OBJECTIVE

ROS1 rearrangement leads to constitutive ROS1 activation with potent transforming activity. In an ongoing phase I trial, the ALK tyrosine kinase inhibitor (TKI) crizotinib shows remarkable initial responses in patients with non-small cell lung cancer (NSCLC) harboring ROS1 fusions; however, cancers eventually develop crizotinib resistance due to acquired mutations such as G2032R in ROS1. Thus, understanding the crizotinib-resistance mechanisms in ROS1-rearranged NSCLC and identification of therapeutic strategies to overcome the resistance are required.

METHODS

The sensitivity of CD74-ROS1-transformed Ba/F3 cells to multiple ALK inhibitors was examined. Acquired ROS1 inhibitor-resistant mutations in CD74-ROS1 fusion were screened by N-ethyl-N-nitrosourea mutagenesis with Ba/F3 cells. To overcome the resistance mutation, we performed high-throughput drug screening with small-molecular inhibitors and anticancer drugs used in clinical practice or being currently tested in clinical trials. The effect of the identified drug was assessed in the CD74-ROS1-mutant Ba/F3 cells and crizotinib-resistant patient-derived cancer cells (MGH047) harboring G2032R-mutated CD74-ROS1.

RESULTS

We identified multiple novel crizotinib-resistance mutations in the ROS1 kinase domain, including the G2032R mutation. As the result of high-throughput drug screening, we found that the cMET/RET/VEGFR inhibitor cabozantinib (XL184) effectively inhibited the survival of CD74-ROS1 wild-type (WT) and resistant mutants harboring Ba/F3 and MGH047 cells. Furthermore, cabozantinib could overcome all the resistance by all newly identified secondary mutations.

CONCLUSIONS

We developed a comprehensive model of acquired resistance to ROS1 inhibitors in NSCLC with ROS1 rearrangement and identified cabozantinib as a therapeutic strategy to overcome the resistance.

Acquired point mutations within the BCR-ABL kinase domain represent a common mechanism of resistance to ABL inhibitor therapy in patients with chronic myeloid leukemia (CML). The BCR-ABL(T315I) mutant is highly resistant to imatinib, nilotinib, and dasatinib, and is frequently detected in relapsed patients. This critical gap in resistance coverage drove development of DCC-2036, an ABL inhibitor that binds the switch control pocket involved in conformational regulation of the kinase domain. We evaluated the efficacy of DCC-2036 against BCR-ABL(T315I) and other mutants in cellular and biochemical assays and conducted cell-based mutagenesis screens. DCC-2036 inhibited autophosphorylation of ABL and ABL(T315I) enzymes, and this activity was consistent with selective efficacy against Ba/F3 cells expressing BCR-ABL (IC(50): 19 nmol/L), BCR-ABL(T315I) (IC(50): 63 nmol/L), and most kinase domain mutants. Ex vivo exposure of CML cells from patients harboring BCR-ABL or BCR-ABL(T315I) to DCC-2036 revealed marked inhibition of colony formation and reduced phosphorylation of the direct BCR-ABL target CrkL. Cell-based mutagenesis screens identified a resistance profile for DCC-2036 centered around select P-loop mutations (G250E, Q252H, Y253H, E255K/V), although a concentration of 750 nmol/L DCC-2036 suppressed the emergence of all resistant clones. A decreased concentration of DCC-2036 (160 nmol/L) in dual combination with either nilotinib or dasatinib achieved the same zero outgrowth result. Further screens for resistance due to BCR-ABL compound mutations (two mutations in the same clone) identified BCR-ABL(E255V / T315I) as the most resistant mutant. Taken together, these findings support continued evaluation of DCC-2036 as an important new agent for treatment-refractory CML.

OBJECTIVE

CBL is a negative regulator of activated receptor tyrosine kinases (RTK). In this study, we determined the frequency of CBL mutations in acute leukemias and evaluated the oncogenic potential of mutant CBL.

METHODS

The cDNA of 300 acute myeloid leukemia (AML)/myelodysplastic syndrome (MDS) and acute lymphoblastic leukemia (ALL) patients and 82 human leukemic cell lines was screened for aberrations in the linker and RING finger domain of CBL. The oncogenic potential of identified mutants was evaluated in hematopoietic cells.

