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Forty-seven patients with metastatic disease at diagnosis or recurrent Ewing sarcoma (EWS) received high-dose chemotherapy (HDC) followed by tandem (n = 20, from February 13, 1997, to October 24, 2002) or single (n = 27, from October 1, 2004, to September 5, 2018) autologous hematopoietic stem cell transplantation (ASCT). To our knowledge, this is the largest single-institution study with sustained long-term follow-up exceeding 10 years. All patients who underwent single ASCT received a novel conditioning regimen with busulfan, melphalan, and topotecan. The overall survival (OS) and disease-free survival (DFS) were 46% and 37% at 10 years and 42% and 37% at 15 years, respectively. Disease status at transplant and the time to disease relapse prior to ASCT were identified as important prognostic factors in OS, DFS, and risk of relapse. At 10 years, patients who underwent transplantation in first complete response (1CR) had an excellent outcome (OS 78%), patients in 1CR/second complete response (2CR)/first partial response (1PR) had an OS of 66%, and patients at third or more complete response, second or more partial response, or advanced disease had an OS of 26%. Ten-year OS for patients without a history of relapse, with late relapse (≥2 years from diagnosis), or with early relapse (2 years from diagnosis) was 75%, 50%, and 18%, respectively. Selected patients in 1CR, 2CR, 1PR, and with late relapse had excellent, sustained 10- and 15-year OS and DFS.

Background Although chemotherapy has improved outcome of osteosarcoma, 30–40% of patients succumb to this disease. Survivors experience substantial morbidity and mortality from anthracycline-induced cardiotoxicity. We hypothesized that the cardioprotectant dexrazoxane would 1) support escalation of the cumulative doxorubicin dose (600 mg/m2) and 2) not interfere with the cytotoxicity of chemotherapy measured by necrosis grading in comparison to historical control data.9

Tumor necrosis factor (TNF), a peptide produced by macrophages with cytostatic and cytolytic effects, demonstrated single agent antitumor activity and synergistic effect when administered with dactinomycin in in vitro tumor cell lines, in vivo xenograft models, and adult and pediatric phase 1 clinic

The purpose of the study was to evaluate the feasibility and safety of two cycles of high-dose chemotherapy (HDT) followed by autologous hematopoietic SCT (HSCT) in patients with poor prognosis Ewing family of tumors (EFT). Twenty patients with primary metastatic bulky disease or recurrent EFT were enrolled to a treatment protocol with two cycles of HDT and HSCT. Patients tolerated well the first (n=20) and second (n=13) cycles, with limited and predictable toxicities. Only one (5%) TRM occurred during the second cycle. Myeloid engraftment occurred at the median of 11 days after both cycles. At 3 years, the overall and EFS were 45% (confidence interval; CI 0.22, 0.69) and 47% (CI 0.25, 0.70), respectively, for the entire group and 58% (CI 0.30, 0.86) for patients who completed two cycles. Dose intensification with two cycles of HDT and HSCT is feasible and safe, with low and acceptable treatment-related morbidity and mortality. Adding a second course of therapy does not impair engraftment. However, only 65% of the patients were able to proceed to the second cycle. Further studies are required to define the optimal mode of delivery of HDT and HSCT in treatment of advanced EFT.

Background The combination of the antiproliferative and differentiation-inducing effects of retinoids together with the antiproliferative, immunostimulatory, and differentiation-potentiating effects of interferon-α (IFN-α) were the basis for the development of this combination in pediatric patients with refractory neuroblastoma or Wilms tumor. Procedure A phase 2 trial of all-trans-retinoic acid (ATRA), administered orally at a dose of 90 mg/m2/day in three divided doses for 3 consecutive days per week, and IFN-α2a, administered subcutaneously daily at a dose of 3 × 106 U/m2/day for 5 consecutive days per week, in 4 week cycles was performed. A two-stage design was used for each disease stratum. Results Seventeen patients (16 evaluable) with neuroblastoma, median age 9 years, and 15 patients (14 evaluable) with Wilms tumor, median age 6 years, were enrolled. Overall, the combination was well tolerated, with headache being the most common toxicity observed. There were no complete or partial responses. The median number of cycles administered was 1 (range 1–9). Four patients with neuroblastoma had stable disease for 12 or more weeks. Conclusions The combination of ATRA and IFN-α2a was inactive in children with relapsed or refractory neuroblastoma and Wilms tumor. The lack of activity with this combination in children with refractory neuroblastoma is similar to the disappointing phase 2 results of single agent 13-cis-retinoic-acid (13cRA) and does not support further development of ATRA for children with relapsed neuroblastoma. Pediatr Blood Cancer 2007;49:661–665. © 2006 Wiley-Liss, Inc.

