Hodgkin lymphoma cell lines: to separate the wheat from the chaff

Advances in Hodgkin lymphoma research

Hodgkin lymphoma (HL) has been and still is the most enigmatic lymphoid malignancy in humans. Since the first molecular analysis of isolated Hodgkin and Reed-Sternberg (HRS) tumor cells of classic HL 30 years ago, substantial advances in our understanding of HL have been made. This review describes the cellular origin of HL, summarizes the current knowledge about the genetic lesions in HRS cells, and highlights the role of Epstein-Barr virus (EBV) in HL pathogenesis. Moreover, the pathobiological roles of altered gene expression and deregulated signaling pathways are discussed and key aspects of the HL microenvironment are presented.

Chemotherapy's effects on autophagy in the treatment of Hodgkin's lymphoma: a scoping review

BACKGROUND

Classical Hodgkin Lymphomas (HL) are a unique malignant growth with an excellent initial prognosis. However, 10-30% of patients will still relapse after remission. One primary cellular function that has been the focus of tumor progression is autophagy. This process can preserve cellular homeostasis under stressful conditions. Several studies have shown that autophagy may play a role in developing HL. Therefore, this review aimed to explore chemotherapy's effect on autophagy in HL, and the effects of autophagy on HL.

METHODS

A scoping review in line with the published PRISMA extension for scoping reviews (PRISMA-ScR) was conducted. A literature search was conducted on the MEDLINE database and the Cochrane Central Register of Controlled Trials (CENTRAL). All results were retrieved and screened, and the resulting articles were synthesized narratively.

RESULTS

The results showed that some cancer chemotherapy also induces autophagic flux. Although the data on HL is limited, since the mechanisms of action of these drugs are similar, we can infer a similar relationship. However, this increased autophagy activity may reflect a mechanism for increasing tumor growth or a cellular compensation to inhibit its growth. Although evidence supports both views, we argued that autophagy allowed cancer cells to resist cell death, mainly due to DNA damage caused by cytotoxic drugs.

CONCLUSION

Autophagy reflects the cell's adaptation to survive and explains why chemotherapy generally induces autophagy functions. However, further research on autophagy inhibition is needed as it presents a viable treatment strategy, especially against drug-resistant populations that may arise from HL chemotherapy regimens.

Epstein-Barr Virus Orchestrates Spatial Reorganization and Immunomodulation within the Classic Hodgkin Lymphoma Tumor Microenvironment

Classic Hodgkin Lymphoma (cHL) is a tumor composed of rare malignant Hodgkin and Reed-Sternberg (HRS) cells nested within a T-cell rich inflammatory immune infiltrate. cHL is associated with Epstein-Barr Virus (EBV) in 25% of cases. The specific contributions of EBV to the pathogenesis of cHL remain largely unknown, in part due to technical barriers in dissecting the tumor microenvironment (TME) in high detail. Herein, we applied multiplexed ion beam imaging (MIBI) spatial pro-teomics on 6 EBV-positive and 14 EBV-negative cHL samples. We identify key TME features that distinguish between EBV-positive and EBV-negative cHL, including the relative predominance of memory CD8 T cells and increased T-cell dysfunction as a function of spatial proximity to HRS cells. Building upon a larger multi-institutional cohort of 22 EBV-positive and 24 EBV-negative cHL samples, we orthogonally validated our findings through a spatial multi-omics approach, coupling whole transcriptome capture with antibody-defined cell types for tu-mor and T-cell populations within the cHL TME. We delineate contrasting transcriptomic immunological signatures between EBV-positive and EBV-negative cases that differently impact HRS cell proliferation, tumor-immune interactions, and mecha-nisms of T-cell dysregulation and dysfunction. Our multi-modal framework enabled a comprehensive dissection of EBV-linked reorganization and immune evasion within the cHL TME, and highlighted the need to elucidate the cellular and molecular fac-tors of virus-associated tumors, with potential for targeted therapeutic strategies.

