Antitumor activity of tumor necrosis factor-alpha conjugated with polyvinylpyrrolidone on solid tumors in mice

We attempted the development of a novel polymer conjugation to further improve the therapeutic potency of antitumor cytokines compared with PEGylation for clinical application. Compared with native tumor necrosis factor (TNF)-alpha in vitro, specific bioactivities of polyvinyl-pyrrolidone (PVP)-modified TNF-alphas (PVP-TNF-alphas) were decreased by increasing the degree of PVP attachment. PVP-TNF-alpha fraction 3, Mr 101,000, had the most effective antitumor activity of the various PVP-TNF-alphas in vivo. PVP-TNF-alpha fraction 3 had >200-fold higher antitumor effect than native TNF-alpha, and the antitumor activity of PVP-TNF-alpha fraction 3 was >2-fold higher than that of MPEG-TNF-alpha (Mr 108,000), which had the highest antitumor activity among the polyethylene glycol (PEG)-conjugated TNF-alphas. Additionally, a high dose of native TNF-alpha induced toxic side effects such as body weight reduction, piloerection. and tissue inflammation, whereas no side effects were observed after i.v. administration of PVP-TNF-alpha fraction 3. The plasma half-life of PVP-TNF-alpha fraction 3 (360 min) was about 80- and 3-fold longer than those of native TNF-alpha (4.6 mm) and MPEG-TNF-alpha (122 min), respectively. The mechanism of increased antitumor effect in vivo caused the prolongation of plasma half-life and increase in stability. These results suggested that PVP is a useful polymeric modifier for bioconjugation of TNF-alpha to increase its antitumor potency, and multifunctionally bioconjugated TNF-alpha may be a potentiated antitumor agent for clinical use.

A bis-cyclodextrin diselenide with glutathione peroxidase-like activity

A diselenide, 2,2'-diseleno-bis-beta-cyclodextrin (2-SeCD), was synthesized to imitate the antioxidant enzyme glutathione peroxidase (GPX). The GPX mimic accepts a variety of hydroperoxides as substrates. The GPX activities, reduction of H(2)O(2), tert-butyl hydroperoxide and cumenyl hydroperoxide by glutathione, are 7.4, 4.5 and 10.2 U/micromol, respectively. In contrast to ebselen (PZ51), the diselenide displays high GPX-like activity. The reduction of hydroperoxide by glutathione in the presence of a radical trap shows that the mimic catalyzes the reaction via a non-radical mechanism. A ping-pong mechanism was observed in the steady-state kinetic studies of the 2-SeCD-catalyzed reaction.

[Intraoperative endoscopic sphincterotomy for common bile duct stones during laparoscopic cholecystectomy]

OBJECTIVE

To assess the effects of approach-intraoperative endoscopic sphincterotomy (IOES) for common bile duct (CBD) stones during laparoscopic cholecystectomy (LC).

METHODS

Twenty-seven patients with secondary CBD stones were treated by IOES during LC. Therapeutic effects were evaluated on the basis of the cure rate, early complications, and days of hospitalization.

RESULTS

IOES was successfully performed in 26 (96.30%) of 27 cases, and their CBD stones were cleared completely. Two cases (7.69%) were complicated by mild acute pancreatitis.

CONCLUSION

IOES as an alternative to the treatment of CBD stones during LC is safe and avoids reoperation.

Thiazolidinedione suppresses the expression of erythroid phenotype in erythroleukemia cell line K562

The activation of PPARgamma:RXR nuclear system induces monocytic differentiation of some myelogeneous leukemia cell lines. The present study was undertaken to examine the effect of PPARgamma ligand, TZD (troglitazone or pioglitazone) and/or RXR selective ligand, LG100268 on the erythroleukaemia cell line K562 which has both an erythroid character and a potential for differentiation into megakaryocytes. TZD suppressed cell proliferation and the erythroid phenotype of K562 cells. The suppression of erythroid phenotype of K562 cells by TZD was synergistically enhanced by the combined treatment with LG100268. Moreover, the marked suppression of erythroid phenotype in K562 cells was also accompanied by the downregulation of the erythroid lineage-transcription factor, GATA-1. These novel actions of troglitazone may provide a biochemical basis for anemia occasionally which is observed after the in vivo administration of TZD.

