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R C Seeger

Publications and source records attributed to R C Seeger.

At least 109 records · Page 6Linked to original sources
PubMed1987

Consistent N-myc copy number in simultaneous or consecutive neuroblastoma samples from sixty individual patients.

Amplification of the N-myc oncogene is detected in about 30% of untreated neuroblastomas. Amplification is associated with advanced stages of disease and rapid tumor progression. However, it was not known if the N-myc copy number was homogeneous in tumor tissue of an individual patient, or if it changed with time in vivo. Therefore, we have made 66 observations on multiple simultaneous or consecutive tumor samples from 60 patients with neuroblastoma. (a) Simultaneous samples were obtained from different areas of 31 tumor masses from 30 patients: a similar N-myc copy number (1-2, 3-10, or greater than 10) was found in all samples from each patient. (b) Simultaneous samples were obtained from different anatomical sites in ten patients. No difference in N-myc copy number was seen. (c) Finally, 25 patients had two or more tumor samples obtained over time. Thirteen patients had a single copy of N-myc in all samples, and 12 had consistent levels of amplification in all samples. Two of the latter cases had single copy of N-myc in a second-look surgery sample, but no tumor was evident histologically. This study demonstrates that the N-myc copy number in human neuroblastomas is usually consistent within a tumor, not only at different tumor sites, but also at different times in vivo. Overall, these findings suggest that N-myc amplification is an intrinsic biological property of a subset of neuroblastomas, and if amplification is going to occur, it is generally present at the time of diagnosis.

Child↗
PubMed1987

Delayed surgery and bone marrow transplantation for widespread neuroblastoma.

From 1983 to 1986, 21 patients with poor prognosis neuroblastoma were treated with bone marrow transplantation. This regimen included induction chemotherapy, delayed surgical resection, local irradiation, and intensive chemoradiotherapy followed by infusion of allogeneic or autologous marrow. This therapeutic approach resulted in a 57% long-term survival rate (follow-up: 14-48 months), which appears to be approximately three times superior to conventional chemotherapy in a comparable group of children. In addition, complete resection was possible in 11 of 17 patients operated on after induction therapy. Recurrence in the primary site after bone marrow transplantation occurred in only one of 18 evaluable patients. Thus, this approach almost always eradicates primary tumor in patients with neuroblastoma with advanced disease.

Adolescent↗
PubMed1987

Graft-vs-leukemia following bone marrow transplantation: a model of immunotherapy in man.

Considerable data in animals suggest an antileukemia reaction associated with transplantation of allogeneic bone marrow cells. In some instances, this graft-vs-leukemia (GVL) reaction may be distinct from graft-vs-host-disease (GVHD). Data in humans also support the concept of a GVL effect associated with bone marrow transplantation. These observations include an increased risk of leukemia relapse in identical twin transplants and in recipients of T-cell depleted allogeneic transplants, and a decreased risk of leukemia relapse in individuals who develop acute or chronic GVHD. Although indirect, these findings are among the most convincing evidence that the immune system plays a role against cancer in man. It may be possible to exploit this effect in other settings and with other cancers.

Animals↗
PubMed1986

Clinical implications of oncogene activation in human neuroblastomas.

Amplification of the oncogene N-myc has been identified in almost all human neuroblastoma cell lines tested. Eighty-nine primary neuroblastomas from untreated patients were studied to determine the frequency and clinical significance of N-myc amplification. Tumor DNA was analyzed by hybridization with the radiolabeled probe pNB-1 for N-myc. Amplification (3-300 copies) of the N-myc gene was found in 34 of the 89 tumors (38%). Amplification was not found in 8 Stage I or 5 Stage IV-S tumors, but it was found in 2 of 16 with Stage II, 13 of 20 with Stage III, and 19 of 40 with Stage IV tumors (P less than 0.01). Correlation of N-myc amplification with progression-free survival (PFS) indicated that N-myc amplification was associated with a worse prognosis (P less than 0.0001). The PFS at 18 months was 70%, 30%, and 5% for patients whose tumors had 1, 3-10, and more than 10 copies, respectively. Even within individual stages, the presence of N-myc amplification correlated with rapid progression. For instance, of 16 patients with Stage II disease, the 2 with N-myc amplification developed progressive disease rapidly, whereas only 1 of 14 without amplification progressed (P = 0.03). Similarly, those with Stage III and IV disease whose tumors have multiple copies of N-myc had a substantially worse prognosis. The correlation between N-myc amplification and age at diagnosis was also analyzed. Although N-myc amplification was detected in only 4 of 28 infants less than 1 year of age, compared to 30 of 61 older patients (P less than 0.005), this difference disappeared when corrected for disease stage. The results suggest that N-myc amplification is a powerful prognostic indicator, and that this gene may play an important role in the progression of certain neuroblastomas.

