Cystic lung lesions as an immune reconstitution inflammatory syndrome (IRIS) in HIV-TB co-infection?
Explore the source record for details and available documents.
Adult↗
Biomedical subjects
L Rubinstein
Publications and source records attributed to L Rubinstein.
Sensitivity of renal cell carcinoma to aminoflavone: role of CYP1A1.
PURPOSE: The aminoflavone analogue (AF) exhibits antitumor activity in vitro, particularly against neoplastic cells of renal origin. We identified cellular correlates of responsiveness to AF in continuous human tumor renal cell carcinoma lines and in tumor cell isolates, termed renal carcinoma cell strains, from patients with clear cell and papillary renal neoplasms. MATERIALS AND METHODS: In vitro antiproliferative activity of AF was evaluated using the sulforhodamine B protein dye assay. In vivo antitumor activity of the drug was determined in mice bearing xenografts. Covalent binding of AF/metabolite(s) was assessed following exposure of cells to AF for 16 hours. CYP1A1 and CYP1B1 mRNA and apoptosis were quantitated by reverse transcriptase-polymerase chain reaction and enzyme-linked immunosorbent assay, respectively. RESULTS: AF produced total growth inhibition in vitro in 3 of 6 human tumor renal cell lines at concentrations of 90 to 400 nM. In vivo treatment of mice bearing xenografts of the Caki-1 renal cell carcinoma, sensitive to AF in vitro, resulted in significant antitumor activity, including tumor-free survivors. Studies in 13 renal cell strains isolated from patients with clear cell (9) or papillary (4) renal cell carcinoma indicated that 3 of 4 papillary strains were sensitive to AF compared with 2 of 9 clear cell strains. AF sensitive renal cell lines and strains exhibited induction of CYP1A1 and CYP1B1 gene expression, increased covalent binding of AF metabolite(s) and apoptosis. CONCLUSIONS: AF has noteworthy antitumor activity against certain human tumor renal cell lines in vitro and in vivo, which correlates with drug metabolism to covalently binding metabolites after CYP1A1 and CYP1B1 gene expression. We hypothesize that it leads to apoptosis induction. AF sensitive renal cell strains are predominantly of the papillary histological type. These results are limited by the small numbers of cell lines and cell strains but they are suggestive of the need for further testing in larger collections of cell strains.
Animals↗
New guidelines to evaluate the response to treatment in solid tumors. European Organization for Research and Treatment of Cancer, National Cancer Institute of the United States, National Cancer Institute of Canada.
Anticancer cytotoxic agents go through a process by which their antitumor activity-on the basis of the amount of tumor shrinkage they could generate-has been investigated. In the late 1970s, the International Union Against Cancer and the World Health Organization introduced specific criteria for the codification of tumor response evaluation. In 1994, several organizations involved in clinical research combined forces to tackle the review of these criteria on the basis of the experience and knowledge acquired since then. After several years of intensive discussions, a new set of guidelines is ready that will supersede the former criteria. In parallel to this initiative, one of the participating groups developed a model by which response rates could be derived from unidimensional measurement of tumor lesions instead of the usual bidimensional approach. This new concept has been largely validated by the Response Evaluation Criteria in Solid Tumors Group and integrated into the present guidelines. This special article also provides some philosophic background to clarify the various purposes of response evaluation. It proposes a model by which a combined assessment of all existing lesions, characterized by target lesions (to be measured) and nontarget lesions, is used to extrapolate an overall response to treatment. Methods of assessing tumor lesions are better codified, briefly within the guidelines and in more detail in Appendix I. All other aspects of response evaluation have been discussed, reviewed, and amended whenever appropriate.
Antineoplastic Agents↗
Treatment of experimental avascular necrosis of the femoral head with hyperbaric oxygen in rats: histological evaluation of the femoral heads during the early phase of the reparative process.
