9. Enhanced detection of chromosomal abnormalities in Hairy Cell Leukemia by conventional cytogenetics using oligonucleotide stimulation

      Hairy cell leukemia (HCL) is a mature B-cell malignancy that accounts for 2% of all adult leukemia. Few cytogenetic studies of HCL have been reported due to the rarity of the disease and the difficulties stimulating hairy-cells to divide in culture. Using a mitogen to stimulate leukemic B-cells to divide in culture can enhance detection of clonal chromosomal abnormalities. CpG oligodeoxynucleotides (CpG ODN) are a robust method for stimulating cell division in another mature B-cell malignancy, chronic lymphocytic leukemia. Therefore, our laboratory investigated culturing HCL with CpG ODN for conventional chromosome analysis. We retrospectively reviewed results from 123 HCL patients with one or more samples submitted for conventional analysis. We compared the karyotypes of samples cultured: 1) 24 hours unstimulated and 72 hours with CpG ODN, or 2) 24 hours unstimulated and 72 hours with a combination of pokeweed mitogen (PWM) and phorbol myristate acetate (PMA). We examined karyotypes for all samples submitted from each patient, and determined if the karyotypes were normal, or had non-clonal or clonal abnormalities. For 27 patients, samples were cultured either unstimulated or stimulated with PWM and PMA (U/PWM-PMA). For 96 patients, samples were cultured either unstimulated or stimulated with CpG ODN (U/CpG ODN). Of the 27 U/PWM-PMA patients, 15 (56%) always showed normal chromosomes, 10 (37%) had at least one sample with a non-clonal abnormality, and 2 (7%) had an abnormal clone. Of the 96 U/CpG ODN patients, 37 (39%) always showed normal chromosomes, 45 (47%) had at least one sample with nonclonal abnormalities, and 14 (14%) had an abnormal clone of cells detected. Of note, 13 out of the 14 abnormal karyotypes in U/CpG ODN patients had abnormalities involving chromosomes 5 or 7. In our laboratory, we found a twofold increase in abnormality detection in HCL patients with samples cultured using CpG ODN.
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