RESULTS

We identified 3 of 279 AML/MDS patients expressing CBL exon 8/9 deletion mutants. Three of four cases at diagnosis expressed deleted transcripts missing exon 8 or exon 8/9. In remission samples a weak or no expression of mutant CBL was detected. No aberrations were found in normal hematopoietic tissues. One of 116 sequenced AML/MDS cases carried a R420G missense mutation. All AML/MDS patients with identified CBL mutants belonged to the core binding factor and 11q deletion AML subtypes. Functionally, CBL negatively regulated FMS-like tyrosine kinase 3 (FLT3) activity and interacted with human FLT3 via the autophosphorylation sites Y589 and Y599 and colocalized in vivo. Expression of CBLDeltaexon8 and CBLDeltaexon8+9 in FLT3-WT-Ba/F3 cells induced growth factor-independent proliferation associated with autophosphorylation of FLT3 and activated the downstream targets signal transducer and activator of transcription 5 (STAT5) and protein kinase B (AKT). FLT3 ligand-dependent hyperproliferation of CBL mutant cells could be abrogated by treatment with the FLT3 PTK inhibitor PKC412 (midostaurin).

CONCLUSIONS

CBL exon8/9 mutants occur in genetically defined AML/MDS subtypes and transform hematopoietic cells by constitutively activating the FLT3 pathway. This phenotype resembles the one of mutated RTKs and suggests that CBL mutant AML patients might benefit from treatment with FLT3 PTK inhibitors.

Most antioxidants show contradictory behaviors because in the biological environment, for unpredictable reasons, they can become prooxidants. Recently, a new simple method to monitor oxidative stress in serum was developed. This test detects the derivatives of reactive oxygen metabolites (D-Roms). Hydroperoxides are converted into radicals that oxidize N,N-diethyl-para-phenylendiamine and that can be detected through spectrophotometric procedures as U.CARR. (Carratelli units). One U.CARR. corresponds to 0.8 mg/L hydrogen peroxide. In normal subjects U.CARR. values range from 250 to 300. Values outside this range indicate a modification of the prooxidant/antioxidant ratio. On the basis of this method, we tested three different formulas of antioxidants (F1, F2, F3) in 14 apparently healthy volunteers (11 men and 3 women). Formula 1 was composed of 5 mg zinc, 48 microg selenium, 400 microg vitamin A (as retinol acetate), 50 microg beta-carotene, 15 mg vitamin E (as dl-alpha-tocopheryl acetate) and 10 mg L-cysteine. Formula 2 was composed of 30 mg bioflavonoids from citrus, 30 mg vitamin C (as L-ascorbic acid), 10 mg coenzyme Q(10) and 1 mg vitamin B-6 (as pyridoxine hydrochloride). Formula 3 was composed of Formula 1 plus Formula 2. Each formula was prepared in dry capsules (formulation D1, D2, D3) or in a fluid form (formulation P1, P2, P3). Each formulation was administered for 1 wk in a crossover design. A 15% deviation of U.CARR. levels was chosen as the cut-off value for a significant change in oxidative stress. Formulas F1 and F3 reduced mean U.CARR. levels in most of the treated subjects (t test, P < 0.05), whereas F2 was not active. Fluid formulations were more active than dry formulations (chi(2) test, P < 0.05). In some cases, a slight increase in oxidative stress was detected. These minimal increases were not related to any particular antioxidant formula. In one subject only, the administration of the dry formulation (D1), increased oxidative stress to a level that reached the cut-off value. In conclusion, when antioxidants are taken in combination at low dosages they reduce oxidative stress, and little relevant prooxidant activity is detectable.

The 8p11 myeloproliferative syndrome (EMS) is an aggressive, atypical stem cell myeloproliferative disorder associated with chromosome translocations that disrupt and constitutively activate FGFR1 by fusion to diverse partner genes. To explore the possibility of targeted therapy for EMS, we have investigated the use of TKI258, a multitargeted receptor tyrosine kinase inhibitor with activity against FGFR, VEGFR, PDGFR, FLT3, and KIT that is currently being assessed for the treatment of a variety of malignancies in phase 1 clinical studies. The viability of Ba/F3 cells transformed to IL3 independence by ZNF198-FGFR1 or BCR-FGFR1 was specifically inhibited by TKI258 with IC(50) values of 150 nM and 90 nM, respectively. Inhibition was accompanied by dose-dependent inhibition of phosphorylation of each fusion gene, ERK, and STAT5. TKI258 also specifically inhibited proliferation and survival of the FGFR1OP2-FGFR1-positive KG1 and KG1A cell lines, resulting in increased levels of apoptosis. Primary cells from EMS patients showed significant, dose-dependent responses in liquid culture and in methylcellulose colony assays compared with controls. This work provides evidence that targeted therapy may be beneficial for patients with EMS.

OBJECTIVE

The acoustic radiation force impulse (ARFI) technology is a novel ultrasound method that provides information about the local elasticity of tissue in real-time. ARFI is integrated in a conventional ultrasound system. The aim of this exploratory study was to evaluate this new technique in the assessment of liver fibrosis in a cohort with chronic viral hepatitis B and C and to ascertain the most reliable hepatic segment for measurements.

