IKZF1 expression is a prognostic marker in newly diagnosed standard-risk multiple myeloma treated with lenalidomide and intensive chemotherapy: a study of the German Myeloma Study Group (DSMM).

Lenalidomide is an immunomodulatory compound with high clinical activity in multiple myeloma. Lenalidomide binding to the Cereblon (CRBN) E3 ubiquitin ligase results in targeted ubiquitination and degradation of the lymphoid transcription factors Ikaros (IKZF1) and Aiolos (IKZF3) leading to growth inhibition of multiple myeloma cells. Recently, Basigin (BSG) was identified as another protein regulated by CRBN that is involved in the activity of lenalidomide. Here, we analyzed the prognostic value of IKZF1, IKZF3, CRBN and BSG mRNA expression levels in pretreatment plasma cells from 60 patients with newly diagnosed multiple myeloma uniformly treated with lenalidomide in combination with intensive chemotherapy within a clinical trial. We found that IKZF1 mRNA expression levels are significantly associated with progression-free survival (PFS). Patients in the lowest quartile (Q1) of IKZF1 expression had a superior PFS compared with patients in the remaining quartiles (Q2-Q4; 3-year PFS of 86 vs 51%, P=0.01). This translated into a significant better overall survival (100 vs 74%, P=0.03). Subgroup analysis revealed a significant impact of IKZF1, IKZF3 and BSG expression levels on PFS in cytogenetically defined standard-risk but not high-risk patients. Our data suggest a prognostic role of IKZF1, IKZF3 and BSG expression levels in lenalidomide-treated multiple myeloma.

Upregulation of Flt3 is a passive event in Hoxa9/Meis1-induced acute myeloid leukemia in mice.

HOXA9, MEIS1 and FLT3 are genes frequently upregulated in human acute myeloid leukemia. Hoxa9 and Meis1 also cooperate to induce aggressive AML with high Flt3 expression in mice, suggesting an important role for Flt3 in Hoxa9/Meis1-induced leukemogenesis. To define the role of Flt3 in AML with high Hoxa9/Meis1, we treated mice with Hoxa9/Meis1-induced AML with the Flt3 inhibitor AC220, used an Flt3-ligand (FL-/-) knockout model, and investigated whether overexpression of Flt3 could induce leukemia together with overexpression of Hoxa9. Flt3 inhibition by AC220 did not delay AML development in mice transplanted with bone marrow cells overexpressing Hoxa9 and Meis1. In addition, Hoxa9/Meis1 cells induced AML in FL-/- mice as rapid as in wild-type mice. However, FL-/- mice had reduced organ infiltration compared with wild-type mice, suggesting some Flt3-dependent effect on leukemic invasiveness. Interestingly, leukemic Hoxa9/Meis1 cells from sick mice expressed high levels of Flt3 regardless of presence of its ligand, showing that Flt3 is a passive marker on these cells. In line with this, combined engineered overexpression of Flt3 and Hoxa9 did not accelerate the progression to AML. We conclude that the Hoxa9- and Meis1-associated upregulation of Flt3 is not a requirement for leukemic progression induced by Hoxa9 and Meis1.

Constitutive IRF8 expression inhibits AML by activation of repressed immune response signaling.

Myeloid differentiation is blocked in acute myeloid leukemia (AML), but the molecular mechanisms are not well characterized. Meningioma 1 (MN1) is overexpressed in AML patients and confers resistance to all-trans retinoic acid-induced differentiation. To understand the role of MN1 as a transcriptional regulator in myeloid differentiation, we fused transcriptional activation (VP16) or repression (M33) domains with MN1 and characterized these cells in vivo. Transcriptional activation of MN1 target genes induced myeloproliferative disease with long latency and differentiation potential to mature neutrophils. A large proportion of differentially expressed genes between leukemic MN1 and differentiation-permissive MN1VP16 cells belonged to the immune response pathway like interferon-response factor (Irf) 8 and Ccl9. As MN1 is a cofactor of MEIS1 and retinoic acid receptor alpha (RARA), we compared chromatin occupancy between these genes. Immune response genes that were upregulated in MN1VP16 cells were co-targeted by MN1 and MEIS1, but not RARA, suggesting that myeloid differentiation is blocked through transcriptional repression of shared target genes of MN1 and MEIS1. Constitutive expression of Irf8 or its target gene Ccl9 identified these genes as potent inhibitors of murine and human leukemias in vivo. Our data show that MN1 prevents activation of the immune response pathway, and suggest restoration of IRF8 signaling as therapeutic target in AML.

Defective DROSHA processing contributes to downregulation of MiR-15/-16 in chronic lymphocytic leukemia.

