LEF1 EXPRESSION IN B-CELL CHRONIC LYMPHOCYTIC LEUKEMIA PATIENTS: A MARKER FOR DIAGNOSIS AND SURVIVAL PREDICTION

Small lymphocytic lymphoma/chronic lymphocytic leukemia (SLL/CLL) is the most common chronic leukemia in adults in Western countries. SLL/CLL is classified as a chronic lymphoproliferative disorder within the category of mature B-cell neoplasms according to the World Health Organization (WHO) classification, and is characterized by the relentless accumulation of mature B lymphocytes displaying a distinctive immunophenotype. The disease may involve peripheral blood, bone marrow, lymph nodes, and the spleen. The median age at diagnosis is approximately 70 years, although about 10% of cases occur in young adults, and males are affected more frequently than females. In Western countries, the incidence is 2-6 cases per 100,000 inhabitants per year, increasing with age.¹ The clinical course of CLL is highly heterogeneous: most patients have an indolent course requiring no therapy or delayed treatment with prolonged survival, whereas others present with an aggressive disease requiring early treatment and experiencing frequent relapses.

SLL/CLL is generally diagnosed during routine blood testing in asymptomatic patients who exhibit absolute lymphocytosis, often with Gumprecht shadows visible on peripheral blood smears (representing fragile lymphocytes disrupted during slide preparation). The diagnosis of SLL/CLL is based on the presence of ≥5,000/µl clonal B lymphocytes in peripheral blood, which on flow cytometry are CD19+, CD5+, CD23+, CD200+, with dim CD20 expression, weak CD22 and/or CD79b, and weak surface immunoglobulin expression with light-chain restriction. Diagnosis is usually achievable through immunophenotyping of peripheral blood, whereas lymph node biopsy and/or bone marrow biopsy may be useful when immunophenotyping is inconclusive.

In the diagnostic work-up of SLL/CLL, CD5, CD19, CD20, CD23, and surface or cytoplasmic kappa/lambda light chains are considered essential markers, while CD10, CD43, CD79b, CD81, CD200, and ROR1 serve as additional antigens useful for differential diagnosis among small B-cell lymphomas/leukemias. Beyond assessing del(11q), del(13q), del(17p), and trisomy 12, TP53 mutational analysis and evaluation of somatic hypermutation (SHM) of the immunoglobulin heavy-chain variable region (IGHV) are essential for comprehensive prognostic assessment in SLL/CLL. IGHV mutational status and TP53 status are included in the CLL International Prognostic Index (CLL-IPI), together with age, clinical stage, and β2-microglobulin levels. Assessment of karyotypic complexity and the mutational status of BTK, PLCG2, and BCL2 remain desirable additional investigations within a targeted-therapy approach.

In recent years, improved understanding of SLL/CLL pathogenesis has clarified preneoplastic conditions (e.g., monoclonal B-cell lymphocytosis), enabled identification of novel diagnostic, prognostic, and predictive markers, refined patient stratification, and expanded the therapeutic armamentarium with new agents targeting key intracellular signaling pathways. Among these, several studies have demonstrated dysregulation of the WNT/β-catenin pathway in SLL/CLL. The final mediator of this pathway is LEF-1 (lymphoid enhancer-binding factor 1), a key transcription factor regulating cell proliferation and survival and playing a fundamental role in lymphopoiesis. LEF-1 is normally expressed in a subset of T cells and in B-cell precursors but is silenced in mature B cells; however, gene expression profiling studies have shown overexpression of LEF-1 in SLL/CLL compared with normal B cells. This expression is detectable by immunohistochemistry in tissue samples, where its presence has been confirmed. Nonetheless, although LEF-1 expression has demonstrated usefulness in distinguishing SLL/CLL from other indolent B-cell lymphomas, its diagnostic application remains limited. Moreover, a subset of CLL patients does not express LEF-1, and the characteristics of these patients have not yet been investigated.

The aim of this study, with an anticipated enrollment of up to 350 patients with a confirmed diagnosis of SLL/CLL and available molecular data at diagnosis, is to re-evaluate immunohistochemical expression on biopsy specimens (most commonly bone-marrow biopsies) to:

1. confirm actual LEF-1 expression positivity, and
2. statistically assess potential clinical correlations between LEF-1-positive and LEF-1-negative subsets, in an effort to identify possible diagnostic, prognostic, or therapeutic implications.

The study is observational, multicenter, national, retrospective/ Prospective cohort.