The helix‐loop‐helix protein Id2 is expressed differentially and induced by myc in T‐cell lymphomas

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Abstract
BACKGROUND. Inhibitor of DNA binding 2 (Id2), a helix-loop-helix protein of the inhibitor of differentiation (ID) family, is involved in hematopoiesis, mainly through interaction with the E-family of transcription factors. Recent studies have shown that Id2 is overexpressed in some types of B-cell lymphoma, including classical Hodgkin lymphoma. The authors of the current study hypothesized that Id2 also is overexpressed in T-cell lymphomas. METHODS. By using reverse-transcriptase polymerase chain reaction (RT-PCR) and Western blot analyses, high Id2 messenger RNA (mRNA) and protein levels, respectively, were detected in all 4 T-cell anaplastic large cell lymphoma (ALCL) cell lines that were tested. RESULTS. Immunohistochemistry results indicated that Id2 was expressed strongly in 21 of 27 (78%) ALCL tumors (79% anaplastic lymphoma kinase [ALK]-negative and 75% ALK-positive), in 5 of 10 (50%) extranodal natural killer/T (NK/T)-cell lymphomas of the nasal type, in 2 of 8 (25%) cutaneous ALCLs, in 2 of 9 (22%) enteropathy type T-cell lymphomas, in 1 of 5 (20%) peripheral T-cell lymphomas not otherwise specified, and in 1 of 8 (13%) T-cell prolymphocytic leukemias. Other types of T-cell lymphoma were negative for Id2. Because it is known that myc is expressed in ALCL, myc was inhibited selectively in 2 ALCL cell lines, resulting in a concentration-dependent decrease in Id2 mRNA and protein levels. Conversely, forced expression of myc in HEK 293T cells using an myc/green fluorescent protein adenoviral vector resulted in Id2 up-regulation. CONCLUSIONS. Taken together, the current data suggest that Id2 commonly is overexpressed in highly proliferative T-cell lymphomas, and its expression may result from transcriptional activation of myc in these tumors. Cancer 2008. © 2007 American Cancer Society.