Sonic hedgehog signaling proteins and ATP-binding cassette G2 are aberrantly expressed in diffuse large B-Cell lymphoma

Abstract

Dysregulation of the sonic hedgehog (SHH) signaling pathway has been shown in several cancer types, but has not been explored in diffuse large B-cell lymphoma. We assessed 67 cases of diffuse large B-cell lymphoma for expression of SHH (ligand), GLI1, GLI2 and GLI3 (transcriptional effectors of SHH signaling), and the ATP-binding cassette (ABC)G2 (a downstream target of SHH signaling), using immunohistochemistry. For comparison, we assessed the expression levels of these proteins in 28 cases of follicular lymphoma, 5 chronic lymphocytic leukemia/small lymphocytic lymphoma, and 5 reactive lymph nodes. In diffuse large B-cell lymphoma, SHH was expressed in 61 of 67 (91%) cases, GLI1 in 62 of 67 (93%), GLI2 in 41 of 56 (73%), and GLI3 in 22 of 56 (39%). Expression of ABCG2 was detected in 52 of 55 (95%) cases and was high in 15 (27%) cases. SHH expression positively correlated with expression levels of ABCG2 (P=0.05). Patients with diffuse large B-cell lymphoma with high ABCG2 expression showed significantly shorter overall survival (P=0.031) and failure-free survival (P=0.029) compared with patients with tumors with low or no expression of ABCG2. Diffuse large B-cell lymphomas expressed SHH, and GLI1, GLI2, and GLI3 more frequently and more intensely than cases of follicular lymphoma or chronic lymphocytic leukemia/small lymphocytic lymphoma. In conclusion, our data show that SHH signaling proteins and ABCG2 are aberrantly expressed in diffuse large B-cell lymphoma and that ABCG2 expression has prognostic implications. These findings also provide evidence that dysregulation of the SHH pathway may be involved in the pathogenesis of diffuse large B-cell lymphoma.