Leticia Quintanilla-Fend

CD20+ T-cell lymphoma: clinicopathologic analysis of 9 cases and a review of the literature.

Rare cases of CD20+ T-cell lymphoma (TCL) have been reported, but the clinicopathologic spectrum of this disorder is not known. We identified 9 cases of CD20+ TCL diagnosed at our institution and 26 additional cases through a search of the English language literature. Among current cases, there were 7 men (ages 71 to 81, median 75 y) and 2 women (ages 36 and 37 y). Five patients presented with predominantly nodal disease (localized in 3 and widespread in 2 cases) and 4 patients presented with purely extranodal disease involving the parotid glands, skin, or small intestine. CD20 was uniformly and strongly expressed in 5 cases and dimly expressed or present on a subset of neoplastic cells in 4 cases. The proportion of CD20+ T cells changed over time in 3 cases. Three cases fulfilled diagnostic criteria for clinicopathologically defined subtypes of TCL (2 mycosis fungoides; 1 enteropathy-type TCL), whereas 6 were peripheral TCL unspecified with variable cytomorphology, T-cell immunophenotype, and sites of involvement. In 8 of 9 cases, a clonal T-cell population was identified by molecular genetic analysis. Among 8 cases with clinical follow-up, 5 behaved aggressively with death from disease within 3 years of diagnosis in 4 cases (median survival: 11 mo, range: 1 to 35 mo), and recurrent disease at 10 months in 1 case; 1 patient died of an EBV+ B-cell lymphoma (BCL) 66 months after the original diagnosis; in the remaining 2 cases, patients were alive and undergoing treatment (follow-up: 4 and 18 mo). Historical cases showed similar clinicopathologic variability. CD20+ TCL is rare, and clinically and pathologically heterogeneous. When CD20 expression is present in TCL, it may be dimmer than that of normal B cells, suggesting neoplastic transformation of a normal CD20dim+ T-cell subset. Cases of CD20+ TCL in which the proportion of CD20+ cells changes over time may reflect aberrant expression of CD20, possibly as an activation marker, by neoplastic T cells. CD20+ TCL may cause diagnostic difficulty, particularly in cases that clinically and pathologically mimic BCL. Knowledge of the unusual phenomenon of CD20 expression in TCL, in conjunction with careful morphologic analysis, the use of a panel of antibodies, and molecular genetic studies, is important in avoiding a misdiagnosis of BCL.

Prevention of multiple low-dose streptozotocin (MLD-STZ) diabetes in mice by an extract from gum resin of Boswellia serrata (BE)

Type 1-diabetes is an autoimmune disease, where a chronic inflammatory process finally causes β-cell death and insulin deficiency. Extracts from gum resin of Boswellia serrata (BE) have been shown to posses anti-inflammatory properties especially by targeting factors/mediators related to autoimmune diseases. Multiple low dose-streptozotocin (MLD-STZ) treatment is a method to induce diabetes in animals similar to Type 1 diabetes in humans. It was aimed to study whether or not a BE could prevent hyperglycemia, inflammation of pancreatic islets and increase of proinflammatory cytokines in the blood in MLD-STZ treated mice. In BK+/+ wild type mice, 5 days of daily treatment with 40 mg/kg STZ i.p. produced permanent increase of blood glucose, infiltration of lymphocytes into pancreatic islets (CD3-stain), apoptosis of periinsular cells (staining for activated caspase 3) after 10 days as well as shrinking of islet tissue after 35 days (H&E staining). This was associated with an increase of granulocyte colony stimulating factor (G-CSF), granulocyte/macrophage colony stimulating factor (GM-CSF) and proinflammatory cytokines (IL-1A, IL-1B, IL-2, IL-6, IFN-γ, TNF-α) in the blood. Whereas BE alone did not affect blood glucose in non diabetic mice, in STZ treated mice simultaneous i.p. injection of 150 mg/kg of BE over 10 days prevented animals from increase of blood glucose levels. Histochemical studies showed, that i.p. injection of 150 mg/kg BE for 10 days starting with STZ treatment, avoided lymphocyte infiltration into islets, apoptosis of periinsular cells and shrinking of islet size 35 days after STZ. As far as the cytokines tested are concerned, there was a significant inhibition of the increase of G-CSF and GM-CSF. BE also significantly prevented the increase of IL-1A, IL-1B, IL-2, IL-6, IFN-γ and TNF-α. It is concluded that extracts from the gum resin of Boswellia serrata prevent islet destruction and consequent hyperglycemia in an animal model of type 1 diabetes probably by inhibition of the production/action of cytokines related to induction of islet inflammation in an autoimmune process.

Cyclin D1-negative blastoid mantle cell lymphoma identified by SOX11 expression.

