Cytogenetics and spectral Karyotyping analysis in CLL Patients: Correlation with FISH and ZAP70 Expression

Abstract 4844

Cytogenetic abnormalities play an important role as prognostic factors in CLL. However, due the low mitotic index of CLL B cells in vitro, analysis of a set of subjects for the most commonly known aberrations is usually done by FISH on interphase cell. The objectives of this investigation were the use of the oligonucleotide DSP30 in combination with IL-2, as a B-cell mitogen for cytogenetic investigation in CLL and correlation among the karyotype analysis obtained (G-banding + SKY), FISH profile from unstimulated cells, ZAP70 expression and stratification status for each patient. For metaphase induction, peripheral blood mononuclear cells were cultured in RPMI 1640 medium with 20% fetal calf serum in the presence of the immunostimulatory CpG-oligonucleotide DSP30 and IL-2. Additionally, one set of cell culture was performed for each patient without any stimulant agent, for FISH analysis. The FISH panel included probes for the detection of +12, and deletions of 11q22.3 (ATM), 13q14 (D13S25 and D13S319), and 17p13 (TP53). The cut off levels for trissomy 12 (>2%), del(13q) (>2.4%), del(11q23.3) (>2.5%), del(17p13.1) (>3%) were established according to the iFISH patterns observed in a group of 4 age and sex-matched normal control peripheral blood samples studied with the same probes. Spectral karyotype analysis (SKY) was performed, according manufactures' instruction. The ZAP70 profile was obtained by flow cytometry analysis. In concordance with literature, the cut off value adopted for ZAP70 was 20%. In a group of 64 subjects studied, the cytogenetic analysis showed chromosomal aberrations in 52 patients (81.25%). The profile of abnormalities observed were del(6)(q24), +8(x2), del(11)(q13~q23), +12, +15(x2), del(12)(p13), -17, +21, +19, +18, del(13)(q31), del(14)(q24), del(17)(p13), +21, +4, +5, +11, t(1;12)(q31;p13), t(11;13)(q23;q12), t(15;18)(q11.1;q11), t(1;10)(p22;p14), t(14;22)(q32;q11), t(17;18)(q10;q10), t(9;13)(q21;q22), t(10;13)(q26;q14), t(9;12)(q12;p11), t(X;12)(p11.2;q24). Twelve patients exhibited normal karyotype (18.75%). All subjects presenting chromosomal abnormalities, by using G-banding analysis, were confirmed by SKY. In patients with normal cytogenetic, SKY analysis did not identified any criptic abnormality. Cells without any stimulant agent showed concordance with the cytogenetic profile obtained (FISH analysis). The ZAP70 expression did not show any relationship between the group of patients with chromosomal abnormalities and the group with normal karyotype. The use of the immunostimulatory oligonucleotide DSP30 in combination with IL-2 showed to be effective to induce cell cycle progression of CLL cells in vitro than others mitogens. Cytogenetic aberrations detected by G-banding in addition to FISH analysis were heterogeneous. The limited spectrum of chromosomal abnormalities seen by FISH analysis may contribute to underestimate the prognostic value, where others abnormalities may be present in patient's karyotype. These results indicate that classical cytogenetic analysis can contribute to the stratification of different subsets of CLL patients with complex karyotype associated with poor prognosis.

Financial support: FAPESP (Proc. 07/52462-7).