Meta-analyses of the efficacy of pharmacotherapies and sublingual allergy immunotherapy tablets for allergic rhinitis in adults and children.

BACKGROUND: Treatment options for seasonal and perennial allergic rhinitis (SAR/PAR) include pharmacotherapies and allergy immunotherapy. These meta-analyses evaluated the efficacy of pharmacotherapies and sublingual immunotherapy tablets (SLIT-tablets) versus placebo on nasal symptoms associated with SAR and PAR. METHODS: Randomized, double-blind, placebo-controlled trials were identified from systematic PubMED/EMBASE searches through 7/18/2019 (PROSPERO protocol CRD42018105632). The primary outcome was mean numerical difference in total nasal symptom score (TNSS; 0-12) between active treatment and placebo at the end of the assessment period. Random-effects meta-analyses estimated the mean difference for each medication group weighted by the inverse of the trial variance. Publication bias assessments and sensitivity analyses were conducted. RESULTS: Rescue symptom-relieving pharmacotherapy was prohibited in most pharmacotherapy trials but was allowed in all SLIT-tablet trials. For adult/adolescent SAR, the mean numerical difference (95% CI) in TNSS versus placebo was: intranasal corticosteroids (INCS)=1.38 (1.18, 1.58; 39 trials); combination intranasal antihistamine/INCS=1.34 (1.15, 1.54; 4 trials); intranasal antihistamines=0.72 (0.56, 0.89; 13 trials); oral antihistamine=0.62 (0.35, 0.90; 18 trials); SLIT-tablets=0.57 (0.41, 0.73; 4 trials); and montelukast=0.48 (0.36, 0.60; 10 trials). For adult/adolescent PAR, mean difference in TNSS versus placebo (95% CI) was: INCS=0.82 (0.66, 0.97; 14 trials); SLIT-tablets=0.65 (0.42, 0.88; 3 trials); and oral antihistamine=0.27 (0.11, 0.42; 3 trials). The number of eligible trials limited meta-analyses for pediatric SAR/PAR. CONCLUSIONS: All treatments significantly improved nasal symptoms versus placebo. SLIT-tablets provided improvement in TNSS despite access to rescue symptom-relieving pharmacotherapy. Extensive trial heterogeneity and strong indications of publication bias preclude the comparison of treatment effects among treatment classes.

Exploring factors associated with health disparities in asthma and poorly controlled asthma among school-aged children in the U.S.

Objective: Certain populations suffer disproportionately from asthma and asthma morbidity. The objective was to provide a national descriptive profile of asthma control and treatment patterns among school-aged children (SAC: aged 6-17) in the U.S. Methods: This was a cross-sectional analysis using the nationally representative 2007-2014 Medical Expenditure Panel Survey. Among SAC with asthma, indicators of poor control included: exacerbation/asthma attack; >3 canisters short-acting beta agonist (SABA)/3 months; and asthma-specific Emergency Department or inpatient visits (ED/IP). Results: Non-Hispanic black, non-Hispanic multiple races, Puerto Rican, obese, Medicaid, poor, ≥2 non-asthma chronic comorbidities (CC), and family average CC ≥ 2 were associated with higher odds of having asthma. The following had significantly higher odds ratios (OR) of excessive SABA use compared to non-Hispanic whites [OR; CI; p < 0.05]: Puerto Rican (3.8; 2.1-6.9), Mexican (3.6; 2.0-6.4), Central/South American (3.0; 1.2-7.7), Hispanic-other (3.1; 1.1-9.0), non-Hispanic black (2.5; 1.6-3.9), and non-Hispanic Asian (4.0; 1.7-9.2). SABA OR were also significant for Spanish spoken at home (2.5; 1.6-3.8), obese (2.1; 1.3-3.3), Medicaid (2.9; 2.0-4.1), no medical insurance (2.1; 1.1-4.1), no prescription insurance (2.5; 1.8-3.5), poor (2.8; 1.7-4.7), CC ≥ 2 (2.1; 1.6-2.8), parent-without high-school degree (2.5; 1.8-3.6), parent-SF-12 Physical Component Scale <50 (1.6; 1.2-2.1) and Mental Component Scale <50 (1.5; 1.1-2.0). Significant differences also existed across subgroups for ED/IP visits. Conclusions: There are disparities in asthma control and prevalence among certain populations in the U.S. These results provide national data on disparities in several indicators of poor asthma control beyond the standard race/ethnicity groupings.

