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.

Bone marrow-generated dendritic cells pulsed with tumor extracts or tumor RNA induce antitumor immunity against central nervous system tumors.

Recent studies have shown that the brain is not a barrier to successful active immunotherapy that uses gene-modified autologous tumor cell vaccines. In this study, we compared the efficacy of two types of vaccines for the treatment of tumors within the central nervous system (CNS): dendritic cell (DC)-based vaccines pulsed with either tumor extract or tumor RNA, and cytokine gene-modified tumor vaccines. Using the B16/F10 murine melanoma (B16) as a model for CNS tumor, we show that vaccination with bone marrow-generated DCs, pulsed with either B16 cell extract or B16 total RNA, can induce specific cytotoxic T lymphocytes against B16 tumor cells. Both types of DC vaccines were able to protect animals from tumors located in the CNS. DC-based vaccines also led to prolonged survival in mice with tumors placed before the initiation of vaccine therapy. The DC-based vaccines were at least as effective, if not more so, as vaccines containing B16 tumor cells in which the granulocytic macrophage colony-stimulating factor gene had been modified. These data support the use of DC-based vaccines for the treatment of patients with CNS tumors.

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).

Tenascin/hexabrachion in human skin: biochemical identification and localization by light and electron microscopy.

Tenascin/hexabrachion is a large glycoprotein of the extracellular matrix. Previous reports have demonstrated that tenascin is associated with epithelial-mesenchymal interfaces during embryogenesis and is prominent in the matrix of many tumors. However, the distribution of tenascin is more restricted in adult tissues. We have found tenascin to be present in normal human skin in a distribution distinct from other matrix proteins. Immunohistochemical studies showed staining of the papillary dermis immediately beneath the basal lamina. Examination of skin that had been split within the lamina lucida of the basement membrane suggested a localization of tenascin beneath the lamina lucida. In addition, there was finely localized staining within the walls of blood vessels and in the smooth muscle bundles of the arrectori pilorem. Very prominent staining was seen around the cuboidal cells that formed the basal layer of sweat gland ducts. The sweat glands themselves did not stain. The distribution of tenascin in the papillary dermis was studied at high resolution by immunoelectron microscopy. Staining was concentrated in small amorphous patches scattered amongst the collagen fibers beneath the basal lamina. These patches were not associated with cell structures, collagen, or elastic fibers. Tenascin could be partially extracted from the papillary dermis by urea, guanidine hydrochloride, or high pH solution. The extracted protein showed a 320-kD subunit similar to that purified from fibroblast or glioma cell cultures. We have developed a sensitive ELISA assay that can quantitate tenascin at concentrations as low as 5 ng/ml. Tests on extracts of the papillary dermis showed tenascin constituted about 0.02-0.05% of the protein extracted.

Identification of an amplified, highly expressed gene in a human glioma.

A gene, termed gli, was identified that is amplified more than 50-fold in a malignant glioma. The gene is expressed at high levels in the original tumor and its derived cell line and is located at chromosome 12 position (q13 to q14.3). The gli gene is a member of a select group of cellular genes that are genetically altered in primary human tumors.

Targeting SPARC expression decreases glioma cellular survival and invasion associated with reduced activities of FAK and ILK kinases.

Secreted protein acidic and rich in cysteine (SPARC) is an extracellular glycoprotein expressed in several solid cancers, including malignant gliomas, upon adoption of metastatic or invasive behaviors. SPARC expression in glioma cells promotes invasion and survival under stress, the latter process dependent on SPARC activation of AKT. Here we demonstrate that downregulation of SPARC expression with short interfering RNA (siRNA) in glioma cells decreased tumor cell survival and invasion. SPARC siRNA reduced the activating phosphorylation of AKT and two cytoplasmic kinases, focal adhesion kinase (FAK) and integrin-linked kinase (ILK). We determined the contributions of FAK and ILK to SPARC effects using SPARC protein and cell lines engineered to overexpress SPARC. SPARC activated FAK and ILK in glioma cells previously characterized as responsive to SPARC. Downregulation of either FAK or ILK expression inhibited SPARC-mediated AKT phosphorylation, and targeting both FAK and ILK attenuated AKT activation more potently than targeting either FAK or ILK alone. Decreased SPARC-mediated AKT activation correlated with a reduction in SPARC-dependent invasion and survival upon the downregulation of FAK and/or ILK expression. These data further demonstrate the role of SPARC in glioma tumor progression through the activation of intracellular kinases that may provide novel therapeutic targets for advanced cancers.