The healing of vascular deprivation-induced necrosis of the femoral head of rats exposed to hyperbaric oxygen was compared with that in untreated rats. The amount of necrotic bone, extent of osteoneogenesis, degree of remodeling, and changes of the articular cartilage were histologically graded on a semiquantitative scale of 0 to 3+. On the 2nd, 7th, and 21st postoperative days, there were no differences between the two groups. Newly formed appositional and intramembranous bone was more abundant and remodeling was more advanced in the femoral heads of the hyperbaric oxygen-treated than untreated rats sacrificed on the 42nd postoperative day; also there was less necrotic debris in the femoral heads of the treated rats. There were no differences in the severity of the degenerative changes of the articular cartilage of the treated and untreated rats. Exposure of rats to hyperbaric oxygen does not preserve tissue viability after all arteries supplying the femoral head are severed. Yet, resulting in an increased oxygen tension of the tissues, it seems to provide the optimal settings for reparative processes. The results suggest that hyperoxygenation-mediated relief of ischemia enhances the fibroblastic, angioblastic, osteoblastic, and osteoclastic activities such that healing of the rats' necrotic femoral heads is expedited.
Animals↗
Secondary leukemia or myelodysplastic syndrome after treatment with epipodophyllotoxins.
PURPOSE: The incidence of secondary leukemia after epipodophyllotoxin treatment and the relationship between epipodophyllotoxin cumulative dose and risk are not well characterized. The Cancer Therapy Evaluation Program (CTEP) of the National Cancer Institute (NCI) has developed a monitoring plan to obtain reliable estimates of the risk of secondary leukemia after epipodophyllotoxin treatment. METHODS: Twelve NCI-supported cooperative group clinical trials were identified that use epipodophyllotoxins at low (<1.5 g/m2 etoposide), moderate (1.5 to 2.99 g/m2 etoposide), or higher (> or =3.0 g/m2 etoposide) cumulative doses. Cases of secondary leukemia (including treatment-related myelodysplastic syndrome) occurring on these trials have been reported to CTEP, as has duration of follow-up for all patients, thereby allowing calculation of cumulative 6-year incidence rates of secondary leukemia for each etoposide dose group. RESULTS: The calculated cumulative 6-year risks for development of secondary leukemia for the low, moderate, and higher cumulative dose groups were 3.3%, (95% upper confidence bound of 5.9%), 0.7% (95% upper confidence bound of 1.6%), and 2.2%, (95% upper confidence bound of 4.6%), respectively. CONCLUSION: Within the context of the epipodophyllotoxin cumulative dose range and schedules of administration encompassed by the monitoring plan regimens, and within the context of multiagent chemotherapy regimens that include alkylating agents, doxorubicin, and other agents, factors other than epipodophyllotoxin cumulative dose seem to be of primary importance in determining the risk of secondary leukemia. Data obtained by the CTEP secondary leukemia monitoring plan support the relative safety of using epipodophyllotoxins according to the therapeutic plans outlined in the monitored protocols.
Adolescent↗
[Disturbance of osmotic equilibrium as a possible cause of invagination or protrusion of plasmalemma on the initial stage od phagocytosis].
Despite the importance of phagocytosis studying for purposes of physiology and medicine, a physical cause of the initial stage of phagosome generation still remains apparently unclear. The original mathematical theory (Rubinstein, 1998) allows to suggest that the disturbance of osmotic equilibrium, resulting from the interaction between lysosomal hydrolases and their specific substrates, may cause the initial stage of phagosome formation in all biochemically diverse cases of phagocytosis. The author developed this theory without a collaboration with biologists, except for several consultations. The purpose of this paper is to attract the biologists attention to the main ideas underlying this theory, and to learn to what degree these ideas may be reasonable from the viewpoints of biologists.
Animals↗
Accelerated titration designs for phase I clinical trials in oncology.
