Smoothened (SMO) regulates insulin-like growth factor 1 receptor (IGF1R) levels and protein kinase B (AKT) localization and signaling

The oncoprotein Smoothened (SMO), a Frizzled-class-G-protein-coupled receptor, is the central transducer of hedgehog (Hh) signaling. While canonical SMO signaling is best understood in the context of cilia, evidence suggests that SMO has other functions in cancer biology that are unrelated to canonical Hh signaling. Herein, we provided evidence that elevated levels of human SMO show a strong correlation with elevated levels of insulin-like growth factor 1 receptor (IGF1R) and reduced survival in diffuse large B-cell lymphoma (DLBCL). As an integral component of raft microdomains, SMO plays a fundamental role in maintaining the levels of IGF1R in lymphoma and breast cancer cells as well IGF1R-associated activation of protein kinase B (AKT). Silencing of SMO increases lysosomal degradation and favors a localization of IGF1R to late endosomal compartments instead of early endosomal compartments from which much of the receptor would normally recycle. In addition, loss of SMO interferes with the lipid raft localization and retention of the remaining IGF1R and AKT, thereby disrupting the primary signaling context for IGF1R/AKT. This activity of SMO is independent of its canonical signaling and represents a novel and clinically relevant contribution to signaling by the highly oncogenic IGF1R/AKT signaling axis.

Shaping of the tumor microenvironment: Stromal cells and vessels

Lymphomas develop and progress in a specialized tissue microenvironment such as bone marrow as well as secondary lymphoid organs such as lymph node and spleen. The lymphoma microenvironment is characterized by a heterogeneous population of stromal cells, including fibroblastic reticular cells, nurse-like cells, mesenchymal stem cells, follicular dendritic cells, and inflammatory cells such as macrophages, T- and B-cells. These cell populations interact with the lymphoma cells to promote lymphoma growth, survival and drug resistance through multiple mechanisms. Angiogenesis is also recognized as an important factor associated with lymphoma progression. In recent years, we have learned that the interaction between the malignant and non-malignant cells is bidirectional and resembles, at least in part, the pattern seen between non-neoplastic lymphoid cells and the normal microenvironment of lymphoid organs. A summary of the current knowledge of lymphoma microenvironment focusing on the cellular components will be reviewed here.

Abstract 3605: The inhibitor of NF-ĸB kinase, IKKβ, regulates the stability of GLI1 transcription factor

Lymphoma microenvironment has a crucial role in lymphoma initiation, progression and drug resistance. Fibroblastic reticular cells (FRCs) participate dynamically in the cytokine microenvironment of the lymph node paracortex as well as the regulation of cell trafficking and access of T-cells into the paracortex. The FRC niche also participates in the cytokine microenvironment of lymphomas providing homing and survival signals including CCL19, CCL21, IL-7, CXCL12 and hedgehog (Hh) ligands. Hh signaling is evolutionary conserved signaling pathway that serves several physiological and development processes mediated by externally secreted Hh ligands. We previously demonstrated that the canonical Hh ligand-PTCH1-SMO-GLI axis is functional and contributes to cell survival, proliferation and enhances chemo tolerance in DLBCL. We further showed that GLI1, Hh signaling transcription factor is aberrantly activated in ∼87% of DLBCL and this activation is in part mediated by sonic Hh ligands secreted by stromal cells. Although the importance of GLI1 in tumor development is well recognized, the molecular mechanisms controlling the transcriptional activity of GLI1 is limited. To identify regulatory components that participate in the transcriptional activity of GLI1, we explored GLI1 putative interacting proteins by liquid chromatography tandem mass spectrometry following immunoprecipitation of endogenous GLI1. We identified the inhibitor of NF-ĸB kinase, IKKβ as a novel GLI1-binding protein. In addition, we found that the kinase activity of IKKβ is critical to recruit and phosphorylate GLI1 in the C-terminal fragment. We further showed that in DLBCL cells stimulated with TNFα, IKKβ phosphorylates GLI1 and restricts the binding between GLI1 with HECT-type E3 ubiquitin ligase (ITCH) resulting in GLI1 stability and increased oncogenic potential. Inhibition of IKKβ-mediated GLI1 phosphorylation restored the binding between GLI1 and ITCH and promoted ubiquitination and degradation of GLI1. Collectively, these results indicate that IKKβ regulates the transcriptional activity of GLI1 by phosphorylating GLI1 and modulating the binding between GLI1 and ITCH. In DLBCL, canonical NF-κB and GLI1 mediated Hh signaling pathways are strongly responsive with tumor microenvironment; our study will help to understand the cross talk between these two pathways which could represents a novel therapeutic approach for DLBCL.