Background B43-pokeweed antiviral protein (B43-PAP) is a high-affinity anti-CD19 immunotoxin that is capable of causing apoptotic death in B-lineage leukemic cells with a drug-resistant phenotype. B43-PAP exhibited in vivo antileukemic activity in preclinical studies as well as on a single-agent phase I clinical trial. This pediatric phase I/II study evaluated the toxicity profile and efficacy of B43-PAP immunotoxin in combination with standard induction chemotherapy in children and adolescents with relapsed CD19-positive B-lineage acute lymphoblastic leukemia (B-ALL). Pharmacokinetic profile and immunogenicity of B43-PAP were assessed. Experimental design B43-PAP in combination with standard 3 and 4-drug induction chemotherapy was administered on days 9-13 and 21-25 of a 28-day treatment course with vincristine, prednisone, L-asparaginase, daunomycin, and intrathecal methotrexate. Thirty patients with relapsed B-ALL were enrolled on study CCG-0957. Results Grade III/IV nonhematologic dose-limiting toxicities were encountered in 4 patients evaluable for toxicity and included myalgias, motor dysfunction, pulmonary toxicity, and elevated liver transaminase. Dose-limiting toxicities occurred only with the 4-drug regimen. Fourteen patients achieved a complete remission at the end of induction among the 20 patients evaluable for response. Conclusions B43-PAP in combination with standard induction chemotherapy can be safely administered and exhibits clinical antileukemic activity against relapsed B-ALL.

Although chemotherapy has improved outcome of osteosarcoma, 30-40% of patients succumb to this disease. Survivors experience substantial morbidity and mortality from anthracycline-induced cardiotoxicity. We hypothesized that the cardioprotectant dexrazoxane would (i) support escalation of the cumulative doxorubicin dose (600 mg/m(2)) and (ii) not interfere with the cytotoxicity of chemotherapy measured by necrosis grading in comparison to historical control data.Children and adolescents with nonmetastatic osteosarcoma were treated with MAP (methotrexate, doxorubicin, cisplatin) or MAPI (MAP/ifosfamide). Dexrazoxane was administered with all doxorubicin doses. Cardioprotection was assessed by measuring left ventricular fractional shortening. Interference with chemotherapy-induced cytotoxicity was determined by measuring tumor necrosis after induction chemotherapy. Feasibility of intensifying therapy with either high cumulative-dose doxorubicin or high-dose ifosfamide/etoposide was evaluated for "standard responders" (SR,98% tumor necrosis at definitive surgery).Dexrazoxane did not compromise response to induction chemotherapy. With doxorubicin (450-600 mg/m(2)) and dexrazoxane, grade 1 or 2 left ventricular dysfunction occurred in five patients; 4/5 had transient effects. Left ventricular fractional shortening z-scores (FSZ) showed minimal reductions (0.0170 ± 0.009/week) over 78 weeks. Two patients (1%) had secondary leukemia, one as a first event, a similar rate to what has been observed in prior trials. Intensification with high-dose ifosfamide/etoposide was also feasible.Dexrazoxane cardioprotection was safely administered. It did not impair tumor response or increase the risk of secondary malignancy. Dexrazoxane allowed for therapeutic intensification increasing the cumulative doxorubicin dose in SR to induction chemotherapy. These findings support the use of dexrazoxane in children and adolescents with osteosarcoma.