BACKGROUND: Many cancer patients in phase I clinical trials are treated at doses of chemotherapeutic agents that are below the biologically active level, thus reducing their chances for therapeutic benefit. Current phase I trials often take a long time to complete and provide little information about interpatient variability or cumulative toxicity. PURPOSE: Our objective was to develop alternative designs for phase I trials so that fewer patients are treated at subtherapeutic dose levels, trials are of reduced duration, and important information (i.e., cumulative toxicity and maximum tolerated dose) needed to plan phase II trials is obtained. METHODS: We fit a stochastic model to data from 20 phase I trials involving the study of nine different drugs. We then simulated new data from the model with the parameters estimated from the actual trials and evaluated the performance of alternative phase I designs on this simulated data. Four designs were evaluated. Design 1 was a conventional design (similar to the commonly used modified Fibonacci method) using cohorts of three to six patients, with 40% dose-step increments and no intrapatient dose escalation. Designs 2 through 4 included only one patient per cohort until one patient experienced dose-limiting toxic effects or two patients experienced grade 2 toxic effects (during their first course of treatment for designs 2 and 3 or during any course of treatment for design 4). Designs 3 and 4 used 100% dose steps during this initial accelerated phase. After the initial accelerated phase, designs 2 through 4 resorted to standard cohorts of three to six patients, with 40% dose-step increments. Designs 2 through 4 used intrapatient dose escalation if the worst toxicity is grade 0-1 in the previous course for that patient. RESULTS: Only three of the actual trials demonstrated cumulative toxic effects of the chemotherapeutic agents in patients. The average number of patients required for a phase I trial was reduced from 39.9 for design 1 to 24.4, 20.7, and 21.2 for designs 2, 3, and 4, respectively. The average number of patients who would be expected to have grade 0-1 toxicity as their worst toxicity over three cycles of treatment is 23.3 for design 1, but only 7.9, 3.9, and 4.8 for designs 2, 3, and 4, respectively. The average number of patients with grade 3 toxicity as their worst toxicity increases from 5.5 for design 1 to 6.2, 6.8, and 6.2 for designs 2, 3, and 4, respectively. The average number of patients with grade 4 toxicity as their worst toxicity increases from 1.9 for design 1 to 3.0, 4.3, and 3.2 for designs 2, 3, and 4, respectively. CONCLUSION: Accelerated titration (i.e., rapid intrapatient drug dose escalation) designs appear to effectively reduce the number of patients who are under-treated, speed the completion of phase I trials, and provide a substantial increase in the information obtained.
Antineoplastic Agents↗
Role of independent data-monitoring committees in randomized clinical trials sponsored by the National Cancer Institute.
PURPOSE: To describe the rationale for independent data monitoring committees (DMCs) for National Cancer Institute (NCI)-sponsored phase III cooperative group clinical trials. DESIGN: We review the necessity for interim monitoring of outcome data during the course of randomized clinical trials and summarize the reasons for establishing DMCs with requisite expertise and with appropriate independence from study investigators. RESULTS: The important components of the policy for cooperative group DMCs are described with a focus on the makeup of these bodies and on the complementary roles of study committee leadership and DMCs in protecting patient safety during the conduct of randomized clinical trials. CONCLUSION: The cooperative group DMCs that are independent of the study committees and that have the requisite expertise to examine accumulating data and to base decisions on monitoring guidelines that are specified in advance by the study committee provide a body able to protect patient safety, to protect the integrity of the clinical experiments on which patients have consented to participate, and to assure the public that conflicts of interest do not compromise either patient safety or trial integrity.
Humans↗
Therapy-related acute myeloid leukemia following treatment with epipodophyllotoxins: estimating the risks.
