THE IMPACT OF MOLECULAR CYTOGENETICS ON CHRONIC LYMPHOID LEUKEMIA

Chronic lymphoid leukaemias are clonal expansions of B and T cells wit h mature membrane phenotype. Cytogenetic study of these cases usually requires mitogenic stimulation and can often be hindered by a lack of response of the tumour cells to mitogen, poor quality metaphases, comp lex markers and proliferation of normal cells. In situ hybridisation w ith fluorescence-labelled chromosome-specific centromeric DNA probe, s ingle or low copy sequences and whole chromosome paints which hybridis e to complementary sequences allow the detection of numerical and stru ctural abnormalities on metaphase and interphase cells with much great er efficiency. Comparative genomic hybridisation uses whole genomic tu mour DNA as probe which is hybridised to normal metaphases. It is part icularly useful for detecting chromosomal changes without being depend ent on the dividing tumour cells. The application of these techniques to the investigation of chronic lymphoid leukaemias is reviewed with e mphasis on the work done in our laboratory on trisomy 12 and the tumou r suppressor region 13q14 in chronic lymphocytic leukaemia, translocat ion t(11;14) (q13;q32) in mantle cell lymphoma and other chronic B cel l leukaemias, inv(14) (q11q32), i(8q) and complex markers in T prolymp hocytic leukaemia.