Protein kinase C-theta participates in NF-kappaB activation induced by CD3-CD28 costimulation through selective activation of IkappaB kinase beta

The NF-kappaB/Rel family of eukaryotic transcription factors plays an essential role in the regulation of inflammatory, antiapoptotic, and immune responses. NF-kappaB is activated by many stimuli including costimulation of T cells with ligands specific for the T-cell receptor (TCR)-CD3 complex and CD28 receptors. However, the signaling intermediates that transduce these costimulatory signals from the TCR-CD3 and CD28 surface receptors leading to nuclear NF-kappaB expression are not well defined. We now show that protein kinase C-theta (PKC-theta), a novel PKC isoform, plays a central role in a signaling pathway induced by CD3-CD28 costimulation leading to activation of NF-kappaB in Jurkat T cells. We find that expression of a constitutively active mutant of PKC-theta potently induces NF-kappaB activation and stimulates the RE/AP composite enhancer from the interleukin-2 gene. Conversely, expression of a kinase-deficient mutant or antisense PKC-theta selectively inhibits CD3-CD28 costimulation, but not tumor necrosis factor alpha-induced activation of NF-kappaB in Jurkat T cells. The induction of NF-kappaB by PKC-theta is mediated through the activation of IkappaB kinase beta (IKKbeta) in the absence of detectable IKKalpha stimulation. PKC-theta acts directly or indirectly to stimulate phosphorylation of IKKbeta, leading to activation of this enzyme. Together, these results implicate PKC-theta in one pathway of CD3-CD28 costimulation leading to NF-kappaB activation that is apparently distinct from that involving Cot and NF-kappaB-inducing kinase (NIK). PKC-theta activation of NF-kappaB is mediated through the selective induction of IKKbeta, while the Cot- and NIK-dependent pathway involves induction of both IKKalpha and IKKbeta.

24-hour blood pressure in Uygur, Kazakh and Han elderly subjects in China

The Uygur in Hotan (Xinjiang, China) are reported to have a long life expectancy. The purpose of this study was to clarify the relationship between variations in blood pressure (BP) and longevity. Cross-sectional surveillance was carried out in both Hotan and Barkol. The subjects were divided into five groups: 1. Uygur longevity subjects in Hotan (103 subjects, age >90 yr); 2. Uygur elderly subjects in Hotan (107 subjects, age 65-70 yr); 3. Han elderly subjects in Hotan (41 subjects, age 65-70 yr); 4. Kazakh elderly subjects in Barkol (117 subjects, age 65-70 yr); 5. Han elderly subjects in Barkol (50 subjects, age 65-70 yr). BP was monitored and analyzed using the fourteen devices of ambulatory BP monitoring. The prevalence of hypertension was lowest in the Uygur (16.2% in Uygur elderly subjects in Hotan; 23.7% in Uygur longevity subjects in Hotan; 27.0% in Han elderly subjects in Hotan; 42.0% in Han elderly subjects in Barkol; 50.0% in Kazakh elderly subjects in Barkol). The ratio of dips in BP was largest in the Han (57% in Han elderly subjects in Barkol; 50% in Han elderly subjects in Hotan; 50% in Uygur longevity subjects in Hotan, 49% in Uygur elderly subjects in Hotan; 17% in Kazakh elderly subjects in Barkol). The 24-h mean systolic BP in Uygur longevity subjects in Hotan was not different from those in Uygur elderly subjects and Han elderly subjects in Hotan, nor did the 24-h mean diastolic BP differ from those in Uygur elderly subjects and Han elderly subjects in Hotan respectively. In conclusion, Uygur subjects seem to be less hypertensive, compared to Kazakh subjects. Uygur longevity subjects had more dipping in their BP variation than did the Kazakh subjects in Xinjiang, China.

Metal ion release from titanium with active oxygen species generated by rat macrophages in vitro

The release of metal ions due to active oxygen species generated by macrophages (Mphi) phagocytosing high-density polyethylene (HDPE) particles was studied in vitro to investigate the mechanism behind the release of metal ions from titanium implants into nearby tissues in the absence of wear and fretting in vivo. To determine the effects of Mphis on metal ion release, titanium disks were immersed in different solutions and the titanium ions released from the titanium disks into each solution were quantified. The results revealed that active oxygen species generated by Mphis induced the metal ion release. In particular, the ion release was accelerated with HDPE because the Mphis that phagocytosed HDPE generated more active oxygen species than Mphis that did not phagocytose any HDPE. Metal ions were also released by organic species in the absence of Mphis. These are some of the causes for metal ion release from titanium implants in the absence of wear and fretting in vivo.