In the past decade, therapy-related acute myeloid leukemia (t-AML) following treatment with regimens that include inhibitors of topoisomerase-II (TOPO-II) has been reported with increasing frequency. These cases of t-AML generally have a shorter latency period than t-AML following alkylator therapy, are associated with chromosomal translocations (especially involving chromosome band 11q23), and usually present as M4 or M5 FAB subtype. Although the epipodophyllotoxins (etoposide and teniposide) have been most often implicated, similar cases of t-AML occur following therapy with other classes of Topo-II inhibitors (e.g., anthracyclines). There is wide variation in published studies in the estimates of risk of t-AML following epipodophyllotoxin therapy. These varying estimates may reflect a number of factors, including: small sample size leading to large confidence intervals around risk estimates; varying susceptibility of different patient populations; varying schedules of epipodophyllotoxin administration; different cumulative doses of epipodophyllotoxins; and administration of epopodophyllotoxins with additional agents that may alter the leukemogenic effect of the epipodophyllotoxins. Available data suggest that children with acute lymphocytic leukemia (ALL) treated with high cumulative doses of epipodophyllotoxins using either weekly or twice-weekly schedules of administration have a relatively high risk of developing t-AML (5-12% cumulative risk). On the other hand, germ cell patients treated with relatively low cumulative doses of etoposide (usually 1,500-2,500 mg/m2) appear to have a low risk for developing t-AML. There is inadequate experience at this time with higher cumulative doses of etoposide (e.g., 4,000-5,000 mg/m2 as used for pediatric solid tumors) given on a daily x 5 schedule to allow estimates of risk to be developed for this schedule and cumulative dose. The Cancer Therapy Evaluation Program (CTEP) of the National Cancer Institute (NCI) has developed a monitoring plan designed to obtain reliable estimates of the risk of t-AML following epipodophyllotoxin treatment. Twelve Cooperative Group clinical trials that use epipodophyllotoxins at either low (< 1,500 mg/m2), moderate (1,500-3,999 mg/m2), or higher cumulative doses (> 4,000 mg/m2) are being prospectively monitored for cases of t-AML occurring among patients entered onto the trials.
Alkylating Agents↗
Adjuvant chemotherapy with cyclophosphamide, doxorubicin, and cisplatin in patients with completely resected stage I non-small cell lung cancer. An LCSG Trial.
OBJECTIVE: Two recent studies in resectable non-small cell lung cancer by the Lung Cancer Study Group (LCSG) suggested an advantage to adjuvant therapy with cyclophosphamide, doxorubicin (Adriamycin), and cisplatin (CAP). Neither study had a no-treatment control arm. The purpose of this study was to compare the CAP regimen with no treatment in patients with resectable early-stage non-small cell lung cancer. METHODS: After complete resection, eligible patients with T1N1 or T2N0 non-small cell lung cancer were randomly assigned to receive or not to receive four courses of CAP at 3-week intervals beginning on day 30 after surgery after stratification for histology, preoperative white blood cell count, and Karnofsky performance status before surgery. The CAP regimen consisted of 400 mg/m2 of cyclophosphamide, 40 mg/m2 of doxorubicin, and 60 mg/m2 of cisplatin. Of the 269 eligible patients entered in the study, 101 had recurrence and 127 had died at the time of analysis. The mean time since randomization is 6.4 years; mean follow-up is 3.8 years. There were no differences in time to recurrence or overall survival between the two groups even when analyses were adjusted for prognostic variables. Only 53% of the eligible patients received all four courses of CAP, and only 57% of such patients received all four cycles on time. Among the patients who had recurrences, 74% had their initial recurrence at a distant site. CONCLUSION: No survival benefit for CAP vs no-treatment control was found in this study. Therefore, adjuvant therapy with CAP should not be recommended for patients with resected early-stage non-small cell lung cancer. Further trials to test adjuvant therapy are indicated, but investigators should use better antiemetics to improve patient compliance as well as more active cisplatin-based chemotherapy regimens.
Antineoplastic Combined Chemotherapy Protocols↗
The comparison of limited resection to lobectomy for T1N0 non-small cell lung cancer. LCSG 821.
The Lung Cancer Study Group, in order to investigate lesser resection within the community as definitive management for T1N0 lung cancers, in 1982 began a prospective trial of limited resection compared to lobectomy for these patients. First reported results demonstrated no significant differences for stratification and other prognostic variables, and no differences in postoperative complication rates. Interim analysis 3 years later suggested a higher local recurrence rate in the limited resection arm of the study. Further comprehensive analysis will be forthcoming.
