A domain of DNA designated N-myc is amplified 20- to 140-fold in human neuroblastoma cell lines but not in cell lines from other tumor types. N-myc has now been found to be amplified in neuroblastoma tissue from 24 of 63 untreated patients (38 percent). The extent of amplification appears to be bimodal, with amplification of 100- to 300-fold in 12 cases and 3- to 10-fold in 10 others. Amplification was found in 0 of 15 patients with stage 1 or 2 disease, whereas 24 of 48 cases (50 percent) with stage 3 or 4 had evidence of N-myc amplification. These data indicate that N-myc amplification is a common event in untreated human neuroblastomas. Furthermore, N-myc amplification is highly correlated with advanced stages of disease (P less than 0.001) and with the ability to grow in vitro as an established cell line, both of which are associated with a poor prognosis.

https://science.sciencemag.org/content/sci/224/4653/1121.full.pdf

Amplification of N-myc in untreated human neuroblastomas correlates with advanced disease stage

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.

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

Transgenic mice bearing the cellular myc oncogene coupled to the immunoglobulin mu or kappa enhancer frequently develop a fatal lymphoma within a few months of birth. Since the tumours represent represent both immature and mature B lymphocytes, constitutive c-myc expression appears to be highly leukaemogenic at several stages of B-cell maturation. These myc mice should aid study of lymphoma development, B-cell ontogeny and immunoglobulin regulation.

The c- myc oncogene driven by immunoglobulin enhancers induces lymphoid malignancy in transgenic mice

From an acute B-cell leukemia cell line, a DNA probe was obtained that was specific for chromosome 18 and flanked the heavy chain joining region of the immunoglobulin heavy chain locus on chromosome 14. This probe detected rearrangement of the homologous DNA segment in the leukemic cells and in follicular lymphoma cells with the t(14:18) chromosome translocation but not in other neoplastic or normal B or T cells. The probe appears to identify bcl-2, a gene locus on chromosome 18 (band q21) that is unrelated to known oncogenes and may be important in the pathogenesis of B-cell neoplasms with this translocation.

https://science.sciencemag.org/content/sci/226/4678/1097.full.pdf

Cloning of the chromosome breakpoint of neoplastic B cells with the t(14;18) chromosome translocation

https://www.cell.com/cell/pdf/0092-8674(84)90077-1.pdf

Philadelphia chromosomal breakpoints are clustered within a limited region, bcr, on chromosome 22

We have previously demonstrated that translocations of VH genes from chromosome 14 to chromosome 8 and of the c-myc oncogene from chromosome 8 to chromosome 14 occur in Burkitt lymphomas with the t(8;14) chromosome translocation. An association of the c-myc gene with the Cμ immunoglobulin gene has been observed in some but not all Burkitt lymphomas studied previously. In the present study, we have investigated the organization of the human heavy chain locus and of the c-myc gene in the P3HR-1 Burkitt lymphoma cell line. Becuase mouse/P3HR-1 somatic cell hybrids that retain only the 14q+ chromosome and no other human chromosome contain the human Cμ and Cγ genes but not VH genes, we have concluded that the breakpoint on chromosome 14 in P3HR-1 cells is distal to Cμ and between Cμ and VH. Thus, the breakpoint of human chromosome 14 differs in different Burkitt lymphoma cell lines. We also found that the human c-myc oncogene translocated to chromosome 14 in the P3HR-1 cell line is not recombined with the Cμ gene. The breakpoint on human chromosome 8 may therefore also differ in different Burkitt lymphoma cell lines, because we have observed DNA rearrangement of the c-myc gene with the Cμ gene in only some of the Burkitt lymphoma cell lines studied elsewhere. Interestingly, high levels of transcripts of the c-myc oncogene were observed in Burkitt lymphomas with translocated c-myc oncogenes both rearranged and unrearranged. Therefore, the translocation of a c-myc oncogene to the heavy chain locus on human chromosome 14 is apparently sufficient for its transcriptional activation and may be an essential step in the pathway leading to neoplasia.

https://www.pnas.org/content/pnas/80/3/820.full.pdf

Transcriptional activation of the translocated c-myc oncogene in Burkitt lymphoma