R-type virus-like particles in avian sarcoma virus-induced rat central nervous system tumors.

Morphologically distinct virus-like particles (VLP), similar to R-type VLP, were observed by electron microscopy in experimental rat central nervous system tumors induced with the B-77-C strain of avian sarcoma virus (ASV). R-type VLP have a characteristic internal radial structure and were observed previously only in hamster cells and in an established bovine cell line. They were not observed in the B-77 ASV inoculum used to induce the rat tumors or in the B-77 induced hamster glioma cells from which the B-77 was rescued. Nevertheless, the genome of an endogenous hamster R-type particle also might have been rescued and carried in the B-77 inoculum. Alternatively, R-type VLP may exist in a number of animal species, including the rat, and may be expressed in certain conditions such as neoplastic transformation.

Cellular immunity in rats with primary brain tumors: inhibition of macrophage migration by soluble extracts of avian sarcoma virus-induced tumors.

Rats bearing primary tumors of the brain induced by avian sarcoma virus (ASV) were studied with the migration-inhibition factor (MIF) assay for the presence of cell-mediated immunity to tumor-associated antigens. Astrocytomas and sarcomas of the brain were induced in 34 neonatal F344 rats by the intracerebral inoculation of Bratislava-77 ASV. At weekly intervals from 4 to 9 weeks after the inoculation with virus, peritoneal exudate cells (PEC) from rats bearing brain tumors were tested an an MIF assay against soluble and KCl-treated extracts of a syngeneic, ASV-induced sarcoma. Incubation of the PEC with a soluble extract of syngeneic liver or with a KCl extract of a syngeneic, chemically induced tumor served as controls. Of 14 rats tested against the soluble tumor extract, 6 (43%) had statistically significant inhibition of migration (P less than or equal to 0.05). Of 23 animals tested against the KCl extract, 16 (70%) had significant inhibition. Immunity to the KCl extract was significant in most rats at each period. Ten rats were tested against a KCl extract of a hamster ASV-induced tumor; 7 gad significant inhibition of migration. None of 3 tested against a soluble extract of a syngeneic, chemically induced tumor had significant inhibition. Rats bearing ASV-induced brain tumors displayed cell-mediated immunity to tumor-associated antigen or antigens of ASV-induced tumors, which could be solubilized.

Concurrent measurements of blood flow and transcapillary transport in xenotransplanted human gliomas in immunosuppressed rats.

Neonatal Fischer 344 rats were immunosuppressed with antithymocyte serum and later were given an injection intracerebrally of cells from the human glioma permanent line D-54MG. Symptomatic tumor-bearing rats were studied with double-label quantitative autoradiography to concurrently measure blood flow and a unidirectional blood-to-tissue transfer constant (K) for alpha-aminoisobutyric acid (AIB). A net extraction fraction (En) was calculated from the measured values for blood flow and K. Mean whole tumor blood flow was 53.5 +/- 4.9 ml/100 g/min (mean +/- SEM), which was significantly less than the blood flow to the tumor-free cortex (198 +/- 15.5 ml/100 g/min) but not significantly different from the blood flow in the tumor-free corpus callosum (50.6 +/- 4.3 ml/100 g/min). Mean whole tumor K-value for AIB was 5.8 +/- 0.5 ml/100 g/min, approximately 30 times the K-value for tumor-free brain. The calculated mean whole tumor En was 0.2 +/- 0.09, nearly 100 times the value for the tumor-free brain. Regionally, blood flow was lower in the tumor center and higher in its tumor periphery, although the difference was not significant. Both K- and En-values were significantly higher for the tumor center and decreased radially for the areas from center out. The values for K and En of AIB in the D-54MG gliomas are the highest of any experimental brain tumor model studied to date and indicate that in some tumor regions in this model, blood-to-tissue transport of the water-soluble compound AIB may be dependent on blood flow as well as on the permeability-surface area product of the tumor capillaries.

Sequential adsorption analysis of antibodies to neuroectodermal cells by an indirect quantitative method.

