Somatic Mutation in Immunoglobulin Gene Variable Region in Patients With Chronic Lymphoid Leukemia and Its Influence on Disease Prognosis

Abstract

Background: Chronic lymphocytic leukemia (CLL) is a common blood cancer in people aged over 40. In addition to clinical and pathologic staging and blood tests, immunoglobulin variable heavy chain (IgVH) mutation analysis is a relevant prognostic factor for CLL. Finding the most prevalent mutation type and conducting a molecular analysis of immunoglobulin in the majority of the patients can contribute to identifying the disease pattern. Objectives: In the present study, we used molecular detection methods to find the relationship between clinical and pathologic findings with immunoglobulin heavy chain mutations in CLL patients in Iran. Patients and Methods: Patients with CLL were randomly selected from patients referred to Imam Khomeini hospital, Tehran, Iran. All patients underwent a clinical staging of the disease and had flow cytometric analysis performed on their blood samples. The panels of cell surface markers used for the diagnosis of chronic lymphoid leukemia include CD19, CD3, CD23, CD10, and CD5. The diagnosis confirmed a minimum of 20% positive expression of dual CD5 and CD19 markers. Genomic DNA was then extracted from the patients’ blood and IgVH mutation analysis was conducted with pGEM-T (easy vector) cloning kit followed by IgVH sequencing. Results: Study patients were 42 to 80 years old, with their mean age of 62 (SE = 1.87) years. About 73% of them were male. The mean white blood cell (WBC) count, lymphocytes percentage, average hemoglobin level, and platelet count were 56,000/µL, 85%, 12 g/dL, and 150,000/µL, respectively. According to their molecular analysis, 38.9% of patients were unmutated and 61.1% showed mutation in the variable heavy chain locus. The most common mutation had occurred in IgVH3 allele (66.66%). The mean overall survival rate of patients, mutated and unmutated, was, respectively, 39 (95% CI, 32 to 46) and 31 (95% CI, 26 to 36) months (P = 0.4). Binet stage had statistically significant relationship with patients’ survival (P = 0.02). Conclusions: According to this study, IgVH3 mutation was found to be prevalent (Although a correlation was found to exist between the patients’ survival and IgVH mutation, it was not statistically significant). We can conclude that clinical methods are still valuable to predict the prognosis of patients with CLL. Given the high cost and need for specialized laboratory, determining the cost and value of examining immunoglobulin heavy chain mutations and types of mutation such as IgVH3 are necessary in further studies.