The clinical pharmacology of antineoplastic agents (first of two parts)

Metabolomics in cancer research and emerging applications in clinical oncology

Cancer has myriad effects on metabolism that include both rewiring of intracellular metabolism to enable cancer cells to proliferate inappropriately and adapt to the tumor microenvironment, and changes in normal tissue metabolism. With the recognition that fluorodeoxyglucose-positron emission tomography imaging is an important tool for the management of many cancers, other metabolites in biological samples have been in the spotlight for cancer diagnosis, monitoring, and therapy. Metabolomics is the global analysis of small molecule metabolites that like other -omics technologies can provide critical information about the cancer state that are otherwise not apparent. Here, the authors review how cancer and cancer therapies interact with metabolism at the cellular and systemic levels. An overview of metabolomics is provided with a focus on currently available technologies and how they have been applied in the clinical and translational research setting. The authors also discuss how metabolomics could be further leveraged in the future to improve the management of patients with cancer.

Metabolism of immune cells in cancer

Through the successes of checkpoint blockade and adoptive cellular therapy, immunotherapy has become an established treatment modality for cancer. Cellular metabolism has emerged as a critical determinant of the viability and function of both cancer cells and immune cells. In order to sustain prodigious anabolic needs, tumours employ a specialized metabolism that differs from untransformed somatic cells. This metabolism leads to a tumour microenvironment that is commonly acidic, hypoxic and/or depleted of critical nutrients required by immune cells. In this context, tumour metabolism itself is a checkpoint that can limit immune-mediated tumour destruction. Because our understanding of immune cell metabolism and cancer metabolism has grown significantly in the past decade, we are on the cusp of being able to unravel the interaction of cancer cell metabolism and immune metabolism in therapeutically meaningful ways. Although there are metabolic processes that are seemingly fundamental to both cancer and responding immune cells, metabolic heterogeneity and plasticity may serve to distinguish the two. As such, understanding the differential metabolic requirements of the diverse cells that comprise an immune response to cancer offers an opportunity to selectively regulate immune cell function. Such a nuanced evaluation of cancer and immune metabolism can uncover metabolic vulnerabilities and therapeutic windows upon which to intervene for enhanced immunotherapy.

Biology of premature ageing in survivors of cancer

Over 30 million cancer survivors exist worldwide. Survivors have an earlier onset and higher incidence of chronic comorbidities, including endocrinopathies, cardiac dysfunction, osteoporosis, pulmonary fibrosis, secondary cancers and frailty than the general population; however, the fundamental basis of these changes at the cellular level is unknown. An electronic search was performed on Embase, Medline In-Process & Other Non-Indexed Citations, and the Cochrane Central Register of Controlled Trials. Original articles addressing the cellular biology of ageing and/or the mechanisms of cancer therapies similar to ageing mechanisms were included, and references of these articles were reviewed for further search. We found multiple biological process of ageing at the cellular level and their association with cancer therapies, as well as with clinical effects. The direct effects of various chemotherapies and radiation on telomere length, senescent cells, epigenetic modifications and microRNA were found. We review the effects of cancer therapies on recognised hallmarks of ageing. Long-term comorbidities seen in cancer survivors mimic the phenotypes of ageing and likely result from the interaction between therapeutic exposures and the underlying biology of ageing. Long-term follow-up of cancer survivors and research on prevention strategies should be pursued to increase the length and quality of life among the growing population of cancer survivors.

The Radiation Stress Response: Of the People, By the People and For the People

The radiation stress response can have broad impact. In this Failla Award presentation it is discussed in three components using terms relevant to the current political season as to how the radiation stress response can be applied to the benefit for cancer care and as service to society. Of the people refers to the impact of radiation on cells, tissues and patients. The paradigm our laboratory uses is radiation as a drug, called "focused biology", and physics as "nano-IMRT" because at the nanometer level physics and biology merge. By the people refers to how the general population often reacts to the word "radiation" and how the Radiation Research Society can better enable society to deal with the current realities of radiation in our lives. For the people refers to the potential for radiation oncology and radiation sciences to improve the lives of millions of people globally who are now beyond benefits of cancer treatment and research.