Carcinoma, Non-Small-Cell Lung↗
Report of the Cancer Therapy Evaluation Program monitoring plan for secondary acute myeloid leukemia following treatment with epipodophyllotoxins.
BACKGROUND: Recent reports have documented the occurrence of treatment-related acute myeloid leukemia (AML) following therapy with epipodophyllotoxins. These reports have led to growing concern among oncologists, which could lead to premature abandonment of these agents at a time when the relationship between cumulative dose of epipodophyllotoxin and risk of treatment-related AML has not been determined. PURPOSE: Because of the increasingly important role of epipodophyllotoxins in the treatment of several types of adult and pediatric tumors, the Cancer Therapy Evaluation Program (CTEP) of the National Cancer Institute (NCI) has developed a monitoring plan to obtain reliable estimates of the risk of treatment-related AML following epipodophyllotoxin treatment. METHODS: We identified 12 NCI-supported Cooperative Group clinical trials in which patients with solid tumors are being treated with epipodophyllotoxins at different cumulative doses. One trial is using a moderate dose of teniposide (900 mg/m2), and 11 trials are using etoposide at a low dose (< 1500 mg/m2), a moderate dose (1500-3999 mg/m2), or a high dose (> or = 4000 mg/m2). Cases of treatment-related AML and treatment-related myelodysplastic syndrome (MDS) (hereafter referred to as treatment-related AML/MDS) occurring in these trials are reported to CTEP, with initial analysis for each cumulative dose group triggered by the reporting of four cases of treatment-related AML/MDS in that group. For each analysis, total patient follow-up for the group is determined and cumulative 6-year incidence rate is calculated. RESULTS: Three cases of treatment-related AML and one case of treatment-related MDS (with documented monosomy 7) were reported in a group of 207 patients who received etoposide at a low cumulative dose. The calculated 6-year rate of development of treatment-related AML/MDS was 3.2% (95% upper confidence interval bounded by 7.2%). CONCLUSIONS: The 6-year cumulative rate of treatment-related AML/MDS (3.2%) is within the range previously reported for alkylator-based regimens that did not include epipodophyllotoxins. IMPLICATIONS: Previous reports have suggested that higher cumulative doses of alkylators are associated with increased risk of treatment-related AML, and a critical goal of the monitoring plan is to determine whether a similar relationship exists for the epipodophyllotoxins. Estimates will be developed for leukemogenic risk for the moderate- and high-cumulative-dose groups when four cases of treatment-related AML/MDS have been identified within each group.
Acute Disease↗
Adjuvant chemotherapy with cyclophosphamide, doxorubicin, and cisplatin in patients with completely resected stage I non-small-cell lung cancer. The Lung Cancer Study Group.
BACKGROUND: Most studies of adjuvant chemotherapy, radiotherapy, or immunotherapy in non-small-cell lung cancer patients with complete surgical resection of disease have shown negative results. However, two studies of stage II and III disease by our Lung Cancer Study Group suggested an advantage to adjuvant therapy with cyclophosphamide, doxorubicin, and cisplatin (CAP). PURPOSE: Since neither of those studies had an untreated control, the Lung Cancer Study Group undertook a trial that included a control group and also offered the potential benefit of adjuvant therapy with CAP to patients with T1, N1 or T2, N0 (stage I) non-small-cell lung cancer. METHODS: After complete resection, eligible patients with stage I disease were classified by known prognostic factors and randomly assigned to receive or not to receive four courses of CAP at 3-week intervals beginning on day 30 after surgery. The CAP regimen consisted of 400 mg/m2 cyclophosphamide, 40 mg/m2 doxorubicin, and 60 mg/m2 cisplatin. Stratification by prognostic factors was as follows: histology (squamous versus nonsquamous), white blood cell count before surgery (> or = 9100/mm3 versus < 9100/mm3), and Karnofsky performance status before surgery (< or = 90% versus 100%). RESULTS: Of the 269 patients entered in the study, 101 had recurrence and 127 have died. Mean time since randomization is 6.4 years; mean follow-up is 3.8 years. There were no differences in time to recurrence or overall survival (not stratified by histology) between the two groups, even when analyses were adjusted for prognostic variables. There was one treatment-related death on the CAP arm due to infection during neutropenia. Only 53% of the eligible patients received all four courses of CAP, and only 57% of such patients received all four cycles on time. In 74% of the patients, the site of initial recurrence was distant. CONCLUSIONS: The most likely explanations for the lack of efficacy of CAP are poor compliance to the protocol and relative inactivity of the regimen, compared with the activity of drug combinations used in more recent studies. On the basis of this trial, adjuvant therapy with CAP should not be recommended for patients with resected stage I lung cancer. IMPLICATIONS: Further trials to test adjuvant therapy are indicated, but investigators should use better antiemetics to improve patient compliance as well as more active chemotherapy regimens.
