Simultaneous detection of multiple genetic aberrations in single cells by spectral fluorescence in situ hybridization.

Spectral fluorescence in situ hybridization (S-FISH) is a novel molecular cytogenetic approach that detects multiple disease-specific chromosomal aberrations in interphase nuclei using combinatorial fluorescence and digital imaging microscopy. A panel of six centromeric probes for chromosomes 7, 8, 9, 10, X, and Y, using a unique two-dye combination of four fluorophores, was developed to assess ploidy in breast tumors, bladder washings, and leukemia. Validation of S-FISH was performed by classic cytogenetics when metaphases were available or by standard fluorescence in situ hybridization (FISH) analyses. S-FISH identified clonal aberrations in newly diagnosed breast tumors and recurrent bladder cancer and revealed minimal residual disease in hyperdiploid acute lymphocytic leukemia, providing "proof of concept." Like standard FISH, aberrations were identified in poor growth/no growth specimen at the single cell level; however, S-FISH provided increased sensitivity over standard FISH by surveying six genetic targets instead of one or two. Disadvantages of the current assay include labor intensive screening and interpretative challenges with signal overlap in highly aneuploid samples and focal plane distortions. S-FISH appears to be a sensitive oncology assay with significant clinical application for early detection of new or reemerging clones, allowing for earlier therapeutic intervention and development of probe panels for individualized therapy.

Minimal residual disease (MRD) in remission t(8;21) AML and in vivo differentiation detected by FISH and CD34+ cell sorting.

Many patients with t(8;21) AML have residual positive cells during remission. We previously developed D-FISH probes that detect both derivative chromosomes and the normal alleles. In negative controls, only 2/44,000 (0.0045%) positive signals were observed. To investigate MRD, we examined specimens from 29 patients who had initially obtained CR. In remission patients, 61% had 1-4/2000 positive cells (0.05-0.19%). Higher frequencies were found in two patients in early relapse and in one patient in early remission. However, a negative test did not exclude relapse. Since false positives were negligible and because most t(8;21) AMLs express CD34, we asked whether cell sorting combined with FISH would increase the sensitivity. In one patient, we observed that 80% of CD34+ cells were t(8;21)+ at 2 months from initial clinical and cytogenetic remission. However, by 5 months the pre- and post-sorted populations contained 0.15% and 0.06% t(8;21) cells, respectively. Whereas essentially all t(8;21) cells in the initial specimen expressed CD34, only 0.6% were subsequently CD34+. These results are consistent with in vitro assays showing that residual t(8;21) cells undergo differentiation. Thus, FISH can identify MRD in a majority of t(8;21) patients and, combined with CD34+ selection, may provide an indirect assessment of the differentiation state of residual t(8;21) cells.

Surface immunoglobulin light chain-positive acute lymphoblastic leukemia of FAB L1 or L2 type: a report of 6 cases in adults.

Acute lymphoblastic leukemia (ALL) of B-cell lineage may be classified using the French-American-British (FAB) classification as L1, L2, or L3 type. L1 and L2 ALLs characteristically express terminal deoxynucleotidyl transferase (TdT) and are surface immunoglobulin (sIg)-negative. In contrast, L3 ALL is typically TdT-negative and sIg-positive. However, in a few large studies of children with ALL, sIg expression has been reported in less than 2% of L1 and L2 neoplasms. In these sIg-positive cases, IgM usually has been detected, with Ig light chain in a subset of tumors. Surface Ig expression in L1 or L2 ALL in adults is extremely rare; we found only 1 case report in the English literature. We report 6 cases of L1 or L2 ALL with an unusual immunophenotype arising in adults. In each tumor, the neoplastic cells expressed monotypic sIg light chain (4 lambda, 2 kappa) and TdT. Three tumors expressed CD34. Cytogenetic studies in 4 cases at diagnosis or relapse revealed no evidence of chromosomal translocations involving the c-myc locus, such as the t(8;14), t(2;8), or t(8;22). Three patients responded completely to chemotherapy and are alive; follow-up ranges from 18 to 57 months. Three patients died at 3, 13, and 14 months after diagnosis.

Acute lymphoblastic leukemia. Survey of immunophenotype, French-American-British classification, frequency of myeloid antigen expression, and karyotypic abnormalities in 210 pediatric and adult cases.

Immunophenotypic studies are essential to distinguish acute lymphoblastic leukemia (ALL) from minimally differentiated acute myeloid leukemia (AMLM0) and to classify ALL into immunologic subtypes. Frequently, immunophenotyping identifies myeloid antigen expression in ALL, causing a potential diagnostic problem. To evaluate the immunophenotype of ALL, we studied 210 cases of pediatric and adult ALL by flow cytometry and compared the results with the French-American-British (FAB) Cooperative Group classification and the karyotypic findings. Myeloid-associated antigens were expressed in 78 (45.6%) of precursor B-cell ALL cases. Pediatric precursor B ALLs had a higher frequency of myeloid antigen expression than did adult cases. All mature B-cell ALL cases were negative for TdT and myeloid antigens. Myeloid antigen expression was less frequent in T-cell ALL cases compared with precursor B-cell ALL cases. Of the 192 cases submitted for cytogenetic analysis, 147 were abnormal. The most common chromosomal translocation was the Philadelphia chromosome, which was more likely to have L2 blast morphology and a precursor B immunophenotype. Myeloid antigen expression was present in 70.8% of Ph-positive cases (P = .008). Chromosome rearrangements involving 11q23 also showed an increased frequency of myeloid antigen expression. Chromosome translocations involving regions of T-cell receptor genes were present in 24% of T-cell ALL cases. A high percentage of ALL cases, however, had various other cytogenetic abnormalities, many of which involved less well-studied chromosomal regions.