Chemical, Physical, and Genetic Factors Interfering with DNA Repair-a Review

Because of its function as transmitter of genetic information, DNA is the most important macromolecule in need of protection from attack by chemical and physical agents, but mechanisms have evolved for repairing such damage to DNA. The presence of the adaptive response and other cellular repair systems (excision, post-replication, SOS, etc.) diminishes the toxicologic effects of low doses of toxic or muta-genic substances. Whether or not these genotoxic effects can be reduced to undetectable levels is not certain. Nonetheless, this repair-mediated diminution of damage due to chemicals constitutes one of the arguments in favor of existence of “safe” threshold levels of chemical exposure (Schendel, 1981).

In turn, the repair process itself may be affected by chemical and physical agents. To determine the mode of action of a specific compound on the process of DNA repair becomes complex when all factors are taken into consideration. There are agents which interfere with DNA repair but they are also as active or more active in suppressing replicative DNA synthesis, as well as RNA and protein synthesis. The interference with repair may arise from other major processes such as alteration of energy metabolism and effects on precursor pathways and/or enzymatic cofactors. Whether or not an agent can specifically inhibit DNA repair enzymes has not been answered. The point must be made, however, that this type of interference with essential protective mechanisms is taking place and it may change anticipated outcomes of chemical or physical exposures. The magnitude of this effect due to the exposure of people to so many chemicals should be recognized and studied for their degree of interference with all the processes of DNA repair.

Serine, glycine and one-carbon units: cancer metabolism in full circle

One-carbon metabolism involving the folate and methionine cycles integrates nutritional status from amino acids, glucose and vitamins, and generates diverse outputs, such as the biosynthesis of lipids, nucleotides and proteins, the maintenance of redox status and the substrates for methylation reactions. Long considered a 'housekeeping' process, this pathway has recently been shown to have additional complexity. Genetic and functional evidence suggests that hyperactivation of this pathway is a driver of oncogenesis and establishes a link to cellular epigenetic status. Given the wealth of clinically available agents that target one-carbon metabolism, these new findings could present opportunities for translation into precision cancer medicine.

Adverse Histopathologic Effects of Chemotherapeutic Agents in Childhood Leukemia and Lymphoma

Pathologic material from 84 children with leukemia or lymphoma who died and were autopsied at the University of Wisconsin Hospital between 1967 and 1980 was reviewed to assess the adverse tissue changes due to the chemotherapy administered. In each case the histopathologic findings were correlated with the chemotherapy given. Individual drug dosage is administered (per m2) correlated with the adverse tissue findings at autopsy. Data presented suggest that the drug dose administered should be correlated not only with tumor response but also with tissue effects (some of which produce no noticeable, immediate, clinically apparent changes) to decrease the likelihood of producing irreversible tissue changes.

Medulloblastoma/primitive neuroectodermal tumour studied as a Matrigel enhanced subcutaneous xenograft model

An important role for pre-clinical models of medulloblastoma/primitive neuroectodermal tumour (MB/PNET) is inhibited by the limitations of conventional heterotransplantation. Nine cohorts of MB/PNET were studied for subcutaneous engraftment in nude mice by both conventional and Matrigel supplemented methods. While no subcutaneous tumours resulted from 63 conventional attempts, an aggregate 41 xenografts from 72 injections (57%) were produced when Matrigel was added to the cell suspension. In subsequent passage, engraftment rate approached 100%. To study the response to chemotherapeutic agents in the model, a total of 221 tumours in 3 cohorts were treated using one of the following: cisplatin, carboplatin, vincristine, cyclophosphamide, diaziquone, or saline control. While all agents demonstrated statistically significant activity, cyclophosphamide proved to be particularly effective. The potential applications of this xenograft model in the biologic as well as therapeutic study of MB/PNET deserve continuing investigation.

