A rapamycin derivative (everolimus) controls proliferation through down-regulation of truncated CCAAT enhancer binding protein β and NF-κB activity in Hodgkin and anaplastic large cell lymphomas

Abstract

The immunosuppressive macrolide rapamycin and its derivative everolimus (SDZ RAD, RAD) inhibit the mammalian target of rapamycin (mTOR) signaling pathway. In this study, we provide evidence that RAD has profound antiproliferative activity in vitro and in NOD/SCID mice in vivo against Hodgkin lymphoma (HL) and anaplastic large cell lymphoma (ALCL) cells. Moreover, we identified 2 molecular mechanisms that showed how RAD exerts antiproliferative effects in HL and ALCL cells. RAD down-regulated the truncated isoform of the transcription factor CCAAT enhancer binding protein ␤ (C/ EBP␤), which is known to disrupt terminal differentiation and induce a transformed phenotype. Furthermore, RAD inhibited constitutive nuclear factor B (NF-B) activity, which is a critical sur- IntroductionHodgkin lymphoma (HL) and anaplastic large cell lymphoma (ALCL) share morphologic and immunophenotypic markers in a subgroup of cases although they are biologically distinct entities. 1 Therefore, pathologic diagnosis is sometimes difficult to achieve and these cases are classified as "gray-zone lymphomas." 2 Moreover, in both entities novel therapeutic options are needed, as curative therapy of HL is compromised by a high risk of long-term complications, and anaplastic lymphoma kinase (ALK)-negative ALCL still has a very unfavorable prognosis with current treatment strategies. [3][4][5] The macrocyclic lactone everolimus (SDZ, RAD) RAD is a rapamycin derivative with potent immunosuppressive and antiproliferative properties. [6][7][8][9][10] It is further known to inhibit growth factor-driven cell proliferation of hematopoietic and nonhematopoietic cells. 6,10 In addition, RAD is a potent inhibitor of human Epstein-Barr virus (EBV)-transformed B lymphocytes in vitro and in vivo, arresting cell-cycle progression and increasing the apoptotic rate of EBV ϩ B cells. 10 Therefore, it has been suggested that RAD might be effective in the prevention and treatment of human posttransplant lymphoproliferative disorders. 10 Here, we investigated whether RAD inhibits tumor cell proliferation of HL and ALCL. We show that RAD significantly inhibits proliferation of HL and ALCL cells in vitro and arrests cell-cycle progression in G 0 /G 1 . Furthermore, we demonstrate that in vivo, RAD markedly suppresses tumor cell proliferation of HL and ALCL cells, xenotransplanted into NOD/SCID mice. Our data suggest that RAD might be used in combination chemotherapy for the treatment of HL and ALCL. Moreover, we studied the mechanisms of proliferation arrest mediated by the mammalian target of rapamycin (mTOR) inhibitor RAD to identify the molecular targets in HL and ALCL. The mTOR pathway controls the translation initiation machinery in response to nutrients and growth factors thereby coordinating cell growth with cell division. 11 A transcription factor that is a critical target of mTOR is the CCAAT enhancer binding protein (C/EBP)␤. 11-13 C/EBP␤ has previously been identified as an essential downstream target in tumors expressing activated cyclin D1. 14 Our dat...

Functional validation of the anaplastic lymphoma kinase signature identifies CEBPB and Bcl2A1 as critical target genes

“…This data are in accordance with the notion that the CEBPB promoter is regulated by several factors, such as CREB/ ATF and Sp1 proteins, and by STAT3 itself, albeit indirectly, and is subject to a tight autoregulation (28). In conjunction with previously published observations on C/EBPβ expression in ALCL (29,30), our data demonstrate for the first time to our knowledge an instrumental and pathogenetic role of C/EBPβ in promoting NPM-ALK oncogenesis.…”

“…The transcription factor C/EBPβ (28) is of particular interest since it is abundantly expressed in Hodgkin lymphoma and ALCL cells (29), and its expression was very recently shown to be regulated by ALK in ALCL cells (30). We then decided to investigate whether C/EBPβ plays a pathogenetic role in ALK-driven transformation.…”

TSC1 controls IL-1β expression in macrophages via mTORC1-dependent C/EBPβ pathway

“…It was reported that C/EBPb isoform production is regulated by mTORC1 pathway: activated mTORC1 enhances generation of LIP while inhibition of mTOR promotes LAP expression 56,57 . In our studies, we found that TSC1 KO macrophages displayed enhanced mTOR activity and decreased C/EBPb protein level.…”

Deregulation of the endogenous C/EBPβ LIP isoform predisposes to tumorigenesis

“…Enhanced expression of C/EBPβ was observed in human tumors, including mammary carcinomas [11][12][13], anaplastic large cell lymphoma (ALCL) [14][15][16], endometrial adenocarcinoma [17], ovarian [18], colorectal [19], liver [7] and skin cancer [20]. Among these, enhanced expression of the truncated C/EBPβ LIP isoform was reported in breast, ALCL, ovarian and colorectal neoplasia.…”