Paternal origin of the rearranged major breakpoint cluster region in chronic myeloid leukemia

The Philadelphia chromosome, t(9;22), is present in virtually all cases of chronic myeloid leukemia (CML). It has previously been shown by cytogenetic studies that the rearranged chromosome 22 in patients with CML is exclusively maternal in origin. To address this issue at a molecular level, the major breakpoint cluster region (M-bcr) on chromosome 22 was examined using Southern blot assays and M-bcr Pvu II and Mae II restriction site polymorphisms in three CML patients. In all three cases, the rearranged allele was paternal in origin. These results indicate that the paternally derived M-bcr allele may also be involved in the M-bcr rearrangement.</jats:p

Paternal origin of the rearranged major breakpoint cluster region in chronic myeloid leukemia

Abstract The Philadelphia chromosome, t(9;22), is present in virtually all cases of chronic myeloid leukemia (CML). It has previously been shown by cytogenetic studies that the rearranged chromosome 22 in patients with CML is exclusively maternal in origin. To address this issue at a molecular level, the major breakpoint cluster region (M-bcr) on chromosome 22 was examined using Southern blot assays and M-bcr Pvu II and Mae II restriction site polymorphisms in three CML patients. In all three cases, the rearranged allele was paternal in origin. These results indicate that the paternally derived M-bcr allele may also be involved in the M-bcr rearrangement.</jats:p

Aberrant methylation of the major breakpoint cluster region in chronic myeloid leukemia

Isolated hypomethylated sites exist in the major breakpoint cluster region (M-bcr) where most Philadelphia chromosome (Ph) breakpoints are located. Twenty of 50 (40%) chronic myeloid leukemia (CML) patients were found to have aberrant hypermethylation of these sites on the rearranged M-bcr when compared with control marrows. The aberrancy correlated strongly with M-bcr breakpoint location; 19 of 20 cases had breakpoints located 5′ of the M-bcr Sca I site, and 28 of 30 cases with normal M-bcr methylation had breakpoints located 3′ of the M-bcr Sca I site. Sequence analysis of the Ph M-bcr breakpoints failed to find an M- bcr nucleotide position that delineated the transition between abnormally and normally methylated cases, indicating that the translocation of a critical M-bcr sequence was not responsible for the methylation abnormality. In 3 of 8 CML patients, cells without the t(9;22) were found to have abnormally methylated, unrearranged M-bcrs. The data indicate that abnormally methylated rearranged M-bcrs are present in CML cases with Ph breakpoints 5′ of the M-bcr Sca I site and that the M-bcr in Ph- cells of patients with CML may also be abnormally methylated.</jats:p

Duplication of small segments within the major breakpoint cluster region in chronic myelogenous leukemia

Abstract The t(9;22) in chronic myelogenous leukemia (CML) may be reciprocal or, in a minority of cases, may result in an extensive deletion of a portion of the major breakpoint cluster region (M-bcr) of the BCR. This report provides evidence of the duplication of small segments within the M-bcr in a small group of patients with CML. Southern blots of Bgl II and Bgl II/BamHI double-digested DNA from the blood or bone marrow of 46 patients with CML were probed with a 5' 1.4-kb Taq I/HindIII M- bcr probe and a 3' 2-kb HindIII/BamHI M-bcr probe. In three patients, rearrangements were noted with both probes in Bgl II-digested DNA, but were not present in Bgl II/BamHI-digested DNA with either probe. Southern analysis of DNA samples double-digested with Bgl II and BspHI from two of these three cases showed no rearrangements with either probe; the M-bcr BspHI site is located 26 bp 3' of the BamHI site in the second intron of the M-bcr. The presence of a rearranged M-bcr with both probes in Bgl II-digested DNA and the lack of rearrangement in Bgl II/BamHI and Bgl II/BspHI double-digested DNA suggest the presence of M- bcr BamHI and BspHI sites on both 9q+ chromosome (9q+) and the Philadelphia chromosome (Ph). This implies a duplication of at least the 26-bp M-bcr BamHI/BspHI fragment in these two samples. Sequence data from one of these two cases confirmed the M-bcr breakpoints to be staggered; the Ph M-bcr breakpoint occurred 258 bp downstream from the 9q+ M-bcr breakpoint. It is concluded that a duplication of small segments within the M-bcr occurs in a small group of patients with CML, which may lead to pseudogermline patterns on Southern blot. Such a duplication may provide insight into the mechanism of some chromosomal translocations in neoplasia.</jats:p

Duplication of small segments within the major breakpoint cluster region in chronic myelogenous leukemia