The MIR-15A/-16-1 tumor suppressor microRNAs (miRNAs) are deleted in leukemic cells from more than 50% of patients with chronic lymphocytic leukemia (CLL). As these miRNAs are also less abundant in patients without genomic deletion, their downregulation in CLL is likely to be caused by additional mechanisms. We found the primary transcripts (pri-miRNAs) of MIR-15a/-16/-15b to be elevated and processing intermediates (precursor miRNAs) to be reduced in cells from CLL patients (22/38) compared with non-malignant B-cells (n=14), indicating a block of miRNA maturation at the DROSHA processing step. Using a luciferase reporter assay for pri-miR processing we validated the defect in primary CLL cells. The block of miRNA maturation is restricted to specific miRNAs and can be found in the cell line MEC-2, but not in MEC-1, even though both are derived from the same CLL patient. In these cells, the RNA-specific deaminase ADARB1 leads to reduced pri-miRNA processing, but full processing efficiency is recovered upon deletion of the RNA-binding domains or nuclear localization of ADARB1. Thus, we show that, apart from genomic deletion or transcriptional downregulation, aberrant processing of miRNA leads to specific reduction of miRNAs in leukemic cells. This represents a novel oncogenic mechanism in the pathogenesis of CLL.

miRNA*: a passenger stranded in RNA-induced silencing complex?

Processing of the pre-microRNA (pre-miRNA) through Dicer1 generates a miRNA duplex, consisting of a miRNA and miRNA* strand (also termed guide strand and passenger strand, respectively). Despite the general consensus that miRNA*s have no regulatory activity, recent publications have provided evidence that the abundance, possible function, and physiological relevance of miRNA*s have been underestimated. This review provides an account of our current understanding of miRNA* origination and activity, mounting evidence for their unique functions and regulatory mechanisms, and examples of specific miRNA*s from the literature.

Comprehensive microRNA expression profiling of the hematopoietic hierarchy.

The hematopoietic system produces a large number of highly specialized cell types that are derived through a hierarchical differentiation process from a common stem cell population. miRNAs are critical players in orchestrating this differentiation. Here, we report the development and application of a high-throughput microfluidic real-time quantitative PCR (RT-qPCR) approach for generating global miRNA profiles for 27 phenotypically distinct cell populations isolated from normal adult mouse hematopoietic tissues. A total of 80,000 RT-qPCR assays were used to map the landscape of miRNA expression across the hematopoietic hierarchy, including rare progenitor and stem cell populations. We show that miRNA profiles allow for the direct inference of cell lineage relations and functional similarity. Our analysis reveals a close relatedness of the miRNA expression patterns in multipotent progenitors and stem cells, followed by a major reprogramming upon restriction of differentiation potential to a single lineage. The analysis of miRNA expression in single hematopoietic cells further demonstrates that miRNA expression is very tightly regulated within highly purified populations, underscoring the potential of single-cell miRNA profiling for assessing compartment heterogeneity.

Identification of additional cytogenetic and molecular genetic abnormalities in acute myeloid leukaemia with t(8;21)/AML1-ETO.

AML1-ETO collaborates with further genetic abnormalities to induce acute myeloid leukaemia (AML). We analysed 99 patients with an AML1-ETO rearrangement for additional aberrations. Frequent genetic abnormalities were, loss of a sex chromosome (56/99, 56.5%) and del(9)(q22) (24/99, 24.2%). The most frequent molecular aberrations were mutations of KITD816 (3/23, 13%) and NRAS (8/89, 8.9%). Further molecular abnormalities were FLT3 mutations (3/87, 3.4%), AML1 (1/26, 3.8%) and PU1 (1/14, 7.1%). MLL-PTD, KRAS and CEBPA mutations were not found. These clinical findings support the model that AML1-ETO collaborates with other genetic alterations, such as mutations of receptor tyrosine kinases, to induce AML.

AML1-ETO needs a partner: new insights into the pathogenesis of t(8;21) leukemia.

The detailed characterization of genetic and molecular aberrations in acute myeloid leukemia (AML) has substantially improved our understanding of the pathogenesis of this disease. With an incidence of up to 12% in all AML cases, the translocation t(8;21), forming the AML1-ETO fusion gene, is one of the most common genetic aberrations in AML. Experimental data have shown that AML1-ETO is not sufficient to induce leukemia by itself, but has to collaborate with other genetic alterations for leukemic transformation. These data are supported by observations in AML patients, who recurrently show activating mutations of the receptor tyrosine kinase FLT3 or c-KIT together with the AML1-ETO fusion gene. These findings might have clinical implications and provide a rationale to test RTK inhibitors in the treatment of patients with core binding factor AML and concurrent activating RTK mutations.