An indirect radioimmunoassay was developed for the sequential adsorption analysis of rabbit antibodies raised against rat neuroectodermal cells. The quantitativee relationship between primary adsorbed rabbit antitumor antibodies and secondary adsorbed goat antibodies to rabbit IgG was explored by paired radioiodine analysis. In the final indirect method, the amount of unlabeled rabbit antibody removed by cultured monolayers of cells at each step in a sequence of cells could be determined from an equation relating the unlabeled amount to values of bound 125I-labeled goat antirabbit IgG. To obtain the total quantity of rabbit antibody in a particular antiserum reagent, a sequential adsorption analysis was done with successive steps of homologous cells. To obtain the amount of antibody that was cross-reactive for other cell lines, we included those lines in the first several steps of the sequence. The sequential adsorption profile was considered as a more important indicator of the quality of a particular antiserum reagent than was the total amount of antibody contained in it. Neuroectodermal cell lines used as illustrative examples included subclones of the C6 astrocytoma and of the RN-2 schwannoma.

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.

Expression of human fetal brain antigens by human tumors of neuroectodermal origin as defined by monoclonal antibodies.

The antigenic relationships between human tumors of neuroectodermal origin and fetal brain were investigated by the production of hybridoma antibodies derived from a fusion of P3-NS1/1-Ag 4-1 (NS1) myeloma cells with splenocytes from a mouse multiply immunized with an homogenate of second-trimester human fetal brain tissue. Two monoclonal antibodies (MAs), 4D2cl 6 and 7H10cl 4, were studied in detail by cell surface radioimmunoassay (CS-RIA), quantitative absorption, indirect immunofluorescence, and peroxidase-anti-peroxidase (PAP) immunohistology. MA 4D2cl 6 binds to 5 of 14 glioblastoma (GBM) cell lines, 1 of 2 melanoma cell lines, 1 of 3 neuroblastoma cell lines, and 1 of 5 fetal fibroblast lines by CS-RIA and to 13 of 13 GBM, 1 neuroblastoma, and fetal brain, liver, spleen, and adult spleen unfixed frozen tissue by PAP analysis. MA 7H10cl 4 binds to 13 of 14 GBM, 1 of 3 neuroblastoma, and 1 medulloblastoma cell line(s) by CS-RIA analysis and to 13 of 13 GBM, 1 neuroblastoma, fetal brain, liver, spleen, thymus, and adult spleen by PAP analysis. Control non-central nervous system tumors and normal adult tissue, including brain, were unreactive with both MAs by CS-RIA, PAP, and absorption analysis. Tissue distribution and localization analyses established that MAs 4D2cl 6 and 7H10cl 4 recognize specificities of shared fetal-neuroectodermal-lymphoid distribution which are operationally specific within the adult central nervous system and which are not related to previously described oncofetal or onconeural antigens.

Influence of age at inoculation on avian oncornavirus-induced brain tumor incidence, tumor morphology, and postinoculation survival in F344 rats.

Intracranial neoplasms were induced by intracerebral inoculation of a standardized, cell-free inoculum of the Bratislava-77 strain of avian sarcoma virus in F344 rats at 1, 9,97 to 99, and 528 days of age. Deaths from diseases that occur spontaneously in aged F344 rats complicated assessment of tumor incidence in rats inoculated at 528 days; 20 of 30 rats inoculated at this age developed brain tumors. All rats inoculated at age 1 day (47 rats), at age 9 days (37 rats), and at 97 to 99 days of age (41 rats) developed brain tumors. The incidence of animals developing tumors was 100% in these three groups, but the incidence of multiple tumors declined with increasing age at inoculation. The mean and variance of postinoculation survival increased from 83.8 +/- 21.5 days for rats inoculated at 1 day of age to 284.6 +/- 151.5 days for rats inoculated at 97 to 99 days of age. Poorly differentiated astrocytomas and astrocytomas of mixed morphology were common among rats inoculated as neonates. Solitary, pilocytic astrocytomas were the most common tumors among rats inoculated as adults.

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.

Demonstration of complex antigenic heterogeneity in a human glioma cell line and eight derived clones by specific monoclonal antibodies.