Facile synthesis of a chitosan hybrid of a laminin-related peptide and its antimetastatic effect in mice

Laminin, a cell adhesion protein, consists of three peptide chains (alpha-1, beta-1 and gamma-1). The beta-1 chain contains a Tyr-Ile-Gly-Ser-Arg (YIGSR) sequence that has been found to inhibit experimental metastasis in mice. We have prepared a hybrid of a water-soluble chitosan and a laminin-related peptide, and have examined its inhibitory effect on experimental metastasis in mice. A laminin-related peptide, acetyl-Tyr-Ile-Gly-Ser-Arg-betaAla-OH (Ac-YIGSRbetaA-OH), was prepared by a solid-phase method. Ac-YIGSRbetaA-OH was then reacted with a water-soluble chitosan. BetaAla is a spacer and was placed to avoid racemization of the Arg residue when the peptide was coupled with chitosan. Although chitosan has amino groups, they did not react with the peptide. Four methods were tried to achieve a coupling reaction, the diphenylphosphoryl azide method, the diisopropylcarbodiimide/1-hydroxybenzotriazole method, the water-soluble carbodiimide (WSC), and the 2-(1H-benzotriazole-1-yl)-1,1,3,3-tetramethyluronium tetrafluoroborate (TBTU) method, but all four methods were unsuccessful. Therefore, a small spacer, tert-butyloxycarbonyl-Gly, was intercalated in chitosan, by the TBTU method, to facilitate its coupling with the peptide. After removal of the protecting group, the Gly-chitosan was coupled with Ac-YIGSRbetaA-OH by the water-soluble carbodiimide method to give Ac-YIGSRbetaAG-chitosan. Conjugation of the peptide with the larger chitosan molecule did not reduce the inhibitory effect of the peptide on experimental metastasis in mice, it actually potentiated the antimetastatic effect, demonstrating that chitosan may be effective as a drug carrier for peptides.

Bioconjugation of laminin-related peptide YIGSR with polyvinyl pyrrolidone increases its antimetastatic effect due to a longer plasma half-life

Polyvinyl pyrrolidone (PVP) which can be radically synthesized and have a long blood residency was used to modify the laminin-related peptide YIGSR, and its inhibitory effect on experimental lung metastasis of B16-BL6 melanoma cells was examined. The antimetastatic effect of PVP-conjugated YIGSR (PVP-YIGSR) was more than 100-fold greater than that of native YIGSR. When injected intravenously, PVP-YIGSR showed more than a 15-fold longer plasma half-life relative to native YIGSR. In addition, the stability of YIGSR in plasma was increased by conjugation with PVP. These findings suggest that PVP is a useful polymeric modifier for increasing the antimetastatic activity of YIGSR.

Thiazolidinedione induces apoptosis and monocytic differentiation in the promyelocytic leukemia cell line HL60

Thiazolidinedione (TZD) is known to be a potent activator of peroxisome proliferator-activated receptor gamma (PPARgamma), a nuclear receptor that constitutes a heterodimer with retinoid X receptor (RXR). Since a considerable amount of PPARgamma is expressed in various hematopoietic cells, the present study was undertaken to examine the effect of TZD in the absence or presence of LG100268, an RXR-selective ligand, on a cultured promyelocytic leukemia cell line, HL60. Treatment with TZD (25-50 microM troglitazone or pioglitazone) markedly suppressed cell proliferation of HL60. A cell cycle analysis revealed that the suppressive effect of troglitazone on HL60 cell proliferations was caused by G0/G1 cell cycle arrest as well as by an apoptotic effect. Treatment with the same concentration of troglitazone also induced the monocytic differentiation of HL60 cells. The apoptotic or the differentiating effect of TZD on HL60 cells was synergistically enhanced by the combined treatment with 1 microM LG100268, while LG100268 alone neither had an apoptotic nor a differentiating effect on HL60 cells. These results suggest that these actions are mediated through the nuclear receptor system constituted by the PPARgamma: RXR heterodimer.

