Parasites lacking the micronemal protein MIC2 are deficient in surface attachment and host cell egress, but remain virulent in vivo

Background: Micronemal proteins of the thrombospondin-related anonymous protein (TRAP) family are believed to play essential roles during gliding motility and host cell invasion by apicomplexan parasites, and currently represent major vaccine candidates against Plasmodium falciparum, the causative agent of malaria. However, recent evidence suggests that they play multiple and different roles than previously assumed. Here, we analyse a null mutant for MIC2, the TRAP homolog in Toxoplasma gondii. Methods: We performed a careful analysis of parasite motility in a 3D-environment, attachment under shear stress conditions, host cell invasion and in vivo virulence. Results: We verified the role of MIC2 in efficient surface attachment, but were unable to identify any direct function of MIC2 in sustaining gliding motility or host cell invasion once initiated. Furthermore, we find that deletion of mic2 causes a slightly delayed infection in vivo, leading only to mild attenuation of virulence; like with wildtype parasites, inoculation with even low numbers of mic2 KO parasites causes lethal disease in mice. However, deletion of mic2 causes delayed host cell egress in vitro, possibly via disrupted signal transduction pathways. Conclusions: We confirm a critical role of MIC2 in parasite attachment to the surface, leading to reduced parasite motility and host cell invasion. However, MIC2 appears to not be critical for gliding motility or host cell invasion, since parasite speed during these processes is unaffected. Furthermore, deletion of MIC2 leads only to slight attenuation of the parasite.

Parasites lacking the micronemal protein MIC2 are deficient in surface attachment and host cell egress, but remain virulent in vivo

Background: Micronemal proteins of the thrombospondin-related anonymous protein (TRAP) family are believed to play essential roles during gliding motility and host cell invasion by apicomplexan parasites, and currently represent major vaccine candidates against Plasmodium falciparum, the causative agent of malaria. However, recent evidence suggests that they play multiple and different roles than previously assumed. Here, we analyse a null mutant for MIC2, the TRAP homolog in Toxoplasma gondii. Methods: We performed a careful analysis of parasite motility in a 3D-environment, attachment under shear stress conditions, host cell invasion and in vivo virulence. Results: We verified the role of MIC2 in efficient surface attachment, but were unable to identify any direct function of MIC2 in sustaining gliding motility or host cell invasion once initiated. Furthermore, we find that deletion of mic2 causes a slightly delayed infection in vivo, leading only to mild attenuation of virulence; like with wildtype parasites, inoculation with even low numbers of mic2 KO parasites causes lethal disease in mice. However, deletion of mic2 causes delayed host cell egress in vitro, possibly via disrupted signal transduction pathways. Conclusions: We confirm a critical role of MIC2 in parasite attachment to the surface, leading to reduced parasite motility and host cell invasion. However, MIC2 appears to not be critical for gliding motility or host cell invasion, since parasite speed during these processes is unaffected. Furthermore, deletion of MIC2 leads only to slight attenuation of the parasite.

[Treatment of patients with radioiodine refractory, differentiated thyroid carcinoma. A Consensus Statement]

There is no clear standard therapy for patients with radioactive iodine (131I)-refractory locally advanced or metastatic differentiated thyroid cancer. The therapeutic options for this indication have expanded with the recently approved multiple kinase inhibitor sorafenib. Recommendations for the definition and the management of iodine refractory patients were worked up by an interdisciplinary expert panel, consisting of endocrine surgeons, medical oncologists and nuclear medicine specialists.

The toxoplasma Acto-MyoA motor complex is important but not essential for gliding motility and host cell invasion

Apicomplexan parasites are thought to actively invade the host cell by gliding motility. This movement is powered by the parasite's own actomyosin system, and depends on the regulated polymerisation and depolymerisation of actin to generate the force for gliding and host cell penetration. Recent studies demonstrated that Toxoplasma gondii can invade the host cell in the absence of several core components of the invasion machinery, such as the motor protein myosin A (MyoA), the microneme proteins MIC2 and AMA1 and actin, indicating the presence of alternative invasion mechanisms. Here the roles of MyoA, MLC1, GAP45 and Act1, core components of the gliding machinery, are re-dissected in detail. Although important roles of these components for gliding motility and host cell invasion are verified, mutant parasites remain invasive and do not show a block of gliding motility, suggesting that other mechanisms must be in place to enable the parasite to move and invade the host cell. A novel, hypothetical model for parasite gliding motility and invasion is presented based on osmotic forces generated in the cytosol of the parasite that are converted into motility.