Nonlinear pharmacokinetics of 5-fluorouracil in rats

The effects of dose on the pharmacokinetics of 5-fluorouracil (5-FU) were investigated following intravenous administration of 5-FU at 10, 50, and 100 mg/kg to adult male Sprague-Dawley rats. Six rats were studied at each dose level. The dose-normalized area under the curve (AUC) was significantly higher after administration of 100 mg/kg (1.14 +/- 0.55 mg.h/L/mg; mean +/- SD) than after 50 mg/kg (0.50 +/- 0.18 mg.h/L/mg) or 10 mg/kg (0.43 +/- 0.11 mg.h/L/mg), indicating nonlinear elimination of 5-FU in rats. Dose- and time-average pharmacokinetic parameters were calculated by area/moment analysis. The systemic clearance of 5-FU following administration of 100 mg/kg was significantly lower (1.1 +/- 0.49 L/h/kg) than after 50 mg/kg (2.2 +/- 0.72 L/h/kg) or 10 mg/kg (2.4 +/- 0.67 L/h/kg). There was no significant difference in renal clearance values between the three doses (0.47 +/- 0.26 L/h/kg). However, nonrenal clearance was significantly lower after the 100-mg/kg dose (0.77 +/- 0.2 L/h/kg) than after the 50-mg/kg (1.65 +/- 0.49 L/h/kg) and 10-mg/kg (1.87 +/- 0.75 L/h/kg) doses. There was no significant difference between the steady-state volume of distribution values (0.91 +/- 0.36 L/kg) at the three doses. The lower nonrenal clearance following the 100-mg/kg dose compared with that after the lower doses of 5-FU suggested nonlinear metabolism of 5-FU in rats. A two-compartment pharmacokinetic model with parallel first-order (renal excretion) and Michaelis-Menten elimination from the central compartment was simultaneously fit to mean plasma 5-FU concentration versus time data for the three doses. The maximum volume (Vmax) and Michaelis constant (Km) values averaged (mean +/- SE) 8.3 +/- 2.3 mg/h and 31.6 +/- 11.9 mg/L, respectively. The information obtained in this study will be valuable for the evaluation of prodrugs of 5-FU that are designed to reduce toxicities and to improve oral bioavailability of the anticancer agent.

Response of brain tumors to chemotherapy, evaluated in a clinically relevant xenograft model

Chemotherapy for brain tumors remains unsatisfactory. Despite increasing participation in clinical trials, there is a clear need for pre-clinical models. Heterotransplantation of surgical specimens directly into the anterior chamber of the nude mouse eye has been demonstrated to produce evaluable xenografts. Drug access in this model is considered to mimic the blood-brain barrier. Five clinical specimens in 3 children with primitive neuroectodermal tumor/medulloblastoma were the sources of 293 intraocular xenografts (5 cohorts by source). Each tumor-bearing mouse received 1 of 5 drugs or normal saline, by intraperitoneal injection, weekly for 5 weeks. Response was monitored for up to 22 weeks, using a staging system which estimates the proportion of the anterior chamber filled by tumor. Results were analysed both as response rates (shrinkage in excess of 50%) at the conclusion of the treatment course and as time to tumor progression by the life table method. Comparison of response rates within cohorts by source of xenografts (exact chi-square test for overall and 2-sided Fisher's exact test for paired comparisons) indicated cyclophosphamide to be the most effective single agent. In logrank analyses cyclophosphamide achieved significantly longer delays to progression than all other drugs in one cohort and longer delays than all but diaziquone in 2 other cohorts. The intraocular xenograft model is a clinically relevant system for the study of therapeutic agents in brain tumors. The effectiveness of intensive dosage cyclophosphamide in a model dependent on access across the blood-aqueous barrier is important and consistent with recent clinical data.

Investigations on the antiproliferative effects of amino acid antagonists targeting for aminoacyl-tRNA synthetases. Part III--Combination experiments

The combined effects of amino acid antagonists with proven or potential inhibitory activities on aminoacyl-tRNA synthetases were investigated on the murine leukemic cell line P388 D1. As the best result a summation of the antiproliferative effects was observed. Combinations with established cytostatic agents like platinum complexes or other antitumor compounds also yielded partly additive effects. In experiments performed with asparaginase L-aspartic acid-beta-hydroxamate gave synergistic growth inhibition of P388 D1 cells in vitro, which was reflected by additive effects against murine leukemia P388 in vivo.