In Doxorubicin-Adapted Hodgkin Lymphoma Cells, Acquiring Multidrug Resistance and Improved Immunosuppressive Abilities, Doxorubicin Activity Was Enhanced by Chloroquine and GW4869

Classical Hodgkin lymphoma (cHL) is a highly curable disease (70-80%), even though long-term toxicities, drug resistance, and predicting clinical responses to therapy are major challenges in cHL treatment. To solve these problems, we characterized two cHL cell lines with acquired resistance to doxorubicin, KM-H2dx and HDLM-2dx (HRSdx), generated from KM-H2 and HDLM-2 cells, respectively. HRSdx cells developed cross-resistance to vinblastine, bendamustin, cisplatin, dacarbazine, gemcitabine, brentuximab vedotin (BV), and γ-radiation. Both HDLM-2 and HDLM-2dx cells had intrinsic resistance to BV but not to the drug MMAE. HDLM-2dx acquired cross-resistance to caelyx. HRSdx cells had in common decreased CD71, CD80, CD54, cyt-ROS, HLA-DR, DDR1, and CD44; increased Bcl-2, CD58, COX2, CD26, CCR5, and invasive capability; increased CCL5, TARC, PGE2, and TGF-β; and the capability of hijacking monocytes. In HRSdx cells less sensitive to DNA damage and oxidative stress, the efflux drug transporters MDR1 and MRP1 were not up-regulated, and doxorubicin accumulated in the cytoplasm rather than in the nucleus. Both the autophagy inhibitor chloroquine and extracellular vesicle (EV) release inhibitor GW4869 enhanced doxorubicin activity and counteracted doxorubicin resistance. In conclusion, this study identifies common modulated antigens in HRSdx cells, the associated cross-resistance patterns, and new potential therapeutic options to enhance doxorubicin activity and overcome resistance.

CD30 induces Reed-Sternberg cell-like morphology and chromosomal instability in classic Hodgkin lymphoma cell lines

Classic Hodgkin lymphoma (cHL) is characterized by multinucleated cells called Reed-Sternberg (RS) cells and genetic complexity. Although CD30 also characterizes cHL cells, its biological roles are not fully understood. In this report, we examined the link between CD30 and these characteristics of cHL cells. CD30 stimulation increased multinucleated cells resembling RS cells. We found chromatin bridges, a cause of mitotic errors, among the nuclei of multinucleated cells. CD30 stimulation induced DNA double-strand breaks (DSBs) and chromosomal imbalances. RNA sequencing showed significant changes in the gene expression by CD30 stimulation. We found that CD30 stimulation increased intracellular reactive oxygen species (ROS), which induced DSBs and multinucleated cells with chromatin bridges. The PI3K pathway was responsible for CD30-mediated generation of multinucleated cells by ROS. These results suggest that CD30 involves generation of RS cell-like multinucleated cells and chromosomal instability through induction of DSBs by ROS, which subsequently induces chromatin bridges and mitotic error. The results link CD30 not only to the morphological features of cHL cells, but also to the genetic complexity, both of which are characteristic of cHL cells.

Targeting tumour-associated macrophages in hodgkin lymphoma using engineered extracellular matrix-mimicking cryogels

Tumour-associated macrophages are linked with poor prognosis and resistance to therapy in Hodgkin lymphoma; however, there are no suitable preclinical models to identify macrophage-targeting therapeutics. We used primary human tumours to guide the development of a mimetic cryogel, wherein Hodgkin (but not Non-Hodgkin) lymphoma cells promoted primary human macrophage invasion. In an invasion inhibitor screen, we identified five drug hits that significantly reduced tumour-associated macrophage invasion: marimastat, batimastat, AS1517499, ruxolitinib, and PD-169316. Importantly, ruxolitinib has demonstrated recent success in Hodgkin lymphoma clinical trials. Both ruxolitinib and PD-169316 (a p38 mitogen-activated protein kinase (p38 MAPK) inhibitor) decreased the percent of M2-like macrophages; however, only PD-169316 enhanced the percentage of M1-like macrophages. We validated p38 MAPK as an anti-invasion drug target with five additional drugs using a high-content imaging platform. With our biomimetic cryogel, we modeled macrophage invasion in Hodgkin lymphoma and then used it for target discovery and drug screening, ultimately identifying potential future therapeutics.