SOX11 expression has been recently shown to be useful in the diagnosis of mantle cell lymphoma (MCL), including cyclin D1-negative MCL with typical morphology. We evaluated SOX11 expression pattern in B-cell non-Hodgkin lymphoma (B-NHL) subtypes to confirm specificity and used it as a feature to identify the first reported cases of cyclin D1-negative blastoid MCL. SOX11 expression was evaluated by immunohistochemistry in 140 cases of mature B-NHL, including 4 cases of suspected blastoid MCL that lacked cyclin D1 expression and 8 cases of CD5-positive diffuse large B-cell lymphoma (DLBL). In addition, 5 cases of B or T lymphoblastic lymphoma were included. Nuclear expression of SOX11 was found in cyclin D1-positive MCL (30/30, 100%) and in a case of cyclin D1-negative MCL with typical morphology. SOX11 was also expressed in Burkitt lymphoma (1/5, 20%) and lymphoblastic lymphoma (2/3 T-LBLs, 2/2 B-LBLs, overall 4/5, 80%), whereas all cases of DLBL (including CD5+ DLBL) and other small B-NHL were negative. The 4 suspected cases of blastoid MCL were also SOX11+. These cases had a complex karyotype that included 12p abnormalities. We confirmed prior reports that stated that SOX11 nuclear expression was a specific marker for MCL, including cyclin D1-negative MCL with typical morphology. To our knowledge, this is the first report regarding its use in identifying cases of cyclin D1-negative blastoid MCL. Routine use of SOX11 in cases of suspected CD5+ DLBL might help identify additional cases of cyclin D1-negative blastoid MCL.

PI3K pathway inhibition achieves potent antitumor activity in melanoma brain metastases in vitro and in vivo

Purpose: Great advances have recently been made in treating patients with metastatic melanoma. However, existing therapies are less effective on cerebral than extracerebral metastases. This highlights the potential role of the brain environment on tumor progression and drug resistance and underlines the need for “brain-specific” therapies. We previously showed that the PI3K-AKT survival pathway is hyperactivated in brain but not extracerebral melanoma metastases and that astrocyte-conditioned medium activates AKT in melanoma cells in vitro. We therefore tested the PI3K inhibitor buparlisib as an antitumor agent for melanoma brain metastases. Experimental Design and Results: Buparlisib inhibited AKT activity, decreased proliferation, and induced apoptosis in metastatic melanoma cell lines and short-term brain melanoma cells, irrespective of their BRAF and NRAS mutation status. In addition, buparlisib inhibited hyperactivated AKT and induced apoptosis in melanoma cells that were stimulated with astrocyte-conditioned medium. The growth of tumors induced by injecting human BRAF- and NRAS-mutant metastatic melanoma cells into the brain of mice was significantly inhibited by buparlisib. Conclusions: These results emphasize the value of targeting the PI3K pathway as a strategy to develop drugs for melanoma brain metastases. Clin Cancer Res; 22(23); 5818–28. ©2016 AACR.

Abnormal Brain Iron Metabolism in Irp2 Deficient Mice Is Associated with Mild Neurological and Behavioral Impairments

Iron Regulatory Protein 2 (Irp2, Ireb2) is a central regulator of cellular iron homeostasis in vertebrates. Two global knockout mouse models have been generated to explore the role of Irp2 in regulating iron metabolism. While both mouse models show that loss of Irp2 results in microcytic anemia and altered body iron distribution, discrepant results have drawn into question the role of Irp2 in regulating brain iron metabolism. One model shows that aged Irp2 deficient mice develop adult-onset progressive neurodegeneration that is associated with axonal degeneration and loss of Purkinje cells in the central nervous system. These mice show iron deposition in white matter tracts and oligodendrocyte soma throughout the brain. A contrasting model of global Irp2 deficiency shows no overt or pathological signs of neurodegeneration or brain iron accumulation, and display only mild motor coordination and balance deficits when challenged by specific tests. Explanations for conflicting findings in the severity of the clinical phenotype, brain iron accumulation and neuronal degeneration remain unclear. Here, we describe an additional mouse model of global Irp2 deficiency. Our aged Irp2−/− mice show marked iron deposition in white matter and in oligodendrocytes while iron content is significantly reduced in neurons. Ferritin and transferrin receptor 1 (TfR1, Tfrc), expression are increased and decreased, respectively, in the brain from Irp2−/− mice. These mice show impairments in locomotion, exploration, motor coordination/balance and nociception when assessed by neurological and behavioral tests, but lack overt signs of neurodegenerative disease. Ultrastructural studies of specific brain regions show no evidence of neurodegeneration. Our data suggest that Irp2 deficiency dysregulates brain iron metabolism causing cellular dysfunction that ultimately leads to mild neurological, behavioral and nociceptive impairments.

