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Biomedical subjects

P García-Miguel

Publications and source records attributed to P García-Miguel.

At least 19 recordsLinked to original sources
PubMed2001

Spectrum of germline RB1 gene mutations in Spanish retinoblastoma patients: Phenotypic and molecular epidemiological implications.

Mutation analysis of retinoblastoma is considered important for genetic counseling purposes, as well as for understanding the molecular mechanisms leading to tumors with different degrees of penetrance or expressivity. In the course of an analysis of 43 hereditary retinoblastoma Spanish patients and kindred, using direct PCR sequencing, we have observed 29 mutations; most of them (62%) have not been reported previously. Of the mutations, 69% correspond to nonsense mutations (mainly CpG transitions) and frameshifts, with the expected outcome of a truncated Rb protein that lacks the functional pocket domains and tail. The remainder corresponds to splicing mutations, most of them (62%) targeted to invariant nucleotides, with the predicted consequence of out of frame exon skipping. Two of the splicing mutations in our study were found associated to families with a low-penetrance phenotype. Additionally, most of the mutations affecting splice junctions corresponded to retinoblastoma cases of either sporadic or hereditary nature with delayed onset (32 months on average). In contrast, most of the nonsense and frameshift mutations are associated with an early age at diagnosis (8.7 months on average). These differences are discussed in the context of the relationships between genotype and low expressivity phenotype. The differences in the spectrum of RB1 mutations found in this and other European surveys are also discussed in the context of alternate DNA methylation and mismatch repair phenotypes.

Age of Onset↗
PubMed2001

Outcome of high-risk neuroblastoma using a dose intensity approach: improvement in initial but not in long-term results.

BACKGROUND: Stage 4 and MYCN amplified (MNA) neuroblastoma in children have a poor prognosis. Our aim was to increase initial and long-term response in this population. PROCEDURE: High-risk children were studied according to the International Neuroblastoma Staging System, then treated with high-dose cyclophosphamide and high-dose carboplatin, followed by surgery and autologous stem cell transplant or maintenance chemotherapy. RESULTS: From June 1992 to December 1998, 83 children were admitted in the study (72 stage 4> 1 year, 5 stage 4 MNA infants, and 6 MNA stage 3 children); tumor tissue was obtained from 73, MYCN was performed in 65, being amplified in 21 (32%). Induction chemotherapy was administered in the expected time in 35% of patients. Its toxicity was mainly hematologic followed by infections, and there were 3 chemotherapy-related deaths. Delayed surgery was performed on 60 patients with complete or >90% resection in 80% of cases. Chemotherapy plus surgery produced some response in 90% of patients, 53% were in CR/VGPR; 49 children received autologous SCT, and 16 received maintenance chemotherapy for 9 months. Follow-up ranges are 1-87 months, mean 30 months. S and EFS at 4 years are 0.33 (SD 0.02). CONCLUSIONS: High-dose cyclophosphamide and high-dose carboplatin are effective in the initial treatment of neuroblastoma; combined with surgery they produce some response in most patients. Nevertheless, the CR/VGPR rate reaches only 53%. Survival time has also been prolonged but most patients relapse with metastases.

Adolescent↗
PubMed2001

A microsatellite fluorescent method for linkage analysis in familial retinoblastoma and deletion detection at the RB1 locus in retinoblastoma and osteosarcoma.

Linkage analysis at the retinoblastoma locus (RB1) is essential for identifying individuals at risk and to offer adequate genetic counseling in familial retinoblastoma. It can also be used to detect large deletions involving RB1, which accounts for 15% of the genetic alterations in hereditary retinoblastoma. These studies are usually carried out with lengthy Southern blot analyses of relatively uninformative restriction fragment length polymorphisms. The authors report an alternative, reliable protocol for genotyping the RB1 locus using two pairs of highly informative intragenic and flanking microsatellites linked closely to the RB1 gene, and analysis of the fluorescent-labeled polymerase chain reaction products with automatic sizing technology. This methodology has successfully identified high risk carriers in five of the five pedigrees of familial retinoblastoma studied. In addition, gross deletions affecting the RB1 gene were identified in two of 12 sporadic bilateral retinoblastomas, and loss of heterozygosity at the RB1 locus has been detected in one of three osteosarcomas using the same experimental protocol. The described protocol is simpler and faster than conventional Southern blot methodologies and can identify a larger number of informative cases.