Hodgkin Lymphoma Cell Lines and Tissues Express mGluR5: A Potential Link to Ophelia Syndrome and Paraneoplastic Neurological Disease

Ophelia syndrome is characterized by the coincidence of severe neuropsychiatric symptoms, classical Hodgkin lymphoma, and the presence of antibodies to the metabotropic glutamate 5 receptor (mGluR5). Little is known about the pathogenetic link between these symptoms and the role that anti-mGluR5-antibodies play. We investigated lymphoma tissue from patients with Ophelia syndrome and with isolated classical Hodgkin lymphoma by quantitative immunocytochemistry for mGluR5-expression. Further, we studied the L-1236, L-428, L-540, SUP-HD1, KM-H2, and HDLM-2 classical Hodgkin lymphoma cell lines by FACS and Western blot for mGluR5-expression, and by transcriptome analysis. mGluR5 surface expression differed significantly in terms of receptor density, distribution pattern, and percentage of positive cells. The highest expression levels were found in the L-1236 line. RNA-sequencing revealed more than 800 genes that were higher expressed in the L-1236 line in comparison to the other classical Hodgkin lymphoma cell lines. High mGluR5-expression was associated with upregulation of PI3K/AKT and MAPK pathways and of downstream targets (e.g., EGR1) known to be involved in classical Hodgkin lymphoma progression. Finally, mGluR5 expression was increased in the classical Hodgkin lymphoma-tissue of our Ophelia syndrome patient in contrast to five classical Hodgkin lymphoma-patients without autoimmune encephalitis. Given the association of encephalitis and classical Hodgkin lymphoma in Ophelia syndrome, it is possible that mGluR5-expression in classical Hodgkin lymphoma cells not only drives tumor progression but also triggers anti-mGluR5 encephalitis even before classical Hodgkin lymphoma becomes manifest.

Downregulation of STAT3 in Epstein-Barr Virus-Positive Hodgkin Lymphoma

STAT3 is a transcription factor which is activated via various signaling transduction pathways or Epstein-Barr virus (EBV) infection and plays an oncogenic role in lymphoid malignancies including Hodgkin lymphoma (HL). The tumor cells of HL are derived from germinal center B-cells and transformed by chromosomal rearrangements, aberrant signal transduction, deregulation of developmental transcription factors, and EBV activity. HL cell lines represent useful models to investigate molecular principles and deduced treatment options of this malignancy. Using cell line L-540, we have recently shown that constitutively activated STAT3 drives aberrant expression of hematopoietic NKL homeobox gene HLX. Here, we analyzed HL cell line AM-HLH which is EBV-positive but, nevertheless, HLX-negative. Consistently, AM-HLH expressed decreased levels of STAT3 proteins which were additionally inactivated and located in the cytoplasm. Combined genomic and expression profiling data revealed several amplified and overexpressed gene candidates involved in opposed regulation of STAT3 and EBV. Corresponding knockdown studies demonstrated that IRF4 and NFATC2 inhibited STAT3 expression. MIR155 (activated by STAT3) and SPIB (repressed by HLX) showed reduced and elevated expression levels in AM-HLH, respectively. However, treatment with IL6 or IL27 activated STAT3, elevated expression of HLX and MIR155, and inhibited IRF4. Taken together, this cell line deals with two conflicting oncogenic drivers, namely, JAK2-STAT3 signaling and EBV infection, but is sensitive to switch after cytokine stimulation. Thus, AM-HLH represents a unique cell line model to study the pathogenic roles of STAT3 and EBV and their therapeutic implications in HL.

Oncolytic Viruses in the Therapy of Lymphoproliferative Diseases

Cancer is a leading causes of death. Despite significant success in the treatment of lymphatic system tumors, the problems of relapse, drug resistance and effectiveness of therapy remain relevant. Oncolytic viruses are able to replicate in tumor cells and destroy them without affecting normal, healthy tissues. By activating antitumor immunity, viruses are effective against malignant neoplasms of various nature. In lymphoproliferative diseases with a drug-resistant phenotype, many cases of remissions have been described after viral therapy. The current level of understanding of viral biology and the discovery of host cell interaction mechanisms made it possible to create unique strains with high oncoselectivity widely used in clinical practice in recent years.