The national burden of poorly controlled asthma, school absence and parental work loss among school-aged children in the United States.

OBJECTIVE: The degree of poorly controlled asthma and its association with missed school days and parental missed work days is not well understood. METHODS: This was a retrospective analysis of missed school days and missed work days for school-aged children (SAC; aged 6-17) and their caregivers in the nationally representative 2007-2013 Medical Expenditure Panel Survey (MEPS). Indicators of poor asthma control included: exacerbation in previous 12 months; use of >3 canisters of short-acting beta agonist (SABA) in 3 months; and annual asthma-specific (AS) Emergency Department (ED) or inpatient (IP) visits. Negative binomial regression was used for missed school days, and a Heckman two-step selection model was used for missed work days. All analyses controlled for sociodemographics and other covariates. RESULTS: There were 44,320 SAC in MEPS, of whom 5,890 had asthma. SAC with asthma and an indicator of poor control missed more school days than SAC without asthma: exacerbation (1.8 times more; p < 0.001); >3 canisters SABA (2.7 times more; p < 0.001) and ED/IP visit (3.8 times more; p < 0.001). The parents/caregivers of SAC with asthma and an exacerbation missed 1.2 times more work days (p < 0.05), while those with SAC with asthma and an ED/IP visit missed 1.8 times more work days (p < 0.01) than the parents of SAC without asthma. CONCLUSIONS: This study provides evidence of the significant national burden of poorly controlled asthma due to missed school and work days in the United States. More effective and creative asthma management strategies, with collaboration across clinical, community and school-based outreach, may help address this burden.

Mismatch repair deficiency: a temozolomide resistance factor in medulloblastoma cell lines that is uncommon in primary medulloblastoma tumours.

BACKGROUND: Tumours are responsive to temozolomide (TMZ) if they are deficient in O(6)-methylguanine-DNA methyltransferase (MGMT), and mismatch repair (MMR) proficient. METHODS: The effect of TMZ on medulloblastoma (MB) cell killing was analysed with clonogenic survival assays. Expression of DNA repair genes and enzymes was investigated using microarrays, western blot, and immunohistochemistry. DNA sequencing and promoter methylation analysis were employed to investigate the cause of loss of the expression of MMR gene MLH1. RESULTS: Temozolomide exhibited potent cytotoxic activity in D425Med (MGMT deficient, MLH1 proficient; IC(50)=1.7 µM), moderate activity against D341Med (MGMT proficient, MLH1 deficient), and DAOY MB cells (MGMT proficient, MLH1 proficient). MGMT inhibitor O(6)-benzylguanine sensitised DAOY, but not D341Med cells to TMZ. Of 12 MB cell lines, D341Med, D283Med, and 1580WÜ cells exhibited MMR deficiency due to MLH1 promoter hypermethylation. DNA sequencing of these cells provided no evidence for somatic genetic alterations in MLH1. Expression analyses of MMR and MGMT in MB revealed that all patient specimens (n=74; expression array, n=61; immunostaining, n=13) are most likely MMR proficient, whereas some tumours had low MGMT expression levels (according to expression array) or were totally MGMT deficient (3 out of 13 according to immunohistochemistry). CONCLUSION: A subset of MB may respond to TMZ as some patient specimens are MGMT deficient, and tumours appear to be MMR proficient.

Bevacizumab continuation beyond initial bevacizumab progression among recurrent glioblastoma patients.