METHODS

57 patients (27 female, 30 male, mean age 54 years) with chronic viral hepatitis B and C underwent ARFI imaging and consecutively liver biopsy. The results were compared to the histological fibrosis degree (F), which served as the reference. 20 healthy volunteers received ARFI quantification of different segments of the liver.

RESULTS

The best ARFI assessments with the lowest rate of invalid measurements were carried out by an intercostal approach to segment VII/VIII of the liver. The ARFI velocities of the healthy group had a mean of 1.09 m/s (range 0.79 - 1.32 m/s), the means of the patient group ranged from 0.83 to 4.19 m/s. ARFI quantification correlated significantly with the histological fibrosis stage (p < 0.001). The area under the receiver operating characteristic (ROC) curves for the accuracy of ARFI imaging was 85 %, 92 % and 87 % for the diagnosis of moderate fibrosis >>or= F2), severe fibrosis >>or= F3) and cirrhosis ( = F 4), respectively.

CONCLUSIONS

This study underscores the usefulness of ARFI as a quick method for assessing liver fibrosis or cirrhosis in patients with HBV or HCV. ARFI measurements of the liver should be performed via an intercostal access. Increasing ARFI velocities correlate with higher degree of hepatic fibrosis.

The present study was undertaken to examine multifaceted therapeutic effects of vascular endothelial growth factor (VEGF) in a rat spinal cord injury (SCI) model, focusing on its capability to stimulate proliferation of endogenous glial progenitor cells. Neural stem cells (NSCs) can be genetically modified to efficiently transfer therapeutic genes to diseased CNS. We adopted an ex vivo approach using immortalized human NSC line (F3 cells) to achieve stable and robust expression of VEGF in the injured spinal cord. Transplantation of NSCs retrovirally transduced to overexpress VEGF (F3.VEGF cells) at 7 days after contusive SCI markedly elevated the amount of VEGF in the injured spinal cord tissue compared to injection of PBS or F3 cells without VEGF. Concomitantly, phosphorylation of VEGF receptor flk-1 increased in F3.VEGF group. Stereological counting of BrdU+ cells revealed that transplantation of F3.VEGF significantly enhanced cellular proliferation at 2 weeks after SCI. The number of proliferating NG2+ glial progenitor cells (NG2+/BrdU+) was also increased by F3.VEGF. Furthermore, transplantation of F3.VEGF increased the number of early proliferating cells that differentiated into mature oligodendrocytes, but not astrocytes, at 6 weeks after SCI. F3.VEGF treatment also increased the density of blood vessels in the injured spinal cord and enhanced tissue sparing. These anatomical results were accompanied by improved BBB locomotor scores. The multifaceted effects of VEGF on endogenous gliogenesis, angiogenesis, and tissue sparing could be utilized to improve functional outcomes following SCI.

Using DNA cross-hybridization, we have isolated and characterized cDNA clones encoding a mouse (mo) IL-12R beta component. Two forms of cDNA were found. The first form encodes a receptor protein that has an overall structure very similar to that of the known human (hu) IL-12R beta with 54% amino acid identity, whereas in the second type of mouse cDNA, the equivalent of the transmembrane region has been deleted. This presumed alternative splicing event also gives rise to a frame shift that results in a receptor with an identical extracellular domain but a different C-terminal sequence. Whether this alternative C terminus is capable of signaling is not yet known. Both types of receptors when expressed in COS-7 cells are membrane associated and bind moIL-12 with an affinity of 1 nM, similar to the affinity of huIL-12R beta for huIL-12. The monomeric size of both moIL-12R beta proteins is about 100 kDa. Similar to huIL-12R beta, moIL-12R beta is expressed at the surface of COS-7 and Ba/F3 cells as a dimer/oligomer whose formation is independent of IL-12 binding. When expressed in Ba/F3 cells, moIL-12R beta binds moIL-12 with two affinities of 50 and 470 pM, corresponding to the medium and high affinity IL-12 binding sites previously identified on mouse Con A lymphoblasts. Despite the higher affinity displayed by the moIL-12R beta in Ba/F3 cells, this receptor alone is not sufficient to transduce a signal, suggesting that another subunit is probably required to generate a functional moIL-12R complex.