The Role of NKL Homeobox Genes in T-Cell Malignancies

Homeobox genes encode transcription factors controlling basic developmental processes. The homeodomain is encoded by the homeobox and mediates sequence-specific DNA binding and interaction with cofactors, thus operating as a basic regulatory platform. Similarities in their homeobox sequences serve to arrange these genes in classes and subclasses, including NKL homeobox genes. In accordance with their normal functions, deregulated homeobox genes contribute to carcinogenesis along with hematopoietic malignancies. We have recently described the physiological expression of eleven NKL homeobox genes in the course of hematopoiesis and termed this gene expression pattern NKL-code. Due to the developmental impact of NKL homeobox genes these data suggest a key role for their activity in the normal regulation of hematopoietic cell differentiation including T-cells. On the other hand, aberrant overexpression of NKL-code members or ectopical activation of non-code members has been frequently reported in lymphoid and myeloid leukemia/lymphoma, demonstrating their oncogenic impact in the hematopoietic compartment. Here, we provide an overview of the NKL-code in normal hematopoiesis and discuss the oncogenic role of deregulated NKL homeobox genes in T-cell malignancies.

NKL-Code in Normal and Aberrant Hematopoiesis

Simple Summary

Gene codes represent expression patterns of closely related genes in particular tissues, organs or body parts. The NKL-code describes the activity of NKL homeobox genes in the hematopoietic system. NKL homeobox genes encode transcription factors controlling basic developmental processes. Therefore, aberrations of this code may contribute to deregulated hematopoiesis including leukemia and lymphoma. Normal and abnormal activities of NKL homeobox genes are described and mechanisms of (de)regulation, function, and diseases exemplified.

Abstract

We have recently described physiological expression patterns of NKL homeobox genes in early hematopoiesis and in subsequent lymphopoiesis and myelopoiesis, including terminally differentiated blood cells. We thereby systematized differential expression patterns of eleven such genes which form the so-called NKL-code. Due to the developmental impact of NKL homeobox genes, these data suggest a key role for their activity in normal hematopoietic differentiation processes. On the other hand, the aberrant overexpression of NKL-code-members or the ectopical activation of non-code members have been frequently reported in lymphoid and myeloid leukemia/lymphoma, revealing the oncogenic potential of these genes in the hematopoietic compartment. Here, I provide an overview of the NKL-code in normal hematopoiesis and instance mechanisms of deregulation and oncogenic functions of selected NKL genes in hematologic cancers. As well as published clinical studies, our conclusions are based on experimental work using hematopoietic cell lines which represent useful models to characterize the role of NKL homeobox genes in specific tumor types.

Apoptotic regulator BCL-2 blockade as a potential therapy in classical Hodgkin Lymphoma

The challenge in classical Hodgkin Lymphoma (cHL) management is the 30-40% of refractory/relapsed cases.

AIMS

The aim of this work was to determine whether NIK and BCL-2 could be useful as prognosis biomarkers in cHL. In addition, we evaluated BCL-2 as a directed-therapy in cHL cell lines using venetoclax.

MAIN METHODS

We evaluated NIK and BCL-2 expression in 112 untreated cHL patients' lymph-node biopsies by immunohistochemistry. cHL cell lines were treated with venetoclax alone or combined with vincristine or doxorubicin. Cell viability, metabolic activity and cell death were analyzed by trypan-blue exclusion method, MTS assay and FDA/IP staining respectively.

KEY FINDINGS

No correlation between NIK or BCL-2 expression and the majority of the clinical parameters was found. Patients with ≥60% BCL-2+ HRS-cells had a shorter disease-free survival (DFS) and overall survival (OS) (p = 0.002, p = 0.02 respectively). A decision tree analysis, in a 30 patients subgroup, showed that patients with <60% NIK+ HRS-cells but with ≥60% BCL-2+ HRS-cells had a worse outcome in terms of DFS and OS. These parameters performed better as prognosis indicators as compared to the diagnosis bone marrow status. Human cHL cell lines U-H01, KM-H2, L1236, SUPHD1, L540 showed sensitivity to venetoclax. The co-treatment effect of venetoclax and vincristine or doxorubicin on cell viability was diverse depending on the cell line evaluated.

SIGNIFICANCE

BCL-2 should be considered as a prognosis biomarker as well as a potential new therapeutic target in cHL. We report for the first time the cytotoxic effect of venetoclax in human cHL cell lines.