Protein intake and 5-fluorouracil toxicity in tumor-bearing animals

The administration of chemotherapy is limited in clinical situations by lack of selective antineoplastic activity resulting in significant host toxicity. Although it has been suggested that nutrition support can reduce chemotherapy-related toxicity, few controlled studies exist to document this clinical impression. This study was performed to determine the effect of enteral protein intake on 5-fluorouracil toxicity in tumor-bearing animals. Seventy-nine female Lewis/Wistar rats with subcutaneous mammary tumor implants (AC-33) were randomized to receive either standard protein (22.0% protein; 4.27 kcal/g) or an isocaloric, protein-depleted diet (0.03% protein; 4.20 kcal/g). One-half of the animals in each group received daily injections of 5-fluorouracil (15- or 25 mg/kg ip) or placebo (saline) for 4 or 5 days. Standard protein intake significantly increased host body weight and decreased leukopenia at low (15 mg/kg) and high (25 mg/kg) 5-fluorouracil therapy. At high-dose 5-Fluorouracil (25 mg/kg), the incidence and duration of diarrhea were decreased in animals receiving standard protein intake. Thus, enteral protein intake significantly reduced clinical and objective 5-fluorouracil toxicity and improved body weight in this tumor-bearing animal model.

Toxicology of oncologic drugs

The drugs used in clinical oncology are inherently toxic because they are designed to kill host cells. For the most part, the toxic effects occur in tissues with high growth fractions--that is, bone marrow, gastrointestinal epithelium, and hair follicles. Nevertheless, certain drugs do cause harm to other organs. At therapeutic doses of anticancer drugs, the toxicoses are usually mild to moderate and can be managed without undue discomfort to the animal. Occasionally, however, life-threatening cytopenias occur. By contrast, with drug overdose, life-threatening toxicoses can be a very real concern.

The folate antagonist, methotrexate, is a potent inhibitor of murine and human cytomegalovirus in vitro

Cytomegalovirus (CMV) is a major source of morbidity for immunocompromised patients, such as AIDS patients. The folic acid antagonists have not been explored as potential antiviral agents against CMV. We examined the effects of methotrexate, compared to acyclovir and ganciclovir, on both murine CMV (MCMV) and human CMV (HCMV) in vitro. Using a plaque assay in mouse embryo cells or human foreskin fibroblasts for MCMV and HCMV respectively, we found that methotrexate, in micromolar concentrations, was a potent inhibitor of both viruses. This effect was due to folic acid antagonism since folinic acid abrogated the antiviral effect of methotrexate, but not ganciclovir. Cellular toxicity due to methotrexate appeared insufficient to account for the antiviral effects. The ability of methotrexate to inhibit CMV in vivo merits exploration.

Reduction of methotrexate toxicity with improved nutritional status in tumor-bearing animals

The administration of chemotherapy in clinical situations is limited frequently because of the associated toxicity to normal bone marrow cells, gastrointestinal epithelium, and other host tissues. Although nutritional support has been advocated to reduce chemotherapy-related toxicity in cancer patients, few studies substantiate this clinical impression. The current study was performed to determine the role of nutritional status and enteral nutrient intake as determinants of methotrexate (MTX) toxicity in a well-controlled, tumor-bearing animal model. After subcutaneous mammary tumor (AC-33) inoculation, 56 female Lewis/Wistar rats were assigned randomly to one of the following two nutritional regimens for 14 days: (1) protein-depleted chow (PC) (0.03% protein; 4.27 kcal/g) or (2) standard chow (RC) (22.0% protein; 3.50 kcal/g). After 7 days of dietary control, all animals received one of three weight-adjusted doses of MTX (5, 10, or 20 mg/kg intramuscularly [IM] ) or placebo. All animals received leucovorin rescue (0.6 mg IM) at 6 and 24 hours after MTX injection. Improved nutritional status was associated with a significant reduction in objective measures of MTX-related morbidity and mortality. At low doses of MTX (5 and 10 mg/kg), the mean duration of clinical signs of toxicity (i.e., hair loss, lethargy, and diarrhea) and severity of leukopenia were greater in protein-depleted (PD) animals. With high-dose MTX (20 mg/kg), mortality was increased significantly in PD animals (100%) compared with well-nourished animals (0%). Equivalent tumor response was observed in PD and well-nourished animals. Thus, improved nutritional status by enteral nutrition reduced the morbidity and mortality associated with MTX significantly in this tumor-bearing animal model.

Actinic cheilitis: a review of the etiology, differential diagnosis, and treatment

With today's increase in sun worshippers, the number of sun-induced skin lesions is increasing. Actinic cheilitis is the counterpart of actinic keratosis of the skin and can also develop into squamous cell carcinoma. In this article we review the etiology, clinical spectrum, histology, differential diagnosis, and treatment of actinic cheilitis. Actinic cheilitis needs to be differentiated from many other lip conditions, and the dermatologist must be attune to its possibility whenever assessing scaly lips. Because of its potential to develop into squamous cell carcinoma, treatment should be instituted as soon as possible.