Novel farnesol and geranylgeraniol analogues: A potential new class of anticancer agents directed against protein prenylation

Protein farnesyltransferase (FTase), the enzyme responsible for protein farnesylation, has become a key target for the rational design of cancer chemotherapeutic agents. Herein it is shown that certain novel prenyl diphosphate analogues are potent inhibitors of mammalian FTase. Furthermore, the alcohol precursors of two of these compounds are able to block anchorage-independent growth of ras-transformed cells. While 3-allylfarnesol inhibits protein farnesylation, 3-vinylfarnesol instead leads to abnormal prenylation of proteins with the 3-vinylfarnesyl group. In a similar manner, 3-allylgeranylgeraniol acts as a highly specific inhibitor of protein geranylgeranylation, while 3-vinylgeranylgeraniol restores protein geranylgeranylation in cells. This study indicates that certain prenyl alcohol analogues can act as prenyltransferase inhibitors in situ, via a novel prodrug mechanism. These analogues may prove to be valuable tools for investigating the therapeutic consequences of inhibiting geranylgeranylation relative to farnesylation. Furthermore, the 3-vinyl alcohol analogues can inhibit transformed cell growth through a mechanism not involving prenyltransferase inhibition.

Captopril and platelet-activating factor (PAF) antagonist prevent cardiac allograft vasculopathy in rats: role of endogenous PAF and PAF-like compounds

Accelerated coronary artery disease (CAD) is the leading cause of late mortality following cardiac transplantation. The vascular lesions are characterized by myointimal proliferation and perivascular mononuclear inflammatory infiltrates. Platelet-activating factor (PAF, 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) is a potent phospholipid mediator produced by inflammatory cells and activated endothelial cells. Angiotensin II is known to activate phospholipase A2, a critical enzyme in PAF synthesis. Using a rat heterotopic cardiac transplant model known to induce graft CAD, we previously reported that chronic administration of captopril, an angiotensin converting enzyme inhibitor, reduces intimal proliferation and maintains luminal patency. The purpose of the current study was to determine if captopril regulates vascular remodeling by suppressing PAF synthesis and whether administration of a PAF antagonist ameliorates graft CAD. Captopril was found to decrease levels of PAF and PAF-like compounds as well as reduce intimal lesions, decrease cellular rejection grade, and diminish allograft heart weights. Treatment with a PAF antagonist significantly decreased proliferation of the intimal component of the vasculopathy and caused regression of the cardiac hypertrophy, but had no significant effect on cellular rejection. In contrast, untreated animals had elevated plasma PAF levels, elevated heart weights, and severe myointimal proliferation with luminal stenosis 21 days post-transplantation. These observations suggest that graft CAD is mediated, in part, by PAF and PAF-like compounds, and suppression of endogenous PAF may prevent cardiac allograft vasculopathy.

Increased expression of transforming growth factor-beta1 and thrombospondin-1 in congenital hepatic fibrosis: possible role of the hepatic stellate cell

BACKGROUND

Congenital hepatic fibrosis is a rare disease characterized by portal tract fibrosis and biliary duct ectasia. It is associated with autosomal recessive polycystic kidney disease and rarely progresses to cirrhosis. The activated stellate cell has been implicated in the pathogenesis of alcohol- or inflammation-mediated cirrhosis through fibrogenic proteins such as transforming growth factor-beta1; however, the role of the stellate cell in pure, noninflammatory fibrosis is unknown. It has been hypothesized that fibrosis in congenital hepatic fibrosis may be caused by upregulation of transforming growth factor-beta1 and thrombospondin-1, and that the hepatic stellate cell may be the mediator of these proteins.

METHODS

Human liver tissue samples from patients with congenital hepatic fibrosis (n = 9) and from normal patients (n = 3) were analyzed. Tissue homogenates from both groups were analyzed for transforming growth factor-beta1 protein and mRNA by Western blot analysis and in situ hybridization, respectively. Immunolocalization studies were performed in fixed tissue sections from both groups. Stellate cells were cultured from livers exhibiting congenital hepatic fibrosis and confirmed by desmin staining. The cells were cultured in serum-free medium for 48 hours, and media were collected and analyzed by Western blot analysis for thrombospondin-1 and transforming growth factor-beta1.

RESULTS

Congenital hepatic fibrosis liver tissue homogenates had higher levels of thrombospondin-1 and transforming growth factor-beta1 protein than in normal livers. In congenital hepatic fibrosis tissue, transforming growth factor-beta1 was more highly expressed in the ectatic biliary epithelium and the perisinusoidal space, whereas thrombospondin-1 localized most intensely to the hepatocytes and spared the bile ducts. Congenital hepatic fibrosis-derived stellate cells secreted both thrombospondin-1 and transforming growth factor-beta1, in vitro.

