Cellular pharmacology of 1-β-d-arabinofuranosylcytosine in human myeloid,B-lymphoid and T-lymphoid leukemic cells

Summary The in vitro inhibitory action and metabolism of 1--d-arabinofuranosylcytosine (ara-C) on human myeloid (HL-60), B-lymphoid (RPMI-8392), and T-lymphoid (Molt-3) leukemic cells was compared. Ara-C produced greater inhibitory effects in Molt-3 cells than in either HL-60 or RPMI-8392 cells. At a 48 h exposure, ara-C was 7 and 10 times more cytotoxic to Molt-3 cells than to HL-60 and RPMI-8392 cells, respectively. The total ara-C uptake to nucleotides and the formation of 1--d-arabinofuranosylcytosine 5-triphosphate (ara-CTP) was about 5 times greater in Molt-3 cells than in either HL-60 or RPMI-8392 cells. The incorporation of ara-C into DNA was also higher in Molt-3 cells than in either HL-60 or RPMI-8392 cells. The mean intracellular half-life of ara-CTP was 31.7, 59.4, and 155 min for RPMI-8392, HL-60, and Molt-3 leukemic cells, respectively. The Km and V_max values of ara-C for deoxycytidine kinase and the feedback inhibition of this enzyme by ara-CTP in the different leukemic cell lines could not explain the differences in metabolism of this analogue in these cells. These data indicate that the increased sensitivity of T-lymphoid leukemic cells to ara-C than as compared with B-lymphoid and myeloid leukemic cells was due to an ireased rate of formation and a longer half-life of ara-CTP in the T-cells.Supported by a grant from the Cancer Research Society. N.O.-P. is a Fellow of the Leukemia Society of America. To whom requests for reprints should be addressed, at Centre de recherche pédiatrique, Hôpital Ste-Justine, 3175 Ch. Côte Ste-Catherine, Montreal, Quebec H3T 1C5, Canada     

Pharmacokinetics and pharmacogenomics of daunorubicin in children: a report from the Children’s Oncology Group

Purpose

We explored the impact of obesity, body composition, and genetic polymorphisms on the pharmacokinetics (PK) of daunorubicin in children with cancer.

Patients and methods

Patients ≤21 years receiving daunorubicin as an infusion of any duration <24 h for any type of cancer were eligible. Plasma drug concentrations were measured by high-performance liquid chromatography. Body composition was measured by dual-energy X-ray absorptiometry. Obesity was defined as a BMI >95 % for age or as body fat >30 %. NONMEM was used to perform PK model fitting. The Affymetrix DMET chip was used for genotyping. The impact of genetic polymorphisms was investigated using SNP/haplotype association analysis with estimated individual PK parameters.

Results

A total of 107 subjects were enrolled, 98 patients had PK sampling, and 50 patients underwent DNA analysis. Population estimates for daunorubicin clearance and volume of distribution were 116 L/m²/h ± 14 % and 68.1 L/m² ± 24 %, respectively. Apparent daunorubicinol clearance and volume of distribution were 26.8 L/m²/h ± 5.6 % and 232 L/m² ± 10 %, respectively. No effect of body composition or obesity was observed on PK. Forty-four genes with variant haplotypes were tested for association with PK. FMO3-H1/H3 genotype was associated with lower daunorubicin clearance than FMO3-H1/H1, p = 0.00829. GSTP1*B/*B genotype was also associated with lower daunorubicin clearance compared to GSTP1*A/*A, p = 0.0347. However, neither of these associations was significant after adjusting for multiple testing by either Bonferroni or false discovery rate correction.

Conclusions

We did not detect an effect of body composition or obesity on daunorubicin PK. We found suggestive associations between FMO3 and GSTP1 haplotypes with daunorubicin PK that could potentially affect efficacy and toxicity.     

