Research on the Characteristics of IGHV Gene In Chronic Lymphocytic Leukemia of China.

The usage, mutation status and prognostic impact of immunoglobulin heavy chain variable (IGHV) gene in Chinese patients with chronic lymphocytic leukemia (CLL) is unclear. We set out to define the characteristics of IGHV gene and its relevance to clinical and biological parameter in our patients.

IGHV gene mutations were detected by multiplex PCR in 202 Chinese CLL patients and the purified PCR amplification products were sequenced. IGHV somatic hypermutation status and gene usage were analyzed by IMGT/V-QUEST software. The association analysis between IGHV somatic mutation status and the clinical and biological features, including Binet staging, immunophenotype, cytogenetic aberrant, were also emphasized in this study.

The results showed that 129 patients had mutated (M) IGHV, and the remaining 73 patients had unmutated (UM) IGHV according to the cutoff value of accordance rate 98%. The most frequent VH gene family was found to be VH3 (47.5%), followed by VH4 (34.7%), VH1 (11.4%), VH2 (2.5%), VH5(1.5%), VH7(1.5%) and VH6(0.9%) gene families, which was similar to other Asian populations. The overall survival (OS) time of UM IGHV group was significant shorter than M IGHV group (P=0.025). Significance was found in the expression of CD38 and ZAP-70 between patients with and without IGHV mutations (P<0.0001 and P=0.015, respectively). Binet staging was significantly different with IGHV mutation status (P<0.001). “Unmutated” sequences had significantly longer heavy chain complementarity-determining region 3 (HCDR3). Seven of these patients used VH1-69, which was similar to other Asia countries, but in striking contrast to those in Western countries, where VH1-69 was one of the most frequently used genes. FISH was performed in 117 cases, del(11q22) was considered as high risk factors, and 10(10/42, 23.8%) cases with UM IGHV gene. On the other hand, there were 7(7/75, 9.3%) cases with M IGHV gene (P=0.033). No significance was found in del(17p),del(13q),del(6q),add(12),IGH translocation between IGHV mutation and unmuatioan patients. A total of five stereotyped BCR were identified, IGHV3-21/IGHD3-9/IGHJ6, IGHV4-34/IGHD2-15/IGHJ6, IGHV1-3/IGHD6-19/IGHJ4, IGHV4-59/IGHD3-22/IGHJ6 and IGHV4-39/IGHD6-13/IGHJ5.

The usage of IGHV gene families indicates significant difference in Chinese CLL patients compared with Western patients, suggesting involvement of ethnic and/or environmental factors in CLL disease initiation. In the development course of CLL, BCR play an important role in the immunological recognition and selection. There are intimate relationships between mutation status of IGHV gene and prognosis. The usage of IGHV provides enlightment for the occurrence mechanism of CLL.

No relevant conflicts of interest to declare.