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 Updated on: Jan 9 2014

Tumor clone characteristics: Cytogenetics analysed by FISH

 

Subject
Cytogenetics has become the strongest prognostic factors in several hematopoietic malignancies, especially acute leukemias. In MM, the extent of clinical application of cytogenetic data is far less advanced.


Present Status
Due to the lower proliferative index of fully differentiated plasma cells (PCs) compared to normal bone marrow myeloid cells, Fluorescence –in –situ hybridisation (FISH), which is independent of metaphases, is the method of choice to assess chromosomal aberrations. However, using interphase FISH in MM requires either staining of plasma cells (with light-chain antibodies) on the bone marrow smears, or enrichment of CD138-positive cells, as the median percentage of PCs within the bone marrow specimens is below 10%.


Del 13, found in ~45% of MM patients by FISH, was shown to be a negative prognostic parameter for patients treated by conventional as well as high-dose therapy. Illegitimate rearrangement of the IgH gene (located at 14q32) was present in 60% to 75% of the patients, with varying translocation partners. The prognostic significance of chromosomal aberrations other than del 13 still have to be elucidated.


Preview of Programme Proposed
In order to assess the prognostic value of chromosomal abnormalities detected by FISH it is essential to evaluate their use in prospective trials, in the context of other known prognostic factors. An essential preliminary step to evaluating the value of FISH is the harmonization of the laboratory practices throughout Europe. The following plan is proposed;

  • to identify core laboratories within national/regional myeloma group
  • to define standard procedures for PC purification, staining, probe hybridization and evaluation
  • to define a set of chromosomal abnormalities to be analyzed by each laboratory and to select, evaluate and further develop probes for each of the set, to establish a homogeneous scoring approach for each probe, and to define a homogeneous way of expressing and recording results.

Deliverables and Cooperations

  • mapping the laboratories and establishing the network
  • to define the technical procedures, internal quality control and which abnormalities should be looked for
  • to set up a training workshop and establish common procedures
  • to disseminate the technique within each laboratory.
     

During this time, a hot line with a reference lab will be established to answer technical questions.

A meeting six months later will concentrate on evaluating the results from each laboratory, the consistency of the results and potential for applying within trials. At this meeting an approach to external quality control will be established.

At year one a further meeting will evaluate the results, the functioning of the EQUAS and value of each of the probe sets. At this point we will initiate a program to develop and optimize the probes.

At year one we will start to map and recruit laboratories to the assay network.

By 18 months we will have a fully established network into which we can introduce the necessary technology.

Secr. Hans E. Johnsen | Depart. of Haematology | Aalborg University Hospital | Sdr. Skovvej 15 | DK-9000 Aalborg | Denmark | T:+45 9766 3871 | F:+45 9766 6369