M cell cycle checkpoints) did not synthesize DNA but were metabolically active and had intact plasma membranes. Although they resembled the senescence-like phenotype reported to be induced by treatment with some antitumor agents, the cells did not express senescence-associated beta-galactosidase, an indicator of the senescence-like state. Treatment of WMC26 growth-arrested cells with 1 microM UCN-01, an abrogator of the G2/M checkpoint, caused a very rapid (1 h) change in morphology and cell death within 72 h. CONCLUSIONS: BIAs do not induce apoptosis in sensitive colon tumor cells. They are highly cytostatic but only marginally toxic to the cells even at concentrations 100-fold higher than those sufficient for complete growth arrest. In this respect WMC26 differs from some other DNA-interacting antitumor agents that produce cell growth arrest at low concentrations but are toxic at higher doses. The complete growth arrest induced by WMC26 in colon cancer cells sensitized them to apoptotic death induced by UCN-01. This finding suggests that a combination of WMC26 and cyclin-dependent kinase inhibitors may be an attractive treatment method for colon cancer that utilizes the highly tumor-selective activity of WMC26.