Porphyromonas gingivalis lipopolysaccharide (LPS) and its bioactive center, lipid A, are known to exhibit very low endotoxic activities and activate LPS-hyporesponsive C3H/HeJ mice that have a point mutation in the cytoplasmic portion of Toll-like receptor (TLR) 4, in contrast to classical enterobacterial LPS and their lipid A. In the present study, we attempted to determine which TLR mediates the response to lipid A from P. gingivalis strain 381. P. gingivalis LPS and its natural lipid A fraction induced NF-kappa B activation primarily in Ba/F3 cells expressing mouse TLR 2 (Ba/mTLR2), rather than in those expressing mouse TLR4 and its accessory protein MD2 (Ba/mTLR4/mMD2). Further purification of the natural lipid A fraction resulted in a significant decrease of NF-kappa B activation in Ba/mTLR2, although not in Ba/mTLR4/mMD2. The synthetic counterpart of P. gingivalis strain 381-lipid A (compound PG-381) also elicited NF-kappa B activation in Ba/mTLR4/mMD2, but not Ba/mTLR2. Furthermore, P. gingivalis purified natural lipid A and compound PG-381 lacked the ability to activate gingival fibroblasts from C3H/HeJ, TLR4 knockout (KO) and myeloid differentiation factor 88 (MyD88) KO mice. These findings demonstrate that the P. gingivalis lipid A molecule induces cell activation via a TLR4/MD2-MyD88-dependent pathway, and suggest the possibility that unknown bacterial components in P. gingivalis LPS and its lipid A may induce cell activation via TLR2.

Previous studies have shown that activation of the signal transducer and activator of transcription 5 (STAT5) plays an essential role in leukemogenesis mediated through constitutive activated protein tyrosine kinases (PTK). Because PIM-1 is a STAT5 target gene, we analyzed the role of the family of PIM serine/threonine kinases (PIM-1 to PIM-3) in PTK-mediated transformation of hematopoietic cells. Ba/F3 cells transformed to growth factor independence by various oncogenic PTKs (TEL/JAK2, TEL/TRKC, TEL/ABL, BCR/ABL, FLT3-ITD, and H4/PDGFbetaR) show abundant expression of PIM-1 and PIM-2. Suppression of PIM-1 activity had a negligible effect on transformation. In contrast, expression of kinase-dead PIM-2 mutant (PIM-2KD) led to a rapid decline of survival in Ba/F3 cells transformed by FLT3-ITD but not by other oncogenic PTKs tested. Coexpression of PIM-1KD and PIM-2KD abrogated growth factor-independent growth of Ba/F3 transformed by several PTKs, including BCR/ABL. Targeted down-regulation of PIM-2 by RNA interference (RNAi) selectively abrogated survival of Ba/F3 cells transformed by various Fms-like tyrosine kinase 3 (FLT3)-activating mutants [internal tandem duplication (ITD) and kinase domain] and attenuated growth of human cell lines containing FLT3 mutations. Interestingly, cells transformed by FLT3 and BCR/ABL mutations that confer resistance to small-molecule tyrosine kinase inhibitors were still sensitive to knockdown of PIM-2, or PIM-1 and PIM-2 by RNAi. Our observations indicate that combined inactivation of PIM-1 and PIM-2 interferes with oncogenic PTKs and suggest that PIMs are alternative therapeutic targets in PTK-mediated leukemia. Targeting the PIM kinase family could provide a new avenue to overcome resistance against small-molecule tyrosine kinase inhibitors.

The current study was undertaken to assess whether fibrosis could regress under venesection therapy in patients with C282Y homozygous genetic hemochromatosis. The 36 patients studied were recruited from a subfile of our database consisting of 125 C282Y homozygotes with either severe fibrosis or cirrhosis (F3 or F4 fibrosis stage, respectively, according to the METAVIR grading system). The second liver biopsy was performed for management of liver cancer, extrahepatic surgery, or assessment of liver fibrosis. All paired biopsies were reviewed by two pathologists without knowledge of clinical data. Among the 13 patients who had F3 fibrosis on their initial liver biopsy, 3 had F0, 6 had F1, and 2 had F2 on their second liver biopsy. Among the 23 patients with cirrhosis on their initial liver biopsy, 1 had F0, 4 had F1, 3 had F2, and 2 had F3 on their second liver biopsy. When defining regression of fibrosis as a decrease of at least 2 METAVIR units, fibrosis regressed in 9 of 13 (69%) F3 and in 8 of 23 (35%) F4. When the ratio of gammaglobulins (g/L) to (platelets [n/mm(3)] x prothrombin activity [%]) was greater than 7.5, fibrosis never regressed. In conclusion, these data extend the concept of regression of fibrosis to patients with treated genetic hemochromatosis and suggest that some simple biochemical tests would be predictive of further regression of fibrosis as a result of venesection therapy. If confirmed on larger series, this could modify the ultrasound screening policy of hepatocellular carcinoma in genetic hemochromatosis.

