Defining key signaling nodes and therapeutic biomarkers in NF1-mutant cancers.

UNLABELLED: NF1 encodes a RAS GTPase-activating protein. Accordingly, aberrant RAS activation underlies the pathogenesis of NF1-mutant cancers. Nevertheless, it is unclear which RAS pathway components represent optimal therapeutic targets. Here, we identify mTORC1 as the key PI3K effector in NF1-mutant nervous system malignancies and conversely show that mTORC2 and AKT are dispensable. However, we find that tumor regression requires sustained inhibition of both mTORC1 and MEK. Transcriptional profiling studies were therefore used to establish a signature of effective mTORC1-MEK inhibition in vivo. We unexpectedly found that the glucose transporter GLUT1 was potently suppressed, but only when both pathways were inhibited. Moreover, unlike VHL- and LKB1-mutant cancers, reduction of (18)F-FDG uptake required the suppression of both mTORC1 and MEK. Together, these studies identify optimal and suboptimal therapeutic targets in NF1-mutant malignancies and define a noninvasive means of measuring combined mTORC1-MEK inhibition in vivo, which can be readily incorporated into clinical trials. SIGNIFICANCE: This work demonstrates that mTORC1 and MEK are key therapeutic targets in NF1-mutant cancers and establishes a noninvasive biomarker of effective, combined target inhibition that can be evaluated in clinical trials.

Challenges with defining response to antitumor agents in pediatric neuro-oncology: a report from the response assessment in pediatric neuro-oncology (RAPNO) working group.

Criteria for new drug approval include demonstration of efficacy. In neuro-oncology, this is determined radiographically utilizing tumor measurements on MRI scans. Limitations of this method have been identified where drug activity is not reflected in decreased tumor size. The RANO (Response Assessment in Neuro-Oncology) working group was established to address limitations in defining endpoints for clinical trials in adult neuro-oncology and to develop standardized response criteria. RAPNO was subsequently established to address unique issues in pediatric neuro-oncology. The aim of this paper is to delineate response criteria issues in pediatric clinical trials as a basis for subsequent recommendations.

Influence of O6-methylguanine-DNA methyltransferase activity on chloroethylnitrosourea chemotherapy in brain tumors.

Chloroethylnitrosoureas (CENUs) alkylate DNA at specific sites and inhibit DNA replication in tumor cells. O6-Alkylguanine moieties resulting from alkylation of guanine bases are thought to be one of most lethal adducts in living cells. Effectiveness of CENUs is known to relate well with an enzymic activity of the DNA repair enzyme O6-methylguanine-DNA methyltransferase (MGMT), which recognizes and removes O6-alkylguanine. To improve therapeutic results of CENUs, we have measured MGMT activity of human brain tumors and studied the relationship between MGMT activity and clinical responsiveness to I-(4-amino-2-methyl-5-pyrimidinyl)methyl-3-(2-chloroethyl)-3-nitrosourea hydrochloride (ACNU). Thirty-seven patients with brain tumors were entered into the study. The neoplasms included gliomas, non-glial tumors, and brain metastases. The MGMT activity of gliomas was significantly lower than that of non-glial tumors and brain metastases. No significant difference in the enzyme activity was noted between low- and high-grade gliomas. Out of the 22 gliomas 5 tumors indicated a value below 60 fmol/mg, suggestive of a methyl excision repair minus (Mer-) tumor. Two out of 3 evaluable patients with a Mer- tumor responded well to post-operative ACNU adjuvant chemotherapy. Our results suggest that brain tumors include a certain percentage of Mer- phenotype tumors, and that CENUs such as ACNU should be applied selectively on tumors with a low MGMT activity in order to increase the therapeutic effectiveness.

Phase II study of ifosfamide in childhood brain tumors: a report by the French Society of Pediatric Oncology (SFOP).