Massive splenomegaly in myeloproliferative disorders treated by splenic artery infusion of cytarabine

Ten patients with myeloproliferative disorders and massive splenomegaly were treated with splenic artery infusions of cytarabine. Nine patients demonstrated a response to treatment with reduction in spleen size. Three patients had the procedure repeated on subsequent occasions. Relief from pain was the most significant clinical benefit; lasting for up to 6 months regardless of the rate of splenic re-enlargement.

Oral manifestations of systemic chemotherapy and their management

Many antineoplastic drugs in use now have cytotoxic side effects that also manifest in the oral cavity or influence dental management. Chemotherapeutic agents that have a high potential for precipitating oral mucosal damage and bone marrow depression are methotrexate, cyclophosphamide, daunorubicin, doxorubicin hydrochloride, 5-fluorouracil, bleomycin, nitrogen mustard, cytosine-arabinoside, 6-mercaptopurine, busulfan, and L-phenylalanine mustard. Mucositis may lead to neglected oral hygiene, which in turn may cause a chain reaction of local infections, bleeding, and septicemia in myelosuppressed patients. Preventive oral care before chemotherapy and active oral care during therapy are necessary for compromised patients. A protocol for oral care is described.

Tumor uptake of 5-fluorouracil, methotrexate, and adriamycin vs gallium

Since the imaging pattern of 67Ga-citrate is well known, it can be the benchmark for evaluation of potential tumor imaging agents. Tritium labeled 5-fluorouracil, Adriamycin, (doxorubicin/Adria) and Methotrexate/Lederle were compared at 2 h to 67Ga-citrate at 2 and 48 h by percent uptake per gram of various tissues and tumor in rats implanted with Walker 256 carcinosarcoma. 67Ga at 48 h showed approximately three times more uptake in the tumor than 5 fluorouracil and eight times more than the others. 5 Fluorouracil showed approximately three times greater uptake than Methotrexate or doxorubicin and 1.4 times the 2 h uptake of 67Ga. 5 Fluorouracil shows potential as an imaging agent especially where the waiting time between injection and imaging must be short.

Ultrasound as a screening procedure for methotrexate-induced hepatic damage in severe psoriasis

Methotrexate has been of proven value in the management of patients with severe psoriasis. Its long-term use, however, can be complicated by progressive hepatic damage which has necessitated regular liver biopsies. We have looked into the efficacy of liver ultrasonography as a non-invasive screening procedure to select those patients who may be developing liver changes. Eighty-seven investigations on 82 patients were performed, comparing liver ultrasound results with liver biopsy. Eight of these showed a degree of hepatic damage which was sufficient to indicate cessation of methotrexate, and all of these were detected by ultrasonography. Our results indicate that patients whose last liver biopsy was normal could be allowed an extended interval between biopsies provided their intervening ultrasound scans remained normal.

High-dose cytosine arabinoside in previously treated patients with poor-prognosis non-Hodgkin's lymphoma

Fourteen previously treated patients with relapsed or refractory poor-prognosis non-Hodgkin's lymphoma were given chemotherapy regimens containing high doses of cytosine arabinoside alone (seven patients) or with an anthracycline or amsacrine (seven patients). Five patients achieved a complete remission and two patients had a partial remission. The durations of remission, however, were short (median, 3 months; range, 2-6 months). Toxicities included conjunctivitis, photophobia, stomatitis, dermatitis, cerebellar dysfunction, diarrhea, nausea, vomiting, liver dysfunction, and severe myelosuppression. Recovery of an absolute granulocyte count greater than 500/microliter and an untransfused platelet count greater than 20,000/microliter required a median of 31 (range, 28-35) and 30 (range, 27-43) days, respectively. Six patients died with recurrent or residual disease before bone marrow recovery. Younger age, good performance status, and a previous complete remission were predictive of a good response. High-dose cytosine arabinoside has major myelotoxicity but significant activity in some patients with poor-prognosis non-Hodgkin's lymphoma.