Phase I clinical and pharmacokinetic study of orally administeredN 4-palmitoyl-1-β-d-arabinofuranosylcytosine

A phase I study ofN ⁴-palmitoyl-1-β-d-arabinofuranosylcytosine (PLAC) was conducted in 88 patients; 36 with solid tumors and 52 with hematological malignancies, using 2 different schedules. Schedule 1 employed a single oral administration and Schedule 2, 5-day consecutive daily oral administration. In Schedule 1, the daily dose was initiated with 1 mg kg^?1 which was escalated up to 24 mg kg^?1 according to the modified Fibonacci’s method. Side effects included nausea, vomiting and skin rashes, but myelosuppression was not seen within this dose range. In Schedule 2, the daily dose was started with 1 mg kg^?1 which was escalated up to 24 mg kg^?1. Major side effects were nausea, vomiting and amorexia, and mild myelosuppression was noted at 12 mg kg^?1 or more. The dose-limiting toxicity was gastrointestinal toxicity, which appeared at 3.3 mg kg^?1 or more and became frequent at 7 mg kg^?1 or more. Pharmacokinetic study revealed that the plasma concentrations of PLAC and ara-C, obtained by the oral intake of 3.3 mg kg^?1 or more of PLAC, were sufficient for these compounds to exert cytotoxic effects on various human leukemia cellsin vitro. Based on these observations and plausible mechanism of action of PLAC, further clinical study should be carried out in a treatment schedule of considerably prolonged administration period with 3.3–6 mg kg^?1 day^?1 of PLAC.     

Phase I clinical and pharmacokinetic study ofN 4-behenoyl-1-β-d-arabinofuranosylcytosine

A phase I study ofN ⁴-behenoyl-1-β-d-arabinofuranosylcytosine (BHAC) was conducted in 66 patients, 41 with solid tumors and 25 with hematological malignancies. The patients received either a 2-h single intravenous (i.v.) drip infusion (Schedule 1) or consecutive daily 2-h i.v. infusions (Schedule 2). In Schedule 1 the daily dose was initiated with 1.5 mg kg^?1 which was escalated up to 7 mg kg^?1. Side-effects were mild, and included nausea, vomiting, epilation, and hot flushes. Because of the presence of the solvent vehicle, HCO-60 and in consideration of the mechanism of action of BHAC, the dose escalation was stopped at 7 mg kg^?1. In Schedule 2, the daily dose was started with 1.5 mg kg^?1 which was escalated up to 8 mg kg^?1 and given for 2–16 days. Myelosuppression was found to be dose-limiting toxicity. The maximum tolerated dose (MTD) in patients with non-hematological solid tumors was assumed to be 5 mg kg^?1 daily × 5 days. The plasma disappearance curve of BHAC looked biphasic, and when 4 mg kg^?1 of BHAC were administered the half-lives of the initial phase (t _1/2α) and the second phase (t _1/2β) were calculated as 0.798 and 5.76 h respectively. In Schedule 2 complete remission was observed in 5 out of 21 patients with acute leukemia, one partial remission in Hodgkin’s disease, and one 1-B response (Karnofsky) in thyroid papillary adenocarcinoma.     

Inability of liposome encapsulated 1-β-d-arabinofuranosylcytosine nucleotides to overcome drug resistance in L1210 cells

The uptake, metabolism and antitumor activity of 1-β-d-arabinofuranosylcytosine nucleotides encapsulated in liposomes were investigated in L1210 cells sensitive and resistant to the drug. These studies were carried out in order to determine whether encapsulation of the presumed active component of the drug, namely, arabinofuranosylcytosine 5′ triphosphate will convert resistant cells to sensitive. The results indicate that liposome entrapment of Ara-CMP and Ara-CTP did not result in increased delivery of these metabolites into L1210 cells. The amount of nucleotide found intracellularly following an in vitro incubation of encapsulated drugs with L1210 cells did not exceed the level expected from a simple extracellular breakdown of liposome releasing their contents with subsequent uptake and phosphorylation of the released nucleoside. Further evidence for lack of enhancement of drug uptake by liposome encapsulation were obtained when the rate of incorporation of TdR into DNA of L1210/Ara-C was not significantly affected by Ara-CTP encapsulation in liposome. The data presented herein also demonstrated that the in vivo sensitivity of L1210 cells resistant to Ara-C could not be modified by encapsulation of Ara-CTP in liposomes. The results strongly suggest that encapsulation of drugs unmodified or untargeted liposomes will not be able to overcome drug resistance related to transport defect and/or deletion of intracellular activating enzyme(s).     