Bone Neoplasms↗
PubMed2000

Results of the cooperative protocol (N-III-95) for metastatic relapses and refractory neuroblastoma.

BACKGROUND: Prognosis of relapsed and refractory neuroblastoma is uniformly fatal; new therapeutic approaches are needed. PROCEDURE: Relapsed and refractory neuroblastoma patients were treated with continuous infusion chemotherapy combined with MIBG. RESULTS: Over 4 years, 35 heavily pretreated patients were registered, 29 with bone or/and bone marrow metastases. Grade 3 or 4 hematologic toxicity was frequent, without toxic deaths. Sixteen patients responded. The probability of 5-year overall survival was 0.19. CONCLUSIONS: This approach is feasible and toxicity manageable; it rescued some patients and prolonged their survival. It merits assay in newly diagnosed high-risk neuroblastoma patients.

3-Iodobenzylguanidine↗
PubMed1999

Prospective evaluation of the International Neuroblastoma Staging System (INSS) and the International Neuroblastoma Response Criteria (INRC) in a multicentre setting.

The aim of this study was to classify prospectively a series of neuroblastoma tumours according to the International Neuroblastoma Staging System (INSS) and the International Neuroblastoma Response Criteria (INRC) and to evaluate the difficulties and pitfalls involved in a multicentre setting. Each hospital provided their data for central review. The surgical procedures and their complications were reported. Kaplan-Meier estimates of survival and event-free survival were calculated according to stage and response to therapy. From June 1992 to December 1996, 194 patients were included in the study, with a mean age of 2 years. Initial studies were performed according to INSS recommendations without major problems. INSS stage was correctly applied to all patients except for 9 (95%). Post-operative complications were observed in 15 patients (8.3%). Response to therapy (INRC) was studied in 63 stage 4 patients, 11 of whom were not classified correctly (17%). Differences in survival according to stage (INSS) and group of response to therapy (INRC) were statistically significant (P < 0.001). In conclusion the INSS was easy to use and separated different prognostic groups. Surgical complications and mortality did not increase in this series because of using the INSS. The feasibility of INRC was evaluated in a small series of stage 4 patients and the designation of response was problematic in a relatively high proportion of cases. The prognostic value of the different responses was highly significant, but less informative than had been hoped for.

Child, Preschool↗
PubMed1998

Hematopoietic cell transplantation using plasma and DMSO without HES, with non-programmed freezing by immersion in a methanol bath: results in 213 cases.

A simplified cryopreservation method for bone marrow (BM) and peripheral blood progenitor cells (PBPC) was utilized in hematopoietic cell transplantation of 213 patients with hematological or solid neoplasms after ablative chemotherapy (187 with peripheral blood progenitor cells and 26 with bone marrow). Cells were cryopreserved, after addition of autologous fresh plasma with DMSO, without HES, by freezing to -80 degrees C in a methanol bath and non-programmed freezer. For the patients autotransplanted with PBPC, the median period necessary for recovery of more than 0.5 x 10(9)/l granulocytes was 11 days (range 6-44), and 15 (8-204) days were required to obtain more than 20 x 10(9)/l platelets. For the patients autotransplanted with BM, the median period necessary to recover >0.5 x 10(9)/l granulocytes was 12 days (range 9-33), and 24 (12-57) days to obtain more than 20 x 10(9)/l platelets. These results support this method as being very effective in achieving high-quality cryopreservation. The procedure, which uses a non-programmed freezer, simplifies and reduces enormously the cost of the technical measures currently in use, enabling its adoption in almost any clinical oncological institution.

Adolescent↗
PubMed1997

Mutational analysis of the p16 gene in human neuroblastomas.

