Clonal Burden, Immunoglobulin Heavy Chain Variable Gene Somatic Hypermutations, and Immunoglobulin Gene Repertoire in Korean Patients with Chronic Lymphocytic Leukemia Assessed by Next-generation Sequencing.

[BACKGROUND] We compared the immunoglobulin () heavy chain () leader and FR1 primer sets to measure clone sizes and detect immunoglobulin heavy chain variable () region somatic hypermutations (SHMs) in Korean patients with chronic lymphocytic leukemia (CLL). We also analyzed and immunoglobulin kappa () to identify Korean-specific s in CLL.

[METHODS] Next-generation sequencing (NGS)-based gene rearrangements and SHMs were assessed in 40 patients using leader, FR1, and primers. Flow cytometry, karyotyping, interphase FISH, and NGS-based variant analyses were performed for 165 genes.

[RESULTS] Clonal and rearrangements were detected in 100.0% and 97.5% of patients, respectively. Clonal size was generally smaller per NGS than per flow cytometry, particularly when using the leader (median: 52.5%) versus the FR1 primer set (73.2%). SHMs occurred in approximately 70% of patients; 10% showed primer set discrepancies. The incidence of SHMs was low in patients at high risk (i.e., with abnormalities; complex karyotypes; and , or variants). was the most common (58.3%), and was most frequently identified (14.6%). and usage differed significantly between Koreans and westerners. was the most common (56.3%). A single gene rearrangement was most frequently observed (18.9%), whereas intron-KDE was the most common rearrangement (30.6%).

[CONCLUSIONS] NGS may underestimate CLL clonal size, particularly when using the leader primer set. SHMs were inversely associated with negative prognostic factors. Our data suggest ethnic differences in CLL pathogenesis.