A family-based study of gene variants and maternal folate and choline in neuroblastoma: a report from the Children’s Oncology Group

Purpose

Neuroblastoma is a childhood cancer of the sympathetic nervous system with embryonic origins. Previous epidemiologic studies suggest maternal vitamin supplementation during pregnancy reduces the risk of neuroblastoma. We hypothesized offspring and maternal genetic variants in folate-related and choline-related genes are associated with neuroblastoma and modify the effects of maternal intake of folate, choline, and folic acid.

Methods

The Neuroblastoma Epidemiology in North America (NENA) study recruited 563 affected children and their parents through the Children’s Oncology Group’s Childhood Cancer Research Network. We used questionnaires to ascertain pre-pregnancy supplementation and estimate usual maternal dietary intake of folate, choline, and folic acid. We genotyped 955 genetic variants related to folate or choline using DNA extracted from saliva samples and used a log-linear model to estimate both child and maternal risk ratios and stratum-specific risk ratios for gene–environment interactions.

Results

Overall, no maternal or offspring genotypic results met criteria for a false discovery rate (FDR) Q-value <0.2. Associations were also null for gene–environment interaction with pre-pregnancy vitamin supplementation, dietary folic acid, and folate. FDR-significant gene–choline interactions were found for offspring SNPs rs10489810 and rs9966612 located in MTHFD1L and TYMS, respectively, with maternal choline dietary intake dichotomized at the first quartile.

Conclusion

These results suggest that variants related to one-carbon metabolism are not strongly associated with neuroblastoma. Choline-related variants may play a role; however, the functional consequences of the interacting variants are unknown and require independent replication.

     

A case–control study of childhood brain tumors and fathers’ hobbies: a Children’s Oncology Group study

Objective  A comprehensive case–control study was conducted to evaluate parental risk factors for medulloblastoma (MB) and primitive neuroectodermal tumor (PNET). This analysis was conducted to evaluate associations between fathers’ hobbies and risk of their children developing MB/PNET. The hobbies chosen for study were those with similar exposures as occupations associated with childhood cancers. Methods  Cases were 318 subjects under six years of age at diagnosis between 1991 and 1997 and registered with the Children’s Cancer Group. An equal number of controls were selected through random digit dialing and individually matched to cases. Results  In multivariate analyses, a significant association was seen for lawn care with pesticides [during pregnancy: odds ratio (OR) = 1.6, 95% confidence interval (CI): 1.0, 2.5; after birth: OR = 1.8, 95% CI: 1.2, 2.8] and a weak association was seen for stripping paint [during pregnancy: OR = 1.4, 95% CI: 0.8, 2.6; after birth: OR = 1.4, 95% CI: 0.7, 2.6]. Conclusions  This study suggests that household exposures from hobbies, particularly pesticides, may increase risk of MB/PNET in children; previous research has been mostly limited to occupational exposures.     

Tolerability and pharmacokinetic profile of a sunitinib powder formulation in pediatric patients with refractory solid tumors: a Children’s Oncology Group study

Purpose  

Sunitinib is an oral tyrosine kinase inhibitor of VEGF, PDGF, c-KIT, and flt-3 receptors. A pediatric phase I study of sunitinib capsules identified the maximum tolerated dose as 15 mg/m²/day. This study was conducted to evaluate sunitinib given as a powder formulation.     

Head injury,diagnostic X-rays,and risk of medulloblastoma and primitive neuroectodermal tumor: a Children’s Oncology Group study

Objective  

A comprehensive case–control study was conducted to determine potential risk factors for medulloblastoma/primitive neuroectodermal tumor (PNET), a common brain tumor in children. This analysis evaluated possible associations between previous head injury and ionizing radiation exposure through diagnostic X-rays and medulloblastoma/PNET.     