Biology and Clinical Applicability of Plasma Thymus and Activation-Regulated Chemokine (TARC) in Classical Hodgkin Lymphoma

Thymus and activation-regulated chemokine (TARC) is produced by different cell types and is highly expressed in the thymus. It plays an important role in T cell development, trafficking and activation of mature T cells after binding to its receptor C-C chemokine receptor type 4 (CCR4) and consecutive signal transducer and activator of transcription 6 (STAT6) activation. Importantly, TARC is also produced by malignant Hodgkin and Reed-Sternberg (HRS) cells of classical Hodgkin lymphoma (cHL). In cHL, HRS cells survive and proliferate due to the micro-environment consisting primarily of type 2 T helper (Th2) cells. TARC-mediated signaling initiates a positive feedback loop that is crucial for the interaction between HRS and T cells. The clinical applicability of TARC is diverse. It is useful as diagnostic biomarker in both children and adults with cHL and in other Th2-driven diseases. In adult cHL patients, TARC is also a biomarker for treatment response and prognosis. Finally, blocking TARC signaling and thus inhibiting pathological Th2 cell recruitment could be a therapeutic strategy in cHL. In this review, we summarize the biological functions of TARC and focus on its role in cHL pathogenesis and as a biomarker for cHL and other diseases. We conclude by giving an outlook on putative therapeutic applications of antagonists and inhibitors of TARC-mediated signaling.

Genomic Landscape of Hodgkin Lymphoma

Simple Summary

Hodgkin lymphoma (HL) is composed of many reactive and only a few cancer cells, so-called Hodgkin and Reed-Sternberg (HRS) or lymphocyte predominant (LP) cells. Due to the scarcity of these cells, it was difficult to perform high-throughput molecular investigations on them for a long time. With the help of recently developed methods, it is now possible to analyze their genomes. This review summarizes the genetic alterations found in HRS and LP cells that impact immune evasion, proliferation and circumvention of programmed cell death in HL. Understanding these underlying molecular mechanisms is essential, as they may be of prognostic and predictive value and help to improve the therapy especially for patients with recurrent or treatment-resistant disease.

Abstract

Background: Hodgkin lymphoma (HL) is predominantly composed of reactive, non-neoplastic cells surrounding scarcely distributed tumor cells, that is, so-called Hodgkin and Reed-Sternberg (HRS) or lymphocyte predominant (LP) cells. This scarcity impeded the analysis of the tumor cell genomes for a long time, but recently developed methods (especially laser capture microdissection, flow cytometry/fluorescence-activated cell sorting) facilitated molecular investigation, elucidating the pathophysiological principles of “Hodgkin lymphomagenesis”. Methods: We reviewed the relevant literature of the last three decades focusing on the genomic landscape of classic and nodular lymphocyte predominant HL (NLPHL) and summarized molecular cornerstones. Results: Firstly, the malignant cells of HL evade the immune system by altered expression of PDL1/2, B2M and MHC class I and II due to various genetic alterations. Secondly, tumor growth is promoted by permanently activated JAK/STAT signaling due to pervasive mutations of multiple genes involved in the pathway. Thirdly, apoptosis of neoplastic cells is prevented by alterations of NF-κB compounds and the PI3K/AKT/mTOR axis. Additionally, Epstein-Barr virus infection can simultaneously activate JAK/STAT and NF-κB, similarly leading to enhanced survival and evasion of apoptosis. Finally, epigenetic phenomena such as promoter hypermethylation lead to the downregulation of B-lineage-specific, tumor-suppressor and immune regulation genes. Conclusion: The blueprint of HL genomics has been laid, paving the way for future investigations into its complex pathophysiology.

Molecular Pathogenesis of Hodgkin Lymphoma: Past, Present, Future

Our understanding of the tumorigenesis of classical Hodgkin lymphoma (cHL) and the formation of Reed–Sternberg cells (RS-cells) has evolved drastically in the last decades. More recently, a better characterization of the signaling pathways and the cellular interactions at play have paved the way for new targeted therapy in the hopes of improving outcomes. However, important gaps in knowledge remain that may hold the key for significant changes of paradigm in this lymphoma. Here, we discuss the past, present, and future of cHL, and review in detail the more recent discoveries pertaining to genetic instability, anti-apoptotic signaling pathways, the tumoral microenvironment, and host-immune system evasion in cHL.