Feasibility of a multdisciplinary lung cancer videoconference between a peripheral hospital and a comprehensive cancer centre

OBJECTIVE

Treatment of lung cancer patients is changing rapidly and new treatment options have emerged in recent years. In 2007, to guarantee the best treatment procedure for lung cancer patients being treated in our peripheral hospital, we decided to introduce an interdisciplinary tumour videoconference between the Haemato-Oncological Day Hospital in Merano and the Comprehensive Cancer Centre Innsbruck. This retrospective analysis aims to describe the feasibility of such a conference.

PATIENTS AND METHODS

Two hundred and three patients with lung cancer treated at the peripheral hospital of Merano between May 2003 until May 2011 were retrospectively analysed. After introduction of the tumour videoconference in 2007, 54% (n = 110) of the patients in this cohort were discussed in the conference.

RESULTS

One hundred and four videoconferences were performed. Videoconference was feasible for 110 patients. Radiotherapeutic treatments were prescribed more frequently in patients from the conference group. Overall, major and minor treatment changes were undertaken in 7% (n = 8) and 18% (n = 20), respectively.

CONCLUSION

Interdisciplinary tumour videoconference is feasible between a peripheral hospital and a comprehensive cancer centre. Radiotherapeutic treatment was prescribed more frequently, suggesting that such a conference facilitates the access to cancer-centre-specific treatment modalities. Accordingly, tumour videoconference between a peripheral hospital and a cancer centre is to be recommend.

Purine antagonists for chronic lymphocytic leukaemia

BACKGROUND

Recent trials suggest improved response rates for purine antagonists compared to alkylator-based regimens in the treatment of B-CLL. However, none was able to show a survival advantage.

OBJECTIVES

To determine if there is any advantage of purine antagonists compared to alkylating agents (alone or in combination) in the treatment of patients with previously untreated B-CLL.

SEARCH STRATEGY

Medical databases (Cochrane Library, MEDLINE, EMBASE), conference proceedings and internet-based trial registers were searched electronically and/or by hand (1990-2003). All references were checked for further trial information. We also contacted experts in the field and pharmaceutical companies.

SELECTION CRITERIA

Randomised controlled trials comparing purine antagonists as single agents with alkylator-based regimens in patients with previously untreated B-CLL were included. We included full-text and abstract publications as well as unpublished data.

DATA COLLECTION AND ANALYSIS

Data extraction and quality assessment were done in duplicate by two independent reviewers. Missing data were obtained from original authors. Endpoints included overall survival, overall response rate, rate of complete remissions, progression-free survival, treatment-related morbidity and mortality.

MAIN RESULTS

Five trials with 1838 randomised patients were included. There is some evidence for improved overall survival after treatment with purine antagonists compared to alkylators, but statistical significance was not reached (HR 0.89 [95% CI 0.78-1.01], 4 trials, n=1638). However, the relative risk for achieving an overall response (RR 1.22 [95% CI 1.13-1.31], 5 trials, n=1751) and complete remission (RR 1.94 [95% CI 1.65-2.28], 5 trials, n=1751) was significantly higher, resulting in a longer progression-free survival (HR 0.70 [95% CI 0.61-0.82], 4 trials, n=1638). Incidence of grade III/IV infections was significantly higher in patients receiving treatment with purine antagonists (RR 1.83 [95% 1.30-2.58], 4 trials, n=1620). There was no significant difference concerning the relative risk for grade III/IV neutropenia (RR 1.14 [95% CI 0.98-1.34], 4 trials, n=1620) and therapy-related mortality (RR 0.94 [95% CI 0.45-1.95]). Overall incidence of hemolytic anemia was low, but significantly increased in the purine antagonist group (RR 3.36 [95% CI 1.27-8.91], 3 trials, n=1258).

