PURPOSE: The normal function of tumor suppressor genes is thought to be related to their ability to regulate cell proliferation and the loss of such function presumably leads to malignant transformation by releasing the transformed cells from growth regulation. One approach to identify these tumor suppressor genes is by loss of heterozygosity (LOH) studies. The rationale of these studies is that the mutation of one allelic copy of a tumor suppressor gene followed by the loss of the remaining wild type allele will result in the total loss of the function of the tumor suppressor gene. Chromosomal loci with frequent LOH in malignant tumors is likely to contain tumor suppressor genes. We want to identify deletions of putative tumor suppressor gene loci in pediatric brain tumors by polymerase chain reaction (PCR)-based LOH studies using microsatellite polymorphic markers of chromosome 9, 22 and 17p as most frequent cytogenetic abnormalities involve chromosome 17p, 22 and 9 in pediatric brain tumors. MATERIAL AND METHOD: Blood and tumor samples were obtained from 12 pediatric brain tumor patients who were operated at Texas Children's Cancer Center from April 1996 to January 1997. The 12 tumors consist of 5 cases of medulloblastomas, 4 cases of juvenile pilocytic astrocytomas, and 1 case each of ependymoma, atypical teratoid rhabdoid tumor and desmoplastic infantile ganglioglioma. Genomic DNA extracted from blood and tumor tissues were amplified by PCR using [gamma-32P]ATP endlabeled primer pairs for the microsatellite polymorphic markers on chromosome 9, 22 and 17p which were D9S171, D9S169, D9S168, D9S165, D9S156, D9S110, D9S146, D9S971, D9S757,D9S176, D9S2105, D9S177, D9S2127, D9S1849, D9S1817, D22S303, D22S33, D22S315, D22S275, D22S299, D22S301, TOP1P2, PDGFB, D22S274, D22S304, D17S1866, D17S1810, D17S796, D17S1566 and D17S1574. The PCR products were separated by electrophoresis in a denaturing 6% polyacrylamide gel and exposed on X-ray films to analyze LOH. RESULTS: 1) There was no evidence of LOH on chromosome 9 in all 12 pediatric brain tumors. 2) Among 12 pediatric brain tumors, only one allelic loss on chromosome 22 (D22S274 : 22q13.31-22q13.33) was observed in an atypical teratoid rhabdoid tumor. 3) LOH for loci on chromosome 17p were detected in 6 cases (50%) of 12 various pediatric brain tumors including 4 cases of medulloblastomas and 1 case each of ependymoma and atypical teratoid rhabdoid tumor. Among 5 cases of medulloblastomas, 4 cases(80%) showed LOH on at least one of 5 markers of chromosome 17p. 4) There was no allelic loss on chromosome 9, 22 and 17p in juvenile pilocytic astrocytomas. CONCLUSION: Our data indicate that there may be a putative tumor suppressor gene located on chromosome 22q13.3 associated with tumorigenesis of atypical teratoid rhabdoid tumor, and other putative tumor suppressor genes located on chromosome 17p13.1-17p13.3 associated with tumorigenesis of medulloblastoma, ependymoma and atypical teratoid rhabdoid tumor. But we need to collect more pediatric brain tumor samples to be studied and allelotype the suggested LOH region in detail.
Alleles ; Astrocytoma ; Brain Neoplasms* ; Brain* ; Carcinogenesis ; Cell Proliferation ; Chromosome Aberrations ; Chromosomes, Human, Pair 22 ; Chromosomes, Human, Pair 9* ; DNA ; Electrophoresis ; Ependymoma ; Ganglioglioma ; Genes, Tumor Suppressor ; Humans ; Loss of Heterozygosity* ; Medulloblastoma ; Microsatellite Repeats ; Polymerase Chain Reaction ; Proto-Oncogene Proteins c-sis ; Rhabdoid Tumor ; Texas ; X-Ray Film

INTRODUCTIONUp to 30% of patients with rheumatoid arthritis (RA) respond inadequately to conventional non-biologic disease modifying antirheumatic drugs (nbDMARDs), and may benefit from therapy with biologic DMARDs (bDMARDs). However, the high cost of bDMARDs limits their widespread use. The Chapter of Rheumatologists, College of Physicians, Academy of Medicine, Singapore aims to define clinical eligibility for government-assisted funding of bDMARDs for local RA patients.

MATERIALS AND METHODSEvidence synthesis was performed by reviewing 7 published guidelines on use of biologics for RA. Using the modified RAND/UCLA Appropriateness Method (RAM), rheumatologists rated indications for therapies for different clinical scenarios. Points reflecting the output from the formal group consensus were used to formulate the practice recommendations.

RESULTSTen recommendations including diagnosis of RA, choice of disease activity measure, initiation and continuation of bDMARD and option of first and second-line therapies were formulated. The panellists agreed that a bDMARD is indicated if a patient has (1) active RA with a Disease Activity Score in 28 joints (DAS28) score of ≥3.2, (2) a minimum of 6 swollen and tender joints, and (3) has failed a minimum of 2 nbDMARD combinations of adequate dose regimen for at least 3 months each. To qualify for continued biologic therapy, a patient must have (1) documentation of DAS28 every 3 months and (2) at least a European League Against Rheumatism (EULAR) moderate response by 6 months after commencement of therapy.

CONCLUSIONThe recommendations developed by a formal group consensus method may be useful for clinical practice and guiding funding decisions by relevant authorities in making bDMARDs usage accessible and equitable to eligible patients in Singapore.

Antirheumatic Agents ; economics ; therapeutic use ; Arthritis, Rheumatoid ; drug therapy ; Financing, Government ; Humans ; Practice Guidelines as Topic ; Singapore

A biosynthetic gene cluster for the bioactive fungal sesterterpenoids variecolin ( 1) and variecolactone ( 2) was identified in Aspergillus aculeatus ATCC 16872. Heterologous production of 1 and 2 was achieved in Aspergillus oryzae by expressing the sesterterpene synthase VrcA and the cytochrome P450 VrcB. Intriguingly, the replacement of VrcB with homologous P450s from other fungal terpenoid pathways yielded three new variecolin analogues ( 5- 7). Analysis of the compounds' anticancer activity in vitro and in vivo revealed that although 5 and 1 had comparable activities, 5 was associated with significantly reduced toxic side effects in cancer-bearing mice, indicating its potentially broader therapeutic window. Our study describes the first tests of variecolin and its analogues in animals and demonstrates the utility of synthetic biology for creating molecules with improved biological activities.