Aged↗
Randomized phase II trial of high-dose interleukin-2 either alone or in combination with interferon alfa-2b in advanced renal cell carcinoma.
PURPOSE: To determine better the activity of high-dose interleukin-2 (IL-2) either alone or in combination with interferon alfa-2b (IFN; Schering-Plough, Kenilworth, NJ) in patients with metastatic renal cell carcinoma, the IL-2 Working Group initiated a randomized phase II trial. PATIENTS AND METHODS: Patients were randomly assigned to receive treatment with either IL-2 (Chiron Corp, Emeryville, CA) 1.33 mg/m2 (approximately 600,000 IU/kg) alone or IL-2 0.8 mg/m2 and IFN 3 x 10(6) U/m2 administered by bolus intravenous injection every 8 hours, days 1 to 5 and 15 to 19 (maximum, 28 doses). All patients had an Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1 and normal organ function. After 28 patients were entered onto each arm, the IL-2/IFN arm was closed because of a failure to meet predetermined efficacy criteria. An additional 43 patients (total, 71) were assigned to receive IL-2 alone. RESULTS: Toxicities were similar for both study arms. Hypotension requiring pressors was the most frequent dose-limiting toxicity. Only 11 of 99 patients experienced severe toxicity; there were no irreversible side effects or treatment-related deaths. Responses were seen in three of 28 patients (11%) on IL-2/IFN (three partial responses [PRs] lasting 14, 7, and 7 months) and 12 of 71 patients (17%) on IL-2 alone (four complete responses [CRs] and eight PRs). Six of the partial responders on IL-2 and two on IL-2/IFN experienced greater than 90% reduction in tumor mass. Ten of the 12 responders to IL-2 have ongoing responses of 12+ to 26+ months in duration. CONCLUSION: We conclude that both IL-2 and IL-2/IFN therapy have activity in metastatic renal cell carcinoma. In particular, therapy with high-dose IL-2 alone produces meaningful and durable responses with manageable and reversible toxicity. This study supports the contention that high-dose IL-2 represents the treatment of choice in selected patients with advanced renal cell carcinoma.
Adult↗
Malignant disease appearing late after operation for T1 N0 non-small-cell lung cancer. The Lung Cancer Study Group.
Occurrences of malignancy in 308 patients who were clinically free of cancer 60 months or more after surgical treatment of T1 N0 non-small-cell lung cancer are summarized. At last report, 210 patients remained alive with no evidence of malignant disease, 43 patients died of nonmalignant causes, and 55 patients had 59 occurrences of malignant disease. Late lung cancer recurrence was observed in 22 patients (concurrent with nasopharyngeal cancer in one patient and with laryngeal cancer in one patient). Metachronous second lung cancer was noted in 20 patients (including concurrent colon cancer in one patient and metastatic recurrence in one patient). Other nonpulmonary malignant tumors appeared in 13 patients. Including second lung cancer, 25 cancers of aerodigestive epithelium were observed in 23 patients. The malignancy-free survival advantage for patients with squamous cancer observed until 60 months after resection was not sustained at 60 months and beyond. At the time of last follow-up, 84 patients (27%) had died; 43 were free of malignancy, and 41 had malignancy (14 patients were alive with malignancy and 210 with no evidence of disease). These data reinforce two conclusions: (1) The probability of lung cancer recurrence or appearance of new lung cancer 5 years or more after successful operation in this select subpopulation of patients with lung cancer is of concern. (2) The malignancy-free survival advantage of patients with squamous cancer disappears after 5 years.
