Activated Notch1 signaling promotes tumor cell proliferation and survival in Hodgkin and anaplastic large cell lymphoma

Abstract

Notch signaling controls cell fate decisions of hematopoietic progenitors by inhibiting certain steps of differentiation and inducing either self-renewal or differentiation toward lymphoid or myeloid lineages. In addition, truncated Notch1 alleles could be associated with 10% of all cases of human T lymphoblastic leukemia and, when introduced into mouse bone marrow stem cells, cause T-cell neoplasms. However, functional links between the abundant expression of intact Notch1 and oncogenesis are still lacking. Here we show that Notch1 is highly expressed in B-and T-cell-derived tumor cells of Hodgkin and anaplastic large cell lymphoma. We demonstrate a novel mechanism for the oncogenic capacity of Notch1 by showing that the interaction between intact Notch1 on tumor cells and its ligand Jagged1 dramatically induces proliferation and inhibition of apoptosis in vitro. We further provide evidence that in Hodgkin and anaplastic large cell lymphoma, Jagged1 is expressed in malignant and in bystander cells colocalizing with Notch1-positive tumor cells. Notch1 signaling may therefore be activated in tumor cells by Jagged1 through homotypic or heterotypic cell-cell interactions, and it seems likely that these interactions contribute to lymphomagenesis in vivo. Thus, our data suggest that activated Notch1 signaling plays an important role in the pathobiology of Hodgkin and anaplastic large cell lymphoma and that it might be a potential new target for treatment. ( It has further been demonstrated that HRS cells contain nonfunctional immunoglobulin (Ig) genes, suggesting that they are derived from germinal center cells that should have been negatively selected but were rescued from apoptosis by cellular transforming events. 3,4 Our previous work has provided evidence that constitutive NF-B activity is a survival factor for HRS cells. [5][6][7][8] We have directly manipulated the NF-B system and overexpressed a dominant-negative version of the inhibitor IB␣. HRS cells depleted of constitutive nuclear NF-B reveal decreased proliferation rates, enhanced apoptotic response, and strongly impaired tumor growth in severe combined immunodeficient mice. 7 To investigate molecular alterations of the NF-B/IB system that might be responsible for constitutive NF-B activity, we have analyzed the IB␣ gene. 9 We and others have demonstrated mutations of the IB␣ gene in a subset of HD cases that contribute to constitutive NF-B activation and are involved in the pathogenesis of HD. 9,10 To evaluate additional molecular mechanisms that lead to constitutive NF-B activity in HRS cells, and because activated Notch signaling has been implicated in the regulation of NF-B, 11-13 we analyzed Notch1 gene expression in cultured and primary HRS cells.Notch1 belongs to a family of transmembrane receptors that control cell proliferation and differentiation in response to extracellular ligands expressed on neighboring cells. 14-18 Notch1 has been isolated as a translocation in human acute T-cell lymphoblastic leukemia-lymphoma, 19 and its constitutively ac...

Notch is an essential upstream regulator of NF-κB and is relevant for survival of Hodgkin and Reed–Sternberg cells

“…22 As shown in Figure 1a, Notch1 was highly expressed in most cultured HRS cells (except in L1236 cells) as previously described. 3 The control cell lines (HEP-G2: hepatocellular carcinoma cells and BJAB: Burkitt lymphoma cells) also expressed significant amounts of Notch1, whereas NIH-3T3 mouse embryonic fibroblasts revealed undetectable levels of Notch1. In addition, we recently demonstrated that all cultured HRS cells and the Burkitt lymphoma cell line BJAB express variable levels of Notch1 IC .…”

“…3 Nuclear extracts were prepared using the Nuclear Extract Kit (Active Motif, Carlsbad, CA, USA). Blots Notch and NF-jB in HRS cells R Schwarzer et al were incubated with monoclonal rabbit anti-Notch1, anti-p50/ p105, anti-p65 antibodies (Epitomics, Burlingame, CA, USA), anti-cleaved Notch1, rabbit polyclonal anti-p52/p100, antiphospho-p100, anti-RelB, anti-c-Rel, anti-poly-(ADP-ribose) polymerase, anti-cleaved poly-(ADP-ribose) polymerase (Asp214) antibodies (Cell Signaling Technologies, Frankfurt, Germany), anti-human CD30 (R&D Systems) or mouse monoclonal anti-tubulin antibodies (Sigma, Deisenhofen, Germany).…”

“…2 We have shown earlier that the Notch family members Notch1 and Notch2 are aberrantly expressed in Hodgkin and Reed-Sternberg (HRS) cells, and that external stimulation of Notch signaling in HRS cells through the Notch ligand Jagged1 promotes their proliferation and protects them from arsenic-induced apoptosis. 3 Jagged1 is expressed in HRS cells and bystander cells in vivo, 3 and the Notch ligands of the Delta-like family (DLL1, DLL3, DLL4) and Jagged2 are expressed in cultured HRS cells to activate Notch signaling. 4 We further demonstrated that absence of the main Notch1 inhibitor Deltex1 and high-level expression of the Notch co-activator of the Mastermind-like family contribute to deregulated Notch signaling in HRS cells.…”

Aberrant expression of Notch1 interferes with the B-lymphoid phenotype of neoplastic B cells in classical Hodgkin lymphoma

“…18 Proteins (30 mg) were resolved by SDS-PAGE and transferred to nitrocellulose membranes. Membranes were incubated with mouse monoclonal anti-Notch1 (clone mN1A, BD Pharmingen, Heidelberg, Germany), rat anti-Notch2 (Developmental Studies Hybridoma Bank at the University of Iowa), anti-PAX5 (clone 24, BD Pharmingen) or anti-tubulin (Sigma-Aldrich, Munich, Germany) antibodies followed by HRP-conjugated secondary antibodies (Promega and Dianova, Hamburg, Germany) and detected by enhanced chemiluminescence (Amersham, Freiburg, Germany).…”

“…17 To identify deregulated processes that extinguish the B-cell phenotype by potentially interfering with E2A and EBF function in HRS cells, we analyzed the role of the transmembrane receptor Notch1, which we recently found to be highly expressed in HRS cells. 18 Notch1 belongs to a family of transmembrane receptors that control cell proliferation and differentiation in response to extracellular ligands expressed on neighbouring cells. 19 Upon ligand binding, the Notch receptor is cleaved and the intracellular part of the receptor is liberated.…”