Purpose To determine whether the addition of ifosfamide and/or muramyl tripeptide (MTP) encapsulated in liposomes to cisplatin, doxorubicin, and high-dose methotrexate (HDMTX) could improve the probability for event-free survival (EFS) in newly diagnosed patients with osteosarcoma (OS). Patients and Methods Six hundred seventy-seven patients with OS without clinically detectable metastatic disease were treated with one of four prospectively randomized treatments. All patients received identical cumulative doses of cisplatin, doxorubicin, and HDMTX and underwent definitive surgical resection of the primary tumor. Patients were randomly assigned to receive or not to receive ifosfamide and/or MTP in a 2 × 2 factorial design. The primary end point for analysis was EFS. Results Patients treated with the standard arm of therapy had a 3-year EFS of 71%. We could not analyze the results by factorial design because we observed an interaction between the addition of ifosfamide and the addition of MTP. The addition of MTP to standard chemotherapy achieved a 3-year EFS rate of 68%. The addition of ifosfamide to standard chemotherapy achieved a 3-year EFS rate of 61%. The addition of both ifosfamide and MTP resulted in a 3-year EFS rate of 78%. Conclusion The addition of ifosfamide in this dose schedule to standard chemotherapy did not enhance EFS. The addition of MTP to chemotherapy might improve EFS, but additional clinical and laboratory investigation will be necessary to explain the interaction between ifosfamide and MTP.

PurposeThe objectives of this study were[colon] 1) to compare the time to hematologic recovery (absolute neutrophil count [lsqb]ANC[rsqb] [ge]1,000/mm3 and platelet count [ge]100,000/mm3) in a randomized prospective study of two doses of granulocyte colony-stimulating factor (G-CSF) (5.0 vs. 10.0 [m

PURPOSE The Children's Cancer Group (CCG) undertook a phase I study (CCG-0922) to determine a tolerable dose of idarubicin given with fludarabine and cytarabine in children with relapsed or refractory leukemia. The phase I study was extended to a limited phase II study to assess the activity of this combination in children with acute myelogenous leukemia (AML). PATIENTS AND METHODS This was a multiinstitutional study within the CCG. Eleven patients were entered onto the phase I study: seven with AML, three with acute lymphoblastic leukemia (ALL), and one with chronic myelogenous leukemia (CML). The maximal-tolerated dose (MTD) of fludarabine and cytarabine determined in a previous study was a fludarabine loading dose (LD) of 10.5 mg/m2 followed by a continuous infusion (CI) of 30.5 mg/m2/24 hours for 48 hours, followed by cytarabine LD 390 mg/m2, then CI 101 mg/m2/h for 72 hours. Idarubicin was given at three dose levels: 6, 9, and 12 mg/m2 intravenously (I.V.) on days 0, 1, and 2. The phase II portion of the trial included 10 additional patients with relapsed or refractory AML. RESULTS A dose of idarubicin 12 mg/m2/d for 3 days given in combination with fludarabine and cytarabine was tolerated. The major toxicity encountered was hematologic. Nonhematologic toxicities included transaminase elevations, hyperbilirubinemia, and infections. Eight of 10 patients with AML in the phase II portion (12 mg/m2 idarubicin) achieved a complete remission (CR). CONCLUSION This combination is active in patients with relapsed or refractory AML. The major toxicity encountered is hematologic. This regimen may be useful therapy for AML and should be compared with standard induction therapy in children with newly diagnosed AML.