Citation Format: Nitin K. Agarwal, Kranthi Kunkalla, Francisco Vega. The inhibitor of NF-ĸB kinase, IKKβ, regulates the stability of GLI1 transcription factor. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3605. doi:10.1158/1538-7445.AM2014-3605

Transcriptional regulation of serine/threonine protein kinase (AKT) genes by glioma-associated oncogene homolog 1

Aberrant activation of Hedgehog signaling has been described in a growing number of cancers, including malignant lymphomas. Here, we report that canonical Hedgehog signaling modulates the transcriptional expression of AKT genes and that AKT1 is a direct transcriptional target of GLI1. We identified two putative binding sites for GLI1 in the AKT1 promoter region and confirmed their functionality using chromatin immunoprecipitation, luciferase reporter, and site-directed mutagenesis assays. Moreover, we provide evidence that GLI1 contributes to the survival of diffuse large B-cell lymphoma (DLBCL) cells and that this effect occurs in part through promotion of the transcription of AKT genes. This finding is of interest as constitutive activation of AKT has been described in DLBCL, but causative factors that explain AKT expression in this lymphoma type are not completely known. In summary, we demonstrated the existence of a novel cross-talk at the transcriptional level between Hedgehog signaling and AKT with biological significance in DLBCL.

Functional inhibition of BCL2 is needed to increase the susceptibility to apoptosis to SMO inhibitors in diffuse large B-cell lymphoma of germinal center subtype

Previously, we have demonstrated that inhibition of Hedgehog pathway induces predominantly apoptosis in diffuse large B-cell lymphoma (DLBCL) cell lines of activated B-cell (ABC) type but predominantly cell cycle arrest in those of germinal center (GC). Here, we explored the possibility of overcoming the resistance to apoptosis to SMO inhibitors in five DLBCL cells of GC type using the combination of the SMO inhibitor HhAntag (Genentech Inc) with the BH3 mimetic ABT-737 (Abbott Laboratories). As controls we have used two DLBCL of ABC type (OCI-LY10 and OCI-LY3). Combinatorial treatments were performed with increasing concentrations of the HhAntag with low doses (equal or less than the IC20) of ABT-737. MTS assays were used to detect changes in cell viability and Annexin-V and PARP1 cleavage assays were used to detect apoptosis. Combining low doses of ABT-737 with increasing concentrations of HhAntag in GC DLBCL cell lines resulted in significantly increase of apoptosis in comparison to treatments with the SMO inhibitor alone. We concluded that in GC DLBCL cell lines, in contrast to those of ABC type, functional inhibition of BCL2 family members is usually needed to overcome the resistance to apoptosis to SMO inhibitors. These findings provide a rationale to explore the use of SMO and BCL2 inhibitors as adjuvant therapy for treatment of DLBCL of GC type.

Rictor encounters RhoGDI2: the second pilot is taking a lead

Rictor's role in cell migration has been first indicated in the original chemotaxis studies in Dictyostelium and more recent studies reported that rictor is required for migration of cancer cells. How rictor promotes cell migration remains poorly characterized. Based on our proteomics study we have identified a novel functional role of rictor in regulation of cell migration. Here, we discuss our recent finding that rictor by suppressing RhoGDI2 maintains activity of the Rac1/cdc42 GTPases and promotes cell migration. Our finding outlines a critical role of rictor in the regulation of RhoGDI2 activity. This study opens new avenues in the investigation of cancer metastasis by analyzing the rictor dependent post-translational modification of RhoGDI2.