Comparison of gas chromatographic/mass spectrometric and microbiological assays for 5-fluorouracil in plasma

The concentrations of 5-fluorouracil in 99 plasma samples were determined by both microbiological and gas chromatographic/mass spectrometric assays. The values determined by the two methods were similar (correlation coefficient = 0.90). A regression of the natural logarithms of the concentrations (0.01-94 micrograms ml-1) determined by the two methods gave a line whose slope and intercept were not statistically different (p greater than 0.05) from 1 and 0 respectively. Thus, the microbiological assay has specificity over a sufficient concentration range to serve as a practical routine laboratory method for the determination of 5-fluorouracil.

Chemotherapy and wound healing

This paper provides a review of common chemotherapeutic agents and the experimental evidence supporting their effects on wound healing. Correlation with clinical studies is used to establish relevance, and therapeutic guidelines are developed.

Chemotherapy in hairy cell leukemia. Preliminary results of a nonaggressive regimen

Three patients with hairy cell leukemia, only one splenectomized, were treated with a combination of vinblastine plus bleomycin at low doses. One achieved a complete remission and another achieved a good partial hematologic and bone marrow remission. Neither of them has relapsed after follow-up periods of 34 and 17 months, respectively. The third patient, although achieving a hematologic improvement, died because of a cytomegalovirus pneumonitis after 2 cycles of chemotherapy. Chemotherapy is not usually employed in the initial management of hairy cell leukemia. However, if life-threatening neutropenia and thrombocytopenia occur secondary to severe bone marrow leukemia infiltration and an improvement does not take place using alternative therapeutic strategies, chemotherapy should be taken into consideration. The nonaggressive chemotherapeutic regimen the authors propose induces a cytoreduction without an evident myelosuppression, and can be also employed on an outpatient basis.

Methotrexate therapy in rheumatoid arthritis: 15 years experience

An increasing amount of clinical data indicates that low-dose methotrexate therapy for rheumatoid arthritis is both effective and free of serious side effects. Since 1967 we treated 78 patients with definite or classic rheumatoid arthritis who showed inadequate response to conventional therapy. Up to 15 mg of methotrexate was given weekly by the intramuscular route. Morning stiffness, severity of pain at rest and with activity, extent of active synovitis, functional capacity, change in steroid dosage, complete blood count, erythrocyte sedimentation rate, and gamma glutamyl transpeptidase were monitored. Overall assessment indicated that 45 of the 78 (58 percent) patients showed marked improvement or complete remission, usually within four weeks. When maximum improvement was obtained, most patients were switched to oral therapy with a variable degree of success, and dosage was decreased as tolerated. No serious toxicity was noted. In 34 patients a total of 67 liver biopsy specimens were obtained, some after as long as 15 years of therapy. Minor changes observed are the same as in patients with rheumatoid arthritis not treated with methotrexate. Because the risks did not appear justified, routine annual biopsies were discontinued. In contrast to other cytotoxic drugs, no carcinogenesis has been demonstrated with methotrexate. It appears that methotrexate is approximately as effective as intramuscular gold and D-penicillamine but that it has a quicker onset of response and less serious toxicity.

Response of methylenetetrahydrofolate levels to methotrexate in Krebs ascites cells

Levels of methylenetetrahydrofolate in Krebs ascites cells subsequent to transplantation and the effects of methotrexate on these levels have been measured. To directly measure methylenetetrahydrofolate in tissue extracts, the cofactor was incorporated into a covalent ternary complex with thymidylate synthase and 3H-labelled fluorodeoxyuridine monophosphate. A 3-4-day lag preceded rapid growth of the tumour cells, and this same kinetic behaviour was observed for methylenetetrahydrofolate levels in the tumour cells. Liver and kidney tissue from the same animals also showed an increase in methylenetetrahydrofolate over the same time period. The impact of methotrexate on methylenetetrahydrofolate in the tumour cells depended upon concentration and the post-transplantation time at which treatment was initiated. Levels of methylenetetrahydrofolate in the tumour cells were most sensitive to the drug at the beginning of the rapid growth phase and were more sensitive to a given level of methotrexate in the presence of phospholipids. A slight but significant increase in methylenetetrahydrofolate occurred in some cases in response to the presence of methotrexate.