AUTHORS' CONCLUSIONS

Despite significantly increased overall response and complete remission rates and longer progression-free survival with first-line treatment of B-CLL patients with single-agent purine antagonists, we were not able to detect a statistically significant improvement of overall survival compared to alkylator-based regimens. Furthermore, the use of purine antagonists also augments the risk for grade III/IV infections and hemolytic anemia.

Characterisation of the transcription factor, SIX5, using a new panel of monoclonal antibodies

SIX5 is a member of the human SIX family of transcription factors, many of which are involved in eye development. However, SIX5 transcripts are known to be present at very low levels in cells and no study has yet convincingly demonstrated detection of endogenous SIX5 protein by Western blotting or immunolocalisation. We have produced a new panel of 18 monoclonal antibodies (mAbs) that recognise at least four different epitopes in order to identify authentic human SIX5 protein in cells and tissues. Phage-displayed peptide libraries were used to identify individual amino-acids important for antibody binding within each epitope. Endogenous SIX5 migrated in SDS-PAGE with an apparent M(r) of 100 kDa and was present at similar levels in all foetal tissues and cell lines tested. In HeLa cells, it was located in the nucleoplasm with a granular distribution. An mRNA for a shorter splicing isoform of SIX5, with an altered carboxy-terminus, has been described, but further mAbs specific for this isoform did not detect any endogenous protein. We conclude that the full-length isoform is the major functional protein in vivo while the putative shorter protein is undetectable and may not be expressed at all.

Transplantation of IL-2-transduced murine bone marrow is associated with dose-dependent toxicity

OBJECTIVE

The purpose of this study was to investigate the effects of interleukin-2 (IL-2) gene-transduced hematopoietic progenitor cells or cytotoxic function and systemic toxicity following syngeneic bone marrow transplantation.

MATERIAL AND METHODS

Marrow of 5-fluorouracil pretreated donor mice were transfected with a retroviral vector containing the murine IL-2 gene and transplanted into lethally irradiated syngeneic hosts.

RESULTS

Productive insertion of the IL-2 gene could be demonstrated at various intervals post-transplant without impairment of hematopoietic engraftment. Endogenously augmented IL-2 release resulted in a selective increase in CD4(+), CD8(+), and NK1.1(+) population in spleen and bone marrow, as well as significant cytolytic activity against syngeneic leukemia cells in vitro. Our results also illustrate the interdependence among the magnitude of systemic IL-2 levels, the number of IL-2-transduced cells in the transplant inoculum, and the appearance of systemic toxicity. Infusion of marrow transduced with high-titer, high-expressing IL-2 retrovirus resulted in significant morbidity and mortality in the recipients. Our studies demonstrate that mortality was secondary to severe lymphocytic infiltration of liver and lung, which was associated with increased expression of intercellular adhesion molecule-1 and vascular adhesion molecule-1. Reducing the number of IL-2-transduced cells in the bone marrow inoculum, however, resulted in significantly improved survival with no adverse events being evident during the post-transplant period.

CONCLUSION

Delivery of IL-2 to the bone marrow can be achieved by transplantation of genetically modified hematopoietic cells, however, the overall feasibility is strongly influenced by the number of transduced cells in the bone marrow inocolum and/or the expression pattern of IL-2 in vivo.

LST1: a gene with extensive alternative splicing and immunomodulatory function

The gene of the leukocyte-specific transcript (LST1) is encoded within the TNF region of the human MHC. The LST1 gene is constitutively expressed in leukocytes and dendritic cells, and it is characterized by extensive alternative splicing. We identified 7 different LST1 splice variants in PBMC; thus, 14 LST1 splice variants (LST1/A-LST1/N) have been detected in various cell types. These isoforms code for transmembrane as well as soluble LST1 proteins characterized by two alternative open reading frames at their 3' end. We demonstrate the presence of the transmembrane variant LST1/C on the cell surface of the monocytic cell lines U937 and THP1. Recombinant expression of LST1/C permitted its profound inhibitory effect on lymphocyte proliferation to be observed. In contrast, the alternative transmembrane variant LST1/A, the extracellular domain of which shows no amino acid sequence homology to LST1/C exerted a weaker but similar inhibitory effect on PBMC. These data demonstrate the protein expression of LST1 on the cell surface of mononuclear cells, and they show an inhibitory effect on lymphocyte proliferation of two LST1 proteins although they have only a very short amino acid homology.