BACKGROUND: Bevacizumab improves outcome for most recurrent glioblastoma patients, but the duration of benefit is limited and survival after initial bevacizumab progression is poor. We evaluated bevacizumab continuation beyond initial progression among recurrent glioblastoma patients as it is a common, yet unsupported practice in some countries. METHODS: We analysed outcome among all patients (n=99) who received subsequent therapy after progression on one of five consecutive, single-arm, phase II clinical trials evaluating bevacizumab regimens for recurrent glioblastoma. Of note, the five trials contained similar eligibility, treatment and assessment criteria, and achieved comparable outcome. RESULTS: The median overall survival (OS) and OS at 6 months for patients who continued bevacizumab therapy (n=55) were 5.9 months (95% confidence interval (CI): 4.4, 7.6) and 49.2% (95% CI: 35.2, 61.8), compared with 4.0 months (95% CI: 2.1, 5.4) and 29.5% (95% CI: 17.0, 43.2) for patients treated with a non-bevacizumab regimen (n=44; P=0.014). Bevacizumab continuation was an independent predictor of improved OS (hazard ratio=0.64; P=0.04). CONCLUSION: The results of our retrospective pooled analysis suggest that bevacizumab continuation beyond initial progression modestly improves survival compared with available non-bevacizumab therapy for recurrent glioblastoma patients require evaluation in an appropriately randomised, prospective trial.

Bifunctional DNA alkylator 1,3-bis(2-chloroethyl)-1-nitrosourea activates the ATR-Chk1 pathway independently of the mismatch repair pathway.

The presence of DNA damage initiates signaling through the ataxia-telangiectasia mutated kinase (ATM) and the ATM- and the Rad3-related kinase (ATR), which phosphorylate, thus activating, the checkpoint kinases (Chk) 1 and 2, which leads to cell cycle arrest. The bifunctional DNA alkylator 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) is cytotoxic primarily by inducing DNA monoadducts and ultimately, interstrand cross-links, which block DNA replication. In this study, we investigated the activation of the ATR-Chk1 pathway in response to BCNU treatment and the dependence of this response on the DNA mismatch repair (MMR) capacity. Medulloblastoma cells were exposed to low and moderate doses of BCNU, and the effects on this DNA damage signaling pathway were examined. In response to BCNU, Chk1 was found to be phosphorylated at serine 345 and exhibited increased kinase activity. Caffeine and wortmannin, which are broad-spectrum inhibitors of ATM and ATR, reduced this phosphorylation. Cell cycle analysis further revealed an accumulation of cells in the S phase in response to BCNU, an effect that was attenuated by caffeine. Small interfering RNA knockdown of ATR also reduced Chk1 phosphorylation after exposure to BCNU. However, knockdown of ATM had no effect on the observed Chk1 phosphorylation, suggesting that ATR was primarily responsible for Chk1 activation. Analysis of Chk1 activation in cells deficient in MMR proteins MutLalpha or MutSalpha indicated that the DNA damage response induced by BCNU was independent of the MMR apparatus. This MMR-independent activation seems to be the result of DNA interstrand cross-link formation.

Metronomic chemotherapy with daily, oral etoposide plus bevacizumab for recurrent malignant glioma: a phase II study.

BACKGROUND: We evaluated bevacizumab with metronomic etoposide among recurrent malignant glioma patients in a phase 2, open-label trial. METHODS: A total of 59 patients, including 27 with glioblastoma (GBM) and 32 with grade 3 malignant glioma, received 10 mg kg(-1) bevacizumab biweekly and 50 mg m(-2) etoposide daily for 21 consecutive days each month. The primary end point was a 6-month progression-free survival, and secondary end points included safety and overall survival. Vascular endothelial growth factor (VEGF), VEGFR-2, carbonic anhydrase 9 (CA9) and hypoxia-inducible factor-2alpha (HIF-2alpha) were assessed semiquantitatively in archival tumours using immunohistochemistry and were correlated with outcome. RESULTS: Among grade 3 and GBM patients, the 6-month progression-free survivals were 40.6% and 44.4%, the radiographic response rates were 22% and 37% and the median survivals were 63.1 and 44.4 weeks, respectively. Hypertension predicted better outcome among both grade 3 and GBM patients, whereas high CA9 and low VEGF were associated with poorer progression-free survival (PFS) among those with GBM. The most common grade > or = 3 adverse events included neutropaenia (24%), thrombosis (12%), infection (8%) and hypertension (3%). Two patients had asymptomatic, grade 1 intracranial haemorrhage and one on-study death occurred because of pulmonary embolism. CONCLUSION: Bevacizumab with metronomic etoposide has increased toxicity compared with previous reports of bevacizumab monotherapy. Its anti-tumour activity is similar to that of bevacizumab monotherapy or bevacizumab plus irinotecan. (ClinicalTrials.gov: NCT00612430).

