Annexin A1 (MRQ-3)

ANXA1 is strongly expressed on the cell membrane and occasionally in the cytoplasm of tumor cells in 97% of samples from patients with hairy cell leukemia. By contrast, B-cell lymphomas other than hairy cell leukemia, including typical splenic lymphoma with villous lymphocytes and patients with variant hairy cell leukemia-as defined by current morphologic, phenotypic, and clinical criteria-are ANXA1-negative. In a study by Falini et al. ANXA1 immunodetection was 100% sensitive and specific for hairy cell leukemia. Normal B cells from different lympho-hemopoietic tissues were ANXA1-negative. In this study the expression of ANXA1 in myeloid cells, macrophages, or T-cell subset served as positive control. These findings validated the results of gene expression profiling in hairy cell leukemia at the protein level by showing that ANXA1 is consistently expressed in this type of leukemic disease, but not in other B-cell lymphomas. Of note is that negativity for ANXA1 was also present in patients with splenic lymphoma with villous lymphocytes, variant hairy cell leukemia, prolymphocytic leukemia, marginal zone and lymphoplasmacytoid lymphomas. Thus, ANXA1 is a molecule specific to hairy cell leukemia that can be used to differentiate this disease from other B-cell lymphomas. Wang et al. showed that high ANXA1 expression is frequent in esophageal and esophagogastric junction adenocarcinomas, is associated with more advanced pathologic T stage and the presence of distant metastasis, and is an independent prognostic factor for patient survival.