CONCLUSIONS

Transforming growth factor-beta1 and thrombospondin-1 may play a role in the pathogenesis of liver fibrosis in patients with congenital hepatic fibrosis. One potential source of these fibrogenic proteins is the hepatic stellate cell.

[Linkage studies of a familial spastic paraplegia pedigree from Tibet]

OBJECTIVE

To study the location of disease-related gene in a hereditary spastic paraplegia family with autosomal dominant inheritance in Tibet.

METHODS

The AD-HSP family in Tibet was analyzed by linkage studies using 9 highly polymorphic microsatellite DNA markers at three chromosomal regions.

RESULTS

The maxium Lod- Score of D14S264 was 0.5163(theta=0.05); of D14S75, 2. 1072 (theta=0);+D14S69, 0.2840 (theta=0.10); of D14S266, 0.9311 (theta=0);of D14S66, 0.7991(theta=0);OF GABRB3, 0(theta =0.40);of D15S128, 0(theta=0.40); of D2S2255, 0 (theta=0.40);and of D2S2347,0(theta=0.40).

CONCLUSION

In this Tibetian family, the disease-related gene is linked to D14S75 locus of SPG3 region.

Bioconjugation of laminin peptide YIGSR with poly(styrene co-maleic acid) increases its antimetastatic effect on lung metastasis of B16-BL6 melanoma cells

A comb-shaped polymeric modifier, SMA [poly(styrene comaleic anhydride)], which binds to plasma albumin in blood was used to modify the synthetic cell-adhesive laminin peptide YIGSR, and its inhibitory effect on experimental lung metastasis of B16-BL6 melanoma cells was examined. YIGSR was chemically conjugated with SMA via formation of an amide bond between the N-terminal amino group of YIGSR and the carboxyl anhydride of SMA. The antimetastatic effect of SMA-conjugated YIGSR was approximately 50-fold greater than that of native YIGSR. When injected intravenously, SMA-YIGSR showed a 10-fold longer plasma half-life than native YIGSR in vivo. In addition, SMA-YIGSR had the same binding affinity to plasma albumin as SMA, while native YIGSR did not bind to albumin. These findings suggested that the enhanced antimetastatic effect of SMA-YIGSR may be due to its prolonged plasma half-life by binding to plasma albumin, and that bioconjugation of in vivo unstable peptides with SMA may facilitate their therapeutic use.

The proto-oncogene Cot kinase participates in CD3/CD28 induction of NF-kappaB acting through the NF-kappaB-inducing kinase and IkappaB kinases

The proto-oncogene Cot/Tpl-2 encodes a MAP3K-related serine-threonine kinase. Expression of wild type Cot activates the IkappaB kinases (IKK) leading to induction of NF-kappaB. Conversely, expression of kinase-deficient Cot inhibits CD3/CD28 but not TNF alpha induction of NF-kappaB. These findings suggest the selective involvement of Cot/Tpl-2 or a closely related kinase in the CD3/CD28 costimulatory pathway leading to induced nuclear expression of NF-kappaB. In contrast, a kinase-deficient mutant of the NF-kappaB-inducing kinase (NIK) inhibits both CD3/CD28 and TNF alpha signaling, indicating that these pathways converge at or prior to the action of NIK. Consistent with such a sequential function of these two kinases, Cot physically assembles with and phosphorylates NIK in vivo.

High angiogenic activity in cells isolated from cystic hygroma: role of bFGF

BACKGROUND

Cystic hygromas are characterized by a proliferation of small vessels and lymphatics with intervening fibrous tissue. Studies have shown malignant tumors and some benign neoplasms are dependent on angiogenesis, the induction of new capillaries from preexisting vessels. Growth and progression of these tumors are associated with a disturbance in the balance of angiogenic inducers and inhibitors. We have postulated that cells derived from cystic hygromas are angiogenic due to secretion of higher levels of angiogenic inducers that promote vascular proliferation.

DESIGN

A large cystic mass was surgically removed and a portion of the sterile tumor was immediately placed in the medium. The tissue was minced, washed in phosphate-buffered saline, and grown to near confluence. Conditioned medium was collected under serum-free conditions after 48 hours. Secreted proteins were concentrated, quantitated, and analyzed in an in vitro endothelial cell migration assay and by Western blot. Antibody to factor VIII-related antigen was performed to confirm endothelial cell origin of the cultured cells.

