RNA-Binding Protein VICKZ Is Expressed in a Germinal Center Associated Pattern among Lymphoma Subtypes.

Recent effort in the molecular characterization of diffuse large B-cell lymphoma (DLBCL) has led to the recognition that patients with DLBCL of germinal center origin exhibit a better overall survival. Thus, identification and characterization of markers of germinal center derivation are of importance in dissecting prognostic subclasses of DLBCL. The VICKZ (Vg1 RBP/Vera, IMP1, 2, 3, CRD-BP, KOC, ZBP-1) family members are RNA-binding proteins that recognize specific RNA targets and have been implicated in diverse cellular functions including cell polarity, migration, proliferation and tumorigenesis/metastasis. We generated an antibody that recognizes all three isoforms of VICKZ protein and characterized its expression in normal lymphoid tissue and in lymphoma subtypes. In normal tonsils, VICKZ protein showed a germinal center-specific pattern of expression with staining localized to the cytoplasm. Among 868 non-Hodgkin and Hodgkin lymphomas tested by immunohistochemistry on tissue microarrays, staining for VICKZ protein was present in 76% (126/165) of follicular lymphoma, 78% (155/200) of DLBCL, 90% (9/10) of mediastinal large B-cell lymphoma, and 100% (2/2) of Burkitt lymphoma. A subset of mantle cell lymphoma (11%, 2/19), extranodal (8%, 2/25), and nodal (20%, 1/5) marginal zone lymphoma and lymphoblastic lymphoma (25%, 4/13), showed VICKZ staining. The majority of lymphocyte predominant Hodgkin (92%, 12/13) and classical Hodgkin (94%, 101/108) lymphoma were found to be positive. Among T cell lymphoma, anaplastic large cell lymphoma were positive (75%, 6/9). Additional work is in progress to correlate VICKZ protein expression with other germinal center markers such as HGAL, BCL6 and CD10 as well as with prognostic subclasses of DLBCL. The differential expression pattern of VICKZ protein in lymphoma subtypes suggests a potential utility for VICKZ in the identification of subgroups of DLBCL associated with different prognoses.