Clinical pharmacology of N4-palmitoyl-1-β-d-arabinofuranosylcytosine in patients with hematologic malignancies

Summary The pharmacokinetics of oral N⁴-palmitoyl-1--d-arabinofuranosylcytosine (PLAC), a lipophilic and deaminase-resistant derivative of 1--d-arabinofuranosylcytosine (ara-C), were determined in patients with hematologic malignancies. The concentration of ara-C and 1--d-arabinofuranosyluracil (ara-U), metabolites of PLAC, were measured by radioimmunoassay and gas chromatography-mass spectrometry-mass fragmentography, respectively. The concentration of PLAC was determined by measuring ara-C, which was derived from PLAC by hydrolyzation. In six patients given an oral bolus of PLAC (300 mg/m²), the plasma-disappearance curve of PLAC corresponded to a one-compartment open model, including first-order absorption. The peak plasma level was 22.9±6.4 ng/ml, and the predicted time to reach the peak level was 2.5±1.0 h. The elimination half-life was 3.8±2.7 h. The plasma ara-C level increased slowly to 6.9 ng/ml during the 1st 2–3 h after administration and remained over 1.0 ng/ml for 12 h. Plasma ara-U was detectable for at least 24 h, with a peak concentration of 376 ng/ml at 6 h. Urinary PLAC excretion was below the limit of detection (5 ng/ml) in all cases. Prolonged urinary ara-C and ara-U excretion was detected, but the total recovery rate was low (6.7% in 24 h) and varied between patients. In spite of the lipophilic nature of the drug, the PLAC concentration in the cerebrospinal fluid, measured at 3 or 6 h, was below the limit of detection in all four patients with no meningeal involvement. This study showed low but persistent levels of PLAC in plasma and tissues, with a continuous release of small amounts of ara-C, which demonstrated antitumor activity in patients with hematologic malignancies.This study was supported in part by Grants-in-Aid from the Ministry of Health and Welfare (62-18 and 63-3), Japan     

Pyrimidine pathways enzymes in human tumors of brain and associated tissues: Potentialities for the therapeutic use of N-(Phosphonacetyl-l-aspartate and 1-β-d-arabinofuranosylcytosine

The activities of aspartate transcarbamylase (de novo pyrimidine biosynthesis pathway) and of deoxycytidine kinase as well as deoxycytidine deaminase (salvage pyrimidine biosynthesis pathway) were determined in extracts prepared from 40 brain tumors of different types in comparison with extracts from normal nervous tissues. Aspartate transcarbamylase, which is undetectable in normal brain tissue, is present in all tumor samples and in some cases rises to very high activities. Deoxycytidine kinase activity is present in all tissues but its level is generally higher in tumors. Deoxycytidine deaminase is present in all the tissues which were analyzed, although its activity is lower in some of the tumor samples. 1-β-d-Arabinofuranosylcytosine is a substrate for both deoxycytidine kinase and deaminase in all the samples used except one. These results suggest some potential for the utilization of 1-β-d-arabinofuranosylcytosine and N-(phosphonacetyl)-l-aspartate in the treatment of brain tumors.     

Efficacy of bevacizumab plus irinotecan in children with recurrent low-grade gliomas—a Pediatric Brain Tumor Consortium study

Background

A phase II study of bevacizumab (BVZ) plus irinotecan (CPT-11) was conducted in children with recurrent low-grade glioma to measure sustained response and/or stable disease lasting ≥6 months and progression-free survival.

Methods

Thirty-five evaluable patients received 2 doses (10 mg/kg each) of single-agent BVZ intravenously 2 weeks apart and then BVZ + CPT-11 every 2 weeks until progressive disease, unacceptable toxicity, or a maximum of 2 years of therapy. Correlative studies included neuroimaging and expression of tumor angiogenic markers (vascular endothelial growth factor [VEGF], VEGF receptor 2, hypoxia-inducible factor 2α, and carbonic anhydrase 9).

Results

Thirty-five evaluable patients (median age 8.4 y [range, 0.6–17.6]) received a median of 12 courses of BVZ + CPT-11 (range, 2–26). Twenty-nine of 35 patients (83%) received treatment for at least 6 months. Eight patients progressed on treatment at a median time of 5.4 months (range, 1–17.8). Six patients (17.7%) still in follow-up have had stable disease without receiving additional treatment for a median of 40.1 months (range, 30.6–49.3) from initiating therapy. The 6-month and 2-year progression-free survivals were 85.4% (SE ± 5.96%) and 47.8% (SE ± 9.27%), respectively. The commonest toxicities related to BVZ included grades 1–2 hypertension in 24, grades 1–2 fatigue in 23, grades 1–2 epistaxis in 18, and grades 1–4 proteinuria in 15. The median volume of enhancement decreased significantly between baseline and day 15 (P < .0001) and over the duration of treatment (P < .037).

