Differential Diagnosis of Lymphoid Enhancer-Binding Factor 1 Between Chronic Lymphocytic Leukemia and Other B-Cell Chronic Lymphoproliferative Disorders

Background : LEF1, lymphoid enhancer factor 1, is a key transcription factor of Wnt signaling pathways. In normal blood cells, the LEF1 mainly expresses in pre-B and T cells, involves in proliferation and differentiation. With mature of the cells, the expression of LEF1 reduces gradually. Its abnormal expression is associated with a variety of tumors, such as various kinds of leukemias and lymphomas. Previous studies have explored the relationship between LEF1 gene and tumorogenesis as well as tumor development, and there is little report on the diagnostic significance of LEF1. Recent studies have shown that the LEF1 protein expression in chronic lymphocytic leukemia (CLL) is significantly higher than other B-cell chronic lymphoproliferative disorders (B-CLPD) and normal controls. Our study aimed to compare the LEF1 gene mRNA expression and the LEF1 protein expression between different subtypes of patients with B-CLPD, then established the differential diagnostic value of LEF1 in B-CLPD.

Methods: We determined the expression level of LEF1 protein by immunohistochemistry in bone marrow samples from 143 patients with leukemic phase B-CLPD including 78 cases of CLL, 17 cases of mantle cell lymphoma (MCL), 20 cases of Waldenström macroglobulinemia (WM), 20 cases of follicular lymphoma (FL), 5 cases of marginal zone lymphoma (MZL), 3 cases of B-cell chronic lymphoproliferative disorders-unclassified (B-CLPD-U). We used real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) to compare the level of LEF1 mRNA expression in malignant cells from 54 B-CLPD patients, including 44 cases of CLL, 3 cases of MCL, 2 cases of MZL, 3 cases of FL, one case of hairy cell leukemia (HCL), one case of B-cell prolymphocytic leukemia (B-PLL) and 5 cases of healthy donors. All statistical analysis of the data were performed using SPASS version 20.0. Mann-Whitney U test was used to compare the difference between the cohorts. P<0.05 was considered statistically significant.

Results: The expression of LEF1 protein was positive in 68 of 78 patients with CLL and 2 of 20 patients with FL, both of whom were pathological low-grade. LEF1 expression of patients with WM, MCL, B-CLPD-U were all negative. The expression level of LEF1 protein in CLL was higher than other B-CLPD patients (including all FL、WM、MCL、B-CLPD-U, P=0.000). Positive expression of LEF1 protein can be used as novel differential diagnostic marker for patients with CLL with higher sensitivity and specificity (sensitivity=87%, specificity=97%). The expression of LEF1 protein was negative in 10 of 78 CLL patients. The 10 patients had atypical immunophenotype. The expression of CD20 was increased, even strong expression in 5 CLL patients. There were 9 CLL with CD200/CD148<1, and 6 cases with CD5 dim expression. The expression level of LEF1 gene in CLL patients was much higher than non-CLL patients and healthy controls (P=0.036, 0.004). The expression level of LEF1 gene had no statistical difference between non-CLL patients and healthy controls (P=0.438). The expression of LEF1 mRNA in 25% CLL patients was lower than healthy controls and 33.3% CLL patients was lower than non-CLL patients.

Conclusions: The expression level of LEF1 protein was significantly higher than non-CLL in B-CLPD. We analyzed LEF1 protein may be a novel marker in the differential diagnosis of B-CLPD with higher sensitivity and specificity. The mRNA expression level of LEF1 gene in CLL patients was significant higher than non-CLL patients, but the expression of LEF1 mRNA in 25% CLL patients was lower than healthy controls and 33.3% CLL patients was lower than non-CLL patients.