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The fat-derived protein adiponectin is an important insulin-sensitizing adipocytokine which is downregulated in insulin resistance and obesity. Recently, two receptors of this adipose-expressed protein called adiponectin receptor 1 (AdipoR1) and 2 (AdipoR2) have been cloned. To clarify expression and regulation of these receptors in fat cells, AdipoR1 and AdipoR2 mRNA was measured by quantitative real-time reverse transcription-polymerase chain reaction during di¡erentiation of 3T3-L1 adipocytes and after treatment with various hormones known to induce insulin resistance. Interestingly, AdipoR2 synthesis was signi¢cantly increased up to 4.8-fold during di¡er-entiation of 3T3-L1 preadipocytes, whereas AdipoR1 expression was only augmented up to 1.4-fold. Furthermore, growth hormone (GH) induced AdipoR2, but not AdipoR1 mRNA by up to 2.4-fold in a dose-and time-dependent fashion with signi¢cant stimulation detectable at concentrations as low as 5 ng/ml GH and as early as 2 h after e¡ector addition. The positive e¡ect of GH on AdipoR2 expression could be reversed by withdrawal of the hormone for 24 h. In contrast, other key hormones involved in the regulation of insulin resistance and energy metabolism such as insulin, isoproterenol, dexamethasone, triiodothyronine, angiotensin 2, tumor necrosis factor K K, and interleukin-6 did not in£uence AdipoR1 and AdipoR2 synthesis in vitro. Taken together, our results suggest that AdipoR2 expression is di¡er-entiation-dependent and selectively regulated by GH implying a potential role of this hormone in adiponectin-associated alterations of insulin sensitivity and energy homeostasis.

Cyclin D1 overexpression is the hallmark of mantle cell lymphoma (MCL). However, the importance of cyclin D1 in the maintenance and progression of the disease remains to be defined. The aim of this study was to elucidate the role of cyclin D1 overexpression using an efficient cyclin D1-shRNA and a lentiviral system in well-characterized MCL cell lines. Surprisingly, the knockdown of cyclin D1 led to a moderate retardation in growth, without induction of apoptosis. The cyclin D1-shRNA-transduced MCL cells showed a 15% shift from S phase to G 1 phase of the cell cycle, a weak induction of p27 Kip1 , decreased Rb (Ser807/811) phosphorylation, and a consistent upregulation of cyclin D2 mRNA and protein expression. However, double knockdown of cyclins D1 and D2 did not intensify the effects observed with cyclin D1 knockdown alone. These data suggest that the moderate effects of cyclin D1 downregulation on survival and proliferation are likely the result of compensatory cyclin-independent mechanisms governing proliferation or alternatively, secondary genetic events that make cyclin D1 dispensable. These findings have important implications for MCL therapy, as strategies targeting only cyclin D1 function might be hampered by compensatory regulatory mechanisms, resulting in a low probability of treatment response.

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BackgroundAnaplastic lymphoma kinase (ALK)-positive anaplastic large cell lymphoma is characterized by the t(2;5) chromosomal translocation, resulting in the expression of a fusion protein formed of nucleophosmin (NPM) and ALK. Recently, we reported the abnormal expression of the transcription factor CCAAT/enhancer binding protein-beta (C/EBPβ) in ALK-positive anaplastic large cell lymphomas, and demonstrated its dependence on NPM-ALK activity. Design and MethodsIn this study, the role of C/EBPβ in proliferation and survival of ALK-positive anaplastic large cell lymphomas was investigated, as well as the mechanism of its expression and activity. Highly effective short hairpin RNA sequences and/or pharmacological inhibitors were used to abrogate the expression or activity of C/EBPβ, signal transducer and activator of transcription 3 (STAT3), AKT, extracellular signal-related kinase 1/2 (ERK1/2) and mammalian target of rapamycin (mTOR). ResultsInterference with C/EBPβ expression resulted in a dramatic decrease in cell proliferation in ALK-positive anaplastic large cell lymphomas, with a mild induction of apoptosis after 6 days. Down-regulation of STAT3 resulted in a marked decrease in C/EBPβ mRNA and protein levels with impairment in cell proliferation and viability, underscoring the important role of these two proteins in ALK-mediated oncogenesis. Additionally, we demonstrated that reduction of ERK1/2 activity led to C/EBPβ Thr 235 dephosphorylation and moderate growth retardation. The AKT/mTOR signaling pathway did not have any influence on C/EBPβ expression or C/EBPβ phosphorylation. ConclusionsThese findings reveal the convergence of STAT3 and ERK1/2 signaling pathways activated by NPM-ALK in mediating the regulation of C/EBPβ expression, a transcription factor central to NPM-ALK transformation.Key words: anaplastic large cell lymphoma (ALCL), C/EBPβ, STAT3, RNA interference, cell proliferation. STAT3 signaling pathway. Haematologica 2010;95:760-767. doi:10.3324/haematol.2009 This is an open-access paper. © F e r r a t a S t o r t i F o u n d a t i o n Citation: Anastasov N, Bonzheim I, Rudelius M, Klier M, Dau T, Angermeier D, Duyster J, Pittaluga S, Fend F, Raffeld M, and Quintanilla-Martinez L. C/EBPβ expression in ALK-positive anaplastic large cell lymphomas is required for cell proliferation and is induced by the C/EBPβ expression in ALK-positive anaplastic large cell lymphomas is required for cell proliferation and is induced by the STAT3 signaling pathway