Conclusion

The combination of BVZ + CPT-11 appears to produce sustained disease control in some children with recurrent low-grade gliomas.     

Phase II study of cisplatin and 5‐fluorouracil in previously treated metastatic breast cancer: an Eastern Cooperative Oncology Group study (PA 185)

Purpose: The present study was conducted to investigate the efficacy and toxicity of a cisplatin and 5fluorouracil (5FU) combination in previously treated advanced breast cancer.Methods: Thirtysix women with recurrent metastatic breast cancer were entered on a phase II study of 5FU 1000mg/m²/day given intravenously as a continuous infusion on days 1–3 and cisplatin 30mg/m²/day given intravenously over 1h on days 2–4, repeated every 21 days. All subjects had received one previous chemotherapy regimen for metastatic disease and either progressed during treatment or relapsed after responding to previous chemotherapy. Fourteen patients had also received previous adjuvant chemotherapy, 17 patients had previous radiation therapy, and 29 patients had previous hormonal therapy.Results: Among 32 responseevaluable patients, there were 10 partial remissions (31%) and 1 complete remission (3%), with an overall objective response rate of 34%. Median duration of response was 4 months. Median survival was 10.5 months for responders and 9.5 months for the entire group. Toxicity was mild to moderate in most patients. Overall twelve patients experienced grade 3 toxicity (10 hematologic, 1 mucositis, and 2 nausea). There were no grade 4 or 5 toxicities.Conclusion: Infusional cisplatin and 5FU is a well tolerated and active regimen in women with previously treated advanced breast cancer.     

Treatment of poor-prognosis extensive disease small-cell lung cancer with an all-oral regimen of etoposide and cyclophosphamide – a Southwest Oncology Group clinical and pharmacokinetic study

Purpose: An all-oral regimen of etoposide and cyclophosphamide was developed for use in poor-prognosis extensive disease small-cell lung cancer. Limited pharmacokinetic sampling was used to derive a pharmacodynamic model predictive of myelosuppression early in the course of therapy. Patients and methods: Eligible patients were chemotherapy-naive and had extensive disease small-cell lung cancer with either SWOG performance status 2 or serum albumin <3.5 g/dl. The first cohort (n = 18) received etoposide orally at 50 mg daily and cyclophosphamide orally at 50 mg daily days 1–14 every 28 days. Due to good hematologic tolerance, the second cohort (n = 39) received both agents orally at 50 mg twice daily days 1–14 every 28 days. Plasma etoposide levels were determined in samples drawn at baseline, and at 1 h, 2 h, and 23.5 h (trough) after the first dose. Linear regression analysis was used to determine pharmacokinetic and demographic parameters predictive of myelosuppression. Results: A total of 173 treatment cycles were delivered. Patients on the daily regimen had a 22% response rate (complete and partial), a 22% unconfirmed response rate, and a 5-month median survival, while patients on the twice-daily regimen had a 28% response rate (complete and partial), a 13% unconfirmed response rate, and a 7-month median survival. Granulocytopenia and alopecia were the most common toxicities seen. Significant granulocytopenia could be predicted for the twice-daily regimen according to the formula ln(AGC nadir)=7.80 − 1.88(trough), with an increased incidence of granulocytopenia if the etoposide trough value was ≥1.49 μg/ml. Conclusion: Oral etoposide and oral cyclophosphamide given days 1–14 every 28 days is well tolerated and results in an acceptable response rate and median survival in poor-prognosis (poor performance status or low serum albumin) extensive disease small-cell lung cancer. A trough etoposide level obtained within 24 h of starting therapy can predict severe granulocytopenia. Received: 27 October 1998 / Accepted: 3 May 1999     

Phase II trial of intravenous lobradimil and carboplatin in childhood brain tumors: a report from the Children’s Oncology Group

