Background. Trisomy 12 was found to be the most frequent chromosomal aberration identified by conventional
cytogenetic studies of bone marrow cells and peripheral lymphocytes of patients with CLL. Molecular-cytogenetic
techniques which enable examination of dividing and/or non-diving interphase nuclei (I-FISH), proved existence of
other chromosomal abnormalities, mainly deletions, which could have in CLL patients relation to the origin, course
and prognosis of the disease.
Methods and Results. During the last two years bone marrow chromosomes of all patients with CLL were
examined by G-banding and by I-FISH. The numerical changes of chromosome 12 were followed by centromeric
DNA probe in dividing and non-dividing cells. The small deletions were ascertained by locus specific probes for
13q14 (Rb gene), 17p13 (p53 protein) and 11q23 (MLL gene). These genes are responsible for cell division and their
function is probably in connection with neoplastic process. It is of interest whether numerical and structural
chromosomal rearrangements are primary or secondary changes and what is their impact on etiology of CLL.
93 patients were examined by DNA prove CEP12 and trisomy 12 was found in 24 of them (25.8 %), the range of
the clone was 2.5-75.5 % of the screened cells. Deletion del(13)(q14) was examined by probe D13S319 in 73 patients
and proved in 24 of them (32.8 %), pathological clone ranged 2.5-80.0 % of the cells. Deletion del(17)(p13) was
found in 14 patients out of 61 examined by probe LSI p53 (22.9 %). The extent of the clone was 2.5-34.0 % of
examined cells. Deletion 11q23 was not ascertained in any of 11 patients by means of probe LSI 11q23 (MLL). All
probes used for FISH were manufactured by VYSIS™.
Conclusions. FISH is very sensitive method, suitable for molecular-cytogenetic examination of leukemic patients.
With I-FISH the deletion of 13q14 was ascertained as the most frequent chromosomal aberration in series of
73 patients with CLL. We continue to increase the number of patients screened by I-FISH with all eligible DNA
probes and start the prospective study on patients with chromosomal pathology. We will correlate the immunophe-
notype, morphology, clinical course and prognosis with karyotypic findings.
CLL, I-FISH, trisomy 12, deletion 13q, deletion 17p, deletion 11q.