Regulation of pituitary hormones and cell proliferation by components of the extracellular matrix

The extracellular matrix is a three-dimensional network of proteins, glycosaminoglycans and other macromolecules. It has a structural support function as well as a role in cell adhesion, migration, proliferation, differentiation, and survival. The extracellular matrix conveys signals through membrane receptors called integrins and plays an important role in pituitary physiology and tumorigenesis. There is a differential expression of extracellular matrix components and integrins during the pituitary development in the embryo and during tumorigenesis in the adult. Different extracellular matrix components regulate adrenocorticotropin at the level of the proopiomelanocortin gene transcription. The extracellular matrix also controls the proliferation of adrenocorticotropin-secreting tumor cells. On the other hand, laminin regulates the production of prolactin. Laminin has a dynamic pattern of expression during prolactinoma development with lower levels in the early pituitary hyperplasia and a strong reduction in fully grown prolactinomas. Therefore, the expression of extracellular matrix components plays a role in pituitary tumorigenesis. On the other hand, the remodeling of the extracellular matrix affects pituitary cell proliferation. Matrix metalloproteinase activity is very high in all types of human pituitary adenomas. Matrix metalloproteinase secreted by pituitary cells can release growth factors from the extracellular matrix that, in turn, control pituitary cell proliferation and hormone secretion. In summary, the differential expression of extracellular matrix components, integrins and matrix metalloproteinase contributes to the control of pituitary hormone production and cell proliferation during tumorigenesis.

Regulation of pituitary hormones and cell proliferation by components of the extracellular matrix.

The extracellular matrix is a three-dimensional network of proteins, glycosaminoglycans and other macromolecules. It has a structural support function as well as a role in cell adhesion, migration, proliferation, differentiation, and survival. The extracellular matrix conveys signals through membrane receptors called integrins and plays an important role in pituitary physiology and tumorigenesis. There is a differential expression of extracellular matrix components and integrins during the pituitary development in the embryo and during tumorigenesis in the adult. Different extracellular matrix components regulate adrenocorticotropin at the level of the proopiomelanocortin gene transcription. The extracellular matrix also controls the proliferation of adrenocorticotropin-secreting tumor cells. On the other hand, laminin regulates the production of prolactin. Laminin has a dynamic pattern of expression during prolactinoma development with lower levels in the early pituitary hyperplasia and a strong reduction in fully grown prolactinomas. Therefore, the expression of extracellular matrix components plays a role in pituitary tumorigenesis. On the other hand, the remodeling of the extracellular matrix affects pituitary cell proliferation. Matrix metalloproteinase activity is very high in all types of human pituitary adenomas. Matrix metalloproteinase secreted by pituitary cells can release growth factors from the extracellular matrix that, in turn, control pituitary cell proliferation and hormone secretion. In summary, the differential expression of extracellular matrix components, integrins and matrix metalloproteinase contributes to the control of pituitary hormone production and cell proliferation during tumorigenesis.

[29-year-old female patient with pneumonia and enlarged abdominal lymph nodes]. / 29-jährige Patientin mit Pneumonie und grossen abdominellen Lymphknoten.

Common variable immunodeficiency (CVID) is the most common clinically manifested primary immunodeficiency disease. A 29-year-old female patient presented with pneumonia and enlarged thoracal and abdominal lymph nodes. Frequently recurring infections, especially in the respiratory tract were observed in the patient's history. A hypogammaglobulinaemia could be detected. By exclusion of other disorders and a complete analysis of the immune status a CVID Ib/B was diagnosed. Regular ambulatory treatment with immune globulin substitution reduced the incidence and severity of infections.

Laminin inhibits lactotroph proliferation and is reduced in early prolactinoma development.

Laminin is a component of the extracellular matrix (ECM) that regulates cell proliferation and hormone secretion. Here we describe the effects of laminin on prolactin secretion in normal and tumor cells and analyze laminin expression pattern during prolactinoma development. Prolactin secretion and cell proliferation were inhibited by laminin in GH3 cells. In contrast, no effect was observed in normal pituitary cells. Laminin showed a dynamic expression pattern during prolactinoma development, which was: (a) strong in normal pituitaries from wild type or dopamine D2 receptor deficient mice, (b) lower in pituitary hyperplasia and (c) markedly reduced in prolactinomas from D2R -/- mice. A similar gradual decrease in laminin was found by comparing normal human pituitaries, human pituitary hyperplasia and human prolactinomas. These results show dynamic changes of laminin expression during prolactinoma formation which, due to laminin action on PRL production and cell proliferation, indicate a possible role for laminin in prolactinoma development.

[Teutschländer disease. A rare benign differential diagnosis in proliferating space-occupying lesions of soft tissues]. / Morbus Teutschländer. Eine seltene benigne Differenzialdiagnose proliferativer Raumforderungen im Weichteilgewebe.

Tumoral calcinosis is a very rare benign soft tissue calcification. It occurs in all age-groups and prefers the shoulder, hip and elbow region as localisation. In most cases, local pain is the leading symptom. The aetiology remains unclear, so far, however, a certain connection to an imbalance of the calcium-/phosphate homeostasis is proposed. The adequate therapy is the complete surgical removal. Our presented case describes an extended occurrence at an unusual localisation and discusses characteristic signs in contrast of the differential diagnoses.