Clinical Applications

Fluorescence in situ hybridization techniques have altered the procedures used in many laboratories and promise to have a more substantial impact in the future.[6] FISH is being used increasingly, providing a means of examining the karyotypic pattern of human tumors to the many institutions that do not have access to cytogenetic

Table 1 Applications of fluorescence in situ hybridization

Analysis of tumors

• Detection of numerical and structural chromosomal abnormalities.

• Identification of marker chromosomes (rearranged chromosomes of uncertain origin).

• Detection of early relapse or minimal residual disease.

• Monitoring the effects of therapy.

• Identification of the origin of bone marrow cells following stem cell transplantation.

• Examination of the karyotypic pattern of nondividing or interphase cells.

• Identification of the lineage of neoplastic cells.

Applications in research

• Molecular analysis of chromosomal abnormalities in human tumors.

• Chromosomal localization of genes and DNA sequences.

• Preparation of cytogenetic maps (including determining the order of and distance between sequences).

• Detection of amplified genes.

• Examination of the organization of DNA/chromosomes in interphase nuclei.

laboratory services. A summary of the applications of FISH following Le Beau[3] is shown in Table 1. The application of FISH to the analysis of leukemia samples has improved the conventional cytogenetic analysis. FISH analysis provides more sensitivity and, in some cases, allows the detection of chromosomal abnormalities in samples that appeared to be normal by G-banding. FISH is most powerful when the analysis is targeted toward those abnormalities that are known to be associated with a particular disease. Cytogenetic analysis should be performed at diagnosis because it is important to obtain an overview of the chromosomal abnormalities of the patient at this time. Thereafter, FISH can be used to detect residual disease or early relapse and to assess the efficacy of therapeutic regimens. As mentioned above, FISH allows a large number of cells being analyzed in a short time with high sensitivity.

Detection of Numerical and Structural Chromosomal Abnormalities

In cancer cytogenetics, the application of FISH has resulted in the recognition of new recurring abnormalities in well-characterized diseases, such as leukemias and lymphomas, and in tumors that have been less amenable to conventional cytogenetic studies. An illustrative example is the finding of the t(12;21)(p13;q22) as the most common abnormality in childhood B-cell acute lympho-blastic leukemia, occurring in at least 25% of patients.[7] This abnormality was not detected by the analysis of banded chromosomes because the banding pattern of the involved chromosome bands and the size of the translocated material were so similar. The identification of this rearrangement has important prognostic and therapeutic implications as the translocation has been associated with a favorable clinical outcome.

Fluorescence in situ hybridization is also a sensitive and accurate means of detecting gene loss or deletion and how it has been demonstrated in the diagnosis of microdeletion syndromes. In CLL, genetic studies have identified recurring unbalanced abnormalities with prognostic significance, and FISH has become a diagnostic test to direct and monitor the treatment. Deletions of 13q14 as the sole genetic abnormality identify a group of patients with good prognosis, whereas deletions of 11q23 or 17p13 are important independent predictors of disease progression and survival.[4] However, in patients with multiple myeloma, the presence of chromosome 13 deletions has an adverse prognostic role.[8]

Fluorescence in situ hybridization has also been used to define the commonly deleted segment in recurring deletions, such as the deletions of chromosome 5 that are observed in myeloid leukemias.[9] By using FISH, several probes that fall within the critical region identified can be used to detect the deletions in interphase cells from BM samples from patients with AML, as well as to identify a putative tumor suppressor gene within the commonly deleted segment.

Monitor the Effects of Therapy and Detect Minimal Residual Disease

Posttreatment samples represent a substantial number of all cases analyzed by most clinical cancer cytogenetics laboratories. The detection of chromosomal rearrangements not only provides a diagnostic aid, but also allows the tumor clone to be quantified during follow-up, and for this, FISH provides a rapid means to detect residual leukemia cells. The monitoring should be performed either by G-banding or by FISH. G-banding only provides information about the dividing cells and FISH about both dividing and nondividing cells, so the percentages of malignant cells detected will not be the same. In general, FISH can be used to determine the proportion of normal and abnormal cells in BM and PB and to detect early relapse, although there are some interesting exceptions. An example is the monitoring of patients with chronic myeloid leukemia (CML). Almost all patients with CML carry a t(9;22)(q34;q11) reciprocal translocation that results in the formation of a BCR-ABL fusion gene. Treatment with imatinib (formerly STI571) induces major cytogenetic remissions or complete cytogenetic remissions (CCRs) in more than 40% of patients resistant or intolerant to interferon-alpha. Unexpectedly, it has been reported that targeted therapy of CML with imatinib favors the manifestation of Ph- clonal disorders in some patients.[10] One immediate conclusion is that patients on imatinib should be followed with conventional cytogenetics, even after induction of CCR. Thus, despite the several advantageous features of FISH for the diagnosis of leukemias and other tumors, this technique suffers from technical limitations, being one of the most important that FISH does not provide a global view of the chromosomal aberrations.

The analysis of genetic markers is also routinely used to evaluate the results of BM transplantation. Several groups have shown the applicability of FISH using X- and Y-chromosome-specific probes in detecting host cells in sex-mismatched transplants. This method is particularly useful for samples obtained shortly after transplantation, in which there is no possible cytogenetic analysis because the cell number is very low.

Getting Started With Dumbbells

Getting Started With Dumbbells

The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.

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