A family with multiple gastrointestinal stromal tumors (GISTs), a new type of germline mutation of KIT gene, and dysphagia is reported. The mutation was observed at Asp-820 in tyrosine kinase (TK) II domain. Mutations in TK II domain have been found in mast cell and germ cell tumors but not in GISTs, and the present family members are the first reported cases of GISTs with TK II domain mutations, including sporadic GISTs. Because interleukin 3-dependent Ba/F3 murine lymphoid cells transfected with the mutant KIT complementary DNA grew autonomously without any growth factors and formed tumors in nude mice, the mutation was considered to be gain-of-function type. Family members with the germline KIT mutation reported dysphagia, but those without the mutation did not. The mechanism of dysphagia was examined with gastrointestinal fiberscopy, endoscopic ultrasonography, and esophageal manometry. No mechanical obstruction was found, and the esophagus was not remarkably dilated. In the family members with dysphagia, endoscopic ultrasonography at the esophagocardiac junction showed a thickened hyperechoic layer between the circular and longitudinal muscle layers, suggesting hyperplasia of interstitial cells of Cajal at the myenteric plexus layer. Manometry showed low resting lower esophageal sphincter pressure and abnormal simultaneous contractions of the esophagus without normal peristalsis. These findings indicate that the dysphagia of the present family is different from typical achalasia. This is the first report of familial dysphagia caused by germline gain-of-function mutation of the KIT gene at the TK II domain.

OBJECTIVE

To investigate the correlation between MR elastography (MRE) assessed spleen stiffness and direct portal vein pressure gradient (D-HVPG) measurements in a large animal model of portal hypertension.

METHODS

Cholestatic liver disease was established in adult canines by common bile duct ligation. A spin echo based echo planar imaging (EPI) MRE sequence was used to acquire three-dimensional/three axis (3D/3-axis) abdominal MRE data at baseline, 4 weeks, and 8 weeks. Liver biopsies, blood samples, and D-HVPG measurements were obtained simultaneously.

RESULTS

Animals developed portal hypertension (D-HVPG: 11.0 ± 5.1 mmHg) with only F1 fibrosis after 4 weeks. F3 fibrosis was confirmed after 8 weeks despite no further rise in portal hypertension (D-HVPG: 11.3 ± 3.2 mmHg). Mean stiffnesses of the spleen increased over two-fold from baseline (1.72 ± 0.33 kPa) to 4 weeks (3.54 ± 0.31 kPa), and stabilized at 8 weeks (3.38 ± 0.06 kPa) in a pattern consistent with changes in portal pressure. A positive correlation was observed between spleen stiffness and D-HVPG (r(2) = 0.86; P < 0.01).

CONCLUSIONS

These findings indicate a temporal relationship between portal hypertension and the development of liver fibrosis in a large animal model of cholestatic liver disease. The observed direct correlation between spleen stiffness and D-HVPG suggest a noninvasive MRE approach to diagnose and screen for portal hypertension.

OBJECTIVE

We evaluated the use of magnetic resonance (MR) elastography (MRE) for staging liver fibrosis in patients with chronic hepatitis C and compared the ability of MRE and serum fibrosis markers for discriminating each stage of fibrosis.

METHODS

We evaluated 114 patients with chronic hepatitis C in whom the pathological fibrosis stage was determined (fibrosis stage 0 [F0], 3; F1, 15; F2, 28; F3, 25; and F4, 43). All patients underwent MRE using a 1.5-tesla MR system and pneumatic driver system. We measured stiffness values (kPa) of the liver in a circular region of interest placed on elastograms. We determined the optimal cutoff value and diagnostic ability for discriminating each stage of fibrosis using receiver operating characteristic (ROC) curve analysis and compared the discriminative ability of MRE with that of serum fibrosis markers.

RESULTS

The mean stiffness values of the liver increased with stage of fibrosis: F0, 2.10±0.10 kPa; F1, 2.42±0.29 kPa; F2, 3.16±0.32 kPa; F3, 4.21±0.78 kPa; and F4, 6.20±1.08 kPa. The mean area under the ROC curve (Az) values for discriminating liver fibrosis stages were: ≥F1, 0.984 (95% confidence interval, 0.933-0.996); ≥F2, 0.986 (0.956-0.996); ≥F3, 0.973 (0.935-0.989); and ≥F4, 0.976 (0.945-0.990). The Az values for discriminating fibrosis stages were significantly higher for MRE than serum fibrosis markers.

CONCLUSIONS

MRE is a reliable technique for staging liver fibrosis and discriminating liver fibrosis stages in patients with chronic hepatitis C.

