We performed a multicentric study to assess the impact of two different culture procedures on the detection of
chromosomal abnormalities in 217 consecutive unselected cases with
chronic lymphocytic leukemia (CLL) referred for routine analysis either at the time of diagnosis (n = 172) or during disease evolution (n = 45). Parallel cultures of
peripheral blood or
bone marrow were set up with the addition of either the conventional
B-cell mitogen 12-O-tetradecanoyl-phorbol-13-acetate (TPA) or a combination of
CpG oligonucleotide (
CpG) and interleukin-2 (IL-2).
Cytogenetic analyses were performed on both cultures. Clonal abnormalities were identified in 116 cases (53%). In 78 cases (36%), the aberrant clone was detected in both cultures. Among these, the percentages of aberrant
metaphases were similar in both conditions in 17 cases, higher in the
CpG/IL-2 culture in 43 cases, and higher in the TPA culture in 18 cases. Clonal aberrations were detected in only one culture, either in
CpG/IL-2 or TPA in 33 (15%) and 5 (2%) cases, respectively. Taken together, abnormal
karyotypes were observed in 51% with
CpG/IL-2 and 38% with TPA (P < 0.0001). Application of FISH (n = 201) allowed the detection of abnormalities not visible by conventional
cytogenetic analysis in 80 cases: del(13q) (n = 71), del(11q) (n = 5), +12 (n = 2), del(14q) (n = 1), and del(17p) (n = 1). In conclusion, our results confirm that
CpG/IL-2 stimulation increases the detection rate of
chromosomal abnormalities in CLL compared with TPA and that further improvement can be obtained by FISH. However, neither conventional
cytogenetics nor FISH detected all aberrations, demonstrating the complementary nature of these techniques.