Expression of LFA-1 identifies different prognostic subgroups in patients with advanced follicle center lymphoma (FCL)

In a retrospective immunohistochemical study based on 27 patients with stage IV follicle center lymphoma (FCL) the expression of CD44standard (CD44s), LFA-1 (CD11a, CD18), VLA-4 (CD49d, CD29) and ICAM-1 (CD54) was analysed on lymphoma cells in bone marrow infiltrates. The results were correlated to clinical data and overall survival. Our data demonstrate that the expression of LFA-1 on lymphoma cells is predictive for the prognosis of patients with advanced FCL. In detail, patients exhibiting weak to moderate expression (+/++) of CD11 and CD18 showed a significantly shorter median survival (51 months and 33 months, respectively) than did those presenting with strong expression ( ) of the LFA-1 adhesion molecule (P = 0.04 and P = 0.0051, respectively). Furthermore, multivariate analysis identified CD18 as a new independent prognostic factor in patients with advanced FCL. Our findings emphasize the relevance of adhesion molecules for the pathology of FCL and give further support for their impact on clinical course and overall survival.

Telomere length and telomerase activity predict survival in patients with B cell chronic lymphocytic leukemia

The telomere-telomerase hypothesis states that the vast majority of human tumors have a prolonged replicative life span throughout expressing telomerase, which compensates the cell division-associated loss of telomere DNA. The use of telomere length and telomerase expression as new biological markers in cancer patients requires their correlation with disease prognosis. We, therefore, correlated the mean telomere length based on a telomere restriction fragment assay and the activity of telomerase measured with a telomeric repeat amplification protocol with clinical data and overall survival in 58 patients with B cell chronic lymphocytic leukemia (B-CLL). Telomere length showed a highly inverse correlation to telomerase activity. Patients with telomeres below 6.0 kb were associated with high telomerase activity, whereas patients with a telomere length >6.0 kb generally showed low enzyme activity (P <0.001). Patients in Binet A exhibited significantly longer telomeres and had less telomerase activity than did patients in Binet B or Binet C, where significantly shorter telomeres and higher telomerase activity were observed (P=0.031). Short telomere length and high telomerase activity were significantly associated with a shorter median survival (P=0.02 and P <0.001), and telomerase activity was the most significant prognostic factor for overall survival in B-CLL (P <0.001). Our data provide evidence that telomere length, as well telomerase activity, exerts a strong impact on the survival of B-CLL patients and that telomerase activity can be used as a new prognostic marker in this disease.

Gene trap integrations expressed in the developing heart: insertion site affects splicing of the PT1-ATG vector

We describe the characterisation of three gene trap integrations in embryonic stem cells in which the lacZ reporter gene is repressed by retinoic acid (RA) in vitro and is expressed in the developing heart in vivo. In one of these, the gene trap vector has integrated into a gene that is located on chromosome 17 and is homologous to the human transcription factor gene, TFEB. Embryonic and adult cardiac expression of both the fusion transcript and the endogenous gene was confirmed. However, we show that the integration has not resulted in a null allele, because wild type transcripts, possibly resulting from splicing around the vector, are observed in homozygous tissue. The other two cardiac-expressing gene trap integrations have occurred into exons on chromosomes 1 and 5 and have used cryptic donor sites within the vector to generate functional fusion transcripts. One of these exon integrations results in a lethal neonatal phenotype.