Human stem cell leukemia-lymphoma syndrome usually presents itself as a myeloproliferative disorder (MPD) that evolves to acute myeloid leukemia and/or lymphoma. The syndrome associated with t(8;13)(p11;q12) results in expression of the ZNF198-fibroblast growth factor receptor (FGFR) 1 fusion tyrosine kinase. Current empirically derived cytotoxic chemotherapy is inadequate for treatment of this disease. We hypothesized that small-molecule inhibitors of the ZNF198-FGFR1 fusion would have therapeutic efficacy. We characterized the transforming activity of ZNF198-FGFR1 in hematopoietic cells in vitro and in vivo. Expression of ZNF198-FGFR1 in primary murine hematopoietic cells caused a myeloproliferative syndrome in mice that recapitulated the human MPD phenotype. Transformation in these assays, and activation of the downstream effector molecules PLC-gamma, STAT5, and phosphatidylinositol 3-kinase/AKT, required the proline-rich domains, but not the ZNF domains, of ZNF198. A small-molecule tyrosine kinase inhibitor, PKC412 (N-benzoyl-staurosporine) effectively inhibited ZNF198-FGFR1 tyrosine kinase activity and activation of downstream effector pathways, and inhibited proliferation of ZNF198-FGFR1 transformed Ba/F3 cells. Furthermore, treatment with PKC412 resulted in statistically significant prolongation of survival in the murine model of ZNF198-FGFR1-induced MPD. Based in part on these data, PKC412 was administered to a patient with t(8;13)(p11;q12) and was efficacious in treatment of progressive myeloproliferative disorder with organomegaly. Therefore, PKC412 may be a useful therapy for treatment of human stem cell leukemia-lymphoma syndrome.

Flavobacterium meningosepticum endo-beta-acetyl-glucosaminidase F preparations have been resolved by hydrophobic interaction chromatography on TSK-butyl resin into at least three activities designated endo F1, endo F2 and endo F3 each with a unique substrate specificity. The 32-kDa endo F1 protein is the principle component representing in excess of 95% of most earlier and currently available commercial endoglycosidase preparations, the remainder being a mixture of five proteins from 32 to 43 kDa. Substrate specificity studies reveal endo F1 and endo H from Streptomyces plicatus to have nearly identical capacities to hydrolyze high-mannose oligosaccharides with a minimum Man1 alpha 3Man1 alpha 6Man1 beta 4GlcNAc1 beta 4GlcNAc structure. Although endo H will hydrolyze fucose-containing hybrid oligosaccharides at rates approaching comparable high-mannose forms, core-linked fucose reduces the hydrolysis rate of endo F1 by over 50-fold relative to high-mannose structures. Neither homogeneous endo F1 nor endo H hydrolyze complex multi-antennary glycans. The biantennary cleaving activity previously reported for endo F preparations (Tarentino, A. L., Gómez, C. M., and Plummer, T. H., Jr. (1985) Biochemistry 24, 4665-4671) is a characteristic of the contaminating endo F2 activity.

OBJECTIVE

Epidermal growth factor receptor (EGFR) genotyping is now standard in the management of advanced lung adenocarcinoma, as this biomarker predicts marked benefit from treatment with EGFR tyrosine kinase inhibitors (TKI). EGFR exon 19 insertions are a poorly described family of EGFR mutations, and their association with EGFR-TKI sensitivity in lung adenocarcinoma is uncertain.

METHODS

Patients with lung cancers harboring EGFR exon 19 insertions were studied. The predicted effects of the insertions on the structure of the EGFR protein were examined, and EGFR exon 19 insertions were introduced into Ba/F3 cells to assess oncogenicity and in vitro sensitivity to EGFR-TKIs. In patients receiving TKI, response magnitude was assessed with serial computed tomographic (CT) measurement.

RESULTS

Twelve tumors harboring EGFR exon 19 insertions were identified; patients were predominately female (92%) and never-smokers (75%). The 11 specimens available for full sequencing all showed an 18-bp insertion that resulted in the substitution of a Pro for Leu at residue 747. The mutant EGFR transformed the Ba/F3 cells, which were then sensitive to EGFR-TKI. Six patients with measurable disease received TKI and five had a response on serial CT.

CONCLUSIONS

EGFR exon 19 insertions are a newly appreciated family of EGFR-TKI-sensitizing mutations, and patients with tumors harboring these mutations should be treated with EGFR-TKI. While these mutations may be missed through the use of some mutation-specific assays, the addition of PCR product size analysis to multigene assays allows sensitive detection of both exon 19 insertion and deletion mutations.