In vitro sensitivity testing of minimally passaged and uncultured gliomas with TRAIL and/or chemotherapy drugs.

TRAIL/Apo-2L has shown promise as an anti-glioma drug, based on investigations of TRAIL sensitivity in established glioma cell lines, but it is not known how accurately TRAIL signalling pathways of glioma cells in vivo are reproduced in these cell lines in vitro. To replicate as closely as possible the in vivo behaviour of malignant glioma cells, 17 early passage glioma cell lines and 5 freshly resected gliomas were exposed to TRAIL-based agents and/or chemotherapeutic drugs. Normal human hepatocytes and astrocytes and established glioma cell lines were also tested. Cross-linked TRAIL, but not soluble TRAIL, killed both normal cell types and cells from three tumours. Cells from only one glioma were killed by soluble TRAIL, although only inefficiently. High concentrations of cisplatin were lethal to glioma cells, hepatocytes and astrocytes. Isolated combinations of TRAIL and chemotherapy drugs were more toxic to particular gliomas than normal cells, but no combination was generally selective for glioma cells. This study highlights the widespread resistance of glioma cells to TRAIL-based agents, but suggests that a minority of high-grade glioma patients may benefit from particular combinations of TRAIL and chemotherapy drugs. In vitro sensitivity assays may help identify effective drug combinations for individual glioma patients.

Assessment of treatment patterns associated with injectable disease-modifying therapy among relapsing-remitting multiple sclerosis patients.

BACKGROUND: Availability of oral disease-modifying therapy (DMT) for relapsing-remitting multiple sclerosis (RRMS) may affect injectable DMT (iDMT) treatment patterns. OBJECTIVE: The objective of this paper is to evaluate iDMT persistency, reasons for persistency lapses, and outcomes among newly diagnosed RRMS patients. METHODS: Medical records of 300 RRMS patients initiated on iDMT between 2008 and 2013 were abstracted from 18 US-based neurology clinics. Eligible patients had ≥3 visits: pre-iDMT initiation, iDMT initiation (index), and ≥1 visit within 24 months post-index. MS-related symptoms, relapses, iDMT treatment patterns (i.e. persistency, discontinuation, switching, and restart), and reasons for non-persistency were tracked for 24 months. RESULTS: At 24 months, iDMT persistency was 61.0%; 28.0% of patients switched to another DMT, 8.0% discontinued, and 3.0% stopped and restarted the same iDMT. The most commonly identified reasons for non-persistency were perceived lack of efficacy (22.2%), adverse events (18.8%), and fear of needles/self-injecting (9.4%). At 24 months, 38.0% of patients had experienced a relapse and 11.0% had changes in MRI lesion counts. Patients without MS-related symptoms at index reported increases in the incidence of these symptoms at 24 months. CONCLUSIONS: Non-persistency with iDMT remains an issue in the oral DMT age. Many patients still experienced relapses and disease progression, and should consider switching to more effective therapies.

Enhancement of nitrosourea activity in medulloblastoma and glioblastoma multiforme.