Forty-two evaluable pediatric patients with a variety of recurrent primary brain tumors participated in a phase II ifosfamide trial. Their mean age was 10 years. All patients were treated with ifosfamide, 3 g/m2/day for 2 days every 2 weeks. Response was assessed on clinical and radiological criteria after at least 2 courses of therapy. The overall response rate was 12% (5/42). One complete and 2 partial responses were documented in 21 patients with medulloblastoma. A partial response was demonstrated in 1 patient with primitive neurectodermal tumor (PNET) and in 1 patient with ependymoma. No activity was observed in astrocytic tumors. Toxicity was primarily neurologic (16 out of 54 patients, 30%). Hematological toxicity, without severe morbidity, was encountered in 9% of courses (16/179). Ifosfamide, administered at this dose regimen has modest efficacy in the treatment of recurrent childhood medulloblastoma and ependymoma and appears inactive for gliomas. Further trials with other dose schedules are necessary to assess the activity of this drug. However, according to the neurotoxicity observed in our trial, we would not recommend building a protocol using ifosfamide for highly progressive brain tumors.

A potential role for intensive chemotherapy in the treatment of small cell neuroendocrine tumors of the cervix.

Small cell neuroendocrine (SCNE) tumors of the cervix constitute a group of malignancies with a predilection for early systemic metastasis which likely contributes to the poor outcome reported to date. Histologic and immunocytochemical similarities exist between SCNE cervical tumors and small cell (oat cell) tumors of the lung. Notable clinical responses to chemotherapy have been reported in both small cell lung tumors and in poor-risk squamous cervical cancers, suggesting the potential for a similar role in the management of SCNE cervical tumors. In this report, four cases are described in which intensive chemotherapy with etoposide, doxorubicin, and cisplatin was used in patients with SCNE tumors. Marked reduction in tumor volume was a feature in three evaluable patients, two of whom received neoadjuvant therapy (one complete and one near-complete pathologic response). The fourth patient received adjuvant chemotherapy and remains without evidence of disease 47 months from diagnosis. Management details of each case have been provided along with a review of the use of chemotherapy in SCNE cervical tumors.

New xenograft model for assessing experimental therapy of central nervous system tumors: human glioblastoma in the intrathecal compartment of the nude mouse.

Ten congenitally athymic "nude" mice and 10 immunocompetent mice underwent intrathecal inoculation with a human glioblastoma cell line (U87MG) via percutaneous lumbar puncture (5 x 10(5) cells/animal). All of the nude mice developed paraplegia with or without incontinence at 2 weeks and routinely died of inanition 3 weeks postimplantation. Histological examination confirmed extensive proliferation of neoplastic cells within the intrathecal space. A second group of animals was inoculated with 5 x 10(4) cells/animal: 20 nude mice, 10 cyclosporine A-immunosuppressed animals, and 10 immunocompetent control mice. The 20 mice were further divided into four subsets. Subset A did not receive chemotherapy, Subset B received 200 mg of carmustine (BCNU) per m2 by intraperitoneal injection, Subset C received a single dose of 4 mg of methotrexate (MTX) per m2 by intrathecal injection 4 hours after tumor inoculation, and Subset D received 12 mg of intrathecal MTX per m2. Decreasing the concentration of cells per animal by 1 log doubled the time interval required for the development of paralysis and incontinence to 4 weeks. Treatment with intrathecal MTX at a dose of 4 mg/m2 extended the symptom-free period by an additional week (to 5 weeks postinoculation), and a dose of 12 mg/m2 allowed an average of 6 weeks before the onset of neurological impairment. The xenografts did not grow in the immunocompetent control mice, the BCNU-treated group, or the cyclosporine A-immunosuppressed animals. An intrathecal xenograft model of central nervous system malignancies allows a novel approach to the evaluation of experimental chemotherapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Examination of newly synthesized 2-chloroethylnitrosoureas in preterminal leukemia L 5222 and in two transplanted neurogenic tumors.