Pharmacokinetics of methotrexate and 7-hydroxy-methotrexate in rabbits after intravenous administration

The pharmacokinetics of methotrexate (MTX) and 7-hydroxy-methotrexate (7-OH-MTX), a major metabolite, were investigated in rabbits after intravenous bolus injection and infusion using a specific HPLC assay. The arterial sampling (from the carotid artery) was used in all the studies since peculiar and significant arterial-venous differences in the plasma concentration of MTX and 7-OH-MTX were found following bolus administration of the drug. The disposition kinetics of MTX appeared polyexponential with a small terminal phase having a half-life of 10.2-27.5 hr. Extensive formation of 7-OH-MTX occurred at the two dose levels (15 and 50 mg/kg). Nonlinear disposition of MTX was reflected in several aspects of data analysis. A disproportionate increase in the AUC with dose was observed. An increase in dose not only reduced the mean total body clearance (7.49 vs. 4.26 ml/min/kg) and renal clearance (4.89 vs. 2.76 ml/min/kg), but also prolonged the mean residence time (26.2 vs. 43.3 min). The steady-state volume of distribution (Vss) of MTX was estimated to range from 0.16 to 0.25 L/kg. More than 90% of the dose was excreted as MTX and 7-OH-MTX within 8 hr after dosing. Renal clearances decreased with the increasing plasma levels, suggesting active tubular secretion as one of the excretion mechanisms. A similar pattern for renal clearance of 7-OH-MTX was obtained. Infusion studies of 7-OH-MTX revealed that this metabolite had a longer residence time and a larger Vss as compared with MTX, which were in accordance with its physicochemical properties. Essentially complete doses of 7-OH-MTX could be recovered in the rabbit urine.

Neurotoxicity of chemotherapeutic agents after blood-brain barrier modification: neuropathological studies

We examined in 47 dogs the effects of 5-fluorouracil, Adriamycin (doxorubicin hydrochloride), cis-platinum (cis-diamminedichloroplatinum) cyclophosphamide, and bleomycin given in association with osmotic blood-brain barrier modification. The dose of drug ranged from 100% to as little as 5 to 10% of the conventional systemic dosage. Serial neurological observation and subsequent postmortem neuropathological evaluation at times varying from 2.5 hours to 52 days after drug administration showed that cis-platinum and Adriamycin were highly neurotoxic, as evidenced by neurological deficits and pathological changes in the central nervous system parenchyma; 5-fluorouracil and bleomycin had much less, but consequential neurotoxicity; and cyclophosphamide was not associated with substantial toxicity. Intracarotid cis-platinum, unlike the other drugs, damaged the blood-brain barrier and resulted in marked neurotoxicity in the absence of osmotic blood-brain barrier opening. The neural lesions produced by these agents were not specific but were manifested as foci of hemorrhagic necrosis and edema. In addition, secondary brainstem hemorrhage was observed in animals that developed transtentorial herniation. On the basis of these studies, of five drugs studied at a wide range of doses, only cyclophosphamide appears to be safe enough to evaluate in clinical trials that utilize blood-brain barrier modification to enhance drug delivery. These studies also suggest that the lack of neurotoxicity associated with the usual administration of most chemotherapeutic agents probably stems from limited entry of drug into the brain through an intact blood-brain barrier.

5-Fluorouracil concentrations in rat plasma, parotid saliva, and bile and protein binding in rat plasma

The pharmacokinetics of 5-fluorouracil were studied over a 60-min period in rats that received 12.5, 25.0, and 50.0 mg/kg iv. The plasma concentration-time relationship and the detectability in bile and parotid saliva (a route of elimination heretofore given little or no attention) were examined. Protein binding of 5-fluorouracil at concentrations chosen to approximate those found in plasma was determined by equilibrium dialysis. Bile-plasma and parotid saliva-plasma concentration ratios were calculated. 5-Fluorouracil concentrations were quantitated by high-performance liquid chromatography. Plasma concentrations at all doses studied appeared to rapidly decline. The half-life, however, at the 50.0-mg/kg dose (27 min) was significantly longer (p less than 0.025) than the corresponding half-life at the 25.0-mg/kg dose (22 min). This may be attributed to an easily saturable hepatic degradation. Although an observed decline in bile-plasma and parotid saliva-plasma concentration ratios at higher doses may represent saturation of these excretary routes, the small amounts of 5-fluorouracil detected in bile and parotid saliva probably contribute negligibly to the elimination of the total drug equivalents administered. Parotid saliva-plasma concentration ratios were not useful in predicting plasma protein binding as determined by equilibrium dialysis. Excretion of intravenously administered 5-fluorouracil in saliva, however, exposes the upper GI tract to this agent and may play a part in causing stomatitis in patients receiving the drug by this route.