There are contrasting results in studies of cardiovascular risk in patients with genotype 1 chronic hepatitis C (G1 CHC). We evaluated the prevalence of carotid atherosclerosis compared with a control population in order to assess the potential association between atherosclerosis, host and viral factors, and liver histological features. In all, 174 consecutive biopsy-proven G1 CHC patients were evaluated by anthropometric and metabolic measurements and 174 patients attending an outpatient cardiology unit were used as controls. Intima-media thickness (IMT) and carotid plaques, defined as focal thickening of >1.3 mm at the level of common carotid, were evaluated using ultrasonography. All G1 CHC biopsies were scored by one pathologist for staging and grading, and graded for steatosis. Carotid plaques were found in 73 (41.9%) G1 CHC patients compared with 40 (22.9%) control patients (P < 0.001). Similarly, G1 CHC patients had a greater IMT compared with control patients (1.04 ± 0.21 versus 0.90 ± 0.16; P < 0.001). Multivariate logistic regression analysis showed that older age (odds ratio [OR] 1.047, 95% confidence interval [CI]: 1.014-1.082, P = 0.005), and severe hepatic fibrosis (OR 2.177, 95% CI: 1.043-4.542, P = 0.03), were independently linked to the presence of carotid plaques. In patients ≤55 years, 15/67 cases with F0-F2 fibrosis (22.3%) had carotid plaques, compared with 11/21 (52.3%) with F3-F4 fibrosis (P = 0.008). By contrast, in patients >55 years the prevalence of carotid plaques was similar in those with or without severe fibrosis (25/43, 58.1% versus 22/43, 51.1%; P = 0.51).

CONCLUSIONS

Severe hepatic fibrosis is associated with a high risk of early carotid atherosclerosis in G1 CHC patients.

We have isolated a cDNA clone that corresponds to the Ht1 locus of petunia which controls the hydroxylation of dihydrokaempferol to dihydroquercetin and of naringenin to eriodictyol by the action of flavonoid 3'-hydroxylase (F3'H). The cDNA encodes a 512 amino acid polypeptide with regions of similarity to petunia flavonoid 3',5'-hydroxylases (F3'5'H). Both F3'H and F3'5'H are cytochromes P450 and are key enzymes in the flavonoid pathway leading to the production of the coloured anthocyanins. The F3 'H transcript is most abundant in petals from flowers at an early stage of development and levels decline as the flower matures. Transcripts are also detected in the ovaries, sepals, peduncles, stems and anthers of the petunia plant. No or very reduced levels of transcripts are detected in ht1/ht1 lines. This is the first report of isolation of a F3 'H cDNA clone from any species.

The growth of pure cultures of Bacteroides thetaiotaomicron LMG 11262 and Bacteroides fragilis LMG 10263 on fructose and oligofructose was examined and compared to that of Bifidobacterium longum BB536 through in vitro laboratory fermentations. Gas chromatography (GC) analysis was used to determine the different fractions of oligofructose and their degradation during the fermentation process. Both B. thetaiotaomicron LMG 11262 and B. fragilis LMG 10263 were able to grow on oligofructose as fast as on fructose, succinic acid being the major metabolite produced by both strains. B. longum BB536 grew slower on oligofructose than on fructose. Acetic acid and lactic acid were the main metabolites produced when fructose was used as the sole energy source. Increased amounts of formic acid and ethanol were produced when oligofructose was used as an energy source at the cost of lactic acid. Detailed kinetic analysis revealed a preferential metabolism of the short oligofructose fractions (e.g., F2 and F3) for B. longum BB536. After depletion of the short fractions, the larger oligofructose fractions (e.g., F4, GF4, F5, GF5, and F6) were metabolized, too. Both Bacteroides strains did not display such a preferential metabolism and degraded all oligofructose fractions simultaneously, transiently increasing the fructose concentration in the medium. This suggests a different mechanism for oligofructose breakdown between the strain of Bifidobacterium and both strains of Bacteroides, which helps to explain the bifidogenic nature of inulin-type fructans.

Ezrin is a member of the ERM (ezrin, radixin, moesin) family of proteins that cross-link the actin cytoskeleton to the plasma membrane and also may function in signaling cascades that regulate the assembly of actin stress fibers. Here, we report a crystal structure for the free (activated) FERM domain (residues 2-297) of recombinant human ezrin at 2.3 A resolution. Structural comparison among the dormant moesin FERM domain structure and the three known active FERM domain structures (radixin, moesin, and now ezrin) allows the clear definition of regions that undergo structural changes during activation. The key regions affected are residues 135-150 and 155-180 in lobe F2 and residues 210-214 and 235-267 in lobe F3. Furthermore, we show that a large increase in the mobilities of lobes F2 and F3 accompanies activation, suggesting that their integrity is compromised. This leads us to propose a new concept that we refer to as keystone interactions. Keystone interactions occur when one protein (or protein part) contributes residues that allow another protein to complete folding, meaning that it becomes an integral part of the structure and would rarely dissociate. Such interactions are well suited for long-lived cytoskeletal protein interactions. The keystone interactions concept leads us to predict two specific docking sites within lobes F2 and F3 that are likely to bind target proteins.

OBJECTIVE

We determined the activity of hsp90 inhibitor, and/or Janus-activated kinase 2 (JAK2) tyrosine kinase inhibitor (TKI), against JAK2-V617F-expressing cultured mouse (Ba/F3-JAK2-V617F) and human (HEL92.1.7 and UKE-1) or primary human CD34(+) myeloproliferative neoplasm (MPN) cells.