BACKGROUND: Although chemotherapy offers promise of increased survival for children with medulloblastoma and glioblastoma multiforme, drug resistance occurs frequently, resulting in tumor progression and death. Resistance to nitrosoureas and methylating agents, which damage DNA, can be mediated by a DNA repair protein, O6-alkylguanine-DNA alkyltransferase (AGAT). Depletion of this protein with alkylguanines or methylating agents, however, restores tumor cell sensitivity to the cytotoxicity of chloroethylnitrosoureas (e.g., carmustine [BCNU]). PURPOSE: This study was designed to determine whether resistance to the activity of nitrosourea (the drug BCNU) in BCNU-resistant human medulloblastoma (D341 Med) and human glioblastoma multiforme (D-456 MG) can be reversed by the methylating agent streptozocin and the O6-substituted guanines O6-methylguanine and O6-benzylguanine. METHODS: Xenografts were grown subcutaneously in athymic BALB/c mice. BCNU was administered as a single intraperitoneal injection at doses of 100 mg/m2, 75 mg/m2, or 38 mg/m2--i.e., 1.0, 0.75, or 0.38, respectively, of the dose lethal to 10% of treated animals (LD10). Mice were treated intraperitoneally with a single dose of O6-benzylguanine or O6-methylguanine (240 mg/m2) or with streptozocin (600 mg/m2) daily for 4 days. Response was assessed by tumor growth delay and tumor regression. AGAT activity in the xenografts was measured at 1 and 6 hours after pretreatment, at the time tumors were excised. RESULTS: Pretreatment with O6-benzylguanine, O6-methylguanine, or streptozocin reduced AGAT activity to 4%, 25%, and 95% of control values, respectively, in D341 Med and 0%, 0%, and 25% of control values, respectively, in D-456 MG 1 hour after injection. After 6 hours, levels changed to 7%, 61%, and 116% of control values in D341 Med and 0%, 79%, and 21% of control values in D-456 MG, respectively. Both D341 Med and D-456 MG xenografts were completely resistant to BCNU at its LD10. Pretreatment with O6-benzylguanine increased BCNU sensitivity in both types of xenograft. In contrast, treatment with BCNU plus O6-methylguanine or streptozocin did not produce growth delays substantially different from those produced by BCNU alone, reflecting the more efficient depletion of AGAT by O6-benzylguanine. Following therapy with BCNU plus O6-benzylguanine at 0.38 LD10, tumor regressions were seen in eight of 10 D341 Med and in all 10 D-456 MG xenografts. CONCLUSION: We recommend comprehensive clinical toxicologic evaluation of combination therapy with O6-benzylguanine plus BCNU, which would allow subsequent design of phase I clinical trials.

Increased melphalan activity in intracranial human medulloblastoma and glioma xenografts following buthionine sulfoximine-mediated glutathione depletion.

In previous studies we demonstrated that administration of buthionine sulfoximine (BSO) to athymic BALB/c mice bearing intracranial human glioma xenografts resulted in highly selective depletion of glutathione in neoplastic tissue with minimal effects on contralateral normal brain tissue. In the present study we treated athymic BALB/c mice bearing intracranial human glioma (D-54 MG) or medulloblastoma (TE-671) xenografts with melphalan alone or BSO followed by melphalan. Administration of BSO depleted intracellular glutathione to 7.5% of the control level. BSO plus melphalan resulted in a significant increase in median survival over that produced by melphalan alone: 45.3% versus 26.4% in TE-671 and 69% versus 27.6% in D-54 MG. These studies justify further efforts to modulate chemotherapeutic and radiotherapeutic interventions of primary malignant brain tumors by depletion of glutathione.

Chemotherapy of subcutaneous and intracranial human medulloblastoma xenografts in athymic nude mice.

The continuous human medulloblastoma cell line TE-671 was grown as s.c. and intracranial xenografts in athymic nude mice. Tumor-bearing animals were treated with chemotherapeutic agents at the 10% lethal dose; s.c. xenografts were sensitive to melphalan, 1-(2-chloroethyl)-3-(2,6-dioxo-1-piperidyl)-1-nitrosourea, and 5-azacytidine. No consistent response could be demonstrated to 9-beta-D-arabinofuranosyl-2-fluoroadenine 5'-monophosphate, and no response to methylglyoxal bis(guanyl hydrazone), N-trifluoroacetyl adriamycin-14-valerate, or to 1-beta-D-arabinofuranosylcytosine was observed. Melphalan produced a significant (P = less than or equal to 0.007) increase in the median survival of mice bearing intracranial xenografts, whereas no response was seen to 1-(2-chloroethyl)-3-(2,6-dioxo-1-piperidyl)-1-nitrosourea or 5-azacytidine. This model will allow analysis of the chemotherapeutic profile of human medulloblastoma, and provides a means to differentiate cellular sensitivity and resistance from drug access to the intracranial site.

Simultaneous measurements of blood flow and blood-to-tissue transport in xenotransplanted medulloblastomas.