We have investigated whether the translocated and the untranslocated human c-myc oncogenes of Burkitt lymphoma cells are equally or differentially expressed in host mouse B cells. The human c-myc mRNA levels in somatic cell hybrids between mouse plasmacytoma cells and Burkitt lymphoma cells with either the t(8;14) or the t(2;8) chromosome translocation were determined by using the nuclease S1 protection procedure. Although both the human parental lines and the hybrid cells carrying the translocated c-muc oncogene expressed high levels of human specific c-myc transcripts, the hybrid cells carrying the untranslocated c-myc gene on normal chromosome 8 did not contain human specific c-myc mRNA. These results suggest that the translocated human c-myc oncogene has escaped the normal transcriptional control to which the untranslocated c-myc gene remains subjected. This interpretation is also supported by the finding that the expression of the c-myc genes of lymphoblastoid cells and of HL-60 promyelocytic leukemia cells are repressed when they are transferred into a mouse plasmacytoma background. The ability of the translocated c-myc oncogene to escape the normal transcriptional control occurring in B cells may be important for the expression of B cell neoplasia in mouse and man. We have also transferred the Burkitt 14q+ chromosome carrying a translocated c-myc oncogene into mouse LM-TK- fibroblasts and studied the levels of human c-myc transcripts in the hybrids. Because the levels of human c-myc transcripts in the fibroblast hybrids are dramatically decreased in comparison to the plasmacytoma hybrids, we conclude that the levels of transcripts of the translocated c-myc oncogene depend on the differentiated state of the cells harboring the translocated chromosome.

https://www.jstor.org/stable/pdfplus/14475.pdf

Differential expression of the normal and of the translocated human c-myc oncogenes in B cells

Two human T-cell leukemias carrying a t(8;14)(q24;q11) chromosome translocation were studied for rearrangements and expression of the c-myc oncogene. For one leukemia, rearrangement was detected in a region immediately distal (3') to the c-myc locus; no rearrangements of c-myc were observed in the second case (DeF). However, studies with hybrids between human and mouse leukemic T cells indicated that in the leukemic cells of DeF, the breakpoint in chromosome 14 occurred between genes for the variable (V alpha) and the constant (C alpha) regions for the alpha chain of the T-cell receptor. The C alpha locus had translocated to a region more than 38 kilobases 3' to the involved c-myc oncogene. Since human c-myc transcripts were expressed only in hybrids carrying the 8q+ chromosome but not in hybrids containing the normal chromosome 8, it is concluded that the translocation of the C alpha locus 3' to the c-myc oncogene can result in its transcriptional deregulation.

https://science.sciencemag.org/content/sci/232/4752/884.full.pdf

Deregulation of c-myc by translocation of the alpha-locus of the T-cell receptor in T-cell leukemias

We have studied somatic cell hybrids between mouse myeloma and JI Burkitt lymphoma cells carrying a t(2;8) chromosome translocation for the expression of human kappa chains. and for the presence and rearrangements of the human c-myc oncogene and kappa chain genes. Our results indicate that the c-myc oncogene is unrearranged and remains on the 8q+ chromosome of JI cells. Two rearranged C kappa genes were detected: the expressed allele on normal chromosome 2 and the excluded kappa allele that was translocated from chromosome 2 to the involved chromosome 8 (8q+). The distribution of V kappa and C kappa genes in hybrid clones retaining different human chromosomes indicated that C kappa is distal to V kappa on 2p and that the breakpoint in this Burkitt lymphoma is within the region carrying V kappa genes. High levels of transcripts of the c-myc gene were found when it resided on the 8q+ chromosome but not on the normal chromosome 8, demonstrating that translocation of a kappa locus to region distal to the c-myc oncogene enhances c-myc transcription.

Translocation of an immunoglobulin kappa locus to a region 3' of an unrearranged c-myc oncogene enhances c-myc transcription.

In chronic myelogenous leukemias (CML) with the t(9;22)(q34;q11) chromosome translocation the breakpoints on chromosome 22 occur within a 58-kilobase segment of DNA referred to as "breakpoint cluster region" (bcr) The same cytogenetically indistinguishable translocation occurs in approximately 10% of patients with acute lymphocytic leukemias (ALL) In this study we have investigated the chromosome breakpoints in several cases of ALL carrying the t(9;22) translocation In three of five cases of ALL we found that the bcr region was not involved in the chromosome rearrangement and that the 22q11 chromosome breakpoints were proximal (5') to the bcr region at band 22q11 In addition, we observed normal size bcr and c-abl transcripts in an ALL cell line carrying the t(9;22) translocation We conclude, therefore, that if c-abl is inappropriately expressed in ALL cells without bcr rearrangements, the genetic mechanism of activation must be different from that reported for CML

https://www.pnas.org/content/pnas/83/6/1807.full.pdf

Abbas Ar-Rushdi

Papers

Transcriptional activation of the translocated c-myc oncogene in Burkitt lymphoma

Differential expression of the normal and of the translocated human c-myc oncogenes in B cells

Deregulation of c-myc by translocation of the alpha-locus of the T-cell receptor in T-cell leukemias

Translocation of an immunoglobulin kappa locus to a region 3' of an unrearranged c-myc oncogene enhances c-myc transcription.

Heterogeneity of chromosome 22 breakpoint in Philadelphia-positive (Ph+) acute lymphocytic leukemia.