METHODS

Following exposure to the hsp90 inhibitor AUY922 and/or JAK2-TKI TG101209, the levels of JAK2-V617F, its downstream signaling proteins, as well as apoptosis were determined.

RESULTS

Treatment with AUY922 induced proteasomal degradation and depletion of JAK2-V617F as well as attenuated the signaling proteins downstream of JAK2-V617F, that is, phospho (p)-STAT5, p-AKT, and p-ERK1/2. AUY922 treatment also induced apoptosis of HEL92.1.7, UKE-1, and Ba/F3-hJAK2-V617F cells. Combined treatment with AUY922 and TG101209 caused greater depletion of the signaling proteins than either agent alone and synergistically induced apoptosis of HEL92.1.7 and UKE-1 cells. Cotreatment with AUY922 and TG101209 also induced significantly more apoptosis of human CD34(+) MPN than normal hematopoietic progenitor cells. As compared with the sensitive controls, JAK2-TKI-resistant HEL/TGR and UKE-1/TGR cells exhibited significantly higher IC(50) values for JAK2-TKI (P < 0.001), which was associated with higher expression of p-JAK2, p-STAT5, p-AKT, and Bcl-xL, but reduced levels of BIM. Unlike the sensitive controls, HEL/TGR and UKE/TGR cells were collaterally sensitive to the hsp90 inhibitors AUY922 and 17-AAG, accompanied by marked reduction in p-JAK2, p-STAT5, p-AKT, and Bcl-xL, with concomitant induction of BIM.

CONCLUSIONS

Findings presented here show that cotreatment with hsp90 inhibitor and JAK2-TKI exerts synergistic activity against cultured and primary MPN cells. In addition, treatment with hsp90 inhibitor may overcome resistance to JAK2-TKI in human MPN cells.

Oxytocin-secreting neurons of the hypothalamoneurohypophysial system undergo reversible morphological changes whenever they are strongly stimulated. In the hypothalamus, such structural plasticity is represented by modifications in the size and shape of their somata and dendrites, in the extent to which their surfaces are covered by glia, and in the density of their synapses. In the neurohypophysis, there is a parallel reduction in glial (pituicyte) coverage of their axons together, with retraction of pituicyte processes from the perivascular basal lamina and an increase in the number and size of their terminals. These changes occur rapidly, within a few hours. On the other hand, the system returns to its prestimulated condition on arrest of stimulation at a rate that depends on the length of time it has remained activated. Such neuronal-glial changes have several functional consequences. In the hypothalamic nuclei, reduction in astrocytic coverage of oxytocinergic neurons and their synapses modifies extracellular ionic homeostasis and glutamate clearance and, therefore, their overall excitability. Since it results in extensive dendritic bundling, it may also lead to ephaptic interactions and may facilitate dendritic electrotonic coupling. A most important indirect effect may be to permit synaptic remodeling that occurs concomitantly and that results in significant increases in the number of excitatory and inhibitory synapses driving their activity. In the stimulated neurohypophysis, glial retraction results in increased levels of extracellular K+ which can enhance neurohormone release while an enlarged neurovascular contact zone may facilitate diffusion of neurohormone into the circulation. Ongoing work aims to unravel the cell mechanisms and factors underlying such plasticity and has revealed that neurons and glia of the hypothalamoneurohypophysial system continue to express juvenile molecular features associated with similar neuronglial interactions and synaptic events during development and regeneration. They include strong expression of cell surface adhesion molecules like F3/contactin and polysialylated neural cell adhesion molecule, extracellular matrix glycoproteins like tenascin C, and cytoskeletal proteins like vimentin and microtubule-associated protein 1D. Some of these molecules reach the cell surface constitutively while others follow the activity-dependent regulated pathway. We consider many of these molecular features permissive, allowing oxytocin neurons and their glia to undergo morphological remodeling throughout life, provided the proper stimulus intervenes. In the hypothalamic nuclei, one such stimulus is centrally released oxytocin; in the neurohypophysis, an adrenergic, cAMP-mediated mechanism appears responsible.

Both cDNA and genomic clones of the T cell receptor (TCR) alpha- and beta-chain genes of the alloreactive cytotoxic T lymphocyte (CTL) clone F3 were examined. Two distinct rearrangement events, one functional and one non-functional, were found for both the alpha and beta loci. Thus only a single functional TCR alpha beta heterodimer could be defined, consistent with allelic exclusion in the TCR genes. The V alpha gene employed by F3 is part of a six-member V alpha subfamily. Genomic clones containing each member of this subfamily were isolated and the V alpha nucleotide sequences determined. Five of these six genes are functional; these genes differ from each other by 7-14% at the amino acid level. A single dominant hypervariable region was defined within this subfamily, in contrast to the pattern of variability seen between V alpha genes in general.