Adult↗
Stage II carcinoma of the ovary: an analysis of survival after comprehensive surgical staging and adjuvant therapy.
Ninety-three women with FIGO stage II epithelial ovarian carcinoma underwent comprehensive surgical staging and were randomized prospectively to therapy consisting of either intraperitoneal radioactive phosphorus or oral melphalan. No patient had gross residual disease at the time of randomization. Ten of the forty-five women treated with melphalan experienced severe bone marrow depression at some time during therapy and two women expired from leukemia. Four of the forty-eight women treated with intraperitoneal phosphorus required surgical reexploration for intestinal obstruction or bowel injury. Twenty-one women died of their disease. Survival was not statistically different between the two treatment arms. The 5-year actuarial survival was 78%.
Adolescent↗
Exploratory data analytic techniques to evaluate anticancer agents screened in a cell culture panel.
Information theory is used to provide a measure of selectivity, i.e., the degree to which a drug has preferential toxicity or growth inhibition for one or a few cell lines from a large panel. The selectivity measure is intended to complement a measure of differential growth inhibition in evaluating the drug development potential of a new compound. Also, a similarity measure obtained from information theory is used to classify drugs according to their pattern of responses on the panel. Some structure-activity relations emerge. This work is applied to 176 agents selected to be tested by the National Cancer Institute in about 50 cell lines.
Animals↗
Modulation of cytosine arabinoside toxicity by 3-deazauridine in a murine leukemia model.
3-Deazauridine (DAUrd), a competitive inhibitor of CTP synthetase, inhibits both RNA and DNA synthesis. Murine leukemia cells resistant to cytosine arabinoside (ara-C) due to a deletion of deoxycytidine kinase are collaterally sensitive to DAUrd, which inhibits the de novo production of CTP and hence results in dCTP depletion. We evaluated DAUrd in combination with the palmitate derivative of ara-C (palmO-ara-C) in mice bearing L1210 leukemia cells with a subpopulation resistant to ara-C. Both simultaneous administration and a sequential schedule of palmO-ara-C at its maximally tolerated dose (MTD), followed by DAUrd treatment, failed to produce a therapeutic gain. We also studied whether non-toxic doses of DAUrd (15-250 mg/kg i.p. at h 0 and 6 on days 4 and 8) could modulate the antileukemic activity of palmO-ara-C (7.5-120 mg/kg i.p. at h 3 on days 4 and 8). The addition of DAUrd produced a modest (but statistically significant) prolongation of life span and a further 2-log10 reduction in tumor burden compared to the same dose of palmO-ara-C alone, and resulted in long-term survivors in five of 30 treated animals. Two-dimensional dose-response analysis of the survival data indicated a positive drug interaction (p less than or equal to 0.01) when the dosage of DAUrd was modeled to reflect an apparent threshold effect. Cyclopentenyl cytosine (CPE-C; 0.625-2.5 mg/kg i.p. at h 0 and 6 on days 4 and 8), a more potent inhibitor of CTP synthetase, was also given with palmO-ara-C. This combination resulted in an additional 2-6 log10 units of cell kill and occasional long-term survivors at palmO-ara-C dosages that alone resulted in no more than 2 log10 units of cell kill and no long-term survivors. However, DAUrd and CPE-C given with palmO-ara-C increased host toxicity, compromising the tolerable dose of palmO-ara-C. Single-agent palmO-ara-C given at its MTD produced a similar reduction in tumor burden and increase in life span compared to the highest palmO-ara-C dose that could be given in combination with either modulator.
3-Deazauridine↗