Brain metastases in breast cancer patients receiving adjuvant chemotherapy

A retrospective analysis was performed comparing the incidence of brain metastases as a site of first recurrence in patients receiving adjuvant chemotherapy during the period from 1973--1979 for node-positive operable carcinoma of the breast, compared to a matched control group of patients presenting during the same period treated by local measures only. Five of 115 patients (4.3%) receiving adjuvant chemotherapy have had brain metastases as first site of distant recurrence compared to zero of 115 (0%) in the control group. This comprised 12.8% of first distant recurrences in the adjuvant group. The authors suggest that this increased incidence of brain metastases, as site of first recurrence, reflects prolonged suppression of systemic disease by adjuvant chemotherapy with less effect in controlling metastases in the brain.

Identification, development, and regional distribution of thymidylate synthetase in adult rabbit brain

The development and regional distribution of thymidylate synthetase (TS) (EC 2.1.1.45) in rabbit brain were determined. After optimization of the assay for brain, TS activity in brain was measured by a nonspecific (3H2O release) and specific method. The specific method involved the conversion of [6-3H]deoxyuridine monophosphate (dUMP) to [3H]thymidine phosphate and the subsequent identification of [3H]thymidine.l The specific activity of the enzyme in whole brain of newborn rabbits declined from 10.35 +/- 1.17 units/mg protein to 0.71 +/- 0.09 units/mg protein at 10-12 weeks of age. Two=year-old rabbits had 0.81 +/- 0.04 units/mg protein. The decline in specific activity with age was not due to an inhibitor of TS activity or a change in the Km for dUMP. The Km for dUMP of the unpurified enzyme in the brains of both 19-day-old and young adult rabbits was 0.8 microM. In young adult rabbits (3 months) the specific activity of TS was similar in the various regions of the brain tested except for the cerebellum, which had 40% higher specific activity than the whole brain. The results show that TS is widely distributed in adult rabbit brain, and, although the activity declines with age, it stabilizes at adult levels at 3 months of age.

Alterations in the oral mucosa caused by chemotherapeutic agents. A histologic study

Histologic changes in the oral mucosa of 120 specimens from 30 patients who had received chemotherapy for a variety of extra-oral malignancies were studied in an attempt to relate the phenomena to pharmacological toxicity of the chemotherapeutic agents and other factors.

Potentiation of myelosuppression from cancer chemotherapy and thiazide diuretics

Fourteen patients with metastatic breast cancer and concomitant essential hypertension received treatment with combination chemotherapy (cyclophosphamide, methotrexate, and 5-fluorouracil) and thiazide diuretics. Significant augmentation of granulocytopenia during thiazide-chemotherapy combination, as compared with chemotherapy without thiazides, was observed in all patients. The most consistent changes in the neutrophil count were observed during the period of maximal myelosuppression from the antitumor drugs. An interaction between the thiazide diuretic and one or more of the cytotoxic agents is a possible explanation for the findings. The implications of this phenomenon are discussed.

Modulation of 5-fluorouracil toxicity by allopurinol in man

Oxipurinol, the major metabolite of allopurinol, decreased the toxicity of 5-fluorouracil (5-FU) to human granulocyte colony-forming units in vitro by a factor of four. The ability of allopurinol to reduce 5-FU toxicity in vivo was studied in 23 advanced cancer patients during 42 courses of treatment. 5-FU was administered by continuous intravenous infusion for five days; allopurinol, 300 mg, po, every 8 hours was started 2 hours before and continued during and for 24 hours after 5-FU infusion. 5-FU was escalated from 1.5 to 2.25 g/m2/day on separate courses; the dose-limiting toxicity was mucositis which occurred at a level of 2.0 g/m2/day. At a 5-FU dose rate of greater than 2.0 g/m2/day 5-FU pharmacokinetics were nonlinear, reflecting saturation of catabolic pathways, and the steady-state 5-FU serum concentration was approximately 4 times that which was tolerable without allopurinol. At these concentrations of 5-FU oxipurinol significantly influenced the clearance of 5-FU. Thus concurrent allopurinol therapy permitted a doubling of the maximum tolerated dose of 5-FU and a four-fold increase in the tolerated concentration x time exposure to 5-FU.