MAIN OUTCOME MEASURES

In vitro angiogenic activity of secreted proteins in a capillary endothelial migration assay was tested by using blocking antibodies to angiogenic inducer, basic fibroblast growth factor, and angiogenic inhibitor, thrombospondin-1. Total protein levels of thrombospondin-1 were determined by Western blot.

RESULTS

Cells isolated from cystic hygroma are angiogenic in vitro and this angiogenic activity is due to secretion of high levels of angiogenic inducer, basic fibroblast growth factor, and lower levels of naturally occurring angiogenic inhibitor, thrombospondin-1.

CONCLUSIONS

Cystic hygromas may represent another neoplasm dependent on angiogenesis. The angiogenic activity is due in part to elevated levels of potent angiogenic inducer, basic fibroblast growth factor. Antiangiogenic therapy directed at the endothelial cell may help suppress the growth of cystic hygromas.

Drug dependence and abuse potential of tramadol

AIM

To assess the drug dependence and abuse liability of tramadol.

METHODS

Subjects of opiate addicts with history of tramadol abuse were 219. Physical dependence of tramadol was assessed using opiate withdrawal scale (OWS), psychic dependence was assessed by association test of Addiction Research Center Inventory-Chinese Version (ARCI-CV); the degrees of craving experienced for tramadol was self-reported on visual analogue scale (VAS).

RESULTS

The scores of OWS of tramadol were 0.05-1.07; 3 scores on scales in particular being used the identify euphoric effects--MBG, sedative effects--PCAG, and psychotomimetic effects--LSD of ARCI were 7.3, 6.1, and 3.4, respectively (F = 38.1, P < 0.01); 57.1% of tramadol abuse subjects had craving for tramadol (chi 2 = 75.86, P < 0.01).

CONCLUSION

Tramadol produced high abuse potential among opiate addicts.

Rapid growth of cutaneous metastases after surgical resection of thrombospondin-secreting small blue round cell tumor of childhood

In animal models, the importance of tumor-derived antiangiogenic factors in controlling metastases has been demonstrated by the growth acceleration of distant metastases after surgical excision of a primary tumor mass. We report the case of an infant who developed rapidly growing cutaneous metastases after surgical resection of a neoplasm of an upper extremity. The tumor was undifferentiated, with some morphological features of primitive neuroectodermal tumor. To test the possibility that the primary tumor was secreting an angiogenic inhibitor, cells from the primary tumor were grown in culture, and the culture medium was tested with an in vitro endothelial cell migration assay and Western blot. The cultured cells secreted sufficiently high levels of an angiogenic inhibitor to overcome the inducing ability of vascular endothelial growth factor and basic fibroblast growth factor. One of the secreted proteins was thrombospondin-1, a potent antiangiogenic glycoprotein. The rapid dissemination of distant metastases after resection of the primary tumor in this case suggests that tumor-derived angiogenic inhibitors are important in maintaining the local net balance of angiogenic mediators controlling the growth of micrometastasis.

Molecular determinants of NF-kappaB-inducing kinase action

NF-kappaB corresponds to an inducible eukaryotic transcription factor complex that is negatively regulated in resting cells by its physical assembly with a family of cytoplasmic ankyrin-rich inhibitors termed IkappaB. Stimulation of cells with various proinflammatory cytokines, including tumor necrosis factor alpha (TNF-alpha), induces nuclear NF-kappaB expression. TNF-alpha signaling involves the recruitment of at least three proteins (TRADD, RIP, and TRAF2) to the type 1 TNF-alpha receptor tail, leading to the sequential activation of the downstream NF-kappaB-inducing kinase (NIK) and IkappaB-specific kinases (IKKalpha and IKKbeta). When activated, IKKalpha and IKKbeta directly phosphorylate the two N-terminal regulatory serines within IkappaB alpha, triggering ubiquitination and rapid degradation of this inhibitor in the 26S proteasome. This process liberates the NF-kappaB complex, allowing it to translocate to the nucleus. In studies of NIK, we found that Thr-559 located within the activation loop of its kinase domain regulates NIK action. Alanine substitution of Thr-559 but not other serine or threonine residues within the activation loop abolishes its activity and its ability to phosphorylate and activate IKKalpha. Such a NIK-T559A mutant also dominantly interferes with TNF-alpha induction of NF-kappaB. We also found that ectopically expressed NIK both spontaneously forms oligomers and displays a high level of constitutive activity. Analysis of a series of NIK deletion mutants indicates that multiple subregions of the kinase participate in the formation of these NIK-NIK oligomers. NIK also physically assembles with downstream IKKalpha; however, this interaction is mediated through a discrete C-terminal domain within NIK located between amino acids 735 and 947. When expressed alone, this C-terminal NIK fragment functions as a potent inhibitor of TNF-alpha-mediated induction of NF-kappaB and alone is sufficient to disrupt the physical association of NIK and IKKalpha. Together, these findings provide new insights into the molecular basis for TNF-alpha signaling, suggesting an important role for heterotypic and possibly homotypic interactions of NIK in this response.