Establishment and characterization of an epithelial cell line from thymus of Catla catla (Hamilton, 1822)

A cell line, CTE, derived from catla (Catla catla) thymus has been established by explant method and subcultured for more than 70 passages over a period of 400 days. The cell line has been maintained in L-15 (Leibovitz) medium supplemented with 10% fetal bovine serum. CTE cell line consists of homogeneous population of epithelial-like cells and grows optimally at 28°C. Karyotype analysis revealed that the modal chromosome number of CTE cells was 50. Partial amplification, sequencing and alignment of fragments of two mitochondrial genes 16S rRNA and COI confirmed that CTE cell line originated from catla. Significant green fluorescent signals were observed when the cell line was transfected with phrGFP II-N mammalian expression vector, indicating its potential utility for transgenic and genetic manipulation studies. The CTE cells showed strong positivity for cytokeratin, indicating that cell line was epithelial in nature. The flow cytometric analysis of cell line revealed a higher number of cells in S-phase at 48 h, suggesting a high growth rate. The extracellular products of Vibrio cholerae MTCC 3904 were toxic to the CTE cells. This cell line was not susceptible to fish betanodavirus, the causative agent of viral nervous necrosis in a large variety of marine fish.

Rictor regulates cell migration by suppressing RhoGDI2

Rictor and its binding partner Sin1 are indispensable components of mTORC2 (mammalian Target of Rapamycin Complex 2). The mTORC2 signaling complex functions as the regulatory kinase of the distinct members of AGC kinase family known to regulate cell proliferation and survival. In the early chemotaxis studies in Dictyostelium, the rictor's ortholog has been identified as a regulator of cell migration. How rictor regulates cell migration is poorly characterized. Here we show that rictor regulates cell migration by controlling a potent inhibitor of Rho proteins known as the Rho-GDP dissociation inhibitor 2 (RhoGDI2). Based on our proteomics study we identified that the rictor-dependent deficiency in cell migration is caused by up-regulation of RhoGDI2 leading to a low activity of Rac and Cdc42. We found that a suppression of RhoGDI2 by rictor is not related to the Sin1 or raptor function that excludes a role of mTORC2 or mTORC1 in regulation of RhoGDI2. Our study reveals that rictor by suppressing RhoGDI2 promotes activity of the Rho proteins and cell migration.

Calreticulin is crucial for calcium homeostasis mediated adaptation and survival of thick ascending limb of Henle's loop cells under osmotic stress

The thick ascending limb of Henle's loop (TALH) is normally exposed to variable and often very high osmotic stress and involves different mechanisms to counteract this stress. ER resident calcium binding proteins especially calreticulin (CALR) play an important role in different stress balance mechanisms. To investigate the role of CALR in renal epithelial cells adaptation and survival under osmotic stress, two-dimensional fluorescence difference gel electrophoresis combined with mass spectrometry and functional proteomics were performed. CALR expression was significantly altered in TALH cells exposed to osmotic stress, whereas renal inner medullary collecting duct cells and interstitial cells exposed to hyperosmotic stress showed no significant changes in CALR expression. Moreover, a time dependent downregulation of CALR was accompanied with continuous change in the level of free intracellular calcium. Inhibition of the calcium release, through IP3R antagonist, prevented CALR expression alteration under hyperosmotic stress, whereas the cell viability was significantly impaired. Overexpression of wild type CALR in TALH cells resulted in significant decrease in cell viability under hyperosmotic stress. In contrast, the hyperosmotic stress did not have any effect on cells overexpressing the CALR mutant, lacking the calcium-binding domain. Silencing CALR with siRNA significantly improved the cell survival under osmotic stress conditions. Taken together, our data clearly highlight the crucial role of CALR and its calcium-binding role in TALH adaptation and survival under osmotic stress.

