Genomic rearrangements of the c-myc proto-oncogene in human malignant lymphomas

c-myc mRNA expression in non-Hodgkin's lymphomas

Steady state c-myc mRNA levels determined by Northern blot analysis were examined in non-Hodgkin's lymphomas (NHL) of both high (n = 29) and low malignancy (n = 18), and in non-specific chronic lymphadenitis (n = 6). High grade NHL, classified according to the updated Kiel classification, revealed significantly larger amounts of c-myc mRNA compared with low grade NHL and lymphadenitis. mRNA levels in non-specific lymphadenitis were lower than in low grade NHL, but the differences were not statistically significant. No correlation between c-myc mRNA levels and the immunologic phenotype was discernible. Growth fractions of the NHL were determined by immunostaining with the monoclonal antibody Ki-67. Significant correlations between the percentages of Ki-67-positive cells, as well as the amounts of c-myc mRNA, and classification into high or low grade NHL were found. However, the percentage of Ki-67 positive cells and c-myc mRNA levels in individual cases and in the various histologic entities of NHL did not correlate. Our results indicate the overexpression of the c-myc gene in NHL, and a highly significant correlation of steady state c-myc mRNA levels with the prognosis-related histomorphologic Kiel classification of NHL into different subgroups of low and high grade malignancy.

Epstein-Barr virus infection rapidly progressing to monoclonal lymphoproliferative disease in a child with selective immunodeficiency

We report on a 30-month-old previously healthy Turkish boy who presented with fever, hepatosplenomegaly and generalized lymphadenopathy. He died 4 months after admission in spite of treatment with steroids, acycloguanosine and cyclophosphamide. Epstein-Barr virus (EBV) DNA was detected in the patient's bone marrow and in a lymph node biopsy. Cells from the lymph node biopsy showed monoclonal rearrangements of immunoglobulin heavy chain genes but no rearrangements of T-cell receptor beta-chain genes or immunoglobulin kappa chain genes. Serological data indicated chronic active EBV infection. There was a slight increase of CD8 positive cells in peripheral blood and a normal response to T-cell mitogens. However, T-cell lines established with interleukin 2 from lymph node biopsy completely failed to kill autologous EBV-transformed B-cells and K 562 target cells. Moreover, in regression tests the patient's peripheral blood mononuclear cells completely failed to limit outgrowth of autologous EBV infected B-cells. We conclude that the patient's selective immuno-deficiency had led to the rapid development of EBV-associated monoclonal lymphoproliferation.

What's new in the application of Southern blot analysis of malignant lymphomas?

With the introduction of gene probes for the immunoglobulin and T cell receptor gene segments and the use of the Southern Blot Analysis a new method for the diagnostic characterization of malignant lymphomas was established. Although the method is not absolutely specific for the determination of lineage and clonality of a given lymphoid neoplasm, it provides a lot of additional information for the pathologist. It is the first method that gives proof to the clonality of T cell lymphomas; reactive lymph node processes can be distinguished from true neoplasms; within lymph nodes of mixed lymphoid populations the clonally proliferated can be detected and the lineage can be determined. Therefore the Southern Blot Analysis is a method that should be applied for the diagnosis of malignant lymphomas together with histology and immunohistochemistry. Using the combination of all these methods an extensive characterization of lymphoid neoplasms can be made.

The c-ets-1 proto-oncogene is rearranged in some cases of acute lymphoblastic leukaemia

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The role of the oncogene c-myc in sporadic large bowel cancer and familial polyposis coli

The human myc gene is homologous to the v-myc gene, which was discovered in the avian oncogenic retrovirus MC29. Abnormally high expression of the cellular oncogenes is suspected to be involved in nonviral carcinogenesis. This article reviews the evidence that elevated expression of the human myc gene is involved in sporadic colon carcinoma and familial polyposis coli. The abundance of myc RNA and protein is frequently higher in colorectal cancer than in normal mucosa. The mechanism of this altered expression is obscure because the structure and quantity of myc DNA are very rarely disturbed. The COLO320 cell line is discussed as one unusual example of myc DNA rearrangement and amplification. There is a correlation between tumor-specific elevated myc RNA level and location in the bowel; tumors distal to the transverse colon are more likely to have elevated myc expression. The site distribution of unselected colorectal malignancies with an elevated myc RNA level is similar to the site distribution of familial polyposis coli tumors. With this observation it is suggested that elevated myc RNA may be a marker of a distinct type of colorectal cancer that involves the same genetic events as precede familial polyposis coli cancer.