KhédOudja Nafa

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired clonal disorder of the hematopoietic stem cell (HSC). Somatic mutations in the PIG-A gene result in the deficiency of several glycosylphosphatidylinositol-linked proteins from the surface of blood cells. This explains intravascular hemolysis but does not explain the mechanism of bone marrow failure that is almost invariably seen in PNH. In view of the close relationship between PNH and idiopathic aplastic anemia (IAA), it has been suggested that the 2 disorders might have a similar cellular pathogenesis, namely, that autoreactive T-cell clones are targeting HSCs. In this paper, we searched for abnormally expanded T-cell clones by size analysis of the complementarity-determining region 3 (CDR3) in the beta variable chain (BV) messenger RNA (mRNA) of the T-cell receptor (TCR) in 19 patients with PNH, in 7 multitransfused patients with hemoglobinopathy. and in 11 age-matched healthy individuals. We found a significantly higher degree of skewness in the TCR BV repertoire of patients with PNH, compared with controls (R(2) values 0.82 vs 0.91, P <.001). The mean frequency of skewed families per individual was increased by more than 2-fold in patients with PNH, compared with controls (28% +/- 19.6% vs 11.4% +/- 6%, P =.002). In addition, several TCR BV families were significantly more frequently skewed in patients with PNH than in controls. These findings provide experimental support for the concept that PNH, like IAA, has an immune pathogenesis. In addition, the identification of expanded T-cell clones by CDR3 size analysis will help to investigate the effect of HSC-specific T cells on normal and PNH HSCs.

We have previously described a type I transforming growth factor (TGF)-beta receptor (TbetaR-I) polymorphic allele, TbetaR-I(6A), that has a deletion of three alanines from a nine-alanine stretch. We observed a higher than expected number of TbetaR-I(6A) homozygotes among tumor and nontumor DNA from patients with a diagnosis of cancer. To test the hypothesis that TbetaR-I(6A) homozygosity is associated with cancer, we performed a case-control study in patients with a diagnosis of cancer and matched healthy individuals with no history of cancer and who were identical in their gender and their geographical and ethnic background to determine the relative germ-line frequencies of this allele. We found nine TbetaR-I(6A) homozygotes among 851 patients with cancer. In comparison, there were no TbetaR-I(6A) homozygotes among 735 healthy volunteers (P < 0.01). We also observed an excess of TbetaR-I(6A) heterozygotes in cancer cases compared to controls (14.6% versus 10.6%; P = 0.02, Fisher's exact test). A subset analysis revealed that 4 of 112 patients with colorectal cancer were TbetaR-I(6A) homozygotes (P < 0.01). Using mink lung epithelial cell lines devoid of TbetaR-I, we established stably transfected TbetaR-I and TbetaR-I(6A) cell lines. We found that, compared to TbetaR-I, TbetaR-I(6A) was impaired as a mediator of TGF-beta antiproliferative signals. We conclude that TbetaR-I(6A) acts as a tumor susceptibility allele that may contribute to the development of cancer, especially colon cancer, by means of reduced TGF-beta-mediated growth inhibition.

We report a detailed longitudinal study of the first patient to be treated (in 1973) for paroxysmal nocturnal hemoglobinuria (PNH) with syngeneic bone marrow transplantation (BMT). The patient subsequently relapsed with PNH in 1983, and still has PNH to date. Analysis of thePIG-A gene in a recent blood sample showed in exon 6 an insertion-duplication causing a frameshift. Polymerase chain reaction (PCR) amplification of the PIG-A exon 6 from bone marrow (BM) slides obtained before BMT showed that the duplication was not present; instead, we found several single base pair substitutions in exons 2 and 6. Thus, relapse of PNH in this patient was not due to persistence of the original clones; rather, it was associated with the emergence of a new clone. These findings support the notion that the BM environment may create selective conditions favoring the expansion of PNH clones. © 1998 by The American Society of Hematology.

We report a detailed longitudinal study of the first patient to be treated (in 1973) for paroxysmal nocturnal hemoglobinuria (PNH) with syngeneic bone marrow transplantation (BMT). The patient subsequently relapsed with PNH in 1983, and still has PNH to date. Analysis of thePIG-A gene in a recent blood sample showed in exon 6 an insertion-duplication causing a frameshift. Polymerase chain reaction (PCR) amplification of the PIG-A exon 6 from bone marrow (BM) slides obtained before BMT showed that the duplication was not present; instead, we found several single base pair substitutions in exons 2 and 6. Thus, relapse of PNH in this patient was not due to persistence of the original clones; rather, it was associated with the emergence of a new clone. These findings support the notion that the BM environment may create selective conditions favoring the expansion of PNH clones. © 1998 by The American Society of Hematology.

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired chronic hemolytic anemia characterized by intravascular hemolysis, often associated with neutropenia and thrombocytopenia. Venous thrombosis, including the Budd-Chiari syndrome, is one of the major complications of PNH, but not all PNH patients develop thrombosis. The basis for the high risk of thrombosis in PNH is not known. Recent reports have shown that Factor V Leiden mutation is a common cause of increased tendency to develop thrombosis. Fifty-six PNH patients were tested for Factor V Leiden mutation using Amplification Created Restriction Enzyme Site methods. PNH patients do not show an increased frequency of Factor V Leiden mutations.