We have investigated the antigenic heterogeneity of human glioma cells and its correlation with other parameters of tumor cell heterogeneity (karyotype, 2':3' cyclic nucleotide 3'-phosphohydrolase expression, in vitro morphology) using the established human glioma cell line D-54 MG and eight single-cell-derived clones. The panel of antibodies used included 3 previously described heterologous sera raised against human gliomas and lamb oligodendroglia and 10 monoclonal antibodies with demonstrated reactivity for tumors of neuroectodermal origin, human fetal tissue, or human Thy-1. Antigen expression was determined by cell surface radioimmunoassay and peroxidase-antiperoxidase immunohistology. The use of a monoclonal antibody panel composed of ten reagents of varied specificity resulted in the demonstration of highly variable and complex antigenic patterns on the cell surfaces of cloned subpopulations of the human glioma cell line D-54 MG. Only one antigen, human Thy-1, was present on the parent line and all clones; the remaining nine antigens exhibited a distribution unrelated to other predictive parameters of genotypic or phenotypic heterogeneity such as karyotype, 2':3' cyclic nucleotide 3'-phosphohydrolase expression, or in vitro morphology. With the exception of clones 3 and 4, which shared a common antigen profile but exhibited distinctly different in vitro morphological patterns, the detected antigenic profile of each clone was distinct, with the proportion of expressed antigens ranging from 2 of 10 (clone 2) to 10 of 10 (clone 1). The demonstration of distinct, selectively maintained cell subpopulations within a human glioma cell line has direct implications for immunotherapeutic designs.

Comparison of intravenous versus intracarotid therapy with 1,3-bis(2-chloroethyl)-1-nitrosourea in a rat brain tumor model.

Currently numerous clinical trials are in progress utilizing intracarotid (i.c.) 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) for the treatment of malignant gliomas based upon the proposed focal nature of these tumors and the assumption that the i.c. route delivers higher levels of drug to the tumor. To date, however, increased efficacy in an animal model has not been clearly demonstrated for the i.c. delivery of BCNU. We have evaluated the dose-response curve for the i.v. and i.c. administration of BCNU in a commonly utilized experimental brain tumor model, the 9L rat gliosarcoma. An initial toxicity trial utilizing the i.p. 10% lethal dose (LD10) of BCNU by the i.v. and i.c. routes failed to demonstrate any significance in toxicity between the two routes. Tumor-bearing animals were then treated on Day 15-16 after tumor inoculations with 1, 10, 25, 50, 75, and 100% of the LD10 dose by either the i.v. or the i.c. route. Both i.v. and i.c. BCNU gave maximum survival increases at 75-100% LD10 doses, and there was no therapeutic advantage seen from i.c. delivery. However, at 50% of the LD10 dose (6.65 mg/kg), triplicate experiments demonstrated that the i.c. but not the i.v. dose maintained maximum efficacy equivalent to 100% of the LD10 given either i.v. or i.c. When the dose was reduced to 25% of the LD10 dose (3.33 mg/kg), two of three experiments showed efficacy of the i.c. delivery of this lower drug dosage to be equivalent to 100% of the LD10 given i.v. or i.c. The i.v. dosage resulted in a significant reduction in survival in all three trials. At 10% of the LD10 dose (1.30 mg/kg), neither the i.v. nor the i.c. administration retained equivalent efficacy to 100% of the LD10. However, in one of two trials, the i.c. groups had statistically better survival than controls, while in neither experiment was any advantage over controls seen in the i.v. treated groups. At 1% of the LD10 dose, neither the i.v. nor the i.c. route demonstrated any therapeutic efficacy. From our data, the advantage of the i.c. delivery of BCNU in the intracranial 9L rat gliosarcoma appears to be in the fact that significantly lower dosages than those given i.v. may be utilized to achieve equivalent survival with potentially less systemic toxicity.

Immunofluorescent analysis of expression of the RNA tumor virus major glycoprotein, gp71, on surfaces of virus-producing murine and other mammalian species cell lines.

The specificity of a single rabbit antiserum pool raised against the purified major glycoprotein, gp71, of Friend murine leukemia virus was determined for a variety of virus-producing mouse, feline, and gibbon ape cell lines by viable cell membrane immunofluorescence absorption. Among murine cells examined, Friend gp71 type specificity was shared only with Rauscher virus-producing cells, and a group specificity was present for all the murine leukemia virus-producing cells tested. Friend and Rauscher murine leukemia virus-infected cells shared interspecies cross-reactivity with feline leukemia and gibbon ape lymphoma virus-producing cells. However, Moloney, Gross, and other virus-producing murine cells shared some, but not all, of these gp71 interspecies determinants with the feline and primate cells. Immunoferritin electron microscopy localized these gp71 antigenic determinants on both virus and cell membranes.