The chemotherapeutic activities of 11 chloroethylnitrosoureas, among them 10 newly synthesized compounds, were investigated in rat leukemia L 5222 and in two neurogenic rat tumors. 1-(4-Amino-2-methyl-5-pyrimidinyl)-methyl-3-(2-chloroethyl)-3-nitrosourea hydrochloride (ACNU, compound 1) and cyclophosphamide (12) served as reference substances. The newly synthesized compounds were 1-(2-chloroethyl)-1-nitroso-3-(2-carboxyethyl)-urea (2-carboxyethyl-CNU, 2), 1-(2-chloroethyl)-1-nitroso-4-methyl-4-formyl-semicarbazide (methyl-formyl-amino-CNU, 3), 1-(2-chloroethyl)-1-nitroso-3-(methylene-2-pyridyl)-urea(methylene-2-pyridyl- CNU, 4), 1-(2-chloroethyl)-1-nitroso-3-(methylene-2-pyridyl)-urea hydrochloride (methylene-2-pyridyl-CNU . HCl, 5) 1-(2-chloroethyl)-1-nitroso-3-(methylene-4-pyridyl)-urea hydrochloride (methylene-4-pyridyl-CNU . HCl, 6), 1-(2-chloroethyl)-1-nitroso-3-(3-pyridino)-urea (pyridyl-3-CNU, 7), 1-(2-chloroethyl)-1-nitroso-3-(3-pyridyl)-urea hydrochloride (pyridyl-3-CNU . HCl, 8), 1-(2-chloroethyl)-1-nitroso-3-[4(2,6-dimethyl-morpholino)]-urea (dimethyl-morpholino-CNU, 9), 1-(2-chloroethyl)-1-nitrosocarbamoyl-morpholine (chloroethyl-nitroso-carbamoyl-morpholine, 10), 1-(2-chloroethyl)-1-nitroso-carbamoyl-2,6-dimethyl-morpholine (chloroethyl-nitroso-carbamoyl-dimethylmorpholine, 11). Against both neurogenic tumors cyclophosphamide was distinctly superior to all nitrosoureas. In leukemia L 5222 all nitrosoureas except compounds 7, 8, 11 effected cures. Remarkable differences in toxicity could be observed between the nitroso compounds investigated.

[Chemotherapy of transplanted neurogenic tumors in the rat (author's transl)]. / Chemotherapie-Versuche an transplantierten neurogenen Tumoren der Ratte.

1. After s.c. and intracerebral (i.c.) inoculation, 4 neurogenic tumors of the rat (3 malignant neurinomas, 1 polymorphcellular glioma) revealed an altogether weak response towards a monotherapy with 1,3-bis(2-chloroethyl)-1-nitrosourea(BCNU), 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU), 1-(2-chloroethyl)-3-(4-Methylcyclohexyl)-1-nitro sourea (MeCCNU), 1-(2-hydroxyethyl)-3-(2-chloroethyl)-3-nitrosourea (OH-ethyl-CCNU), 2-[3-(2-chloroethyl)-3-nitrosoureidol]-D-glucopyranose (chlorozotocin), 5-(3,3-dimethyl-1-triazeno)-imidazol-4-carboxamide (DTIC). Cyclophosphamide (CPA) which was investigated for comparison showed the greatest therapeutic activity; in an equitoxic dosage (less than or equal to LD10), in all 4 s.c. tumors, partial or complete regression were effected only by CPA. 2. If the passage number increases, the response of transplanted neurogenic rat tumors to monochemotherapy can both increase and decrease. 3. In the monotherapy of 3 malignant neurinomas we were unable, on the whole, to observe a higher sensitivity after s.c. inoculation as compared with an i.c. inoculation of the tumor, despite a varying effectiveness of the single substances. 4. In the monotherapy of the polymorphcellular glioma a better response of the i.c. inoculated tumor was recognizable compared to the s.c. inoculated tumor. 5. A combination chemotherapy of a malignant neurinoma after s.c. and i.c. inoculation with vincristine, CPA, OH-ethyl-CNU and MeCcNU yielded a significant increase in life-span of animals with i.c. tumor, whereas s.c. tumors showed no significant growth inhibition. y. Transplanted neurogenic tumors of the rat could serve at less sensitive models for the investigation of new nitrosoureas.

[The chemotherapy of tumors of the central nervous system (author's transl)]. / La chemioterapia delle neoplasie del sistema nervoso centrale

The rational application of chemotherapy in tumors of the central nervous system is discussed in particular the use of the new derivatives of nitrosourea: BCNU (1-3 bis-(2-cloroetil) 1-nitrosourea) and CCNU (cloroetil-cicloesil-nitrosourea). The results of therapy with antimetabolites, alkylating agents, antibiotics, and plant alcaloids, are reported as well as those obtained with radio - sensitizing substances (containing B10 or BUdR, IUdR, FUdR). The results obtained in the United States and in Japan with BCNU and CCNU are considered as well as the personal data of 43 cases treated with BCNU and 10 cases treated with CCNU (including intracranial glial tumors, spinal glial tumors and metastatic tumors of the central nervous system).