The LL-100 Cell Lines Panel: Tool for Molecular Leukemia-Lymphoma Research

Certified cell line models provide ideal experimental platforms to answer countless scientific questions. The LL-100 panel is a cohort of cell lines that are broadly representative of all leukemia–lymphoma entities (including multiple myeloma and related diseases), rigorously authenticated and validated, and comprehensively annotated. The process of the assembly of the LL-100 panel was based on evidence and experience. To expand the genetic characterization across all LL-100 cell lines, we performed whole-exome sequencing and RNA sequencing. Here, we describe the conception of the panel and showcase some exemplary applications with a focus on cancer genomics. Due diligence was paid to exclude cross-contaminated and non-representative cell lines. As the LL-100 cell lines are so well characterized and readily available, the panel will be a valuable resource for identifying cell lines with mutations in cancer genes, providing superior model systems. The data also add to the current knowledge of the molecular pathogenesis of leukemia–lymphoma. Additional efforts to expand the breadth of available high-quality cell lines are clearly warranted.

Deregulated NKL Homeobox Genes in B-Cell Lymphoma

Recently, we have described physiological expression patterns of NKL homeobox genes in early hematopoiesis and in subsequent lymphopoiesis. We identified nine genes which constitute the so-called NKL-code. Aberrant overexpression of code-members or ectopically activated non-code NKL homeobox genes are described in T-cell leukemia and in T- and B-cell lymphoma, highlighting their oncogenic role in lymphoid malignancies. Here, we introduce the NKL-code in normal hematopoiesis and focus on deregulated NKL homeobox genes in B-cell lymphoma, including HLX, MSX1 and NKX2-2 in Hodgkin lymphoma; HLX, NKX2-1 and NKX6-3 in diffuse large B-cell lymphoma; and NKX2-3 in splenic marginal zone lymphoma. Thus, the roles of various members of the NKL homeobox gene subclass are considered in normal and pathological hematopoiesis in detail.

Development of a Bispecific Antibody Targeting CD30 and CD137 on Hodgkin and Reed-Sternberg Cells

Hodgkin Lymphoma (HL) is a malignancy that frequently affects young adults. Although, there are effective treatments not every patient responds, necessitating the development of novel therapeutic approaches, especially for relapsed and refractory cases. The two TNF receptor family members CD30 and CD137 are expressed on Hodgkin and Reed Sternberg (HRS) cells, the malignant cells in HL. We found that this co-expression is specific for HRS cells. Based on this discovery we developed a bispecific antibody that binds preferentially to the CD30, CD137-double positive HRS cells. The CD30, CD137 bispecific antibody gets internalized into HRS cells opening up the possibility to use it as a carrier for a toxin. This antibody also induces antibody-dependent, cell-mediated cytotoxicity in CD30, CD137-double positive HRS cells. The enhances specificity of the CD30, CD137 bispecific antibody to HRS cells makes it a promising candidate for development as a novel HL treatment.

Cancer Cell Lines Are Useful Model Systems for Medical Research

Cell lines are in vitro model systems that are widely used in different fields of medical research, especially basic cancer research and drug discovery. Their usefulness is primarily linked to their ability to provide an indefinite source of biological material for experimental purposes. Under the right conditions and with appropriate controls, authenticated cancer cell lines retain most of the genetic properties of the cancer of origin. During the last few years, comparing genomic data of most cancer cell lines has corroborated this statement and those that were observed studying the tumoral tissue equivalents included in the The Cancer Genome Atlas (TCGA) database. We are at the disposal of comprehensive open access cell line datasets describing their molecular and cellular alterations at an unprecedented level of accuracy. This aspect, in association with the possibility of setting up accurate culture conditions that mimic the in vivo microenvironment (e.g., three-dimensional (3D) coculture), has strengthened the importance of cancer cell lines for continuing to sustain medical research fields. However, it is important to consider that the appropriate use of cell lines needs to follow established guidelines for guaranteed data reproducibility and quality, and to prevent the occurrence of detrimental events (i.e., those that are linked to cross-contamination and mycoplasma contamination).