Splenic abscess is an infrequent complication in the immunocompromised patient. Six patients underwent splenectomy for presumed splenic abscess from 1987 to 1991. Chemotherapy altered the immune system of four patients; the human immunodeficiency virus (HIV) rendered the other two vulnerable to infection. Five presented with fever but none had leukocytosis; only one exhibited palpable splenomegaly; three had abdominal pain. Cultures documented systemic infection in all but one, an HIV-positive individual. Respiratory embarrassment was the indication for surgery in one patient. In five cases the decision for surgical intervention was made after computed tomography (CT) indicated the presence of multiple splenic lesions and systemic antibiotics failed to resolve the fevers. CT additionally showed hepatic and/or renal microabscesses in four patients. Signs and symptoms experienced preoperatively resolved with splenectomy in all six patients. No additional surgery was required for the patients with extrasplenic abscesses. Surgical pathology determined that three spleens had fungal and two had mycobacterial abscesses. The other was shown to be a spindle cell sarcoma; no abscess was present. This patient had preoperative blood cultures positive for mycobacteria, and the same organism was recovered from retroperitoneal nodes sampled at the time of splenectomy for the sarcoma. Follow-up indicates that no patients experienced surgical complications or sequelae related to their splenic pathology. Splenectomy is necessary and effective in treating splenic abscesses in immunocompromised patients and is appropriate for diagnosis as well as therapy.

Pleuropulmonary blastoma (PPB) is a rare and highly aggressive tumor in children and is distinct from ordinary pulmonary blastoma or carcinosarcoma of the lung. This report describes the phenotypical characteristics of seven PPB tumors. The patients were five females and two males, all diagnosed in their third year of life. Five tumors were located within the pulmonary parenchyma, one in the mediastinum, and one involved both lung and mediastinum. Two children are alive and five have died of disease. Histologically, PPB showed a diffuse proliferation of undifferentiated blastemal cells with additional areas of chondroblastic foci (six tumors), storiform pattern (three tumors), alveolar pattern (one tumor), and lipoblastic differentiation (one tumor). Immunohistochemically, tumor cells were positive for vimentin in five of five tumors, histiocytic markers (A1AT and A1ACT, four of six cases; lysozyme, two of six; KP1, three of five) and myogenic markers (desmin, four of six; HHF35, five of six). S-100 was expressed in the chondroblastic areas (in three of four cases). Epithelial membrane antigen and cytokeratin were positive only in epithelial or mesothelial cells entrapped in the tumor. Ultrastructural examination demonstrated a similarity between the proliferating cells in PPB and those seen in malignant fibrous histiocytoma; that is, PPB tumor was mainly composed of a mixture of primitive, fibroblastic, myofibroblastic, histiocytoid, and fibrohistiocytoid cells. Also identified were cells with rhabdomyoblastic differentiation (two tumors) showing thick and thin filaments with Z-discs. In conclusion, PPB showed phenotypical diversity and was composed of MFH-type cells and cells with more specific mesenchymal differentiation.

Objective: Empirically based data support the validity of the distress thermometer recommended by the National Comprehensive Cancer Network as a standard screen for patient distress. However, the feasibility and utility of the distress thermometer has not been studied in the pediatric oncology setting. We conducted a study to: (1) investigate the validity of an adapted distress thermometer with pediatric oncology patients, (2) assess the degree of agreement among different respondents, including physician and psychosocial staff, with respect to (a) the pediatric cancer patient's distress and (b) the caregiver/parent's distress, and (3) to evaluate the relationship between distress levels and the psychosocial services provided to patients and families. Methods: Ninety-one patients and their English and Spanish-speaking caregivers were prospectively assessed at 3-month intervals for 1 year. The quantity of psychosocial services provided to each family was logged for a 12-month period. Results: Convergent validity was demonstrated by reasonable agreement between the pediatric distress rating tool and standardized measures. Additionally, the demographic and medical predictors of distress were consistent with previously reported findings using more extensive assessment. There was reasonable agreement among multiple raters of the child's distress; however, there was discrepancy between self-ratings of caregiver distress and psychosocial staff ratings of caregiver distress. This difference in perception impacted the quantity of psychosocial services provided following the baseline assessment. Conclusion: The single-item distress thermometer is a viable option as a rapid screening tool of patient and caregiver distress to help efficiently identify those who should be evaluated further. Copyright © 2010 John Wiley & Sons, Ltd.