The t(9;22) in chronic myelogenous leukemia (CML) may be reciprocal or, in a minority of cases, may result in an extensive deletion of a portion of the major breakpoint cluster region (M-bcr) of the BCR. This report provides evidence of the duplication of small segments within the M-bcr in a small group of patients with CML. Southern blots of Bgl II and Bgl II/BamHI double-digested DNA from the blood or bone marrow of 46 patients with CML were probed with a 5' 1.4-kb Taq I/HindIII M- bcr probe and a 3' 2-kb HindIII/BamHI M-bcr probe. In three patients, rearrangements were noted with both probes in Bgl II-digested DNA, but were not present in Bgl II/BamHI-digested DNA with either probe. Southern analysis of DNA samples double-digested with Bgl II and BspHI from two of these three cases showed no rearrangements with either probe; the M-bcr BspHI site is located 26 bp 3' of the BamHI site in the second intron of the M-bcr. The presence of a rearranged M-bcr with both probes in Bgl II-digested DNA and the lack of rearrangement in Bgl II/BamHI and Bgl II/BspHI double-digested DNA suggest the presence of M- bcr BamHI and BspHI sites on both 9q+ chromosome (9q+) and the Philadelphia chromosome (Ph). This implies a duplication of at least the 26-bp M-bcr BamHI/BspHI fragment in these two samples. Sequence data from one of these two cases confirmed the M-bcr breakpoints to be staggered; the Ph M-bcr breakpoint occurred 258 bp downstream from the 9q+ M-bcr breakpoint. It is concluded that a duplication of small segments within the M-bcr occurs in a small group of patients with CML, which may lead to pseudogermline patterns on Southern blot. Such a duplication may provide insight into the mechanism of some chromosomal translocations in neoplasia.</jats:p

Myelodysplastic syndrome after autologous bone marrow transplantation: an additional late complication of curative cancer therapy [see comments]

Abstract Myelodysplastic syndrome (MDS) is a complication of conventional antineoplastic therapy but has rarely been reported after autologous bone marrow transplantation (ABMT). We reviewed records of 206 patients who underwent ABMT for lymphoma at the University of Minnesota (Minneapolis, MN) between 1974 and 1993. Of 206 patients who underwent ABMT for non-Hodgkin's lymphoma (NHL) or Hodgkin's disease (HD), 9 patients developed an MDS or secondary acute leukemia between 5 and 60 months (median 34 months) post-BMT. Two patients had relapsed after transplant and received additional therapy before the diagnosis of MDS. They were censored from the statistical analysis, resulting in a cumulative incidence of 14.5% +/- 11.6% (95% confidence interval) at 5 years. Three patients (15.2% +/- 18.0%) had HD, and four (14.0% +/- 14.7%) had NHL. In vitro BM purging had no affect on the incidence of MDS, although patients receiving peripheral blood stem cells had a projected MDS incidence of 31% +/- 33% versus 10.5% +/- 12% if BM cells were used (p = .0035). The patients had received a median of 14 cycles (range, 6 to 40) of chemotherapy before autologous transplantation; Five of nine patients received radiation therapy before BMT conditioning, and all patients received radiation before the diagnosis of MDS. No BM cytogenetic abnormalities were evident pretransplant in three of three patients studied, and all nine had normal pretransplant BM morphology. All patients had morphologic BM findings typical of MDS, and six of six studied had clonal cytogenetic abnormalities. At the diagnosis of MDS, all nine patients were without clinical, radiographic, or autopsy evidence of recurrent lymphoma; Three of the nine patients have died from complications of cytopenias at 23, 36, and 45 months after transplant (3 to 10 months after the diagnosis of MDS), whereas 6 survive 8 to 63 months after transplantation (1 to 34 months post-MDS). These data emphasize the cumulative leukemogenic potential of standard and salvage radiation and chemotherapy regimens and highlight treatment-induced MDS as an important and frequent late complication of potentially curative BM transplant therapy.</jats:p

Myelodysplastic syndrome after autologous bone marrow transplantation: an additional late complication of curative cancer therapy [see comments]

Myelodysplastic syndrome (MDS) is a complication of conventional antineoplastic therapy but has rarely been reported after autologous bone marrow transplantation (ABMT). We reviewed records of 206 patients who underwent ABMT for lymphoma at the University of Minnesota (Minneapolis, MN) between 1974 and 1993. Of 206 patients who underwent ABMT for non-Hodgkin's lymphoma (NHL) or Hodgkin's disease (HD), 9 patients developed an MDS or secondary acute leukemia between 5 and 60 months (median 34 months) post-BMT. Two patients had relapsed after transplant and received additional therapy before the diagnosis of MDS. They were censored from the statistical analysis, resulting in a cumulative incidence of 14.5% +/- 11.6% (95% confidence interval) at 5 years. Three patients (15.2% +/- 18.0%) had HD, and four (14.0% +/- 14.7%) had NHL. In vitro BM purging had no affect on the incidence of MDS, although patients receiving peripheral blood stem cells had a projected MDS incidence of 31% +/- 33% versus 10.5% +/- 12% if BM cells were used (p = .0035). The patients had received a median of 14 cycles (range, 6 to 40) of chemotherapy before autologous transplantation; Five of nine patients received radiation therapy before BMT conditioning, and all patients received radiation before the diagnosis of MDS. No BM cytogenetic abnormalities were evident pretransplant in three of three patients studied, and all nine had normal pretransplant BM morphology. All patients had morphologic BM findings typical of MDS, and six of six studied had clonal cytogenetic abnormalities. At the diagnosis of MDS, all nine patients were without clinical, radiographic, or autopsy evidence of recurrent lymphoma; Three of the nine patients have died from complications of cytopenias at 23, 36, and 45 months after transplant (3 to 10 months after the diagnosis of MDS), whereas 6 survive 8 to 63 months after transplantation (1 to 34 months post-MDS). These data emphasize the cumulative leukemogenic potential of standard and salvage radiation and chemotherapy regimens and highlight treatment-induced MDS as an important and frequent late complication of potentially curative BM transplant therapy.</jats:p