Age Factors↗
PubMed1986

Identification and characterization of the protein encoded by the human N-myc oncogene.

The human N-myc gene is related to the c-myc proto-oncogene, and has been shown to have transforming potential in vitro. Many studies have reported amplification of N-myc in human neuroblastoma and retinoblastoma cell lines. In primary tumors, amplification of the gene was found to correlate directly with behavior of the tumor. Specific restriction fragments of a partial complementary DNA clone of N-myc from LA-N-5 human neuroblastoma cells were placed into a bacterial expression vector for the purpose of producing antigens representative of the N-myc protein. Rabbits immunized with these antigens produced antisera that recognized a protein of 62-64 kilodaltons in neuroblastoma cells. By several criteria, this protein appears to be part of the same proto-oncogene family as the c-myc protein. Moreover, the antisera to fragments of this protein were capable of histochemically identifying malignant cells in clinical specimens.

Animals↗
PubMed1986

Gene amplification in human neuroblastomas: basic mechanisms and clinical implications.

Extrachromosomal double minutes (DM) and homogeneously staining regions (HSR) of metaphase chromosomes have been reported frequently in human neuroblastomas and tumor derived cell lines. We and other investigators have determined that virtually all DM- and HSR-bearing neuroblastoma cell lines have multiple copies of the oncogene N-myc. Circumstantial evidence suggests that the extrachromosomal DM may be the level at which amplification takes place, with subsequent linear integration into HSR. Indeed, DM may represent circular molecules. The global organization and fine structure of the amplified sequences remains to be determined, but the unit of amplification is probably between 2 X 10(5) and 2 X 10(6) base pairs (bp). In some cases, the process of amplification may involve somatic recombination with distant DNA segments. We have determined that N-myc amplification is a common finding in primary neuroblastomas from untreated patients. We identified N-myc amplification, ranging from 3- to 300-fold, in 34 of 89 cases (38%). N-myc amplification is found almost exclusively in tumors from patients with advanced stages of disease (stages III and IV, p less than 0.01). In addition, the presence of amplification is highly correlated with rapid tumor progression (p less than 0.001). Thus, amplification of the N-myc oncogene is a new intrastage prognostic factor, and N-myc amplification appears to play an important role in determining disease progression.

Cell Line↗
PubMed1986

Amplification units containing human N-myc and c-myc genes.

The amplification units in human tumors containing amplified myc genes were examined. The amplification unit in all cases consisted of a large genomic region coamplified with the coding region of the myc genes themselves. In eight independent neuroblastomas containing N-myc amplifications, the amplification unit was estimated to be 290 to 430 kilobases. This amplification unit was highly conserved among the different neuroblastomas, with some neuroblastomas containing almost identical units. In contrast, five tumor cell lines containing c-myc amplifications exhibited amplification units that were more variable in size (90 to 300 kilobases) and sequence content; at least three different patterns of c-myc amplification units could be discerned.

Brain Neoplasms↗
PubMed1986

Recipient immune-competent T lymphocytes can survive intensive conditioning for bone marrow transplantation.

Bone marrow transplantation is usually preceded by intensive chemotherapy and radiation therapy designed to completely eliminate recipient immune-competent cells that might reject the donor bone marrow. We show that seven of 14 bone marrow transplant recipients who received intensive conditioning retained circulating T lymphocytes that proliferate after incubation with interleukin 2 and phytohemagglutinin and function as effector cells in an in vitro model of graft rejection. These T cells may mediate graft rejection.

Adult↗
PubMed1986

Amplification and rearrangement of DNA sequences from the chromosomal region 2p24 in human neuroblastomas.

Seven DNA fragments which map to or very near human chromosome band 2p24 are shown to be differentially amplified in DNA from specific subsets of an enlarged series of human neuroblastoma cell lines and primary neuroblastomas. Of these DNA fragments, the probe NB-19-21 for the oncogene N-myc is the most frequently amplified, with a second expressed sequence (pG21) amplified in 9 of those 11 cell lines and 16 of those 25 tumors exhibiting amplification of N-myc. The remaining probes are in turn each amplified in progressively smaller, nested subsets of the cell lines and tumors in which both N-myc and pG21 are amplified. These data permit construction of models for the organization of a "neuroblastoma amplicon," i.e., an originally amplified DNA domain, with N-myc positioned most central and the other DNA fragments increasingly peripheral; comparable models result for the cell lines and the tumors. Five of the seven probes examined detect novel DNA fragments in these specimens, reinforcing previous observations that extensive DNA rearrangement can occur during DNA amplification in neuroblastoma cell lines and in primary neuroblastomas. Such rearrangements could contribute significantly to the evolution of the neuroblastoma amplicon in different specimens to progressively smaller units, preserving, in the limit, amplification of N-myc.

