Genotypic analyses of Richter's syndrome
Article Abstract:
Richter's syndrome is defined as the occurrence of a diffuse lymphoma (malignancy involving lymph tissue) in a patient with chronic lymphocytic leukemia (CLL), perhaps following the diagnosis of CLL by months or years. Some investigators have suggested that the lymphoma represents an independent and unrelated tumor, while others have maintained that the lymphoma represents some sort of transformation or differentiation of the leukemic cells. It has been possible to resolve this question by making use of the genetic rearrangements that occur in lymphocytes. In the process of developing the enormous variety of possible antibody molecules, or T-cell receptors, the corresponding genes within the lymphocytes are chopped up and rearranged in a unique way. Therefore, two sets of lymphocytes arising from different sources would be exceedingly unlikely to share gene rearrangements. When such analyses are performed, it is found that the genetic rearrangements found in the lymphoma cells are identical to those demonstrated in the leukemic cells. This indicates that the two sets of cells have a common origin. The authors present two more cases of Richter's syndrome and their molecular biological analysis. In both cases, the rearrangements of the immunoglobulin genes were identical for both the leukemic cells and the lymphomas, indicating that the cells in these cases had a B cell heritage and confirming the relatedness of the two conditions in this syndrome. However, in one patient it was found that a rearrangement of the T cell receptor genes, which could be identified in the lymphoma, was not present in the leukemic cells. This unusual observation might have several explanations. The original malignant cell may have been pluripotent, that is, capable of giving rise to both T and B cells. The observed rearranged genes might actually represent a clonal population of T cells which has arisen from a population of T cells responding to the lymphoma. However, the authors consider the most likely explanation to be that an unusual clone of cells, containing a rearrangement of T cell receptor genes, has arisen from among the proliferating B cell lymphoma cells. (Consumer Summary produced by Reliance Medical Information, Inc.)
Publication Name: Cancer
Subject: Health
ISSN: 0008-543X
Year: 1991
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Tumor suppressor genes, tissue pattern control, and tumorigenesis
Article Abstract:
Tumor supressor genes or recessive oncogenes can cause cancer when their functions are lost. It is hypothesized that these oncogenes are developmental regulatory genes that trigger a series of downstream genes, which induce stem cells and their progeny to express certain phenotypic features. Incomplete and incorrect expression of the tumor suppressor genes result in loss of identification receptors such that cells may continue to appear undifferentiated or would be more heterogenous. These cells eventually proliferate and metastasize into surrounding normal tissues.
Publication Name: Perspectives in Biology and Medicine
Subject: Health
ISSN: 0031-5982
Year: 1992
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