PTEN, NHERF1 and PHLPP form a tumor suppressor network that is disabled in glioblastoma

The PI3K-Akt pathway is activated in cancer by genetic or epigenetic events and efforts are under way to develop targeted therapies. PTEN tumor suppressor is the major brake of the pathway and a common target for inactivation in glioblastoma, one of the most aggressive and therapy-resistant cancers. To achieve potent inhibition of the PI3K-Akt pathway in glioblastoma, we need to understand its mechanism of activation by investigating the interplay between its regulators. We show here that PTEN modulates the PI3K-Akt pathway in glioblastoma within a tumor suppressor network that includes NHERF1 and PHLPP1. The NHERF1 adaptor, previously characterized by our group as a PTEN ligand and regulator, shows also PTEN-independent Akt-modulating effects that led us to identify the PHLPP1/PHLPP2 Akt phosphatases as NHERF1 ligands. NHERF1 interacts via its PDZ domains with PHLPP1/PHLPP2 and scaffolds heterotrimeric complexes with PTEN. Functionally, PHLPP1 requires NHERF1 for membrane localization and growth suppressive effects. PHLPP1 loss boosts Akt phosphorylation only in PTEN-negative cells and cooperates with PTEN loss for tumor growth. In a panel of low-grade and high-grade glioma patient samples, we show for the first time a significant disruption of all three members of the PTEN-NHERF1-PHLPP1 tumor suppressor network in high-grade tumors, correlating with Akt activation and patients’ abysmal survival. We thus propose a PTEN-NHERF1-PHLPP PI3K-Akt pathway inhibitory network that relies on molecular interactions and can undergo parallel synergistic hits in glioblastoma.

Modulation of pentylenetetrazole-induced kindling and oxidative stress by curcumin in mice

Epilepsy is a chronic neurological disorder affecting 1% population worldwide. A number of experimental studies have reported anticonvulsant, neuroprotective and antioxidant activity of certain natural products like curcumin, an active ingredient of turmeric. The present study was designed to explore the effect of acute administration of curcumin at doses 50, 100 and 200 mg/kg, orally (p.o.) pentylenetetrazole-induced kindling in mice. Further two oxidative stress markers viz., malondialdehyde (MDA) and glutathione were estimated in brain tissues of rodents. Curcumin (50, 100 and 200 mg/kg, p.o.) dose dependently suppressed the progression of kindling in mice. In addition, the increased levels of MDA and glutathione were also reduced by curcumin in kindled animals. These results suggest that curcumin appears to possess protective activity against kindling in mice.

Rictor phosphorylation on the Thr-1135 site does not require mammalian target of rapamycin complex 2

In animal cells, growth factors coordinate cell proliferation and survival by regulating the phosphoinositide 3-kinase/Akt signaling pathway. Deregulation of this signaling pathway is common in a variety of human cancers. The PI3K-dependent signaling kinase complex defined as mammalian target of rapamycin complex 2 (mTORC2) functions as a regulatory Ser-473 kinase of Akt. We find that activation of mTORC2 by growth factor signaling is linked to the specific phosphorylation of its component rictor on Thr-1135. The phosphorylation of this site is induced by the growth factor stimulation and expression of the oncogenic forms of ras or PI3K. Rictor phosphorylation is sensitive to the inhibition of PI3K, mTOR, or expression of integrin-linked kinase. The substitution of wild-type rictor with its specific phospho-mutants in rictor null mouse embryonic fibroblasts did not alter the growth factor-dependent phosphorylation of Akt, indicating that the rictor Thr-1135 phosphorylation is not critical in the regulation of the mTORC2 kinase activity. We found that this rictor phosphorylation takes place in the mTORC2-deficient cells, suggesting that this modification might play a role in the regulation of not only mTORC2 but also the mTORC2-independent function of rictor.

Deep vein thrombosis in acute spinal cord injury

STUDY DESIGN

Randomized study.

OBJECTIVES

To find out the incidence of deep vein thrombosis (DVT) in acute spinal cord injury (SCI) patients with and without therapeutic prophylaxis.

SETTING

Patients admitted in the department of Physical Medicine & Rehabilitation, SMS Medical College, Jaipur, India.