Backround: Lobradimil is a synthetic bradykinin analog that rapidly and transiently increases the permeability of the blood-brain barrier (BBB). The combination of lobradimil and carboplatin was studied in pediatric patients with primary brain tumors in a phase II trial, the primary endpoints of which were to estimate the response rate and time to disease progression. Patients and methods: Patients were stratified by histology into five cohorts: brainstem glioma, high-grade glioma, low-grade glioma, medullobastoma/primitive neuroectodermal tumor (PNET), and ependymoma. Patients received carboplatin adaptively dosed to achieve a target AUC of 3.5 mg min/ml per day (7 mg·min/ml/cycle) intravenously over 15 min on 2 consecutive days and lobradimil 600 ng/kg ideal body weight/day on 2 consecutive days each 28 day cycle. Results: Forty-one patients, age 2–19 years, were enrolled; 38 patients, including 1 patient ultimately determined to have atypical neurocytoma, were evaluable for response. No objective responses were observed in the brainstem glioma (n=12) and high-grade glioma (n=9) cohorts, although two patients with high-grade glioma had prolonged disease stabilization (>6 months). The study was closed for commercial reasons prior to achieving the accrual goals for the ependymoma (n=8), medulloblastoma/PNET (n=6) and low-grade glioma (n=2) cohorts, although responses were observed in 1 patient with PNET and 2 patients with ependymoma. Conclusion: The combination of lobradimil and carboplatin was inactive in childhood high-grade gliomas and brainstem gliomas.     

Mechanistic implications of alterations in HL-60 cell nascent DNA after exposure to 1-β-d-arabinofuranosylcytosine

Summary To improve our understanding of the mechanism of 1--d-arabinofuranosylcytosine (ara-C) incorporation into DNA, we investigated the physical properties (size, position of nucleoside incorporation) of small fragments of nascent DNA (nDNA) obtained by pH-step alkaline elution of intact HL-60 cells following their exposure to ara-C. In the pH-step alkaline elution procedure, the smallest fragments of nDNA elute at pH 11. Anion-exchange high-performance liquid chromatography (HPLC) of nDNA obtained by 1 h elution at pH 11.0 of lysed HL-60 cells revealed a preponderance of nDNA fragments ranging from 0.5 to 40 kb in control ([³H]-dThd-labeled) cells. Exposure of cells to ara-C (0.8–1 m) resulted in a loss of the preponderance of radiolabel in fragments of 0.5–40 kb along with redistribution of the radiolabel (from [³H]-dThd or [³H]-ara-C) into smaller nDNA fragments (predominantly <100 bases in length) as determined by HPLC. We used the ability of pH-step alkaline elution to provide these small nDNA fragments produced by ara-C to investigate the paradoxical behavior of ara-C as a chain terminator in cell-free DNA synthetic systems while being incorporated into an internucleotide position in intact cells. Following the digestion of purified nDNA with micrococcal nuclease and spleen phosphodiesterase II, the proportion of radiolabel in 3-dNMP (indicating an internucleotide position) or free nucleoside (indicating a chain terminus position) was determined by reverse-phase HPLC. In digests of prelabeled genomic DNA, as expected, <90% of the radiolabel from [¹⁴C]-dThd or [³H]-ara-C was found to exist in an internucleotide position (as determined by co-chromatography with authentic 3-dTMP or 3-ara-CMP). In contrast, digests of nDNA that eluted at pH 11.0 revealed a significantly higher proportion of radiolabel in the chain terminus position (29%–35%) when the nDNA was obtained from cells exposed to 1 m [³H]-ara-C as compared with cells exposed to [³H]-dThd or [³H]-dCyd alone (<10%). These data obtained from pH-step alkaline elution of intact cells suggest that by causing the inhibition of chain elongation while failing to inhibit the formation of new nDNA replication intermediates, ara-C exposure leads to the production of very small nDNA fragments. This relative chain-terminating effect of ara-C is most apparent in the small nDNA replication fragments that elute at pH 11.0. Since ara-C is accumulated predominantly in an internal position, even in the small nDNA fragments that elute at pH 11.0, ligation and gap-filling mechanisms in the intact cell must rapidly transform ara-C from a chain terminus to an internal position.Abbreviations ara-C 1--d-arabinofuranosylcytosine ara-CMP, 1--d-arabinofuranosylcytosine monophosphate - ara-CTP 1--d-arabinofuranosylcytosine 5-triphosphate - dNMP deoxynucleoside monophosphate - nDNA nascent DNA - dThd dCyd, 2-deoxycytosine - PBS phosphatebuffered saline (0.85% NaCl, 6.7mm potassium phosphate, pH 7.4); nuclease buffer, 0.5mm TRIS, 2mm CaCl₂, pH 8 - HPLC high-performance liquid chromatography - EDTA ethylenediaminetetraacetic acid Supported in part by grant RO-1-CA40188 from the NIH, National Cancer Institute. Presented in part at the 81st and 82nd Annual Meetings of the American Association for Cancer Research in Washington, D. C. (May 1990), and Houston, Texas (May 1991), respectively     