Key Role of Reactive Oxygen Species (ROS) in Indirubin Derivative-Induced Cell Death in Cutaneous T-Cell Lymphoma Cells

Cutaneous T-cell lymphoma (CTCL) may develop a highly malignant phenotype in its late phase, and patients may profit from innovative therapies. The plant extract indirubin and its chemical derivatives represent new and promising antitumor strategies. This first report on the effects of an indirubin derivative in CTCL cells shows a strong decrease of cell proliferation and cell viability as well as an induction of apoptosis, suggesting indirubin derivatives for therapy of CTCL. As concerning the mode of activity, the indirubin derivative DKP-071 activated the extrinsic apoptosis cascade via caspase-8 and caspase-3 through downregulation of the caspase antagonistic proteins c-FLIP and XIAP. Importantly, a strong increase of reactive oxygen species (ROS) was observed as an immediate early effect in response to DKP-071 treatment. The use of antioxidative pre-treatment proved the decisive role of ROS, which turned out upstream of all other proapoptotic effects monitored. Thus, reactive oxygen species appear as a highly active proapoptotic pathway in CTCL, which may be promising for therapeutic intervention. This pathway can be efficiently activated by an indirubin derivative.

NKL homeobox gene NKX2-2 is aberrantly expressed in Hodgkin lymphoma

NKL homeobox genes encode basic transcriptional regulators of cell and tissue differentiation. Recently, we described a hematopoietic NKL-code comprising nine specific NKL homeobox genes expressed in normal hematopoietic stem cells, lymphoid progenitors and during lymphopoiesis, highlighting their physiological role in the development of T-, B- and NK-cells. Here, we identified aberrant expression of the non-hematopoietic neural NKL homeobox gene NKX2-2 in about 12% of both, classical Hodgkin lymphoma (HL) and nodular lymphocyte predominant (NLP) HL patients. The NKX2-2 expressing NLPHL-derived cell line DEV served as a model by analysing chromosomal configurations and expression profiling data to reveal activating mechanisms and downstream targets of this developmental regulator. While excluding chromosomal rearrangements at the locus of NKX2-2 we identified t(3;14)(p21;q32) resulting in overexpression of the IL17 receptor gene IL17RB via juxtaposition with the IGH-locus. SiRNA-mediated knockdown experiments demonstrated that IL17RB activated NKX2-2 transcription. Overexpression of IL17RB-cofactor DAZAP2 via chromosomal gain of 12q13 and deletion of its proteasomal inhibitor SMURF2 at 17q24 supported expression of NKX2-2. IL17RB activated transcription factors FLI1 and FOXG1 which in turn mediated NKX2-2 expression. In addition, overexpressed chromatin-modulator AUTS2 contributed to NKX2-2 activation as well. Downstream analyses indicated that NKX2-2 inhibits transcription of lymphoid NKL homeobox gene MSX1 and activates expression of basic helix-loop-helix factor NEUROD1 which may disturb B-cell differentiation processes via reported interaction with TCF3/E2A. Taken together, our data reveal ectopic activation of a neural gene network in HL placing NKX2-2 at its hub, highlighting a novel oncogenic impact of NKL homeobox genes in B-cell malignancies.

Synthesis and biological evaluation of N-biphenyl-nicotinic based moiety compounds: A new class of antimitotic agents for the treatment of Hodgkin Lymphoma

We previously demonstrated that some N-biphenylanilides caused cell-cycle arrest at G2/M transition in breast cancer cells. Among them we choose three derivatives, namely PTA34, PTA73 and RS35 for experimentation in solid tumor cell lines, classical Hodgkin Lymphoma (cHL) cell lines and bona fide normal cell lines. Almost all tumor cells were sensitive to compounds in the nanomolar range whereas, they were not cytotoxic to normal ones. Interestingly the compounds caused a strong G2/M phase arrest in cHL cell lines, thus, here we investigated whether they affected the integrity of microtubules in such cells. We found that they induced a long prometaphase arrest, followed by induction of apoptosis which involved mitochondria. PTA73 and RS35 induced the mitotic arrest through the fragmentation of microtubules which prevented the kinethocore-mitotic spindle interaction and the exit from mitosis. PTA34 is instead a tubulin-targeting agent because it inhibited the tubulin polymerization as vinblastine. As such, PTA34 maintained the Cyclin B1-CDK1 regulatory complex activated during the G2/M arrest while inducing the inactivation of Bcl-2 through phosphorylation in Ser70, the degradation of Mcl-1 and a strong activation of BIML and BIMS proapoptotic isoforms. In addition PTA34 exerted an antiangiogenic effect by suppressing microvascular formation.