PURPOSE Because there is a compelling need to develop new agents for intrathecal use, we investigated the safety, efficacy, and CSF pharmacokinetics of diaziquone (AZQ) following intrathecal administration in patients with refractory meningeal malignancies. PATIENTS AND METHODS Thirty-nine patients received 45 courses of intrathecal AZQ. Two schedules were studied; twice-weekly administration of a 1- or 2-mg dose and "concentration times time" (C x T) administration of 0.5 mg every 6 hours for three doses, administered once weekly. RESULTS Dose-limiting toxicity consisting of headache, nausea, or vomiting occurred in only three patients and only at the 2-mg, twice weekly dose. The schedules of 1 mg twice-weekly and 0.5 mg every 6 hours for three doses were well tolerated. Thirty-seven courses were assessable for response. The overall response rate was 62%. Complete responses (CRs) occurred in 14 of 37 courses (38%) and partial responses (PRs) occurred in nine of 37 courses (24%). Among patients with meningeal leukemia, CRs were observed in 11 of 26 courses (42%) and PRs in nine of 26 courses (35%). There was no difference in response rate related to dose or schedule. The pharmacokinetic behavior of intrathecally administered AZQ was characterized by biexponential disappearance from ventricular CSF, with mean half-lives of 18.2 and 78.6 minutes. The mean clearance rate was 0.37 mL/min. CONCLUSION Intrathecal AZQ is safe, well tolerated, and highly active against refractory meningeal malignancies.

A young girl with a history of chondroblastic osteosarcoma of the tibia developed a pulmonary metastasis which was treated by metastasectomy, chemotherapy and lung irradiation. There years later, at the age of 15, she developed a breast mass which was excised and which proved to be a poorly differentiated sarcoma. This was almost certainly a metastasis rather than a radiation-induced second primary tumour, in view of the short interval since radiotherapy. The ultrasonographic features of this lesion are presented here and the differential diagnosis is discussed in this context.

BACKGROUND. Effective chemotherapy is lacking for most types of central nervous system (CNS) tumors in children. Temozolomide, an agent with activity against adult brain tumors, was investigated in children and adolescents with recurrent CNS tumors. METHODS. Temozolomide was administered orally as monthly 5-day courses at doses of 200 mg/m 2 /d (patients with no prior craniospinal irradiation [CSI]) or 180 mg/m 2 /d (prior CSI). Patients with a complete (CR) or partial (PR) response or stable disease (SD) could continue temozolomide for up to 12 cycles. RESULTS. The cohort comprised 122 patients, including 113 with CNS tumors. Median age was 11 years (range, 1–23 years). Among 104 evaluable patients with CNS tumors, 5 PRs and 1 CR were observed. PRs occurred in 1 of 23 evaluable patients with high-grade astrocytoma, 1 of 21 with low-grade astrocytoma, and 3 of 25 with medulloblastoma/primitive neuroectodermal tumor (PNET). The CR occurred in an additional patient with medulloblastoma/PNET. No responses were observed in patients with ependymoma, brain-stem glioma, or other CNS tumors. Notably, 41% of patients with low-grade astrocytoma had SD through 12 courses. The most frequent toxicities were grade 3 or 4 neutropenia (19%) and thrombocytopenia (25%); nonhematologic toxicity was infrequent. CONCLUSIONS. Although overall objective responses were limited, further exploration of temozolomide may be warranted in children with medulloblastoma and other PNETs, or in patients with low-grade astrocytoma, perhaps in a setting of less pretreatment than the patients in the current study, or in the context of multiagent therapy. Cancer 2007;110:1542–50. � 2007 American Cancer Society.