Human T-cell leukemia virus type 1 Tax induction of NF-kappaB involves activation of the IkappaB kinase alpha (IKKalpha) and IKKbeta cellular kinases

Tax corresponds to a 40-kDa transforming protein from the pathogenic retrovirus human T-cell leukemia virus type 1 (HTLV-1) that activates nuclear expression of the NF-kappaB/Rel family of transcription factors by an unknown mechanism. Tax expression promotes N-terminal phosphorylation and degradation of IkappaB alpha, a principal cytoplasmic inhibitor of NF-kappaB. Our studies now demonstrate that HTLV-1 Tax activates the recently identified cellular kinases IkappaB kinase alpha (IKKalpha) and IKKbeta, which normally phosphorylate IkappaB alpha on both of its N-terminal regulatory serines in response to tumor necrosis factor alpha (TNF-alpha) and interleukin-1 (IL-1) stimulation. In contrast, a mutant of Tax termed M22, which does not induce NF-kappaB, fails to activate either IKKalpha or IKKbeta. Furthermore, endogenous IKK enzymatic activity was significantly elevated in HTLV-1-infected and Tax-expressing T-cell lines. Transfection of kinase-deficient mutants of IKKalpha and IKKbeta into either human Jurkat T or 293 cells also inhibits NF-kappaB-dependent reporter gene expression induced by Tax. Similarly, a kinase-deficient mutant of NIK (NF-kappaB-inducing kinase), which represents an upstream kinase in the TNF-alpha and IL-1 signaling pathways leading to IKKalpha and IKKbeta activation, blocks Tax induction of NF-kappaB. However, plasma membrane-proximal elements in these proinflammatory cytokine pathways are apparently not involved since dominant negative mutants of the TRAF2 and TRAF6 adaptors, which effectively block signaling through the cytoplasmic tails of the TNF-alpha and IL-1 receptors, respectively, do not inhibit Tax induction of NF-kappaB. Together, these studies demonstrate that HTLV-1 Tax exploits a distal part of the proinflammatory cytokine signaling cascade leading to induction of NF-kappaB. The pathological alteration of this cytokine pathway leading to NF-kappaB activation by Tax may play a central role in HTLV-1-mediated transformation of human T cells, clinically manifested as the adult T-cell leukemia.

Amino acids and peptides. XXXIII. A bifunctional poly(ethylene glycol) hybrid of laminin-related peptides

A novel amino acid type poly(ethylene glycol) (aaPEG) was prepared and its application as a drug-carrier was examined. The peptides, Pro-Asp-Ser-Gly-Arg (PDSGR) and Tyr-Ile-Gly-Ser-Arg (YIGSR) which are active fragments of Laminin (a cell adhesion protein), were previously reported to be inhibitors of experimental metastasis. Both peptides were conjugated with aaPEG (average molecular weight, 3,000) to prepare a bifunctional peptide-PEG hybrid. The hybrid, PDSGR-aaPEG-YIGSR, was manually prepared by the solid-phase fluorenylmethyloxycarbonyl (Fmoc) strategy. The antimetastatic activity of the peptides in mice was not lost when conjugated to form a larger aaPEG molecule. YIGSR(375 nmol) and PDSGR (375 nmol and 750 nmol) did not demonstrate antimetastatic activity, but a mixture of PDSGR (187 nnmol) and YIGSR (187 nmol) exhibited an inhibitory effect. The inhibitory effect of the hybrid (187 nmol) was more potent than that of the mixture (PDSGR and YIGSR), indicating that the inhibitory effect of the peptides was potentiated by hybrid formation with aaPEG.