Trisomy 14 in myelodysplastic syndromes: report of two cases and review of the literature.

OBJECTIVE: To describe the pathologic features of two cases of myelodysplastic syndrome associated with trisomy 14 and to summarize the relevant literature. RESULTS: In both cases, trisomy 14 was identified using conventional cytogenetic and fluorescence in situ hybridization methods. The patients were elderly men, 70 and 77 years old, who presented with anemia and thrombocytopenia. According to the French-American-British classification, case 1 was classified as refractory anemia with ringed sideroblasts, and case 2 was classified as chronic myelomonocytic leukemia. In both cases, the aspirate smears revealed obvious abnormalities in erythroid and megakaryocytic maturation, with more subtle abnormalities in myeloid maturation. The biopsy sections were hypercellular, and there was marked myeloid hyperplasia in case 2. Both patients received only supportive therapy after the diagnosis was established. Clinical follow-up was available for both patients. The patient in case 1 died 67 months after disease onset of an unrelated illness, and the patient in case 2 was alive at last follow-up, 12 months after diagnosis. LITERATURE REVIEW: Thirty-five cases of trisomy 14 have been previously reported in the literature, predominantly in cytogenetics journals, and the description of the pathologic findings for the majority of these cases is limited or not provided. According to published data, the majority of these cases are myelodysplastic syndromes or acute myeloid leukemias associated with myelodysplasia. CONCLUSIONS: The detection of trisomy 14 in the bone marrow strongly correlates with the presence of a myelodysplastic syndrome. The two cases of myelodysplastic syndrome associated with trisomy 14 we describe here did not exhibit characteristic morphologic findings that might suggest the presence of the cytogenetic abnormality.

Natural size classes in DNA from Chinese hamster metaphase chromosomes.

DNA from isolated Chinese hamster ovary (CHO) metaphase chromosomes can be obtained in three different molecular weight classes. The two largest forms have sedimentation coefficients of 80 and 120 S at 7,500 rpm. Based on sedimentation and speed dependence analysis these have molecular weights of 220 million and above 5,000 million, and are thought to be analogs of DNA classes observed in a prior study of human metaphase chromosomes. An extract can be converted to primarily the 80 S form through alkaline pH treatment of metaphase DNA. The third class (45 S DNA) is formed as a result of metaphase chromosome exposure to the nuclease Bal31, and has a mass distribution analogous to the CHO replicon.

Ticlopidine-induced aplastic anemia: development of chromosomal abnormalities and response to immunosuppressive therapy.

Severe aplastic anemia is a well-recognized complication of ticlopidine therapy that carries a high mortality. Therapy with colony-stimulating factors or corticosteroids has been largely ineffective in this disorder. We report a case of ticlopidine-induced aplastic anemia that was successfully treated with cyclosporine and high-dose dexamethasone. The patient rapidly responded to immunosuppressive therapy and had a normal hemogram after cessation of immunosuppression. On long-term follow-up, the patient developed a progressive macrocytic anemia. Repeat bone marrow evaluation demonstrated myelodysplasia with erythroid hypoplasia. An associated chromosomal abnormality consisting of a t(3;16) (q21; p13.3) translocation was detected. This is the first report of a chromosomal abnormality associated with ticlopidine induced marrow aplastic anemia.

Twenty-four-color spectral karyotyping reveals chromosome aberrations in cytogenetically normal acute myeloid leukemia.

Multicolor spectral karyotyping allows simultaneous visualization of all human chromosomes and screening for chromosomal rearrangements without a priori knowledge of any abnormalities involved. Based on this potentially increased sensitivity, we investigated, in a preliminary manner, whether spectral karyotyping could detect cytogenetic aberrations in karyotypically normal leukemia. The test population was comprised of 28 cryopreserved, cytogenetically normal acute myeloid leukemia (AML) samples from patients registered to a randomized trial for previously untreated AML (SWOG 9031). Two normal and 12 samples with known cytogenetic aberrations were used to validate and establish the diagnostic accuracy of the spectral karyotyping assay and instrumentation in a clinical setting. Enumeration and region-specific DNA fluorescence in situ hybridization (FISH) probes verified discrepant results. In the validation data set, spectral karyotyping refined complex karyotypic rearrangements in six cases and defined the chromosomal origin of a "jumping" homogeneously staining region; however, the technology was less sensitive in the detection of subtelomeric rearrangements and double minute chromosomes. In the test population, spectral karyotyping identified previously undetected cytogenetic aberrations in two cases (7%) of karyotypically normal AML: a cryptic 11q23 translocation in 20/20 cells and a minor monosomy 7 clone in 3/21 cells (FISH, 10.5%). Both of these abnormalities are considered to confer a poor prognosis when based on classical cytogenetic prognostic criteria. As an adjunct to classical cytogenetics and standard FISH analyses, the additive resolution of spectral karyotyping, in particular, with chromosome paints spiked with subtelomeric and/or locus-specific probes, may allow significant gains to be made in diagnostic accuracy and recognition of genotype/phenotype prognostic relationships, and in defining underlying biologic mechanisms in cancer. Genes Chromosomes Cancer 28:318-328, 2000.