Base Sequence↗
PubMed1986

Model system for removing neuroblastoma cells from bone marrow using monoclonal antibodies and magnetic immunobeads.

Variables effecting removal of neuroblastoma cells from bone marrow using monoclonal antibodies and magnetic immunobeads were studied. Human neuroblastoma cell lines were labeled with the supravital DNA stain Hoechst 33342, seeded into normal bone marrow, incubated with monoclonal antibodies recognizing neuroblastoma cell surface antigens (HSAN 1.2, antibody 459, antibody 390, BA-1, and Leu-7), and then mixed with magnetic microspheres coated with goat anti-mouse immunoglobulin. Tumor cells that attached to the magnetic immunobeads were then removed from the marrow with magnets. The efficacy of tumor cell removal depended on the amount of monoclonal antibody bound to tumor cells and the immunobead/tumor cell ratio. In addition, two cycles of purging with both monoclonal antibodies and immunobeads was superior to one cycle. Using a cocktail of the five antibodies, 3 to 4 logs of tumor cells could be depleted from marrow with good recovery of viable hematopoietic cells.

Antibodies, Monoclonal↗
PubMed1985

Association of multiple copies of the N-myc oncogene with rapid progression of neuroblastomas.

Eighty-nine patients with untreated primary neuroblastomas were studied to determine the relation between the number of copies of the N-myc oncogene and survival without disease progression. Genomic amplification (3 to 300 copies) of N-myc was detected in 2 of 16 tumors in Stage II, 13 of 20 in Stage III, and 19 of 40 in Stage IV; in contrast, 8 Stage I and 5 Stage IV-S tumors all had 1 copy of the gene (P less than 0.01). Analysis of progression-free survival in all patients revealed that amplification of N-myc was associated with the worst prognosis (P less than 0.0001); the estimated progression-free survival at 18 months was 70 per cent, 30 per cent, and 5 per cent for patients whose tumors had 1, 3 to 10, or more than 10 N-myc copies, respectively. Of 16 Stage II tumors, 2 with amplification metastasized, whereas only 1 of 14 without amplification did so (P = 0.03). Stage IV tumors with amplification progressed most rapidly: nine months after diagnosis the estimated progression-free survival was 61 per cent, 47 per cent, and 0 per cent in patients whose tumors had 1, 3 to 10, or more than 10 copies, respectively (P less than 0.0001). These results suggest that genomic amplification of N-myc may have a key role in determining the aggressiveness of neuroblastomas.

Adolescent↗
PubMed1985

Altered expression of cell surface membrane antigens in a common acute lymphoblastic leukemia-associated antigen-expressing neuroblastoma cell line (SJ-N-CG) with morphological differentiation.

The expression of common acute lymphoblastic leukemia antigen (CALLA) on a human neuroblastoma cell line, SJ-N-CG, was demonstrated by indirect membrane immunofluorescence, complement-dependent cytotoxicity, and quantitative absorption, using two monoclonal antibodies (J-5 and BA-3) directed against CALLA. Immunoprecipitation of solubilized 125I-labeled membrane proteins from SJ-N-CG cells with J-5 antibody revealed a protein with a molecular weight of 100,000 as determined on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Morphological differentiation of SJ-N-CG cells could be induced in the presence of 2.0 mM dibutyryl adenosine 3'-5'-cyclic monophosphoric acid for 10 days of culture. Changes in cell surface membrane antigens associated with morphological differentiation were studied by indirect immunofluorescence and complement-dependent cytotoxicity using a panel of seven monoclonal antibodies. Increases in the antigens recognized by BA-2 (detecting leukemia-associated antigen), anti-Thy-1, and antibody 390 (Thy-1 antigen) were found in "differentiated cells," while those detected by BA-1 (B-cell-associated antigen) and J-5 (CALLA) were unchanged. In contrast, the antitransferrin receptor defined by B3/25 was inhibited, and expression of B7/21-defined la-like antigen was not induced. Kinetic studies on antigenic alterations showed that the expression of BA-2-defined antigen rose on Day 2 and remained at the same level until Day 10. The expression of CALLA was not changed from Days 2 to 10. The augmentation of Thy-1 antigen was noted on Day 4 and reached the maximum on Day 10. These results show that dibutyryl adenosine 3'-5'-cyclic monophosphoric acid is capable of inducing phenotypic changes in SJ-N-CG cells. The changes of expression of some antigens on exposure of cells to dibutyryl adenosine 3'-5'-cyclic monophosphoric acid may enable us to have a greater understanding of the differentiation of neuroblastoma to a more mature ganglioneuroblastoma phenotype.

Antibodies, Monoclonal↗