Rina J. Jaju

Novel translocations that disrupt the platelet-derived growth factor receptor beta (PDGFRB) gene in BCR-ABL-negative chronic myeloproliferative disorders.

The BCR–ABL‐negative chronic myeloproliferative disorders (CMPD) and myelodysplastic/myeloproliferative diseases (MDS/MPD) are a spectrum of related conditions for which the molecular pathogenesis is poorly understood. Translocations that disrupt and constitutively activate the platelet‐derived growth factor receptor β(PDGFRB) gene at chromosome band 5q33 have been described in some patients, the most common being the t(5;12)(q33;p13). An accurate molecular diagnosis of PDGFRB‐rearranged patients has become increasingly important since recent data have indicated that they respond very well to imatinib mesylate therapy. In this study, we have tested nine patients with a CMPD or MDS/MPD and a translocation involving 5q31–33 for disruption of PDGFRB by two‐colour fluorescence in situ hybridization (FISH) using differentially labelled, closely flanking probes. Normal control interphase cells gave a false positive rate of 3% (signals more than one signal width apart). Six patients showed a pattern of one fused signal (from the normal allele) and one pair of signals separated by more than one signal width in > 85% of interphase cells, indicating that PDGFRB was disrupted. These individuals had a t(1;5)(q21;q33), t(1;5)(q22;q31), t(1;3;5)(p36;p21;q33), t(2;12;5)(q37;q22;q33), t(3;5) (p21;q31) and t(5;14)(q33;q24) respectively. The remaining three patients with a t(1;5)(q21;q31), t(2;5)(p21;q33) and t(5;6)(q33;q24–25) showed a normal pattern of hybridization, with ≥ 97% interphase cells with two fusion signals. We conclude that two‐colour FISH is useful to determine the presence of a PDGFRB rearrangement, although, as we have shown previously, this technique may not detect subtle complex translocations at this locus. Our data indicate that several PDGFRB partner genes remain to be characterized.

Molecular cytogenetic delineation of the critical deleted region in the 5q- syndrome.

The 5q− syndrome is a distinct type of myelodysplastic syndrome (MDS) characterised by refractory anaemia, morphological abnormalities of megakaryocytes, and del(5q) as the sole cytogenetic abnormality. In contrast to patients with therapy‐related MDS with 5q deletions, 5q− syndrome patients have a favourable prognosis and a low rate of transformation to acute leukaemia. We have previously delineated a common deleted region of 5.6 Mb between the gene for fibroblast growth factor acidic (FGF1) and the subunit of interleukin 12 (IL12B) in two patients with 5q− syndrome and small deletions, del(5)(q31q33). The present study used fluorescence in situ hybridisation (FISH) analysis of these and a third 5q− syndrome patient with a small deletion, del(5)(q33q34), to refine further the critical deleted region. This resulted in the narrowing of the common deleted region within 5q31.3‐5q33 to approximately 3 Mb, flanked by the adrenergic receptor β2 (ADRB2) and IL12B genes. The common region of loss in these three 5q− syndrome patients includes the macrophage colony‐stimulating factor‐1 receptor (CSF1R), secreted protein, acidic, cysteine‐rich (SPARC), and glutamate receptor (GRIA1) genes. This 5q− syndrome critical region is telomeric to and distinct from the other critical regions on 5q associated with MDS and acute myeloid leukaemia. Genes Chromosomes Cancer 22:251–256, 1998.

Cytogenetic and molecular evidence of marrow involvement in extramedullary acute myeloid leukaemia

A diagnosis of granulocytic sarcoma was made in a 2‐year‐old child based on the detection of myelomonocytic blasts in tissue obtained from a subcutaneous nodule with no evidence of concomitant disease in the bone marrow. The child responded to systemic chemotherapy and is in remission 3 years later. An identical clone with an in frame fusion of the MLL and AF10 genes was identified from both tissue and bone marrow samples. The generation of an in frame MLL–AF10 fusion requires complex intra‐ and interchromosomal exchanges between chromosomes 10 and 11. In this case, an intrachromosomal rearrangement of chromosome 5 was also observed. This case illustrates the presence of systemic disease in extramedullary leukaemia, its response to systemic rather than topical therapy and suggests that the events leading to chromosomal translocations in leukaemia may be part of a generalized intracellular event.

Detection of Chromosome Abnormalities in Leukemia Using Fluorescence In Situ Hybridization

1 Molecular Analysis of Cancer: An Overview Ken Mills ................................................................................................. 1 2 Detection of Chromosome Abnormalities in Leukemia Using Fluorescence In Situ Hybridization Lyndal Kearney, Sabrina Tosi, and Rina J. Jaju ................................ 7 3 Spectral Karyotyping in Cancer Cytogenetics Eva Hilgenfeld, Cristina Montagna, Hesed Padilla-Nash, Linda Stapleton, Kerstin Heselmeyer-Haddad, and Thomas Ried ............................................................................ 29 4 Comparative Genomic Hybridization Analysis Binaifer R. Balsara, Jianming Pei, and Joseph R. Testa ................ 45 5 Detection of Chromosomal Deletions by Microsatellite Analysis Rachel E. Ibbotson and Martin M. Corcoran .................................... 59 6 Detection and Quantification of Leukemia-Specific Rearrangements Andreas Hochhaus .............................................................................. 67 7 Detection of t(2;5)(p23;q35) Translocation by Long-Range PCR of Genomic DNA Yunfang Jiang, L. Jeffrey Medeiros, and Andreas H. Sarris .......... 97 8 Use of DNA Fingerprinting to Detect Genetic Rearrangements in Human Cancer Vorapan Sirivatanauksorn, Yongyut Sirivatanauksorn, Arthur B. McKie, and Nicholas R. Lemoine ............................... 107 9 Mutation Analysis of Large Genomic Regions in Tumor DNA Using Single-Strand Conformation Polymorphism: Lessons from the ATM Gene Igor Vorechovsky ............................................................................... 115 10 Mutational Analysis of Oncogenes and Tumor Suppressor Genes in Human Cancer Using Denaturing Gradient Gel Electrophoresis Per Guldberg, Kirsten Grønbæk, Jesper Worm, Per thor Straten, and Jesper Zeuthen .......................................................................... 125