BACKGROUND. Patients with metastatic osteosarcoma have a poor prognosis. The objectives of the study were to determine the antitumor activity and toxicity of topotecan (daily ×5) in newly diagnosed patients with metastatic osteosarcoma followed by chemotherapy (ifosfamide, carboplatin, etoposide [ICE], alternating with cisplatin and doxorubicin [CD]). METHODS. Newly diagnosed patients (≤30 years of age) with extensive metastatic disease (primary and ≥5 pulmonary nodules and/or bone metastases) with normal hepatic, renal, and cardiac function were eligible. Patients were eligible to receive further topotecan after standard chemotherapy if they exhibited a response. Twenty-eight patients were enrolled. Seventeen had metastases to the lung only and 11 had metastases to the bone or multiple sites. Of 28 patients enrolled, 27 could be evaluated for response. A limited dose escalation was incorporated. RESULTS. No responses were seen in the 11 patients treated at 3 mg/m2/day. One partial response (PR) and 1 clinical response (CLR) were reported among 15 patients who received topotecan at 3.5 mg/m2/day. No dose-limiting toxicity was observed. Principal nondose-limiting toxicities were hematologic and gastrointestinal. The 2- and 5-year event-free survival rates were low, 7% and 4%, respectively, but the 2- and 5-year overall survival rates were 44% and 22%, respectively. CONCLUSIONS. Topotecan at dose of 3.5 mg/m2/day can be safely administered upfront to newly diagnosed patients without excessive toxicity. Insufficient activity was seen with topotecan in this schedule to warrant further studies in osteosarcoma. The combination of ICE and CD was tolerable when delivered after initial topotecan therapy. Cancer 2007. © 2007 American Cancer Society.

Objective: To describe platinum-based chemotherapy combined with local treatment modalities as an alternative to external beam radiotherapy for intraocular retinoblastoma. Design: Platinum levels were measured by atomic absorption analysis in the tumors of 2 patients with retinoblastoma given carboplatin 5 or 2.5 hours before enucleation. Platinum levels in heated vs nonheated Greene melanoma tumors in rabbits were compared. A retrospective review of 172 affected eyes in 136 consecutive patients treated for retinoblastoma between January 1990 and December 1995 was performed. From 1990 to 1992, all treatable eyes initially received systemic carboplatin, 560 mg/m 2 , followed by 15 to 30 minutes of continuous diode laser hyperthermia (thermochemotherapy). Since 1992, larger tumors were treated initially with 3 monthly cycles of carboplatin, etoposide, and vincristine sulfate to reduce tumor volume (chemoreduction) followed by sequential aggressive local therapy (SALT) during examinations under anesthesia every 2 to 3 weeks. Outcome Measure: Treatment success was defined as eradication of tumor without enucleation or external beam radiotherapy. Results: Significant therapeutic platinum levels were measured in the human tumors 2.5 and 5 hours after carboplatin administration. Increasing the temperature by 9°C for 15 minutes doubled platinum levels in the rabbit model. Of the 38 eyes with Reese-Ellsworth group 1 through 5b tumors that were treated primarily with thermochemotherapy, all 24 eyes with group 1 and 2 tumors were treated successfully and two of the 4 eyes with group 3 tumors and all 10 eyes with group 5b tumors were treated unsuccessfully. Chemoreduction plus SALT was the primary treatment in 35 eyes and was successful in all 10 eyes with group 1 through 4 tumors and unsuccessful in all 7 eyes with extensive subretinal seeding and all 18 eyes with group 5b tumors with vitreous seeding. Seventy patients received carboplatin or carboplatin, vincristine, and etoposide, with myelosuppression, occasionally associated with bacteremia, being the main side effect. Transfusions were required in 15% of patients. Radiation retinopathy occurred in all 6 eyes treated with iodine 125 plaques. Conclusions: Thermochemotherapy is successful primary treatment for Reese-Ellsworth group 1 and 2 retinoblastomas. For larger tumors in the absence of vitreous or extensive subretinal seeding, 3 cycles of chemoreduction followed by SALT eradicates residual viable tumor. Chemoreduction plus SALT was not successful in eyes with diffuse vitreous or extensive subretinal seeding. Prior chemotherapy increases the risk for radiation retinopathy following 125 I plaque therapy. External beam radiotherapy can safely be avoided in the primary treatment of Reese-Ellsworth groups 1 through 4 nondispersed retinoblastoma.