The relevance of cell kinetics for optimal scheduling of 1-β-d-Arabinofuranosyl cytosine and methotrexate in a slow growing acute myeloid leukemia (BNML)

Summary 1--d-Arabinosyl cytosine and methotrexate were studied for their antitumor activity in acute myeloid leukemia of the BN rat (BNML), which is characterized by a slow growth rate due to the presence of a high proportion of nonproliferating cells.It was found that the two drugs showed the maximal cytotoxic action when given separately. The effect was highly dependent on the interval between the administration of each drug.The variation of the cell kinetic parameters produced by the recruitment into cycle of the resting population, as determined by labeling indices, correlates well with the antileukemic action of the drug combination.Abbreviations used Ara-C 1--d-arabinosyl cytosine - MTX methotrexate - ³H-TDR tritiated thymidine - LI labeling index     

β1 integrin is required for anchorage-independent growth and invasion of tumor cells in a context dependent manner

Recent studies suggest that extracellular matrix (ECM) components within the tumor microenvironment can influence malignant progression, thus we investigated the influence of the ECM binding receptor β1 integrin, on the hallmark properties of tumorigenesis. Small interfering (si) or short hairpin (sh) RNA approaches were used to deplete β1 integrin in cancer cell lines. β1 integrin-depleted cells were then assessed for their growth and invasive capabilities using 2-dimensional (2D) or 3D culture conditions. Depletion of β1 integrin expression did not impact cell growth in 2D assay systems; however, β1 integrin and its ligand fibronectin were required for growth in 3D. β1 integrin-depleted cells also had reduced invasive capabilities, in part due to increased tissue inhibitor of metalloprotease (TIMP)-2 expression in conjunction with down-regulation of matrix metalloprotease (MMP)-9 levels in β1 integrin-depleted cells. Our results suggest that despite no apparent effect on 2D cell growth, fibronectin-β1 integrin signaling is a critical mediator of the 3D growth and invasive properties of tumor cells. These observations highlight the importance of investigating the role of adhesion molecules in the appropriate context and furthermore identify β1 integrin as a possible therapeutic target to inhibit the aggressive growth and invasion of tumor cells.     

Influence of PPAR -γligand on radiation - induced PAI - 1 and TGF -βmRNA in fibroblast cells

Objective To observe the influence of peroxisome proliferator activated receptor-γligand (PPAR-γ, pioglatazone) on expression of PAI-1 and TGF-β mRNA and proliferation in fibroblast cells before and after X-ray radiation, and to study the effect of PPAR-γon normal cells during radiation induced fibrosis process. Methods RT-PCR method was used to measure PPAR-γgene expression in L929 cells.After X-ray irradiation of 10 Gy,4 Gy or 2 Gy, the expressions of PAI-1 and TGF-β mRNA in mouse lung fibroblast cells (L929) were measured using RT-PCR. After X-ray irradiation and pioglatazone treatment,the influence of pioglatazone on PAI-1 and TGF-β was measured using RT-PCR method. MTT method was used to test cell proliferation after the treatment of irradiation and pioglatazone. Results PPAR-γ mRNA expression was observed in L929 cells. Expression of PAI-1 and TGF-β mRNA reached the highest level 483.40,P =0. 090) ). At 48 h after the treatment of pioglatazone and 10 Gy radiation, pioglatazone decreased 0. 36, 0. 34 and 0. 32( F = 3.90, P = 0. 040) ). The inhibitory effect was significantly increased when L9292. 50,P =0. 005)). Conclusions X-ray irradiation can increase the expression of PAI-1 and TGF-β in L929 cells. Pioglatazone can decrease the expression of radiation-induced PAI-1 and TGF-β, and restrain the fibroblast proliferation.