We used double-label quantitative autoradiography to study blood flow (with [131I]iodoantipyrine) and blood-to-tissue transport (with [14C]-alpha-aminoisobutyric acid) in 20 TE-671 medulloblastomas xenotransplanted into nude rats. Microscopically, two distinct patterns of tumor growth were observed: (a) a solid tumor mass; and (b) a tumor in which nearly all tumor cells were located perivascularly. These two tumor patterns differed markedly in values of blood flow (F) and the transfer constant (K) of alpha-aminoisobutyric acid. The solid tumors (N = 17) had averaged mean values of F = 36.8 +/- 5.3 (SE) and K = 8.0 +/- 0.7 ml/100 g/min. The perivascular tumors, which were fewer in number (N = 3), had averaged mean values of F = 83.8 +/- 9.8 and K = 0.4 +/- 0.06 ml/100 g/min. Calculated values of the net extraction fraction (En) of alpha-aminoisobutyric acid were 0.54 +/- 0.07 for the solid tumors and 0.009 +/- 0.001 for the perivascular tumors. K and En for the solid tumors are the highest for any brain tumor model reported to date. The high rates of blood-to-tissue transport may explain why intracranial TE-671 medulloblastomas in nude mice respond to treatment with water-soluble chemotherapeutic drugs, unlike most other brain tumor models.

Chemotherapy and radiation therapy of human medulloblastoma in athymic nude mice.

The human medulloblastoma cell line TE-671 was grown s.c. and intracranially in athymic nude mice. Tumor-bearing animals treated with chemotherapeutic agents or radiation were compared to untreated tumor-bearing controls. Tumors growing s.c. were sensitive to cyclophosphamide and vincristine with growth delays in duplicate trials of 15.8/16.5 and 12.9/15.0 days, respectively. These tumors were minimally responsive to the 2,5-bis(1-aziridinyl-3,6-dioxodiethyl ester of 1,4-cyclohexadiene-1,4-dicarbamic acid (NSC 182986) and cis-diamminedichloroplatinum II and unresponsive to methotrexate, 2,4-diamino-6-(2,5-dimethoxybenzyl)-5-methylpyrido(2,3-d)pyrimidine (NSC 351521), 1,3-bis(2-chloroethyl)-1-nitrosourea (NSC 409962), and procarbazine. Radiation therapy with 2500 or 1500 rads as a single fraction produced a marked response, with growth delays of 39.5 and 21.1 days, respectively. Cyclophosphamide produced a significant (p less than 0.0005) increase in the median survival of mice with intracranial tumors. Vincristine produced a minimal increase in the median survival while no response was seen to the 2,5-bis(1-aziridinyl-3,6-dioxodiethyl ester of (1,4-cyclohexadiene-1,4-dicarbamic acid at the dose level and schedule tested. This model system will allow further analysis of the therapeutic sensitivity of human medulloblastoma to other agents or combined-modality regimens.

Treatment of human glioma and medulloblastoma tumor lines in athymic mice with diaziquone and diaziquone-based drug combinations.

We used diaziquone (NSC 182986) alone and in combination with other antineoplastic drugs to treat six human glioma and one human medulloblastoma tumor lines growing s.c. in athymic mice. Pharmacokinetic studies of diaziquone in the plasma of athymic mice indicated rapid clearance with a half-life of approximately 11.5 min. Diaziquone produced significant growth delays in at least one experiment using each of seven different tumor lines, and it produced consistent and significant delays in five of the seven. There was no obvious difference between a single dose and a dose administered once daily for 5 days, and tumor regressions to a volume smaller than that at treatment were uncommon in any of the single-drug experiments. Using our most extensively characterized human glioma line, D-54 MG, we found striking enhancement of the therapeutic effect by using nontoxic combinations of either diaziquone and carmustine (1,3-bis(2-chloroethyl)-1-nitrosourea, NSC 409962) or diaziquone and procarbazine (NSC 77213). These combinations produced significant increases in the median growth delay, significant increases in the number of tumor regressions, and some instances in which no palpable tumors were present 100 days after treatment. In contrast, in experiments using diaziquone -based chemotherapy combinations with either cyclophosphamide, cis-platinum, or vincristine, there was only slight enhancement of the therapeutic effect. These results, using human glioma and medulloblastoma tumor lines in athymic mice, suggest a broad range of activity of diaziquone against primary nervous system tumors and enhancement of its therapeutic effect with either 1,3-bis(2-chloroethyl)-1-nitrosourea or procarbazine. If Phase II and Phase III clinical trials corroborate these findings, the value of the nude mouse system for the evaluation of new therapeutic approaches to brain neoplasms would be further confirmed.