The clathrin-binding domain of CALM and the OM-LZ domain of AF10 are sufficient to induce acute myeloid leukemia in mice

The t(10;11)(p13-14;q14-21) translocation, giving rise to the CALM–AF10 fusion gene, is a recurrent chromosomal rearrangement observed in patients with poor prognosis acute myeloid leukemia (AML). Although splicing of the CALM–AF10 fusion transcripts has been described in AML patients, the contribution of different CALM and AF10 domains to in vivo leukemogenesis remains to be defined. We therefore performed detailed structure-function studies of the CALM–AF10 fusion protein. We demonstrate that fusion of the C-terminal 248 amino acids of CALM, which include the clathrin-binding domain, to the octapeptide motif–leucine-zipper (OM-LZ) domain of AF10 generated a fusion protein (termed CALM–AF10 minimal fusion (MF)), with strikingly enhanced transformation capabilities in colony assays, providing an efficient system for the expeditious assessment of CALM–AF10-mediated transformation. Leukemias induced by the CALM–AF10 (MF) mutant recapitulated multiple aspects of full-length CALM–AF10-induced leukemia, including aberrant Hoxa cluster upregulation, a characteristic molecular lesion of CALM–AF10 leukemias. In summary, this study indicates that collaboration of the clathrin-binding and the OM-LZ domains of CALM–AF10 is sufficient to induce AML. These findings further suggest that future approaches to antagonize CALM–AF10-induced transformation should incorporate strategies, which aim at blocking these key domains.

MTO1-Deficient Mouse Model Mirrors the Human Phenotype Showing Complex I Defect and Cardiomyopathy

Recently, mutations in the mitochondrial translation optimization factor 1 gene (MTO1) were identified as causative in children with hypertrophic cardiomyopathy, lactic acidosis and respiratory chain defect. Here, we describe an MTO1-deficient mouse model generated by gene trap mutagenesis that mirrors the human phenotype remarkably well. As in patients, the most prominent signs and symptoms were cardiovascular and included bradycardia and cardiomyopathy. In addition, the mutant mice showed a marked worsening of arrhythmias during induction and reversal of anaesthesia. The detailed morphological and biochemical workup of murine hearts indicated that the myocardial damage was due to complex I deficiency and mitochondrial dysfunction. In contrast, neurological examination was largely normal in Mto1-deficient mice. A translational consequence of this mouse model may be to caution against anaesthesia-related cardiac arrhythmias which may be fatal in patients.

The leukemogenicity of Hoxa9 depends on alternative splicing.

Although the transforming potential of Hox genes is known for a long time, it is not precisely understood to which extent splicing is important for the leukemogenicity of this gene family. To test this for Hoxa9, we compared the leukemogenic potential of the wild-type Hoxa9, which undergoes natural splicing, with a full-length Hoxa9 construct, which was engineered to prevent natural splicing (Hoxa9FLim). Inability to undergo splicing significantly reduced in vivo leukemogenicity compared to Hoxa9-wild-typed. Importantly, Hoxa9FLim could compensate for the reduced oncogenicity by collaborating with the natural splice variant Hoxa9T, as co-expression of Hoxa9T and Hoxa9FLim induced acute myeloid leukemia (AML) after a comparable latency time as wild-type Hoxa9. Hoxa9T on its own induced AML after a similar latency as Hoxa9FLim, despite its inability to bind DNA. These data assign splicing a central task in Hox gene mediated leukemogenesis and suggest an important role of homeodomain-less splice variants in hematological neoplasms.

Cks1 Promotion of S Phase Entry and Proliferation Is Independent of p27Kip1 Suppression.

ABSTRACT Cks1 is an activator of the SCFSkp2 ubiquitin ligase complex that targets the cell cycle inhibitor p27Kip1 for degradation. The loss of Cks1 results in p27Kip1 accumulation and decreased proliferation and inhibits tumorigenesis. We identify here a function of Cks1 in mammalian cell cycle regulation that is independent of p27Kip1. Specifically, Cks1−/−; p27Kip1−/− mouse embryonic fibroblasts retain defects in the G1-S phase transition that are coupled with decreased Cdk2-associated kinase activity and defects in proliferation that are associated with Cks1 loss. Furthermore, concomitant loss of Cks1 does not rescue the tumor suppressor function of p27Kip1 that is manifest in various organs of p27Kip1−/− mice. In contrast, defects in mitotic entry and premature senescence manifest in Cks1−/− cells are p27Kip1 dependent. Collectively, these findings establish p27Kip1-independent functions of Cks1 in regulating the G1-S transition.

Controlled stem cell amplification by HOXB4 depends on its unique proline-rich region near the N terminus

There is high interest in understanding the mechanisms that drive self-renewal of stem cells. HOXB4 is one of the few transcription factors that can amplify long-term repopulating hematopoietic stem cells in a controlled way. Here we show in mice that this characteristic of HOXB4 depends on a proline-rich sequence near the N terminus, which is unique among HOX genes and highly conserved in higher mammals. Deletion of this domain substantially enhanced the oncogenicity of HOXB4, inducing acute leukemia in mice. Conversely, insertion of the domain into Hoxa9 impaired leukemogenicity of this homeobox gene. These results indicate that proline-rich stretches attenuate the potential of stem cell active homeobox genes to acquire oncogenic properties.