Pathologic features of eight cases of undifferentiated (embryonal) sarcoma of the liver (USL) in childhood were studied. Light microscopic examination showed a diffuse growth of spindle cells with occasional polygonal cells and multinucleated giant cells and also revealed focal areas of storiform pattern in four tumors, cambium layer formation in one tumor, and alveolar arrangement in one tumor. Immunohistochemical study showed positive staining of proliferating cells for suggestive histiocytic markers (A1AT in 6/6, A1ACT in 5/6, lysozyme in 4/6, and KP1 in 4/6) and for muscle markers (desmin in 4/6 and HHF35 in 3/6). Ultrastructural examination demonstrated that the individual tumors were composed of a mixture of cells having fibroblastic, histiocytoid, fibrohistiocytoid, myofibroblastic, and undifferentiated (primitive mesenchymal) morphologies. Also identified were cells with definite myoblastic morphology in three tumors: leio-myoblastic in one and rhabdomyoblastic in two. In conclusion, the tumor cells in USL show phenotypical diversity comparable to those of malignant fibrous histiocytoma with or without additional rhabdomyosarcomatous or leiomyosarcomatous differentiation.

10547 Background: The prognosis in metastatic or recurrent ESFT remains poor despite the success of multiagent chemotherapy for localized tumors. In a Children’s Oncology Group phase II study (Ped....

Commercially available 5-formyltetrahydrofolate (5-CHO-H4PteGlu) is chemically prepared in a reaction that introduces an asymmetric center at the 6 carbon, and hence is the mixture of diastereomers differing in chirality about this position. (6R)-5-CHO-H4PteGlu, the diastereomer that is not normally found in vivo, was prepared from folic acid. Folic acid was chemically reduced and (6R)-tetrahydrofolate (H4PteGlu) was obtained from the resultant (6R,S)-H4PteGlu by enzymatic consumption of the natural diastereomer of (6R,S)-5,10-CH2-H4PteGlu (reversibly formed from (6R,S)-H4PteGlu in the presence of formaldehyde) with Lactobacillus casei thymidylate synthase. The 5 position of purified (6R)-H4PteGlu was directly formylated in a carbodiimide-catalyzed reaction. The level of contamination of these preparations with the corresponding 6S diastereomers was estimated using the binding of fluorodeoxyuridylate to thymidylate synthase promoted by folate cofactor (for H4PteGlu) and by the growth of folate requiring bacteria (for 5-CHO-H4PteGlu). Purified preparations of (6R)-H4PteGlu promoted the binding of fluorodeoxyuridylate to L. casei thymidylate synthase (in the presence of formaldehyde) only at concentrations greater than 1000-fold higher than equiactive levels of (6S)-H4PteGlu. Likewise, the (6R)-5-CHO-H4PteGlu made by this method was 600 times less active as a growth factor for Pediococcus cerevisiae than was authentic (6S)-5-CHO-H4PteGlu. Hence, the minimum stereochemical purity of these preparations was 99.9% for (6R)-H4PteGlu and 99.8% for (6R)-5-CHO-H4PteGlu.

Dihydrofolate reuctase from human osteosarcoma cell lines resistant to Methotrexate (MTX) were examined. MTX resistance in TE85 osteosarcoma sublines was produced by exposing cells to gradually increasing concentrations of MTX. Cloned sublines of MTX-resistant cells are maintained in media containing 10−8 (TE85/F.8), 10−7 (TE85/R7), or 10−6M MTX (TE85/R6). Partial purification of human dihydrofolate reductase from both sensitive and resistant osteosarcoma cell lines was achieved using folate-sepharose affinity chromatography. Although the TE85/R6 cell line was 120-fold more resistant to MTX than the MTX-sensitive cells, the amplification of enzyme activity was only 3.3-fold. Monoclonal antibodies raised against dihydrofolate reductase from a MTX-resistant subline of L1210 murine leukemia cells (Proc. Am. Assoc. Cancer Res. 26:229, 1985) cross-reacted with reductases from human cells. Immunostaining with these antibodies was used to rapidly visualize elevated amounts of dihydrofolate reductase in MTX-resistant osteosarcoma cells. Further delineation of the exact mechanisms(s) accounting for the MTX resistance in these human osteosarcoma cells is currently under investigation.