Combination chemotherapy in vitro exploiting glutamine metabolism of human glioma and medulloblastoma.

The human glioma-derived cell line D-54 MG and the human medulloblastoma-derived cell line TE-671 have been shown to be sensitive in culture to the pharmacological interference with glutamine metabolism by acivicin, 6-diazo-5-oxo-L-norleucine, and methionine sulfoximine. Using as a guide the multiple contributions of glutamine to the biosynthesis of proteins, purines, and pyrimidines, we now have identified six additional antimetabolites active against these lines in vitro at clinically relevant concentrations. The 50% growth-inhibitory levels of the drugs against D-54 MG in 6-day continuous exposure experiments were: L-asparaginase, 0.057 IU/ml; 5-fluorouracil, 0.5 micrograms/ml; 6-mercaptopurine, 0.8 micrograms/ml; actinomycin D, 0.0007 micrograms/ml; N-phosphonacetyl-L-aspartic acid, 2.3 micrograms/ml; and 5-azacytidine, 0.2 micrograms/ml (3-day exposure. The corresponding 50% growth-inhibitory values in TE-671 were: L-asparaginase, 0.54 IU/ml; 5-fluorouracil, 1.5 micrograms/ml; 6-mercaptopurine, 4.7 micrograms/ml; actinomycin D, 0.00044 micrograms/ml; N-phosphonacetyl-L-aspartic acid, 4.5 micrograms/ml; and 5-azacytidine, 0.49 micrograms/ml. Dipyridamole up to 10 micrograms/ml was inactive against both lines. The isobologram method was used to evaluate the effectiveness of several two-drug combinations which were biochemically designed. The sums of the optimal fractional inhibitory concentrations for the pairs were: acivicin plus L-asparaginase, 0.14; acivicin plus methionine sulfoximine, 0.40; 6-diazo-5-oxo-L-norleucine plus methionine sulfoximine, 0.60; acivicin plus 6-mercaptopurine, 1.0, all in TE-671; and acivicin plus 5-fluorouracil, 0.79, in D-54 MG. Our findings suggest that an antimetabolite regimen exploiting glutamine sensitivity might improve the chemotherapy of some human gliomas and medulloblastomas.

Influence of glutamine on the growth of human glioma and medulloblastoma in culture.

Cellular supply of glutamine, an essential substrate for growth, is derived from extracellular fluid and de novo synthesis. We investigated the relative importance of these sources to the growth of six human anaplastic glioma- and one human medulloblastoma-derived permanent cell lines. Exogenous glutamine was limiting for the proliferation of glioma-derived lines D-54 MG, U-118 MG, and U-251 MG. In contrast, medulloblastoma-derived line TE-671 and glioma-derived lines U-373 MG, D-245 MG, and D-259 MG grew in the absence of supplemental glutamine. Two cell lines with contrasting glutamine requirements, D-54 MG and TE-671, were used to explore the pharmacological interference with glutamine metabolism. DL-alpha-Aminoadipic acid, a reported glutamic acid analogue with gliotoxic properties, significantly inhibited the growth of both lines. These effects were reversed by increasing glutamine, suggesting that the major action of DL-alpha-aminoadipic acid is as a glutamine antagonist. In contrast, the glutamine synthetase inhibitor delta-hydroxylysine demonstrated activity only against TE-671. Acivicin and 6-diazo-5-oxo-L-norleucine, glutamine analogues available for clinical use, reduced the proliferation of both cell lines at pharmacological concentrations. Methionine sulfoximine, a glutamine synthetase inhibitor previously used clinically, produced marked growth inhibition only against TE-671. These findings indicate that the synthesis and utilization of glutamine are potentially exploitable targets for the chemotherapy of some human gliomas and medulloblastomas.

