ABSTRACT
Aberrant overexpression of the miR-17-92 polycistron is strongly associated with B-cell lymphomagenesis. Recent studies have shown that miR-17-92 down-regulates the proapoptotic protein Bim, leading to overexpression of Bcl2, which likely plays a key role in lymphomagenesis. However, the fact that Jeko-1 cells derived from mantle cell lymphoma exhibit both homozygous deletion of BIM and overexpression of miR-17-92 suggests other targets are also involved in B-cell lymphomagenesis. To identify essential target(s) of miR-17-92 in lymphomagenesis, we first transfected miR-17-92 into 2 genetically distinct B-cell lymphoma cell lines: Raji, which overexpress c-Myc, and SUDHL4, which overexpress Bcl2. Raji transfected with miR-17-19b-1 exhibited down-regulated expression of Bim and a slight up-regulation in Bcl2 expression. On the other hand, SUDHL4 transfectants showed aggressive cell growth reflecting facilitated cell cycle progression at the G(1) to S transition and decreased expression of CDKN1A mRNA and p21 protein (CDKN1A/p21) that was independent of p53 expression. Conversely, transfection of antisense oligonucleotides against miR-17 and miR-20a into Jeko-1 led to up-regulation of CDKN1A/p21, resulting in decreased cell growth with G(1) to S arrest. Thus, CDKN1A/p21 appears to be an essential target of miR-17-92 during B-cell lymphomagenesis, which suggests the miR-17-92 polycistron has distinct targets in different B-cell lymphoma subtypes.
Subject(s)
Gene Expression Regulation, Leukemic , Lymphoma, B-Cell/metabolism , MicroRNAs/metabolism , Neoplasm Proteins/biosynthesis , RNA, Neoplasm/metabolism , Animals , Apoptosis/drug effects , Apoptosis/genetics , Cell Line, Tumor , G1 Phase/drug effects , G1 Phase/genetics , Gene Expression Regulation, Leukemic/drug effects , Humans , Lymphoma, B-Cell/genetics , MicroRNAs/antagonists & inhibitors , MicroRNAs/genetics , Neoplasm Proteins/genetics , Oligodeoxyribonucleotides, Antisense/genetics , Oligodeoxyribonucleotides, Antisense/pharmacology , RNA, Neoplasm/antagonists & inhibitors , RNA, Neoplasm/genetics , Rats , S Phase/drug effects , S Phase/geneticsABSTRACT
A 43-year-old female was admitted with therapy-resistant pancreatitis and an abdominal tumor around the pancreatic head. Laboratory data revealed leukocytosis with a white blood cell count of 18200/microl, 25% atypical cells and an LDH of 13410 IU/l. The bone marrow was comprised of 78.4 percent lymphoblastoid cells which were positive for CD10, CD19 and CD20, and the cytogenetic study of which demonstrated the presence of t(8;14) (q24;q32) and t(14;18) (q32;q21) in the same clone. The patient was diagnosed as having Burkitt's lymphoma (BL) with t(8;14) and t(14;18). Although CODOX-M and IVAC therapy combined with rituximab achieved complete remission, she died of rapid progressive disease during whole brain irradiation before autologous peripheral blood stem cell transplantation. Even if the intensive chemotherapy with rituximab is given adequately, durable remission may not be achieved in BL with translocation of t(8;14) and t(14;18). A more effective therapy remains to be established for the treatment of this disease.