METHODS

All 297 patients received physical therapy measures and were randomly divided into two groups. 166 patients received prophylactic heparin, whereas 131 patients did not.

RESULTS

A total of three cases (1.8%) in study group and four cases (3%) in control group developed DVT. This difference was statistically insignificant (P>0.05).

CONCLUSION

Incidence of DVT in SCI is low in our study.

Proteomic Analysis of Cellular Response to Osmotic Stress in Thick Ascending Limb of Henle’s Loop (TALH) Cells

Epithelial cells of the thick ascending limb of Henle's loop (TALH cells) play a major role in the urinary concentrating mechanism. They are normally exposed to variable and often very high osmotic stress, which is particularly due to high sodium and chloride reabsorption and very low water permeability of the luminal membrane. It is already established that elevation of the activity of aldose reductase and hence an increase in intracellular sorbitol are indispensable for the osmotic adaptation and stability of the TALH cells. To identify new molecular factors potentially associated with the osmotic stress-resistant phenotype in kidney cells, TALH cells exhibiting low or high levels of resistance to osmotic stress were characterized using proteomic tools. Two-dimensional gel analysis showed a total number of 40 proteins that were differentially expressed in TALH cells under osmotic stress. Twenty-five proteins were overexpressed, whereas 15 proteins showed a down-regulation. Besides the sorbitol pathway enzyme aldose reductase, whose expression was 15 times increased, many other metabolic enzymes like glutathione S-transferase, malate dehydrogenase, lactate dehydrogenase, alpha enolase, glyceraldehyde-3-phosphate dehydrogenase, and triose-phosphate isomerase were up-regulated. Among the cytoskeleton proteins and cytoskeleton-associated proteins vimentin, cytokeratin, tropomyosin 4, and annexins I, II, and V were up-regulated, whereas tubulin and tropomyosins 1, 2, and 3 were down-regulated. The heat shock proteins alpha-crystallin chain B, HSP70, and HSP90 were found to be overexpressed. In contrast to the results in oxidative stress the endoplasmic reticulum stress proteins like glucose-regulated proteins (GRP78, GRP94, and GRP96), calreticulin, and protein-disulfide isomerase were down-regulated under hypertonic stress.

Development and validation of a simple liquid chromatographic method with ultraviolet detection for the determination of imatinib in biological samples

The aim of this study was to develop a rapid and sensitive HPLC method with UV detection for the estimation of imatinib from the plasma of patients with chronic myeloid leukemia (CML). The robustness of the method was checked by conducting first dose pharmacokinetics on blood samples from four patients who had been administered Gleevec (100 mg) in an oral dose. Samples were prepared in a simple and single step by precipitating the plasma proteins with methanol and injecting 50 microl aliquot from supernatant was subjected for analysis. Assay was conducted using a C8 column (250 mm x 4.6 mm, 5 microm particle size) under isocratic elution with 0.02 M potassium dihydrogen phosphate-acetonitrile (7:3, v/v) at a flow rate of 1 ml/min and detected using photodiode array at 265 nm. Calibration plots in spiked plasma were linear in a concentration range of 0.05-25 microg/ml. The inter and intra-day variation of standard curve was <4% (R.S.D.). This method could be a simple and quick method for the estimation of imatinib from the patient's plasma.

Medical certification in respect of alleged torture victims

Torture is a global problem and affects a large number of people worldwide. The opinion of doctors in certifying various types of physical, and psychological injuries being caused accidentally or resulting from attempted suicide or by torture is very significant. A number of times, discrepancies between complaints and physical findings are noted. Meticulous examination is desirable in order to prove guilt or innocence.

The adhesion of thin carbon films to metallic substrates

As part of the development of carbon-coated prosthetic devices, the adhesion of thin carbon films to metallic substrates has been studied. The bond strength of carbon films about 5000 A thick on Ti-6A1-4V and stainless steel was measured in a pull test and found to be greater than 4700 psi. Auger electron spectroscopy showed a reactive film/substrate interface. The ultimate bond strength was found to be dependent on the substrate and the deposition parameters.