Neuroblastoma is one of the most frequent tumors in infancy. We analyzed 26 neuroblastomas, two ganglioneuromas, and a neuroblastoma metastasis for mutations and homozygous deletions of the p16 (or MTS1 or CDKN2) gene by means of the polymerase chain reaction (PCR) in combination with the single-strand conformation polymorphism (SSCP) technique and by multiplex PCR analysis. We detected mobility shifts in the SSCP gels in seven cases in the 3 half of exon 2 (named exon 2C) of the p16 gene. By PCR amplification of this particular region and SacII restriction enzyme digestion, we confirmed that those cases had a known polymorphism at codon 140 of the p16 gene. Neither mutations nor homozygous deletions were detected. Our results confirm those of Beltinger et al. (Cancer Res 55:2053-2055, 1995), which showed no p16 mutations or homozygous deletions in 18 primary neuroblastomas and nine tumor-derived cell lines. We conclude that the common pattern of p16 inactivation by homozygous deletion or mutation does not seem to be relevant to the development of neuroblastomas.

Carrier Proteins↗
PubMed1995

Allelic status of chromosome 1 in neoplasms of the nervous system.

By using five highly polymorphic markers, the allelic status of chromosome 1 was established in a series of 236 tumors of the nervous system, including all major histologic subtypes: gliomas, meningiomas, neurinomas, neuroblastomas, medulloblastomas, etc. Loss of alleles at 1p was observed at significant frequencies in neuroblastomas (26% of cases), meningiomas (32%), and malignant gliomas (37%) (primarily oligodendrogliomas [94%]). This anomaly was also detected in two of 23 neurinomas, two of three neurofibrosarcomas, one primary lymphoma, and two metastatic tumors of the brain. The analysis of tumors displaying partial 1p deletions suggests the existence of two distinct regions, 1p36 and 1p35-p32, in which loci nonrandomly involved in the development of neurogenic neoplasms might be located.

Alleles↗
PubMed1995

The treatment of advanced neuroblastoma. Results of the Spanish Neuroblastoma Study Group (SNSG) studies.

The Spanish Neuroblastoma Study Group has conducted a study on advanced neuroblastoma (N-I-87), which included 33 stage III and 60 stage IV neuroblastoma children more than 1 year of age, enrolled between October 1987 and April 1992. They were staged according to Evans and treated with induction chemotherapy (IC) consisting of 3 courses of cyclophosphamide-doxorubicin alternating with 3 of high-dose cisplatin-teniposide. Evaluation after IC and surgery demonstrated an overall response rate of 88% for stage III and 69% for stage IV. In the latter, complete responses and good partial responses were 33 and 14%, respectively. After surgery, children received maintenance chemotherapy (all stage III except 2 and 30 stage IV) or autologous bone marrow transplantation (ABMT) (11 stage IV), the distribution was not randomised. Probability of survival at 5 years was 0.60 +/- 0.12 for stage III and 0.24 +/- 0.07 for stage IV. A significant difference in survival at 5 years was found between "good responders" and "non-responders" to initial chemotherapy.

Adolescent↗
PubMed1995

[Sensibility and specificity of N-myc oncogene with respect to other prognostic factors in 15 neuroblastomas].

Several biologic features of tumor cells correlate closely with a favorable or unfavorable outcome. To aid in assessing correlation in the various number of prognostic factors including the age, stage, VMA/HVA ratios, and the serum levels of NSE and ferritin, the histopathological features, ploidy, partial monosomy for the short arm of chromosome 1, and the tumor N-myc gene copy number, are examined. We determined the sensitivity and specificity of classical markers above the amplification of the N-myc oncogene. A striking new observation is the positive correlation between genomic amplification and some prognostic factors (stage, ferritin, NSE, pathologic anatomy and 1p deletion.

Brain↗
PubMed1994

No TP53 mutations in neuroblastomas detected by PCR-SSCP analysis.

We have analysed 29 neuroblastomas for TP53 mutations in exons 5 to 8 by means of the polymerase chain reaction in combination with the single-strand conformation polymorphism technique. We could not detect any mutation. These results indicate that, in contrast to the majority of tumors so far studied, TP53 mutations do not seem to be important for the development of neuroblastomas.

DNA, Neoplasm↗