Differential activity of P-glycoprotein in normal blood lymphocyte subsets

To better understand the phenomenon of P-glycoprotein (P-170) expression we investigated lymphocyte subpopulations for P-170 function in healthy volunteers. Studies were based on three-colour flow cytometry including the fluorescent probe rhodamine 123 (Rh123), which is transported by P-170. Marked Rh123 efflux was detected in CD8+ T lymphocytes with CD8+/CD45RA+ T cells (naive cells) showing significantly higher P-170 activity as compared with CD8+/CD45RA- cells (P<0.04). Vice versa, CD8+/CD45RO+ T cells (memory cells) demonstrated less P-170 activity than CD8+/CD45RO- cells (P<0.04). P-170 function was less prominent in CD4+ T cells, however, Rh123 efflux was higher in the CD4+/CD45RA+ and CD4+/CD45RO- subpopulations (P<0.025) corresponding to the CD8+ results. Dye efflux differed significantly between activated and non-activated CD8+ and CD4+ as well as CD8+/CD11b+ and CD8+/CD11b- T lymphocytes. Since CD16+ natural killer cells (NK) expressed the highest level of P-170, the NK cytotoxicity against 51Cr-labelled K562 target cells was assayed in the presence or absence of P-170 inhibitors. NK related cytotoxicity was significantly reduced in the presence of R-verapamil and dexnigaldipine-HCP in a dose-dependent manner. The differential expression of P-170 activity in naive and memory T cells together with the reduced NK related cytotoxicity in the presence of MDR-modulators suggest a physiological role of P-170 in immunological functions of these lymphocyte subsets. Consequently, the addition of MDR modulators to conventional chemotherapy as a strategy to overcome drug resistance should consider possible adverse immunosuppressive effects.

Multidrug resistance in acute leukemia: a comparison of different diagnostic methods

Accurate measurement of P-glycoprotein (P-170) expression in clinical samples still remains a controversial issue. In this study tumor cell P-170 expression was assessed in 29 patients suffering from acute leukemia (17 acute myeloid leukemia (AML) and 12 acute lymphoblastic leukemia (ALL)) using three different techniques: flow cytometry measuring rhodamine 123 (Rh123) efflux (functional level), immunocytochemistry (protein level) and RT-PCR (mRNA level). Rh123 efflux was detectable in 10/29 (34%) of all cases, in 9/17 (53%) of AML and in 1/12 (8%) of ALL samples. In AML patients a significant association of CD34 expression and P-170 activity was observed (P < 0.02). All AML patients with the FAB subtype M5 were Rh123 negative (P < 0.007). Cytospin preparations were analyzed for staining with monoclonal antibodies JSB1 and MM4.17. Eight of 16 (50%) AML and 0/9 (0%) ALL cases expressed the multidrug resistance (MDR) protein assessed by JSB1. With MM4.17 87% of AML and 50% of ALL patients were scored positive. Agreement between both antibodies was found in only 13/23 (57%) samples. Extracted RNA from 12 patients was analyzed by RT-PCR to evaluate the expression of MDR1 and multidrug resistance-associated protein (MRP) mRNA. An increased level of MDR1 mRNA was detectable in 4/7 AML and 0/5 ALL cases. MRP expression was found in 3/7 AML and 0/5 ALL patients. Comparison of Rh123 assay and immunocytochemistry revealed a very good correlation when using MoAb JSB1 (P < 0.004) but not with MM4.17 (not significant (NS)). JSB1 also showed a much better association with the PCR results (P < 0.05) than MM4.17 (NS). Finally, we compared the results of the functional Rh123 assay and RT-PCR and observed a high correlation for Rh123/MDR1 (r = 0.819, P < 0.001) but low for Rh123/MRP (r = 0.562, NS). We conclude that measurement of Rh123 efflux and immunocytochemical staining of cytospin preparations with JSB1 allows the accurate monitoring of P-170 expression in acute leukemia. The simplicity of these two MDR assays suggests their use for routine MDR screening.

Exposure to retinoic acid before or after the onset of somitogenesis reveals separate effects on rhombomeric segmentation and 3′ HoxB gene expression domains

We have compared the relationship between the patterns of altered morphogenesis and of altered gene expression in mouse embryos exposed to excess retinoic acid (RA) (a) just before and (b) just after the onset of somitic segmentation (day 7.75 to day 8.25). Exposure to RA prior to the onset of somitic segmentation results in suppression of rhombomeric (but not somitic) segmentation, and conversion of the genetic identity of the whole preotic hindbrain to that of rhombomere 4. In contrast, exposure to RA at early somite stages results in near-normal rhombomeric segmentation; rhombomeric gene expression domains indicate that only rhombomere 2 has changed its genetic identity to that of rhombomere 4, the other preotic segments showing normal expression patterns for HoxB genes and Krox-20. The results indicate that RA has separable effects (1) on the genes mediating the process of rhombomeric segmentation per se, such as Krox-20, and (2) on the genes that influence the nature of the structures that subsequently develop from the individual rhombomeres, such as the Hox genes.