In vitro versus in vivo correlations of chemosensitivity of human medulloblastoma.

An in vitro clonogenic assay was used to test the chemosensitivity of the human medulloblastoma cell line TE-671. Dose-response relationships for reduction in colony formation were generated for cyclophosphamide, vincristine, Adriamycin, 1,3-bis(2-chloroethyl)-1-nitrosourea (NSC 409962), and 1,4-cyclohexadiene-1,4-dicarbamic acid, 2,5-bis(1-aziridinyl)-3,6-dioxo-diethylester (NSC 182986); and the in vitro drug dose at which there is a 75% reduction in the number of colonies in comparison to controls (ID75S) were derived from these data. Methotrexate produced no colony reduction at any dose tested up to 1000 micrograms/ml. The in vitro results were compared to growth delays in s.c. TE-671 xenografts in athymic mice treated with the same agents. Agents with an ID75 less than assumed in vivo plasma drug concentrations were all active in vivo, whereas two of the three agents with an ID75 greater than assumed in vivo plasma drug concentrations demonstrated no in vivo activity. These results suggest that for these agents, the relationship between the ID75 of the drug and its in vivo concentration allows in vitro clonogenic assay results to agree with in vivo growth delay responses.

Rate of buthionine sulfoximine entry into brain and xenotransplanted human gliomas.

Buthionine sulfoximine (BSO) is an inhibitor of glutathione synthesis and can be used to potentiate the effects of chemotherapeutic alkylating agents and radiotherapy. We examined the rates of influx and efflux of [35S]BSO administered to athymic mice with and without xenografted D-54MG human gliomas. Three analytic approaches were applied to the experimental data to obtain values of the blood-to-tissue influx constant, K1, of BSO. Multiple time point experiments in tumor-bearing mice were analyzed with a two-compartment model and nonlinear fitting routines, and by graphical analysis which assumed no backflux of BSO from tissue to blood. A third approach used single time point data in nontumor-bearing mice and assumed no backflux. Calculated values of the K1 of BSO ranged from 0.23 to 1.35 microliters/g/min in tumor-free cortex, and from 5.3 to 6.3 microliters/g/min in the D-54MG gliomas. The tissue-to-blood efflux constant, k2, was zero in both cortex and tumor, suggesting that BSO entered cells and was trapped once it crossed the blood-brain barrier. Estimates of plasma vascular space (Vp) ranged from 2 to 20 microliters/g in cortex, and from 103 to 169 microliters/g in tumor. Another set of experiments, done in normal mice with different doses of BSO, suggested that BSO competes for neutral amino acid transport sites at the blood-brain barrier, but that the capacity of the carrier-mediated transport system is low and saturates at administered doses of about 0.5 mmol/kg (corresponding to plasma concentrations of about 12 mumol/ml). The rate of entry into brain was proportional to the octanol/water partition coefficient and molecular weight of BSO, which also supports passive diffusion as the means of entry. Consequently, although the rate of BSO entry into D-54MG gliomas was between 4 and 30 times higher than the rate of entry into tumor-free cortex, the results of these experiments suggest that most of the BSO that enters brain tumors in the doses commonly used in experimental situations will cross capillaries by passive diffusion.

Amplification of the c-myc gene in human medulloblastoma cell lines and xenografts.

Cultured cell lines and xenografts derived from 7 human medulloblastomas were evaluated for amplification of the c-myc, N-myc, epidermal growth factor receptor, and gli genes by Southern blot analysis. Karyotypes of the original biopsies and early passaged cells demonstrated double minute chromosomes in 4 of the 7 cases. All 7 samples (3 cell lines and 4 xenografts) from the 4 tumors with double minute chromosomes contained amplification of the c-myc gene. Cell lines and xenografts derived from the 3 biopsies without double minute chromosomes failed to demonstrate amplification of the 4 genes which were tested, but a rearrangement of the c-myc gene occurred in 1 of the 3 tumors. These observations demonstrate that the c-myc gene is often amplified and/or rearranged in human medulloblastomas and suggest that amplification of this gene provides a growth advantage for medulloblastoma cells in vitro and in vivo.